Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Cover crops provide ecosystem services such as storing atmospheric carbon in soils after incorporation of their residues. Cover crops also influence soil water balance, which can be an issue in temperate climates with dry summers as for example in southern France and Europe. As a consequence, it is necessary to understand cover crops’ long-term influence on greenhouse gases (GHG) and water balances to assess their potential to mitigate climate change in arable cropping systems. We used the previously calibrated and validated soil-crop model STICS to simulate scenarios of cover crop introduction to assess their influence on rainfed and irrigated cropping systems and crop rotations distributed among five contrasted sites in southern France from 2007-2052. Our results showed that cover crops can improve mean direct GHG balance by 315 kg CO2e ha⁻¹ yr⁻¹ in the long term compared to that of bare soil. This was due mainly to an increase in carbon storage in the soil despite a slight increase in N2O emissions which can be compensate by adapting fertilization. Cover crops also influence the water balance by reducing mean annual drainage by 20 mm yr⁻¹ but increasing mean annual evapotranspiration by 20 mm yr⁻¹ compared to those of bare soil. Using cover crops to improve the GHG balance may help to mitigate climate change by decreasing CO2e emitted in cropping systems which can represent a decrease from 4.5 to 9% of annual GHG emissions of the French agriculture and forestry sector. However, if not well managed, they also could create water management issues in watersheds with shallow groundwater. Relationships between cover crop biomass and its influence on several variables such as drainage, carbon sequestration and GHG emissions could be used to extend our results to other conditions to assess the cover crops influence in a wider range of areas.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... 6 How the anaerobic digestion of energy cover crops affects carbon dynamics By fixing atmospheric carbon dioxide, cover crops can increase the amount of carbon stored in the soil (Blanco-Canqui et al. 2015;Poeplau and Don 2015;Kaye and Quemada 2017;Tribouillois et al. 2018;Jian et al. 2020). Incorporating the above-and belowground biomass of cover crops could result in the storage of 320 kg C/ha per year, based on a meta-analysis by Poeplau and Don (2015), or even 560 kg C/ha per year, according to a meta-analysis by Jian et al. (2020). ...
... Depending on climatic conditions, this reduction in drainage may represent a small or a large percentage of annual water drainage, which could have major implications for water recharge in dry regions. Cover crop biomass seems to be one of the main determinant factors, with seeding date close behind Tribouillois et al. 2018). Tribouillois et al. (2018) observed that increases in cover crop biomass were strongly correlated with increases in evapotranspiration and decreases in drainage. ...
... Cover crop biomass seems to be one of the main determinant factors, with seeding date close behind Tribouillois et al. 2018). Tribouillois et al. (2018) observed that increases in cover crop biomass were strongly correlated with increases in evapotranspiration and decreases in drainage. However, at a certain threshold of biomass (< 2.5 t dry matter/ha) or leaf area index values, evapotranspiration showed no further increases . ...
Article
Some European countries are exploring the idea of replacing dedicated crops with energy cover crops for biogas production. Indeed, energy cover crops can generate consequential biomass without competing with food crops for land use. However, the potential benefits and impacts of this choice are not fully understood. Here, we review what is known about the consequences of energy cover crop usage by examining management regimes and digestate use, including impacts on the environment and cropping system performance. First, compared to cover crops, energy cover crops are intensively managed to produce more biomass (< 5 t DM/ha vs. up to 16 t DM/ha). Second, nitrogen is conserved during anaerobic digestion and is more readily available to crops in digestate than in cover crops residues. However, ammonia is lost via volatilization, which could reduce nitrogen use efficiency, depending on the storage conditions and application method. Third, 43–80% of the crops’ initial carbon is transformed into biogas. That said, levels of soil carbon storage may nonetheless resemble those obtained with cover crops left behind because carbon is stabilized during anaerobic digestion and the energy cover crops’ roots and stubble are left behind in the soil. Fourth, energy cover crops can act as multiservice cover crops, reducing nitrate leaching, improving soil microbial activity, and enhancing soil physical properties during the fallow period. Fifth, energy cover crop usage can have certain disservices, such as soil compaction, the need for additional inputs (e.g., irrigation, fertilization, pesticides), reduced groundwater recharge, and reduced following crop yield. In summary, expanding the usage of energy cover crops for biogas production does not seem to be an environmental threat. However, care must be taken to avoid the intensification of irrigation and lengthening growing periods to boost biomass, which could reduce food production.
... Sown during the fallow period between two annual cash crops and usually terminated long or immediately before sowing the succeeding cash crop, they are returned to the soil. Cover crops can provide a wide range of ecosystem services, such as provision of a green manure effect; storage of carbon in the soil; reduction of nitrate leaching and erosion, a better greenhouse gas balance and weed control (Constantin et al., 2010;Ryder and Fares, 2008;Schipanski et al., 2014;Tonitto et al., 2006;Tosti et al., 2014;Tribouillois et al., 2018). ...
... The increase in water and mineral N uptake can decrease water and N availability for the succeeding crop, and this pre-emptive competition occurs particularly in dry regions (Thorup-Kristensen et al., 2003). In the context of climate change, with temperatures and lower rainfall in arid and temperate regions (IPCC, 2013), sowing cover crops during the fallow period could increase issues for groundwater recharge and decrease yield of the succeeding cash crop, by reducing drainage (Tribouillois et al., 2018) and soil water and N availability for the following crop (Alonso-Ayuso et al., 2018;Meyer et al., 2020). ...
... These authors classified STICS' predictions as "satisfactory" to "very good" for most of the variables analysed, especially the SWC and crop biomass under differing levels of N and water availability. STICS has been used to simulate cover crops, in particular to predict their influence in the short to long terms on the SWC, SNC and the green manure effect (Constantin et al., 2012;Tribouillois et al., 2018). Cover crop species simulated in the present study were previously calibrated and validated for STICS based on several field experiments (Constantin et al., 2015b;Meyer et al., 2020). ...
Article
Cover crops are crucial to diversify cropping systems into more agroecological systems by providing ecosystem services, such as reduction of nitrate leaching, provision of a green manure effect, and soil carbon storage. However, they can influence water drainage and nitrogen (N) or water availability for the succeeding crop, depending on their management and the climate. In this simulation study, we used the STICS model to predict the influence of cover crop species, date of sowing and termination, and cover crop residue management on N and water balances, and the yield and stress of the succeeding cash crop. We performed 25-year simulations for five contrasting sites in south-western France, which is a temperate region of Europe with dry summers. As expected, cover crops decreased nitrate leaching effectively but also decreased drainage by a mean of 5–40 mm. This decrease depended mainly on the sowing and termination dates, while the decrease in nitrate leaching varied greatly among sites and depended most on sowing date, followed by cover crop species and then termination date. Cover crops had little influence on soil water content in the upper 0.1 m of soil at sowing of the succeeding cash crop, but decreased soil water content of the total soil profile by 0–30 mm. Soil water content depended most on termination date, followed by species and then site. Total soil mineral N content (SNC) also decreased, by 5–40 kg N.ha⁻¹, at the three driest sites and up to 10 kg N.ha⁻¹ at the rainiest site. Termination date, the second-most influential factor on SNC, indicated that later termination resulted in lower SNC than that after bare soil. N uptake by the succeeding cash crop depended on species and termination date, and a legume cover crop and earlier termination date resulted in higher N uptake. The decrease in maize and sunflower yield was due mainly to changes in the N stress index during the vegetative phase for maize, and both vegetative and reproductive phases for sunflower. No water stress or increase in irrigation volumes was predicted or was correlated with yield changes, except at dry sites for the few years that experienced a severe drought in spring. While cover crops decreased nitrate leaching effectively, they decreased drainage and could induce N stress for the succeeding crop, particularly in dry regions. Including legumes in mixtures and adapting the termination date to local climate conditions could decrease or avoid these negative effects.
... Hence, Blanco-Canqui et al. (2012) showed that cover crops increased soil total N pool (by 270 kg ha −1 for the 0 to 7.5-cm depth) and a meta-analysis of Tonitto et al. (2006) showed that a cover crop correctly managed can increase N availability for the next main cash crop by returning organic matter to the soil. Similar results have been reported in several studies and metaanalyses, which have shown that cover crops could increase soil organic carbon/carbon storage (Blanco-Canqui et al., 2015;Poeplau et Don, 2015;Kaye et Quemada, 2017;Tribouillois et al., 2018b;Chahal et al., 2020) and long term N supply (Blanco-Canqui et al., 2012;Schipanski et al., 2014;Büchi et al., 2018). ...
... Therefore, this increased N availability can allow to better meet N needs of the next cash crop, and thus can contribute to the increase of the agricultural production of cash crop in situation where nitrogen is a limiting factor of the production. Thus, this water drainage reduction during cover crop contributes increase water provision to crops service (Qi et Helmers, 2010;Tribouillois et al., 2018b). However, while Meyer et al. (2018); Tribouillois et al. (2018b) showed that cover crops can significantly reduce water drainage over a large range of situation productions, in our study the effect on drainage, and so blue water provision, is low at the rotation scale whole over the simulation period. ...
... Thus, this water drainage reduction during cover crop contributes increase water provision to crops service (Qi et Helmers, 2010;Tribouillois et al., 2018b). However, while Meyer et al. (2018); Tribouillois et al. (2018b) showed that cover crops can significantly reduce water drainage over a large range of situation productions, in our study the effect on drainage, and so blue water provision, is low at the rotation scale whole over the simulation period. ...
Thesis
Full-text available
Les écosystèmes fournissent de nombreux bénéfices essentiels au bien-être humain, dénommés services écosystémiques (SE). Dans certains cas, ces SE peuvent présenter des antagonismes (augmentation d’un SE et diminution d’un autre) ou des synergies (deux SE ou plus varient dans le même sens). Analyser et quantifier ses relations (antagonismes ou synergies) à l’échelle des écosystèmes demeure un défi scientifique majeur pour leur gestion durable. Dans cette thèse, nous avons analysé et quantifié à l’échelle des écosystèmes cultivés de la France métropolitaine, les relations entre différents SE et biens liés au fonctionnement du sol : la production agricole (biens végétaux), deux services rendus à l’agriculteur – fourniture en azote et en eau verte aux plantes cultivées – et trois services rendus à la société – stockage et restitution de l’eau bleue, régulation de la qualité de l’eau et régulation du climat global via le stockage du carbone dans le sol. En général, nos résultats contribuent à améliorer les connaissances actuelles sur les relations entre SE à l’échelle des écosystèmes cultivés et les moyens de leur gestion.
... In this context, the recent '4 per 1000' initiative (Chabbi et al., 2017a;Minasny et al., 2017a) aims at increasing global soil organic carbon (SOC) stocks of all non-permafrost soil by 4‰ per year in order to counterbalance the anthropogenic GHG emissions. Several studies identified cover crops (CC) as an efficient management practice to sequester carbon in the soils (Kaye and Quemada, 2017a;Lugato et al., 2020a;Tribouillois et al., 2018a) as the CC biomass is incorporated into the soil enabling to increase SOC stocks. This practice can thus be considered as CDR effective but recent studies showed that they can also increase surface albedo. ...
... De plus, lorsque des analyses couplées sont réalisées sur des temps courts, comme c'est le cas dans ce chapitre, cela tend à surestimer certains effets et à en sous-évaluer voire omettre d'autres. Ainsi, l'effet stockage de C dans le sol est probablement limité dans le temps puisque les stocks de C du sol vont finir par atteindre un nouvel équilibre (Lugato et al., 2020a;Tribouillois et al., 2018a). Ainsi, l'effet de stockage est important les premières années, puis décroit les années suivante pour finir par disparaitre au bout de 45-50 ans (Tribouillois et al., 2018a). ...
... Ainsi, l'effet stockage de C dans le sol est probablement limité dans le temps puisque les stocks de C du sol vont finir par atteindre un nouvel équilibre (Lugato et al., 2020a;Tribouillois et al., 2018a). Ainsi, l'effet de stockage est important les premières années, puis décroit les années suivante pour finir par disparaitre au bout de 45-50 ans (Tribouillois et al., 2018a). Par ailleurs, certains phénomènes ne sont pas du tout pris en compte dans les études appliquées sur de courtes échelles temporelles. ...
Thesis
Les changements climatiques et la croissance démographique de la population mondiale amènent aujourd'hui le monde agricole à s'adapter pour faire face à ces deux enjeux majeurs. Si les surfaces agricoles, qui représentent près d'un tiers des terres émergées, contribuent largement aux émissions mondiales de gaz à effet de serre, elles offrent également la possibilité de mettre en place des leviers d'atténuation des changements climatiques. Dans ce contexte, ces travaux de thèse ont vocation à enrichir nos connaissances sur le fonctionnement des surfaces agricoles, à fournir des outils d'évaluation de la contribution des surfaces cultivées aux évolutions du climat, et à quantifier les effets biogéochimiques (stockage de C) et biogéophysiques (effet albédo) d'atténuation des changements climatiques via la mise en œuvre de cultures intermédiaires. Pour répondre à ces objectifs, deux approches de modélisation ont été développées au cours de ces travaux. Le premier volet de cette thèse s'est intéressé à développer une approche de modélisation spatialisée, permettant de fournir des estimations des productions (biomasses et rendements), des flux de CO2 et d'eau, ces variables servant à la quantification des bilans de carbone et d'eau pour les parcelles de grandes cultures. À cette fin, le modèle agro-météorologique SAFYE-CO2 assimilant des produits satellites d'indice de végétation à hautes résolutions spatiale et temporelle a été développé et appliqué à différentes cultures (blé, maïs et tournesol) et végétations d'intercultures (repousses spontanées, mauvaises herbes, cultures intermédiaires). Cette approche a pu être validée sur un réseau de parcelles du Sud-Ouest de la France, en tirant parti d'un grand nombre d'images satellites et de données de validation sur la zone de l'Observatoire Spatial Régional. Elle a notamment permis d'estimer avec précision les productions de blé, de tournesol et de maïs, ainsi que les flux de CO2 et d'eau sur les cultures de blé et de tournesol. La végétation, pouvant se développer sur les parcelles pendant les périodes d'interculture, a également été prise en compte afin d'améliorer l'estimation des flux de CO2 et d'eau. Cela a notamment permis de quantifier l'impact des cultures intermédiaires sur les composantes du bilan C des parcelles allouées aux grandes cultures sur la zone d'étude. Le second volet visait à développer un modèle d'introduction de cultures intermédiaires à l'échelle européenne, afin d'estimer le forçage radiatif induit par la modification de l'albédo de surface engendré par cette pratique. Grace à des produits albédo moyenne résolution (1/20°), développés par le CNRM (et en collaboration avec ce laboratoire), cette approche de modélisation a permis de fournir des estimations de l'effet albédo relatifs aux cultures intermédiaires. Plusieurs scenarii d'introduction ont été simulés pour rendre compte de l'impact de certains facteurs, tels que la neige ou la pluie. Ils ont permis d'alerter sur le potentiel impact négatif de l'assombrissement du sol, induit à long terme (via l'enrichissement des sols en matière organique) par les cultures intermédiaires sur le forçage radiatif des surfaces cultivées. Enfin, comme tout changement de pratique agricole induit des effets biogéochimiques et biogéophysiques sur le climat, une analyse de ces effets couplés a été menée grâce à l'utilisation combinée de ces deux approches de modélisation. Nous en concluons qu'une fois les cultures intermédiaires mises en place, le sol devrait être couvert en permanence pour que l'effet assombrissement du sol ne fasse pas perdre les autres bénéfices climatiques engendrés par cette pratique agricole.
... Benefits of growing cover crops, as a conservation management practice, has been documented in recent literatures (e.g. Kaye and Quemada, 2017;Basche et al., 2016a, 2016b, Daigh et al., 2014a, 2014bQi et al., 2011;Tribouillois et al., 2018;Blanco-Canqui et al., 2015;Dabney et al., 2007). In particularly, Basche et al. (2016b) demonstrated that soil water storage can be improved by the long-term use of a winter rye cover crop without sacrificing main crop growth. ...
... Daigh et al. (2014b) and Qi et al. (2011) found that cover crops can significantly reduce cumulative drainage. Studies also found that cover crops may help to mitigate the negative impact of climate change by decreasing CO 2 released from cropping systems (Tribouillois et al., 2018), and reduce diurnal temperature range of day and night soil temperature (Blanco-Canqui et al., 2015;Dabney et al., 2007). Given these identified effects over the historical period, there is a potential to incorporate cover crops into agricultural mitigation and adaption strategies under future climate conditions. ...
... The RZWQM model (Ma et al., 2000), which includes detailed crop growth, soil water, and soil nutrient modules (Ma et al., 2007), has been widely used to simulate hydrologic transport, effects of manage practices, and crop yields (Malone et al., 2004;Schwartz and Shuman, 2005). The second verision of RZWQM (RZWQM2) has been combined with DSSAT crop growth model (Jones et al., 2003), and was used to simulate crop yields, evapotranspiration (ET), drainage, and runoff in different cropping systems (Ma et al., 2017Tribouillois et al., 2018;Yang et al., 2019). In the previous studies, RZWQM2 was used to assess potential impacts of climate change and elevated CO2 on crop yields and water demands, especially under arid and semiarid lands and climate conditions (Anapalli et al., 2016;Chen et al., 2019;Islam et al., 2012). ...
Article
Climate change led to increased temperature and variable rainfall, which may pose great threats to both agricultural productions and environmental impacts. In this study, we aim to explore how changing climate and its extremes in the 20th and 21st-century influence system water use efficiency (sWUE) of a corn-soybean cropping rotation in a humid sub-tropic environment, and how much can cover crops mitigate these impacts. Different from the traditional yield-focused water use efficiency (WUE), sWUE addresses both production and environmental quality goals by considering grain yields and all major system water losses (evapotranspiration, runoff, and drainage). A calibrated crop simulation model, Root Zone Water Quality Model version 2 (RZWQM2), was applied to simulate grain yields and all major system water losses. The model was forced by daily climate data from in situ observations during 1956–2015 and 10 downscaled and bias corrected General Circulation Model (GCMs) projections under the representative concentration pathways (RCP) 4.5 and 8.5 scenarios during 2020–2079. The results showed that, under the historical baseline and the future RCP4.5 and RCP8.5 scenarios, due to the growth of cover crops, the sWUE for corn were improved by 1.7%, 2.6% and 2.3%, respectively (p-value < 0.001), and for soybean by 0.7% (p = 0.06), 1.0% (p-value < 0.001) and 0.9% (p-value < 0.001). Soil evaporation, as the largest source of water loss from the cropping system, was significantly decreased by 1.7%, 2.6% and 2.3% during the corn growing season, and by 0.7%, 1.0% and 0.9% during the soybean growing season. The annual drainage was decreased by 38 mm, 53 mm and 67 mm, under the baseline, RCP4.5 and RCP8.5, respectively. With the incorporation of wheat cover crops, the correlations of temperature or precipitation extremes with grain yields and major water losses were mostly decreased, suggesting that growing cover crop is an effective means to mitigate the impact of climate extremes on sWUE of a corn-soybean cropping.
... They also found that there was a 20 mm yr −1 decrease in actual evaporation simulated in April-June after the rye was terminated compared to no rye CC treatment. Under temperate climate with dry summers, incorporating CC reduced mean annual subsurface drainage by 20 mm yr −1 but increased mean annual ET by 20 mm yr −1 as simulated by STICS model over 45 yr (Tribouillois, Constantin, & Justes, 2018). Dietzel et al. (2016) used 28-yr historical precipitation data in APSIM-model to simulate the optimum growing season rainfall, runoff, and drainage for maintaining optimum system WUE for corn and soybean in the northwestern United States. ...
... Qi et al. (2011) noted a 29-mm (5%) reduction for annual subsurface drainage in the 40-yr CC system in Iowa. The result was 16 mm higher than the simulation study of Tribouillois et al. (2018) in temperate climate with dry summers in France, as most annual rainfall was in early October through early April. Based on previous long-term simulation studies (30-80 years), the increase of annual ET is responsible for reduction of deep drainage across sites (Qi et al., 2011;Tribouillois et al., 2018;Yang et al., 2019a). ...
... The result was 16 mm higher than the simulation study of Tribouillois et al. (2018) in temperate climate with dry summers in France, as most annual rainfall was in early October through early April. Based on previous long-term simulation studies (30-80 years), the increase of annual ET is responsible for reduction of deep drainage across sites (Qi et al., 2011;Tribouillois et al., 2018;Yang et al., 2019a). However the reduction in drainage with rye CC-cultivated agricultural production was variable, mainly due to difference in CC biomass and rainfall amount between years (Blanco-Canqui et al., 2015;Malone et al., 2014). ...
Article
Full-text available
The impact of cover crop (CC) on soil water balance and agricultural production is closely related to rainfall amount, duration, and distribution in rainfed cropping systems. This study used the RZWQM2 model calibrated and validated with 4‐yr field measurements to predict the impact of planting a winter wheat (Triticum aestivum L.) CC in a no‐till rainfed corn (Zea mays L.)‐soybean (Glycine max L.) rotation on soil water balance, crop yield, and grain water‐use efficiency (WUE) in northeast Mississippi, USA. Seasonal rainfall for 80 consecutive years (1938 to 2017) was classified as ‘wet’, ‘normal’, and ‘dry’ years using frequency analysis and the data sets matched chronologically to wheat, corn, and soybean growth periods were used as an input parameter in RZWQM2 simulations. During autumn and spring (early October to early April), the CC reduced deep drainage by 69 mm (11%), 53 mm (15%), and 51 mm (21%) mm and increased evapotranspiration by 79 mm (55%), 81 mm (57%), and 73 mm (56%) mm in wet, normal, and dry years, respectively. Averaged across 40 years, the CC decreased surface evaporation by 64 mm (32%) and 38 mm (24%) mm for corn and soybean growth periods, respectively. Wheat CC also improved soil water storage in early crop growth period during April‐June in any of the three rainfall patterns. Regardless of rainfall patterns, the increase in WUE can be attributed to a decrease in evapotranspiration during cash crop period without sacrificing cash crop yield in the CC system. Introducing CC into cropping systems is beneficial to reduce annual deep drainage and evaporation while maintaining higher crop yields under different rainfall patterns. This article is protected by copyright. All rights reserved
... When well-managed, they also reduce nitrate leaching and increase the green manure effect, which increases soil nitrogen content in cropping systems Tribouillois et al. 2015). Cover crops also increase the carbon content of soils (Poeplau and Don 2015;Tribouillois et al. 2018), which helps to mitigate effects of climate change, as highlighted in the international "4 per 1000" initiative (Demenois 2017). While government policies and climate change may therefore increase the use of cover crops, the IPCC reports that the future will have more droughts and greater variability in rainfall (IPCC 2013), which will increase water management challenges. ...
... Then, a wider use of cover crops could pose a problem at the watershed scale if groundwater is shallow. According to the IPCC (2013), which predicts more droughts, extreme events, and a greater variability in rainfall in certain temperate regions, this reduction could become a crucial issue, as Tribouillois et al. (2018) have shown. Consequently, for shallow groundwater that is recharged mainly by drainage under soils of arable cropping systems, the reduction in drainage caused by cover crops could decrease groundwater reserves, which provide water for cities and irrigation, sustain the base flow of rivers, and support aquatic biodiversity. ...
Article
Cover crops provide many ecosystem services, such as soil protection, nitrate pollution of water mitigation, and green manure effects. However, the impact of cover crops on soil water balance is poorly studied, despite its potential impact on groundwater recharge. Some studies reported a reduction of the water drainage due to an increase of the evapotranspiration by plant cover transpiration. However, there is no real consensus on the intensity of this phenomenon, which highlights the importance to quantify the impact of cover crops on drainage compared to that of bare soil. We performed a meta-analysis of published papers presenting studies on the impact of cover crops on drainage compared to that of bare soil under temperate climates. Of the 436 papers identified, 28 of them were included in the analysis based on criteria required for performing a relevant meta-analysis. The originality of our study lies in two following results: (1) the quantification of drainage reduction with cover crops by a mean effect size of 27 mm compared to that of bare soil and (2) within the large variability of soils, climates, and cropping systems, no main determining factor was found significant to explain the variability of water drainage reduction. The cover crops provide a service of nitrate pollution mitigation, but the drainage reduction could be considered as a disservice, because they can lead to a reduction in groundwater recharge due to a higher evapotranspiration in comparison to bare soil. This highlights the need of research for optimizing trade-offs between services and disservices of cover crops for water balance.
... Additionally, in such climates, cover crops compete with the primary crop for nutrients (Unger and Vigil, 1998) and consequently, have negative impacts on crop growth and productivity. Wortman et al. (2012) and Tribouillois et al. (2018) reported that the large quantity of soil water used by the cover crops, at the cost of the subsequent primary crop and immobilisation of soil N due to incorporation of low quality cover crop residues into the soil is also a major concern. These problems appear mostly in arid and semiarid environments (< 500 mm annual rainfall) where water storage in soils declines with the establishment of cover crops, and results in reduced crop yields (Cherr et al., 2006;Nielsen and Vigil, 2005 (CTS, 2011), and thereby could also increase GHG emissions (Smeaton et al., 2011). ...
... Non legume cover crops reduced soil NO 3 content which is vulnerable to N leaching during autumn and winter(Thorup-Kristensen et al., 2003), and made additional soil N available for the primary crop following mineralisation of their residues (Kaspar and Singer, 2011). In studying future scenarios over a period of 45years,Tribouillois et al. (2018) found that non-legume cover crops continuously decreased N leaching compared to that of bare soil, but legume cover crop scenarios did not. Moreover, some simulation studies have suggested that the efficiency of legume cover crops species to ...
Article
Full-text available
Cover crops play an increasingly important role in improving soil quality, reducing agricultural inputs and improving environmental sustainability. The main objectives of this critical global review and systematic analysis were to assess cover crop practices in the context of their impacts on nitrogen leaching, net greenhouse gas balances (NGHGB) and crop productivity. Only studies that investigated the impacts of cover crops and measured one or a combination of: nitrogen leaching, soil organic carbon (SOC), nitrous oxide (N2O), grain yield and nitrogen in grain of primary crop, and had a control treatment were included in the analysis. Long‐term studies were uncommon, with most data coming from studies lasting 2‐3 years. The literature search resulted in 106 studies carried out at 372 sites and covering different countries, climatic zones and management. Our analysis demonstrates that cover crops significantly (p<0.001) decreased N leaching and significantly (p<0.001) increased SOC sequestration without having significant (p>0.05) effects on direct N2O emissions. Cover crops could mitigate the NGHGB by 2.06 ±2.10 Mg CO2‐eq ha⁻¹ y⁻¹. One of the potential disadvantages of cover crops identified was the reduction in grain yield of the primary crop by ≈4%, compared to the control treatment. This drawback could be avoided by selecting mixed cover crops with a range of legumes and non‐legumes, which increased the yield by ≈13%. These advantages of cover crops justify their widespread adoption. However, management practices in relation to cover crops will need to be adapted to specific soil, management and regional climatic conditions. This article is protected by copyright. All rights reserved.
... As shown in Table 6, planting CC in the corn and soybean rotation system, relative to NCC scenario, reduced annual percolation by on average 6% (36 mm) as simulated by RZWQM2 during 1938-2017. Simulated value was 7 mm higher than that reported by Qi et al. (2011b) and 16 mm than that reported by Tribouillois et al. (2018). These differences in simulated percolation between the study and others were mainly related to CC aboveground growth and its effect on ET. ...
... In this study, the simulated and measured cover crop biomass lowered to previous studies ( Fig. 5; Qi et al., 2011b). There was a better positive linear regression between cover crop aboveground biomass and annual ET, and a negative linear regression between cover crop biomass and annual percolation in the cropping system ( Tribouillois et al., 2018). Therefore, the increase of annual ET was an attributor to the reduction of annual percolation while annual runoff was not changed based on soil water budget under CC system. ...
Article
Incorporating cover crops into row crop production systems can affect soil water dynamics and crop production. However, the effect of this practice has not been well investigated in the northeast Mississippi USA. We calibrated and validated the cropping system model (Root Zone Water Quality Model, RZWQM2) using 4-yr (2014–2017) field data in the humid Mississippi Blackland Prairie, and also used this model to simulate the long-term (1938–2017) effects of a winter wheat (Triticum aestivum L.) cover crop on hydrological variables, crop yield, and water use efficiency (WUE, grain yield per unit of evapotranspiration) in a rainfed and no-tilled corn (Zea mays L.) and soybean (Glycine max L.) cropping system. Compared to no cover crop scenarios, long-term simulation demonstrates that average annual percolation under the cover crop system was decreased by 36 mm. Average annual actual evapotranspiration were 36 mm higher under cover crop system than no cover crop system. Simulated annual runoff for cover crop scenario was not different from values simulated for no cover crop scenario. Predicted actual evaporation during cash crop growth periods under cover crop plots was 25% less than under no cover crop plots due to mulch cover when averaged over the whole modeling period. Compared with no cover crop scenarios, the estimated crop evapotranspiration under cover crop scenario was reduced by 6.6% (31 mm) during corn growth period and by 3.7% (19 mm) during soybean growth period. Yearly predicted crop yields for corn and soybean did not improve, respectively, in the cover crop-based cropping system. Compared to the plots with no cover crop, the simulation of WUE for corn and soybean were respectively improved by 6.4% (1.49 kg m ⁻³ versus 1.40 kg m ⁻³ ) and by 5.0% (0.63 kg m ⁻³ versus 0.60 kg m ⁻³ ) for the plots with cover crop, largely due to the decrease in surface evaporation without sacrificing crop growth. These results suggest that long-term use of wheat cover crop to summer crops rotation is a promising practice to decrease deep percolation and restrict surface evaporation, and also improved crops WUE in the corn and soybean rotation in subtropical agro-system.
... Representing the heterogeneity of production systems in a region or country is one of the main methodological challenges when attempting to estimate the balance between SOC storage and GHG emissions of agriculture (Lal, 2004a(Lal, , 2004b. The use of cropping system models along with databases that cover the heterogeneity of production systems forms the basis for addressing this challenge (e.g., Liu et al., 2011;Tribouillois et al., 2018). In addition, a model-based approach has the advantage of being able to simulate both climate change and cropping system scenarios (e.g., Tribouillois et al., 2018). ...
... The use of cropping system models along with databases that cover the heterogeneity of production systems forms the basis for addressing this challenge (e.g., Liu et al., 2011;Tribouillois et al., 2018). In addition, a model-based approach has the advantage of being able to simulate both climate change and cropping system scenarios (e.g., Tribouillois et al., 2018). Due to a dearth of data and modeling issues (Brilli et al., 2017;Rosenzweig et al., 2013), however, few studies have applied this approach to large spatial (km 2 resolution) and temporal scales (several decades) to estimate the past, current and/or potential balance between SOC storage and GHG emissions (see e.g., Liu et al., 2011). ...
Article
Many studies have assessed the potential of agricultural practices to sequester carbon (C). A comprehensive evaluation of impacts of agricultural practices requires not only considering C storage but also direct and indirect emissions of greenhouse gases (GHG) and their side effects (e.g., on the water cycle or agricultural production). We used a high-resolution modeling approach with the Simulateur mulTIdisciplinaire pour les Cultures Standard soil-crop model to quantify soil organic C (SOC) storage potential , GHG balance, biomass production and nitrogen-and water-related impacts for all arable land in France for current cropping systems (baseline scenario) and three mitigation scenarios: (i) spatial and temporal expansion of cover crops, (ii) spatial insertion and temporal extension of temporary grasslands (two sub-scenarios) and (iii) improved recycling of organic resources as fertilizer. In the baseline scenario, SOC decreased slightly over 30 years in crop-only rotations but increased significantly in crop/temporary grassland rotations. Results highlighted a strong trade-off between the storage rate per unit area (kg C ha −1 year −1) of mitigation scenarios and the areas to which they could be applied. As a result, while the most promising scenario at the field scale was the insertion of temporary grassland (+466 kg C ha −1 year −1 stored to a depth of 0.3 m compared to the baseline, on 0.68 Mha), at the national scale, it was by far the expansion of cover crops (+131 kg C ha −1 year −1 , on 17.62 Mha). Side effects on crop production, water irrigation and nitrogen emissions varied greatly depending on the scenario and production situation. At the national scale, combining the three mitigation scenarios could mitigate GHG emissions of current cropping systems by 54% (−11.2 from the current 20.5 Mt CO 2 e year −1), but the remaining emissions would still lie far from the objective of C-neutral agriculture. K E Y W O R D S cover crops, cropping system, large scale, organic fertilization, STICS model, temporary grasslands 2 | LAUNAY et AL.
... Representing the heterogeneity of production systems in a region or country is one of the main methodological challenges when attempting to estimate the balance between SOC storage and GHG emissions of agriculture (Lal, 2004a(Lal, , 2004b. The use of cropping system models along with databases that cover the heterogeneity of production systems forms the basis for addressing this challenge (e.g., Liu et al., 2011;Tribouillois et al., 2018). In addition, a model-based approach has the advantage of being able to simulate both climate change and cropping system scenarios (e.g., Tribouillois et al., 2018). ...
... The use of cropping system models along with databases that cover the heterogeneity of production systems forms the basis for addressing this challenge (e.g., Liu et al., 2011;Tribouillois et al., 2018). In addition, a model-based approach has the advantage of being able to simulate both climate change and cropping system scenarios (e.g., Tribouillois et al., 2018). Due to a dearth of data and modeling issues (Brilli et al., 2017;Rosenzweig et al., 2013), however, few studies have applied this approach to large spatial (km 2 resolution) and temporal scales (several decades) to estimate the past, current and/or potential balance between SOC storage and GHG emissions (see e.g., Liu et al., 2011). ...
Article
Many studies have assessed the potential of agricultural practices to sequester carbon (C). A comprehensive evaluation of impacts of agricultural practices requires not only considering C storage but also direct and indirect emissions of greenhouse gases (GHG) and their side effects (e.g. on the water cycle or agricultural production). We used a high‐resolution modeling approach with the STICS soil‐crop model to quantify soil organic C (SOC) storage potential, GHG balance, biomass production and nitrogen‐ and water‐related impacts for all arable land in France for current cropping systems (baseline scenario) and three mitigation scenarios: (i) spatial and temporal expansion of cover crops, (ii) spatial insertion and temporal extension of temporary grasslands (two sub‐scenarios) and (iii) improved recycling of organic resources as fertilizer. In the baseline scenario, SOC decreased slightly over 30 years in crop‐only rotations but increased significantly in crop/temporary grassland rotations. Results highlighted a strong trade‐off between the storage rate per unit area (kg C ha‐1 yr‐1) of mitigation scenarios and the areas to which they could be applied. As a result, while the most promising scenario at the field scale was the insertion of temporary grassland (+466 kg C ha‐1 yr‐1 stored to a depth of 0.3 m compared to the baseline, on 0.68 Mha), at the national scale, it was by far the expansion of cover crops (+131 kg C ha‐1 yr‐1, on 17.62 Mha). Side effects on crop production, water irrigation and nitrogen emissions varied greatly depending on the scenario and production situation. At the national scale, combining the three mitigation scenarios could mitigate GHG emissions of current cropping systems by 54% (‐11.2 from the current 20.5 Mt CO2e yr‐1), but the remaining emissions would still lie far from the objective of C‐neutral agriculture.
... Their residues are retained as a mulch or incorporated into the soil by plowing or shallow tillage, such as disking. Cover crops provide a wide range of ecosystem services, including reducing nitrate leaching (Tonitto et al., 2006); providing a "green manure" effect (Tosti et al., 2014;Tribouillois et al., 2015); improving physical properties of soil that reduce erosion or compaction (Chen and Weil, 2010;Ryder and Fares, 2008); decreasing greenhouse gas emissions; increasing carbon (C) storage in the soil (Poeplau and Don, 2015;Tribouillois et al., 2018a); and controlling pests, diseases, and weeds (Couëdel et al., 2018a;Haramoto and Gallandt, 2005;Schipanski et al., 2014). Using cover crops could also help mitigate and adapt to climate change (Kaye and Quemada, 2017). ...
... STICS was evaluated as accurate for a wide range of agroenvironmental contexts in France for plant, water, and N outputs for bare soil and many types of cash crops (Brisson et al., 2003(Brisson et al., , 2009. STICS was also used to simulate cover crops and analyze water, C and N balances and the associated ecosystem services (Tribouillois et al., 2018a). STICS was also successfully evaluated for water drainage (Beaudoin et al., 2008;Constantin et al., 2012). ...
Article
Cover crops are a potential component of agroecological cropping systems, since they may render crop rotations more sustainable. They simultaneously provide multiple ecosystem services, such as decreasing nitrate leaching, decreasing erosion, and increasing soil organic matter. However, cover crops increase evapotranspiration and reduce drainage, which results in a potential disservice for groundwater recharge. Little attention has focused on management of cover crop residues after destruction or their influence on water flux dynamics, particularly in dry and temperate climates. The objective of our study was to analyze and quantify the impact of cover crop management on soil water content and water flux dynamics to understand the main mechanisms of system functioning. We combined a two-year field experiment with crop-model simulations. We performed the field experiment in southwestern France that compared three cover crop treatments, with bare soil as the control. The treatments included (1) living cover crops lasting ca. 9 months from August-April, (2) crushing cover crops in November and leaving them as mulch on the soil, and (3) plowing up cover crops in November to promote residue decomposition and the green manure effect. The STICS soil-crop model was used to predict water fluxes that were not measured and to perform a 20-year independent simulation study based on recent climate series for the experimental site. Our main results indicated that cover crops (1) always reduce water drainage by 20-60 mm compared to that under bare soil; and (2) could significantly reduce soil water content (0-120 cm deep) for the next cash crop by a mean of 20-50 mm, and up to 80 mm in dry spring conditions, but early destruction could decrease this negative impact. The simulations clearly showed that the interaction between climate variability, i.e., rainfall distribution during the fallow period, and cover crop management should be considered to explain the impact of inter-annual variability on the water balance. Thus, destroying cover crops mechanically in late autumn and retaining the residues as mulch could be a good compromise between the multiple services the cover crop provides during the fallow period and avoiding the negative impact on soil water availability for the next cash crop.
... The practices promoting the mineralization of soil organic matter can contribute to the release of carbon dioxide (CO 2 ) into the atmosphere, while the practices promoting soil carbon sequestration have the inverse effect. Once again, cover cropping is more favorable, while soil management systems promoting the degradation of the organic substrates, such as tillage, and those restricting the entry of organic substrate into the soil, such as bare free-weed soil by herbicides, accentuate the level of CO 2 emissions (Montanaro et al., 2012;Tribouillois et al., 2017). ...
... The increase of the organic pool may accelerate the turnover of organic matter with a positive balance on the emission of N oxides. However, cover cropping is not expected to increase nitrous oxide (N 2 O) emission, since they can uptake N (NH 4 + and NO 3 À ) reducing nitrification and denitrification, soil processes that increase N 2 O emissions (Guardia et al., 2016;Tribouillois et al., 2017). Cover cropping with grasses can be more effective than with legumes due to their higher ability to absorb water and reduce inorganic N in the soil (Kallenbach et al., 2010). ...
... Some authors have suggested that conservation agriculture and diversified crop rotation can help preserve food security, restore soil health and thereby minimize the potential effects of global warming (Parihar et al., 2018;Necpalova et al., 2018;Angulo et al., 2013;Burney et al., 2010;Chadwick et al., 2011). These benefits rely on the increased global potential for CO2 sequestration of soils containing large amounts of organic C. Carbon sequestration appears to be an efficient strategy to boost agricultural production, and to purify surface and underground waters (Lal, 2004;Autret et al., 2016;de Gryze et al., 2011;Tribouillois et al., 2018). ...
Article
Crops, livestock and seafood are major contributors to global economy. Agriculture and fisheries are especially dependent on climate. Thus, elevated temperatures and carbon dioxide levels can have large impacts on appropriate nutrient levels, soil moisture, water availability and various other critical performance conditions. Changes in drought and flood frequency and severity can pose severe challenges to farmers and threaten food safety. In addition, increasingly warmer water temperatures are likely to shift the habitat ranges of many fish and shellfish species, ultimately disrupting ecosystems. In general, climate change will probably have negative implications for farming, animal husbandry and fishing. The effects of climate change must be taken into account as a key aspect along with other evolving factors with a potential impact on agricultural production, such as changes in agricultural practices and technology; all of them with a serious impact on food availability and price. This review is intended to provide critical and timely information on climate change and its implications in the food production/consumption system, paying special attention to the available mitigation strategies.
... For instance, Bayer et al. (2016) compared different CC species (including legume-cereal mixtures), but the comparison against bare soil (as well as several GHG components) was not included. Tribouillois et al. (2018) simulated the effect of CCs on direct GHG emissions, SOC balance and NO 3 À leaching in France, although emissions from inputs and operations or the effect of albedo were not considered. The life cycle assessment of Prechsl et al. (2017), which compiled data from a rotation including CCs in Switzerland, included field emissions (estimated using default emission factors, EFs), inputs and operations in their GWP component. ...
Article
In this study, field-specific data was collected from a 10-year experiment in central Spain in which vetch (Vicia sp. L.) and barley (Hordeum vulgare L.) were established as cover crops and compared to the traditional fall-winter fallow between two irrigated cash crops, maize (Zea mays L.) and sunflower (Helianthus annuus L.). The global warming potential (GWP) balance included direct and indirect (nitrous oxide (N2O) resulting from the deposition of ammonia (NH3) or from leached nitrate (NO3⁻)) soil greenhouse gas (GHG) emissions, changes in soil organic carbon (SOC) and albedo, and carbon dioxide equivalent (CO2eq) emissions from inputs, irrigation and farm operations. Several scenarios involving i) changes in the termination method of the cover crops, ii) consideration of the application of a distinct nitrogen (N) source (urea, slurry or manure instead of ammonium nitrate) or nitrification inhibitors, iii) employing the same N rate for all treatments (i.e., conventional instead of integrated fertilization), iv) modelling SOC accumulation over a 100-year horizon, and v) using default emission factors, were also analysed. Under the conditions of our experiment, cover crops mitigated yield-scaled emissions by 77.4% (barley) and 91.9% (vetch). Synthetic N fertilization (particularly the industrial production of fertilizer) contributed 38% to the balance of the cover cropping treatments, followed by SOC (22.5%), irrigation (14.7%) and albedo (14.5%). All scenarios led to notable mitigation efficacies, ranging from 39% mitigation (in barley when considering default or non-specific emission factors) to a net CO2eq sink (i.e., >100% mitigation) in the scenario consisting of the replacement of ammonium nitrate by urea or organic fertilizers although with side effects on NH3 volatilization and/or yields. Based on these results, the combined use of cover cropping and integrated soil fertility management could lead to the design of C-neutral irrigated cropping systems in semi-arid regions.
... This second effect was more evident in scenarios that maintain legumes for a longer time due to higher N availability. These results are consistent with recent simulation studies by Tribouillois, Constantin, and Justes (2018) when applying the STICS soil-crop model to 12 cropping systems in five locations in France, and with Lugato, Bampa, Panagos, Montanarella, and Jones (2014) when conducting large-scale simulations with CENTURY in Europe. Similar results were reported from field experiments conducted under various environmental conditions (García-González, Hontoria, Gabriel, Alonso-Ayuso, & Quemada, 2018;Mazzoncini, Sapkota, Bàrberi, Antichi, & Risaliti, 2011;Quemada, Cabrera, & McCracken, 1997;Thomsen & Christensen, 2004) and summarized in two meta-analysis (Abdalla et al., 2019;Aguilera et al., 2013;Poeplau & Don, 2015). ...
Article
Cover crops (CC) promote the accumulation of soil organic carbon (SOC), which provides multiple benefits to agro‐ecosystems. However, additional nitrogen (N) inputs into the soil could offset the CO2 mitigation potential due to increasing N2O emissions. Integrated management approaches use organic and synthetic fertilizers to maximize yields while minimizing impacts by crop sequencing adapted to local conditions. The goal of this work was to test whether integrated management, centered on CC adoption, has the potential to maximize SOC stocks without increasing the soil greenhouse gas (GHG) net flux and other agro‐environmental impacts such as nitrate leaching. To this purpose, we ran the DayCent bio‐geochemistry model on 8,554 soil sampling locations across the European Union. We found that soil N2O emissions could be limited with simple crop sequencing rules, such as switching from leguminous to grass CC when the GHG flux was positive (source). Additional reductions of synthetic fertilizers applications are possible through better accounting for N available in green manures and from mineralization of soil reservoirs, while maintaining cash crop yields. Therefore, our results suggest that a CC integrated management approach can maximize the agro‐environmental performance of cropping systems while reducing environmental trade‐offs.
... A critical global review reported cover crops significantly decreased N leaching and increased soil organic carbon sequestration and could mitigate net greenhouse gas balances [26]. Studies using agricultural system models suggest that winter cover crops under projected climate change reduce soil erosion, increase soil carbon, and reduce CO 2 emission from soil [27,28]. Malone et al. [29] reported that the effectiveness of winter rye cover crop to reduce drainage N loads increased with higher spring and fall temperatures, which suggests winter rye cover crop may be more effective under projected climate change than baseline climate. ...
Article
Full-text available
To help reduce future N loads entering the Gulf of Mexico from the Mississippi River 45%, Iowa set the goal of reducing non-point source N loads 41%. Studies show that implementing winter rye cover crops into agricultural systems reduces N loads from subsurface drainage, but its effectiveness in the Mississippi River Basin under expected climate change is uncertain. We used the field-tested Root Zone Water Quality Model (RZWQM) to estimate drainage N loads, crop yield, and rye growth in central Iowa corn-soybean rotations. RZWQM scenarios included baseline (BL) observed weather (1991–2011) and ambient CO2 with cover crop and no cover crop treatments (BL_CC and BL_NCC). Scenarios also included projected future temperature and precipitation change (2065–2085) from six general circulation models (GCMs) and elevated CO2 with cover crop and no cover crop treatments (CC and NCC). Average annual drainage N loads under NCC, BL_NCC, CC and BL_CC were 63.6, 47.5, 17.0, and 18.9 kg N ha−1. Winter rye cover crop was more effective at reducing drainage N losses under climate change than under baseline conditions (73 and 60% for future and baseline climate), mostly because the projected temperatures and atmospheric CO2 resulted in greater rye growth and crop N uptake. Annual CC drainage N loads were reduced compared with BL_NCC more than the targeted 41% for 18 to 20 years of the 21-year simulation, depending on the GCM. Under projected climate change, average annual simulated crop yield differences between scenarios with and without winter rye were approximately 0.1 Mg ha−1. These results suggest that implementing winter rye cover crop in a corn-soybean rotation effectively addresses the goal of drainage N load reduction under climate change in a northern Mississippi River Basin agricultural system without affecting cash crop production.
... Also, Kunrath et al. (2015) observed that soil dried out more rapidly under pastures than crops. In southwestern France, Tribouillois et al. (2018) showed that, compared to bare soil, cover crops, including some in the form of ley pastures (e.g., Italian ryegrass/ Lolium multiflorum, vetch/Vicia sativa), increased evapotranspiration by a mean of 20 mm/year and accordingly decreased water drainage by 21 mm/year. Conversely, cover crops induced a decrease in soil evaporation proportional to their biomass, due to greater soil coverage. ...
Article
Full-text available
Diversification of cropping systems has been proposed as a major mechanism to move towards sustainable cropping systems. To date, a diversification option that has received little attention is introduction of ley pastures into cropping systems, but the use of ley pastures is challenged by most future-oriented scenarios aiming to feed the world sustainably. In these scenarios, ruminant livestock feed only on permanent pastures, while cropping systems focus completely on production of crop-based human food. Diversification of cropping systems with ley pastures is thus compromised by knowledge gaps and future-oriented policy options. Here, we review ecosystem services provided by introducing ley pastures into cropping systems to increase sustainability of agriculture, discuss types of ley pastures and their management liable to promote these services, and raise future challenges related to introducing ley pastures into cropping systems. We conclude that (1) ley pastures provide a large set of input (soil conservation, nutrient provision and recycling, soil water retention, biological control of pests) and output (water purification, climate regulation, habitat provision for biodiversity conservation, forage production) ecosystem services of primary importance to cropping systems and society, respectively, as long as their spatial and temporal insertion within cropping systems is well-managed; otherwise, disservices may be produced. (2) To benefit from ecosystem services provided by ley pastures in cropping systems while limiting their disservices, it appears necessary to define a safe operating space for ley pastures in cropping systems. Moving towards this space requires changing plant breeding programs towards multiservice ley pastures, producing knowledge about emerging ways of introducing ley pastures into cropping systems (e.g., living mulch, green manure) and better quantifying the bundles of ecosystem services provided by ley pastures in cropping systems.
... In addition, our results show that, in soils with low SOC content, post-harvest vegetative events (e.g. cover crops) increase soil organic carbon storage which is consistent with other studies (Kaye and Quemada, 2017;Pellerin et al., 2019;Poeplau and Don, 2015;Tribouillois et al., 2018). ...
Article
Croplands contribute to greenhouse gas emissions but also have the potential to mitigate climate change through soil carbon storage. However, there is a lack of tools based on objective observations for assessing cropland C budgets at the plot scale over large areas. Such tools would allow us to more precisely establish the contribution of an agricultural plot to net CO2 emissions according to the plot management and identify levers for improving the C budget. In this study, we present a diagnostic regional modelling approach, called SAFY-CO2, that assimilates high spatial and temporal resolution (HSTR) optical remote sensing data in a simple crop model and evaluate the performance of this approach in quantifying crop production and the main components of the annual carbon budget for winter wheat. The SAFY-CO2 model simulates daily crop development (biomass, partition to leaves, etc.), the components of net ecosystem CO2 fluxes, and the annual yield and net ecosystem carbon budget (NECB). Multi-temporal green area index (GAI) maps derived from HSTR data from the Formosat-2 and SPOT satellites were used to calibrate the light-use efficiency and phenological parameters of the model. Data from the literature were used to set a priori values for a set of model parameters, and a large dataset of in situ data was used for model validation. This dataset includes 8 years of eddy-covariance net CO2 flux measurements and GAI, biomass and yield data acquired at 2 instrumented sites in southwest France. Biomass and yield data from 16 fields in the study area between 2005 and 2014 were also used for validation. The SAFY-CO2 model is able to reproduce both GAI dynamics (RRMSE = 14%, R² = 0.97) and biomass production and yield (RRMSE of 27% and 21%, respectively) with high precisions under contrasting climatic, environmental and management conditions. Additionally, the net CO2 flux components estimated by the model generally agreed well with in situ data and presented very good and significant correlations (RMSE of 1.74, 1.13 and 1.29 gC.m⁻².d⁻¹ for GPP, Reco and NEE, respectively; R² of 0.90, 0.75 and 0.85 for GPP, Reco and NEE, respectively) over the 8 studied years. This study also highlights the importance of accounting for post-harvest vegetative events (spontaneous re-growth, weed development and cover crops) for an accurate calculation of the annual net CO2 flux. This approach requires a limited number of input parameters for estimating yield and net CO2 flux components, which is promising for regional/global-scale applications based on Sentinel 2-like data; however, the approach requires plot-scale data concerning organic amendments and straw management (exportation) in animal farming systems to calculate field C budgets.
... Other studies have shown that cover crops can increase water storage capacity in fields by enhancing soil aggregation and matrix flow through the water column (Basche & DeLonge, 2017;Six et al., 2004). Furthermore, in spring, vegetation is actively growing, removing water from fields via transpiration (Basche et al., 2016;Tribouillois, Constantin, & Justes, 2018). ...
Article
Subsurface tile drainage speeds water removal from agricultural fields that are historically prone to flooding. While managed drainage systems improve crop yields, they can also contribute to the eutrophication of downstream ecosystems, as tile‐drained systems are conduits for nutrients to adjacent waterways. The changing climate of the Midwestern US has already altered precipitation regimes which will likely continue into the future, with unknown effects on tile drain water and nutrient loss to waterways. Adding vegetative cover (i.e., as winter cover crops) is one approach that can retain water and nutrients on fields to minimize export via tile drains. In the current study, we evaluate the effect of cover crops on tile drain discharge and soluble reactive phosphorus (SRP) load using bi‐monthly measurements from 43 unique tile outlets draining fields with or without cover crops in two watersheds in northern Indiana. Using four water years of data (n=844 measurements), we examined the role of short‐term antecedent precipitation conditions and variation in soil biogeochemistry in mediating the effect of cover crops on tile drain flow and SRP loads. We observed significant effects of cover crops on both tile drain discharge and SRP loads, but these results were season and watershed specific. Cover crop effects were identified only in spring, where their presence reduced tile drain discharge in both watersheds and SRP loads in one watershed. Varying effects on SRP loads between watersheds were attributed to different soil biogeochemical characteristics, where soils with lower bioavailable P and higher P sorption capacity were less likely to have a cover crop effect. Antecedent precipitation was important in spring, and cover crop differences were still evident during periods of wet and dry antecedent precipitation conditions. Overall, we show that cover crops have the potential to significantly decrease spring tile drain P export, and these effects are resilient to a wide range of precipitation conditions. This article is protected by copyright. All rights reserved.
... Cover crops are commonly grown during the fallow period between two main cash crops to provide ecosystem services, such as i) water quality regulation by reducing nitrate leaching (Abdalla et al., 2019;Ascott et al., 2017;Justes et al., 2012), ii) nitrogen supply through the "green manure" effect (Thorup-Kristensen et al., 2003;Tonitto et al., 2006), iii) climate change regulation by storing soil carbon (Launay et al., 2021;Poeplau and Don, 2015) and reducing greenhouse gas emissions (Kaye and Quemada, 2017;Plaza-Bonilla et al., 2017;Tribouillois et al., 2018a), v) erosion regulation due to continuous protection of soil in winter (Dabney et al., 2001;Langdale et al., 1991;Ryder and Fares, 2008), and vi) pest, disease, and weed regulation and biodiversity maintenance (Schipanski et al., 2014). However, Meyer et al. (2019) highlighted that the influence of these multiple services of cover crops on water-balance components remains little studied. ...
Article
Full-text available
Cover crops have multiple benefits, such as improving water quality, providing a green manure effect, and storing carbon in the soil. They can, however, reduce drainage significantly during key periods of hydrosystem recharge, especially in winter. The objective of this study was to evaluate the influence of cover crops and/or crop diversification at the watershed scale on water in the downstream watershed of the Aveyron River, based on three scenarios with different management practices. It is an illustrative case study of situations of water imbalance involving 1150 farms, with agricultural fields covering 40,000 ha, of which ca. 40% may be irrigated. The MAELIA model was used to simulate 10 years (2007–2016) of dynamics to estimate the influence of cover crops on water flows. Simulations showed that short-duration cover crops terminated in autumn generally had little influence on water: they decreased drainage slightly in autumn, but the recharge in winter compensated for this decrease and thus did not influence the water dynamics or yields of the succeeding cash crops. Although long-duration cover crops grow for a longer period and are sown more frequently in fields, they also had relatively little influence on water in the region, except for decreasing drainage. A scenario with long-duration cover crops and diversification of rotations was a good compromise for quantitative water management. Diversifying rotations, notably by replacing maize with crops that required less water, compensated for potential negative effects of long-duration cover crops. Although this scenario increased variability depending on the weather year and reduced autumn drainage, it influenced irrigation withdrawals and river flows little over the 10-year period. However, greater variability occurred at the field scale, where cover crops can have more influence. Thus, it is important to adapt the management practices for cover crops in rotations to decrease negative effects, particularly on water availability, which could increase withdrawals in an area that already has a water deficit, and not to decrease yields and thus farmers' profits. Our results are valid for the study area, but these scenarios should be extrapolated to other soil and climate conditions and other rotations and management systems.
... ).Changes in crop use(Tribouillois et al. 2018), especially in forest cover, affect the balance between sink and release of CO2 and the emissions of biogenic volatile organic compounds (BVOCs) in the atmosphere (Doblas-Miranda et al. 2017)(Sections 2.4.1.2 and 3.1.2.1). ...
Chapter
Full-text available
This Chapter 2, “Drivers”, focuses on the physical, bio-chemical and human drivers of climate and environmental changes, distinguishing between climate, pollution, land/sea use and management, and invasive species.
... According to Kaye and Quemada [22], the benefits of cover crops in mitigating and adaptation to the impact of climate change is derived from reduced soil erosion by wind and water, and N fixation and reduction of its leaching. Tribouillois et al. [23] found that cover crops were the vital agents in carbon sequestration through incorporation of residues to the soils as well as improving water retention. ...
Article
Full-text available
This study assessed the adaptation measures to climate change applied by the out-growers to the sustainable production of sugarcane (Saccharum officinarum L.) in Tanzania. Out-growers at Kilombero Sugar Company Ltd, one of the five sugarcane companies in Tanzania were the study population due to high volume of sugarcane production. The data was collected using interviews of key informants and survey questionnaires in the sugarcane community (out-growers). A sample used in this study was 63% of the study population plus 30 key informants. Results indicated that climate adaptation measures of out-growers included land intensification (15.4% and 19.4%), use of field borders (49.3% and 53.3%), enhanced nutrient management (11.8% and 15.8%), crop rotation (7.6% and 11.6%), cover crops (5.6% and 9.6%), use of nitrogen (N) fertilizers at 50 and 100 kg N ha-1 (5.4% and 9.4%) in cane fields, reduced tillage (1.4% and 5.4%), irrigation (1.4% and 5.4%), and use of pesticides (2.1% and 6.1%). The test for association showed that Likelihood Chi-square was not significant (p = 0.676) hence the practices were independent of the site and the out-growers. Results also indicated that the climate non-adaptation practices were deforestation during land preparation (32.3%), industrial emissions during cane processing (12.9%), and overgrazing and farming near catchment areas (9.7%) in closer proximity to the sugarcane industry. The test for association showed that Likelihood Chi-square was significant (p = 0.002) hence each practice is site-specific and it does not have any association with the same practice performed in either of the site. Furthermore, of the identified additional practices that favour adaptation to climate change, the test showed that Likelihood Chi-square was significant (p = 0.051) indicating that if any practice is conducted at one site, then the same practice and its magnitude is equally to be applied to the other site as a climate adaptation measure for the sustainable sugarcane production by the out-growers.
... Behnke and Villamil (2019) reported that CC introductions to the soil increased GHG emissions, which affected the initial C sequestration. In contrast, CCs mulching effectively reduced the GHG emissions (Tribouillois et al., 2018). CCs may accelerate soil CO 2 efflux compared to conventional farming by increasing SOC and microbiological properties at the 0 to 2.5 cm soil surface (Peregrina, 2016). ...
Article
Full-text available
Sustainable reduction of fertilization with technology acquisition for improving soil quality and realizing green food production is a major strategic demand for global agricultural production. Introducing legume (LCCs) and/or non-legume cover crops (NLCCs) during the fallow period before planting main crops such as wheat and corn increases surface coverage, retains soil moisture content, and absorbs excess mineral nutrients, thus reducing pollution. In addition, the cover crops (CCs) supplement the soil nutrients upon decomposition and have a green manure effect. Compared to the traditional bare land, the introduction of CCs systems has multiple ecological benefits, such as improving soil structure, promoting nutrient cycling, improving soil fertility and microbial activity, controlling soil erosion, and inhibiting weed growth, pests, and diseases. The residual decomposition process of cultivated crops after being pressed into the soil will directly change the soil carbon (C) and nitrogen (N) cycle and greenhouse gas emissions (GHGs), and thus affect the soil microbial activities. This key ecological process determines the realization of various ecological and environmental benefits of the cultivated system. Understanding the mechanism of these ecological environmental benefits provides a scientific basis for the restoration and promotion of cultivated crops in dry farming areas of the world. These findings provide an important contribution for understanding the mutual interrelationships and the research in this area, as well as increasing the use of CCs in the soil for better soil fertility, GHGs mitigation, and improving soil microbial community structure. This literature review studies the effects of crop biomass and quality on soil GHGs emissions, microbial biomass, and community structure of the crop cultivation system, aiming to clarify crop cultivation in theory.
... Additionally, they found that the radiative cooling effects would be reinforced by a decrease/increase in the sensible/latent heat fluxes at the surface. In another study, Tribouillois et al (2018), showed that, compared to bare soil, cover crops increased evapotranspiration (i.e. latent heat fluxes) without limiting the water resources for the next crop, if the cover crop were buried one month before seeding. ...
Article
Full-text available
Land cover management in agricultural areas is a powerful tool that could play a role in the mitigation of climate change and the counterbalance of global warming. First, we attempted to quantify the radiative forcing that would increase the surface albedo of croplands in Europe following the inclusion of cover crops during the fallow period. This is possible since the albedo of bare soil in many areas of Europe is lower than the albedo of vegetation. By using satellite data, we demonstrated that the introduction of cover crops into the crop rotation during the fallow period would increase the albedo over 4.17% of Europe's surface. According to our study, the effect resulting from this increase in the albedo of the croplands would be equivalent to a mitigation of 3.16 MtCO2-eq.year⁻¹ over a 100 year time horizon. This is equivalent to a mitigation potential per surface unit (m²) of introduced cover crop over Europe of 15.91 gCO2-eq.year⁻¹.m⁻². This value, obtained at the European scale, is consistent with previous estimates. We show that this mitigation potential could be increased by 27% if the cover crop is maintained for a longer period than 3 months and reduced by 28% in the case of no irrigation. In the second part of this work, based on recent studies estimating the impact of cover crops on soil carbon sequestration and the use of fertilizer, we added the albedo effect to those estimates, and we argued that, by considering areas favourable to their introduction, cover crops in Europe could mitigate human-induced agricultural greenhouse gas emissions by up to 7% per year, using 2011 as a reference. The impact of the albedo change per year would be between 10% and 13% of this total impact. The countries showing the greatest mitigation potentials are France, Bulgaria, Romania, and Germany.
Article
Agricultural crop diversity has the potential to alter soil microbial communities and greenhouse gas (GHG) emissions. To test this hypothesis, we conducted a field study on silty clay loam soil in south-east South Dakota under two crop rotations; 2-yr, maize (Zea mays L.)-soybean (Glycine max L.) and 4-yr, maize-soybean-oat (Avena sativa)-winter wheat (Triticum aestivum) managed with a winter cover crop and fallow management under no-till system. Phospholipid fatty acid (PLFAs) profiles were used to assess relative abundance of broad taxonomic groups of soil microorganisms in four active growing seasons. The static chamber technique was used to weekly monitor CO2, CH4, N2O fluxes during the growing seasons of maize and soybean phases in 2017 and 2018, respectively. Total PLFAs and relative abundance of total bacterial and fungal biomass were not affected by the treatments within the sampling event. However, averaged over the study period, the total PLFAs and abundance of total bacterial biomass as well as their sub-groups (Gm⁺, Gm–, and actinomycetes) were statistically greater with the 4-yr rotation as compared to the 2-yr rotation, whereas, there was no difference between cover crop and fallow plots. Regardless of cover cropping management, the 2-yr rotation had greater CO2 emissions than the 4-yr during the 2017 growing season. However, the 4-yr rotation increased the GHG fluxes during spring thaw of 2018, whereas, its effect was convoluted with cover cropping system (i.e. interaction effect) for summer and fall sampling dates. Cumulative CO2 tended to be greater under cover crop than the fallow when averaged over rotations during 2017 (p = 0.106), however, significant interaction effect during 2018 suggested that cover crops had lower CO2 emissions than the fallow under 2-yr rotation (p = 0.009). This study suggests that cropping system diversification achieved by extending length of rotations through small grains and by growing winter cover crops such as winter rye under no-till system has the potential to alter microbial community composition and mitigate GHG emissions.
Article
Mediterranean agriculture is markedly threatened by climate change and extreme events (drought and flooding). For the first time, the EPIC model was used in a long-term organic vegetable field experiment to evaluate the performance of agro-ecological practices, as adaptation and mitigation measures to cope with climate change in Southern Italy. These practices were a soil hydraulic arrangement (consisting of ridges and flat strips) combined with crop rotation (winter and summer cash crops), organic fertilization (poultry manure vs. no fertilization), and cover crops (pure or in mixture vs. no cover) managed as living mulch, green manure, or flattened by roller crimper. Seven treatments were selected for the simulation procedure. EPIC was calibrated and validated using measured crop yield and soil organic carbon stock values. The statistical metrics of EPIC showed r to be between 0.96 and 0.97, the Nash–Sutcliffe model efficiency between 0.54 and 0.94, and the relative root mean square error between 2 and 18%. Then, the model was run under baseline current climate (1985–2014) and near-future climate change (2015–2044) scenarios. Climate change increased both microbial respiration and nitrate leaching compared to the baseline, while soil organic carbon stock change and nitrous oxide emissions were mainly influenced by agro-ecological practices. Cover crop management could be an effective solution to limit negative climate effects, since it allowed improving summer cash crop yield (32%) and soil organic carbon stock change (2%), and reducing nitrogen losses (–34%), as compared to the no-cover-crop system. Finally, under climate change, green manure increased microbial respiration (5%) and reduced nitrogen losses (− 19%), compared to roller crimper flattening. Our findings indicated that the tested agro-ecological practices contribute to re-designing new climate change-resilient vegetable systems, by involving the stakeholders in promoting a co-innovation and co-research knowledge platform and fine-tuning agro-ecological practices in a wider range of environments.
Article
Full-text available
Growing mixtures of species instead of sole crops is expected to increase the ecosystem services provided by cover crops. This study aimed at understanding the interactions between species and investigating how they affect the performance of the mixture. Four species were combined in six bispecific mixtures in a field experiment. The performance of each species when grown in a mixture was compared to its performance as a sole crop at different sowing densities, to characterise the influence of intra- and interspecific competition for each species. Intra- and interspecific competition coefficients were quantified using a response surface design and the hyperbolic yield-density equation. Interactions between the four species ranged from facilitation to competition. Most of the mixtures exhibited transgressive overyielding. Without nitrogen (N) fertilisation, high complementarity between species allowed to achieve the highest biomass. With N fertilisation, high dominance of one mixture component should be avoided to achieve good performance. A revised approach in the use of the land equivalent ratio for the evaluation of cover crop mixtures is also proposed in this study. It allows to better identify transgressive overyielding in mixtures and to better characterise the effect of one species on the other within the mixture.
Article
Full-text available
Cover crops have long been touted for their ability to reduce erosion, fix atmospheric nitrogen, reduce nitrogen leaching, and improve soil health. In recent decades, there has been resurgence in cover crop adoption that is synchronous with a heightened awareness of climate change. Climate change mitigation and adaptation may be additional, important ecosystem services provided by cover crops, but they lie outside of the traditional list of cover cropping benefits. Here, we review the potential for cover crops to mitigate climate change by tallying all of the positive and negative impacts of cover crops on the net global warming potential of agricultural fields. Then, we use lessons learned from two contrasting regions to evaluate how cover crops affect adaptive management for precipitation and temperature change. Three key outcomes from this synthesis are (1) Cover crop effects on greenhouse gas fluxes typically mitigate warming by ~100 to 150 g CO2 e/m²/year, which is higher than mitigation from transitioning to no-till. The most important terms in the budget are soil carbon sequestration and reduced fertilizer use after legume cover crops. (2) The surface albedo change due to cover cropping, calculated for the first time here using case study sites in central Spain and Pennsylvania, USA, may mitigate 12 to 46 g CO2 e/m²/year over a 100-year time horizon. And (3) Cover crop management can also enable climate change adaptation at these case study sites, especially through reduced vulnerability to erosion from extreme rain events, increased soil water management options during droughts or periods of soil saturation, and retention of nitrogen mineralized due to warming. Overall, we found very few tradeoffs between cover cropping and climate change mitigation and adaptation, suggesting that ecosystem services that are traditionally expected from cover cropping can be promoted synergistically with services related to climate change.
Article
Full-text available
Agronomical and environmental benefits are associated with replacing winter fallow by cover crops (CCs). Yet, the effect of this practice on nitrous oxide (N2O) emissions remains poorly understood. In this context, a field experiment was carried out under Mediterranean conditions to evaluate the effect of replacing the traditional winter fallow (F) by vetch (Vicia sativa L.; V) or barley (Hordeum vulgare L.; B) on greenhouse gas (GHG) emissions during the intercrop and the maize (Zea mays L.) cropping period. The maize was fertilized following integrated soil fertility management (ISFM) criteria. Maize nitrogen (N) uptake, soil mineral N concentrations, soil temperature and moisture, dissolved organic carbon (DOC) and GHG fluxes were measured during the experiment. Our management (adjusted N synthetic rates due to ISFM) and pedo-climatic conditions resulted in low cumulative N2O emissions (0.57 to 0.75kgN2O-Nha⁻¹yr⁻¹), yield-scaled N2O emissions (3-6gN2O-Nkg aboveground N uptake⁻¹) and N surplus (31 to 56kgNha⁻¹) for all treatments. Although CCs increased N2O emissions during the intercrop period compared to F (1.6 and 2.6 times in B and V, respectively), the ISFM resulted in similar cumulative emissions for the CCs and F at the end of the maize cropping period. The higher C:N ratio of the B residue led to a greater proportion of N2O losses from the synthetic fertilizer in these plots when compared to V. No significant differences were observed in CH4 and CO2 fluxes at the end of the experiment. This study shows that the use of both legume and nonlegume CCs combined with ISFM could provide, in addition to the advantages reported in previous studies, an opportunity to maximize agronomic efficiency (lowering synthetic N requirements for the subsequent cash crop) without increasing cumulative or yield-scaled N2O losses.
Article
Full-text available
The Midwestern United States, a region that produces one-third of maize and one-quarter of soybean grain globally, is projected to experience increasing rainfall variability. One approach to mitigate climate impacts is to utilize crop and soil management practices that enhance soil water storage and reduce the risks of flooding as well as drought-induced crop water stress. While some research indicates that a winter cover crop in maize-soybean rotations increases soil water availability, producers continue to be concerned that water use by cover crops will reduce water for a following cash crop. We analyzed continuous in-field soil water measurements from 2008 to 2014 at a Central Iowa research site that has included a winter rye cover crop in a maize-soybean rotation for thirteen years. This period of study included years in the top third of the wettest on record (2008, 2010, 2014) as well as drier years in the bottom third (2012, 2013). We found the cover crop treatment to have significantly higher soil water storage at the 0–30 cm depth from 2012 to 2014 when compared to the no cover crop treatment and in most years greater soil water content on individual days analyzed during the cash crop growing season. We further found that the cover crop significantly increased the field capacity water content by 10–11% and plant available water by 21–22%. Finally, in 2013 and 2014, we measured maize and soybean biomass every 2–3 weeks and did not see treatment differences in crop growth, leaf area or nitrogen uptake. Final crop yields were not statistically different between the cover and no cover crop treatment in any of the seven years of this analysis. This research indicates that the long-term use of a winter rye cover crop can improve soil water dynamics without sacrificing cash crop growth in maize-soybean crop rotations in the Midwestern United States.
Article
Full-text available
Background and aims During the fallow period, non-legume cover crop species can capture mineral nitrogen (N) and thus decrease nitrate leaching, whereas legume cover crop species can provide a green manuring service that increases N availability for the subsequent crop. The aim of our study was to investigate the ability of bispecific mixtures to simultaneously produce these two services of N management in relation to their interspecific interactions. Methods Three field experiments were conducted at contrasting sites from summer to autumn to evaluate 25 mixtures and 10 sole crops. We measured biomass, N acquisition, C:N ratio and soil mineral N. Ecosystem services were assessed using both experimental data and simulation model predictions. Results Overall, prediction of N mineralized from cover crop residues was significantly higher for mixtures than for non-legume sole crops. Predictions of nitrate leached after mixtures did not differ significantly from those after non-legume sole crops and remained significantly lower than those under bare soil, especially for mixtures with turnip rape which benefitted greatly from being in mixtures. Conclusions Some of the mixtures provided a choice of compromises between the two ecosystem services, which helps define solutions for adapting mixture choice according to the site’s soil and climate characteristics and to fallow period management.
Article
Full-text available
Methods are needed for the design and evaluation of cropping systems, in order to test the effects of introducing or reintroducing crops into rotations. The interaction of legumes with other crops (rotational effects) requires an assessment at the cropping system scale. The objective of this work is to introduce a cropping system framework to assess the impacts of changes in cropping systems in a participatory approach with experts, i.e., the integration of legumes into crop rotations and to demonstrate its application in two case studies. The framework consists of a rule-based rotation generator and a set of algorithms to calculate impact indicators. It follows a three-step approach: (i) generate rotations, (ii) evaluate crop production activities using environmental, economic and phytosanitary indicators, and (iii) design cropping systems and assess their impacts. Experienced agronomists and environmental scientists were involved at several stages of the framework development and testing in order to ensure the practicability of designed cropping systems. The framework was tested in Västra Götaland (Sweden) and Brandenburg (Germany) by comparing cropping systems with and without legumes. In both case studies, cropping systems with legumes reduced nitrous oxide emissions with comparable or slightly lower nitrate-N leaching, and had positive phytosanitary effects. In arable systems with grain legumes, gross margins were lower than in cropping systems without legumes despite taking pre-crop effects into account. Forage cropping systems with legumes had higher or equivalent gross margins and at the same time higher environmental benefits than cropping systems without legumes. The framework supports agronomists to design sustainable legume-supported cropping systems and to assess their impacts.
Article
Full-text available
Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] farmers in the upper Midwest are showing increasing interest in winter cover crops. The effects of winter cover crops on soil quality in this region, however, have not been investigated extensively. The objective of this experiment was to determine the effects of a cereal rye (Secale cereale L.) winter cover crop after more than 9 yr in a corn silage-soybean rotation. Four cereal rye winter cover crop treatments were established in 2001: no cover crop, rye after soybean, rye after silage, and rye after both. Soil organic matter (SOM), particulate organic matter (POM), and potentially mineralizable N (PMN) were measured in 2010 and 2011 for two depth layers (0-5 and 5-10 cm) in both the corn silage and soybean phases of the rotation. In the 0- to 5-cm depth layer, a rye cover crop grown after both main crops had 15% greater SOM, 44% greater POM, and 38% greater PMN than the treatment with no cover crops. In general, the treatments that had a rye cover crop after both crops or after corn silage had a positive effect on the soil quality indicators relative to treatments without a cover crop or a cover crop only after soybean. Apparently, a rye cover crop grown only after soybean did not add enough residues to the soil to cause measureable changes in SOM, POM, or PMN. In general, rye cover crop effects were most pronounced in the top 5 cm of soil.
Article
Full-text available
The way we grow and consume food is changing both landscapes and societies globally. The constraints and challenges we face in meeting the anticipated large increase in global food demand out to 2050 are examined to show that while they present significant difficulties on many fronts, we have a large range of choices in the way this food demand might be met. Meeting this future food demand has frequently been articulated as a crisis of supply alone by some dominant institutions and individuals with prior ideological commitments to a particular framing of the food security issue. Our analysis indicates that the crisis can be avoided by the choices we make. The food security debate will be enriched by a rigorous evaluation of all these choices and recognition that the eventual solution will reside in a mixture of these choices. We could shift from our current paradigm of productivity enhancement while reducing environmental impacts, to a paradigm where ecological sustainability constitutes the entry point for all agricultural development. If we embraced this new paradigm, sustainable governance and management of ecosystems, natural resources and earth system processes at large, could provide the framework for practical solutions towards an intensification of agriculture. Such a paradigm shift could reposition world food production from its current role as the world’s single largest driver of global environmental change, to becoming a critical part of a world transition to work within the boundaries of the safe operating space for humanity with respect to the planet’s biophysical processes and functions. © 2015, Springer Science+Business Media Dordrecht and International Society for Plant Pathology.
Article
Full-text available
There are many environmental benefits to incorporating cover crops into crop rotations, such as their potential to decrease soil erosion, reduce nitrate (NO 3) leaching, and increase soil organic matter. Some of these benefits impact other agroecosystem processes, such as greenhouse gas emissions. In particular, there is not a consensus in the literature regarding the effect of cover crops on nitrous oxide (N 2 O) emissions. Compared to site-specific studies, meta-analysis can provide a more general investigation into these effects. Twenty-six peer-reviewed articles including 106 observations of cover crop effects on N 2 O emissions from the soil surface were analyzed according to their response ratio, the natural log of the N 2 O flux with a cover crop divided by the N 2 O flux without a cover crop (LRR). Forty percent of the observations had negative LRRs, indicating a cover crop treatment which decreased N 2 O, while 60% had positive LRRs indicating a cover crop treatment which increased N 2 O. There was a significant interaction between N rate and the type of cover crop where legumes had higher LRRs at lower N rates than nonlegume species. When cover crop residues were incorporated into the soil, LRRs were significantly higher than those where residue was not incorporated. Geographies with higher total precipitation and variability in precipitation tended to produce higher LRRs. Finally, data points measured during cover crop decomposition had large positive LRRs and were larger than those measured when the cover crop was alive. In contrast, those data points measuring for a full year had LRRs close to zero, indicating that there was a balance between periods when cover crops increased N 2 O and periods when cover crops decreased emissions. Therefore, N 2 O measurements over the entire year may be needed to determine the net effect of cover crops on N 2 O. The data included in this meta-analysis indicate some overarching crop management practices that reduce direct N 2 O emissions from the soil surface, such as no soil incorporation of residues and use of non-legume cover crop species. However, our results demonstrate that cover crops do not always reduce direct N 2 O emissions from the soil surface in the short term and that more work is needed to understand the full global warming potential of cover crop management.
Article
Full-text available
Healthy soils provide a wide range of ecosystem services. But soil erosion (one component of land degradation) jeopardizes the sustainable delivery of these services worldwide, and particularly in the humid tropics where erosion potential is high due to heavy rainfall. The Millennium Ecosystem Assessment pointed out the role of poor land-use and management choices in increasing land degradation. We hypothesized that land use has a limited influence on soil erosion provided vegetation cover is developed enough or good management practices are implemented. We systematically reviewed the literature to study how soil and vegetation management influence soil erosion control in the humid tropics. More than 3600 measurements of soil loss from 55 references covering 21 countries were compiled. Quantitative analysis of the collected data revealed that soil erosion in the humid tropics is dramatically concentrated in space (over landscape elements of bare soil) and time (e.g. during crop rotation). No land use is erosion-prone per se, but creation of bare soil elements in the landscape through particular land uses and other human activities (e.g. skid trails and logging roads) should be avoided as much as possible. Implementation of sound practices of soil and vegetation management (e.g. contour planting, no-till farming and use of vegetative buffer strips) can reduce erosion by up to 99%. With limited financial and technical means, natural resource managers and policy makers can therefore help decrease soil loss at a large scale by promoting wise management of highly erosion-prone landscape elements and enhancing the use of low-erosion-inducing practices. ã 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Conference Paper
Full-text available
society/index.php/iemss-2014-proceedings Abstract: Sustainable water resource management is typical of environmental management problems emerging from complex social-ecological systems. It deeply depends upon water user strategies, land use management and water governance systems. MAELIA, a "policy issue" modelling platform, allows performing integrated assessment at watershed level of a wide range of scenarios regarding water and land use management strategies in combination with global changes. It has been developed through a strong analysis of different French water management situations and an inductive modelling process. It allows representing dynamic interactions between human activities (farming practices), ecological processes (hydrology and crop growth), and governance systems (water regulations and releases from dams) at fine spatiotemporal resolutions in order to handle actual problems of water managers and issues of the main water users (farmers). MAELIA includes original farmer, dam manager and state services (software) agents.
Article
Full-text available
Using the Farm Energy Analysis Tool (FEAT), we compare energy use and greenhouse gas (GHG) emissions from the cultivation of different crops, highlight the role of sustainable management practices, and discuss the impact of soil nitrous oxide (N2 O) emissions and the uncertainty associated with denitrification estimates in the northeastern United States. FEAT is a transparent, open-source model that allows users to choose parameter estimates from an evolving database. The results show that nitrogen fertilizer and N2O emissions accounted for the majority of differences between crop energy use and GHG emissions, respectively. Integrating sustainable practices such as no tillage and a legume cover crop reduced energy use and GHG emissions from corn production by 37% and 42%, respectively. Our comparisons of diverse crops and management practices illustrate important trade-offs and can inform decisions about agriculture. We also compared methods of estimating N2O emissions and suggest additional research on this potent GHG.
Chapter
Full-text available
Continuation of current trends in fossil-fuel and land use is likely to lead to significant climate change, with important adverse consequences for both natural and human sys-tems. This has led to the investigation of various options to reduce greenhouse gas emis-sions or otherwise diminish the impact of human activities on the climate system. Here, we review options that can contribute to managing this problem and discuss fac-tors that could accelerate their development, deployment, and improvement. There is no single option available now or apparent on the horizon that will allow stabilization of radiative forcing from greenhouse gases and other atmospheric con-stituents. A portfolio approach will be essential. The portfolio contains two broad options: • Reducing sources of carbon (or carbon equivalents) to the atmosphere (e.g., reduce dependence on fossil fuels, reduce energy demand, reduce releases of other radiatively active gases, limit deforestation) • Increasing sinks of carbon (or carbon equivalents) from the atmosphere (e.g., augment carbon uptake by the land biosphere or the oceans over what would have occurred in the absence of active management) A variety of options could make a significant contribution in the short term. These include: changing agricultural management practice to increase carbon storage and reduce non-CO 2 gas emission; improving appliances, lighting, motors, buildings, indus-trial processes, and vehicles; mitigating non-CO 2 greenhouse gas emissions from indus-try; reforestation; and geoengineering Earth's climate with stratospheric sulfate aerosols.
Article
Full-text available
Utilization of cereal rye (Secale cereale L. ssp. cereal) as a winter cover crop has potential benefits for subsurface drainage and NO(3) loss reduction. The objective of this study was to quantify the soil water balance components and impacts of a rye cover crop on subsurface drainage in central Iowa. Rye was planted in lysimeters in mid-October and terminated in early June in 3 yr and the lysimeters were left fallow during the summer months. Subsurface drainage water was generally pumped out weekly along with taking soil moisture measurements; however, multiple appreciable rain events in a given week required more frequent pumping. During May through July of the 3 yr, monthly subsurface drainage was significantly reduced by 21% when comparing the rye system to bare soil (P < 0.1). Drainage of individual pumping events was significantly lower in the rye lysimeters than the bare lysimeters when averaged across 3 yr (P < 0.05). Soil water storage in the rye treatment was also significantly lower than the bare treatment (P < 0.05) in all 3 yr. The winter cover crop effectively reduced subsurface drainage, which would then be expected to decrease the NO(3) load, which is essential to water quality improvement. During the main growing month, May, estimated evapotranspiration of rye was 2.4 mm d(-1), significantly higher than evaporation from the bare treatment (1.5 mm d(-1), P < 0.1). Soil water depletion by rye in May could reduce the drainage volume and may also help facilitate trafficability, but it is still unknown what impact there may be on crop production in dry years.
Article
Full-text available
Human activity increases the atmospheric water vapour content in an indirect way through climate feedbacks. We conclude here that human activity also has a direct influence on the water vapour concentration through irrigation. In idealised simulations we estimate a global mean radiative forcing in the range of 0.03 to +0.1Wm–2 due to the increase in water vapour from irrigation. However, because the water cycle is embodied in the climate system, irrigation has a more complex influence on climate. We also simulate a change in the temperature vertical profile and a large surface cooling of up to 0.8K over irrigated land areas. This is of opposite sign than expected from the radiative forcing alone, and this questions the applicability of the radiative forcing concept for such a climatic perturbation. Further, this study shows stronger links than previously recognised between climate change and freshwater scarcity which are environmental issues of paramount importance for the twenty first century.
Article
Full-text available
Catch crops can effectively decrease nitrate leaching in arable cropping systems but their long-term impacts on nitrogen mineralization are not well known. This study quantified the effects of continuous catch crops on net N mineralization, crop N uptake, crop N use efficiency and N leaching in three long-term (13–17years) field experiments in northern France. Mustard was grown every year at Boigneville, radish every year at Thibie and ryegrass every 2years at Kerlavic. The mean N content of catch crop residues at these sites was 33, 36 and 35kg ha−1 yr−1 and their mean C:N ratio was 13, 17 and 28, respectively. Net mineralization was calculated with a mass balance of soil mineral N using measured inputs and outputs. Catch crop establishment enhanced annual mineralization by on average 26, 18 and 9kg N ha−1 yr−1 respectively during the 13–17year period. The difference in mineralization rate between catch crop and control treatments (extra mineralization) was positive from the first year at Boigneville, whereas it was negative or nil during the first 3–5years at Thibie and Kerlavic. At the latter sites, the extra mineralization rate increased significantly over time at a rate of 2.0 and 2.6kg N ha−1 yr−2. At the end of the experiment, cumulative extra mineralization represented 72%, 60% and 23% of the total N added by catch crop residues at Boigneville, Thibie and Kerlavic, respectively. Repeated catch crops significantly increased N uptake and N use efficiency by main crops at Kerlavic and Thibie, but not at Boigneville. The efficiency of catch crops in reducing N leaching persisted over the years at all sites. A model simulating C and N dynamics during catch crop decomposition was able to reproduce the pattern of extra N mineralization kinetics with the various catch crop species, but underestimated the range of variation between sites. Better predictions were obtained when C or N inputs due to catch crops were increased by 10–57%, suggesting that the actual inputs could be markedly greater than those measured in catch crop residues. According to the model, the C:N ratio of catch crop residues largely explained differences in mineralization due to different catch crop species. KeywordsCover crop–Nitrate–Long-term–Modelling
Article
Full-text available
C and N mineralization kinetics of 25 catch crop (CC) residues, whose organic C:N ratio varied from 9.5 to 34.0, were studied during soil incubations under controlled conditions. Decomposition rates were rather similar for the different CC residues, 59% to 68% residue-C being mineralized after 168days incubation. C mineralized during the first weeks was mainly correlated to the soluble C content of the residue. N mineralized from CC residues was much more variable (−4.9 to +38.0mg N g−1 added C at day 168), and was mainly related to the organic N content in residues. C and N mineralization kinetics were simulated with STICS residue decomposition model, using the previous parameterization mostly based on mature crop residues (Nicolardot et al. Plant Soil 228:83–103, 2001). A reasonable agreement was found between measured and simulated C kinetics but N mineralization was underestimated by the model. A new parameterization was carried out to improve N predictions. The fitting procedure was first applied independently to each CC residue in order to optimise the five parameters of the model. The relationships found between each optimised parameter and the C:N ratio of CC residues were similar to those obtained previously, indicating that the same model was applicable to all residues. The parameters of these relationships were fitted on a combined dataset including CC and mature residues. The new parameterisation lead to better simulations for CC residues, the errors of prediction (RMSE) for C and N mineralization being 32 and 1.8mg g−1 added C, respectively. For the whole dataset (68 residues), the RMSE were 50 and 3.3mg g−1 added C. The prediction quality is satisfactory with respect to the model simplicity and the single criterion of residue quality (C:N ratio).
Article
Full-text available
stics is a model that has been developed at INRA (France) since 1996. It simulates crop growth as well as soil water and nitrogen balances driven by daily climatic data. It calculates both agricultural variables (yield, input consumption) and environmental variables (water and nitrogen losses). From a conceptual point of view, stics relies essentially on well-known relationships or on simplifications of existing models. One of the key elements of stics is its adaptability to various crops. This is achieved by the use of generic parameters relevant for most crops and on options in the model formalisations concerning both physiology and management, that have to be chosen for each crop. All the users of the model form a group that participates in making the model and the software evolve, because stics is not a fixed model but rather an interactive modelling platform. This article presents version 5.0 by giving details on the model formalisations concerning shoot ecophysiology, soil functioning in interaction with roots, and relationships between crop management and the soil–crop system. The data required to run the model relate to climate, soil (water and nitrogen initial profiles and permanent soil features) and crop management. The species and varietal parameters are provided by the specialists of each species. The data required to validate the model relate to the agronomic or environmental outputs at the end of the cropping season. Some examples of validation and application are given, demonstrating the generality of the stics model and its ability to adapt to a wide range of agro-environmental issues. Finally, the conceptual limits of the model are discussed.
Article
Cover crops are increasingly used in agriculture to provide a variety of ecosystem services (e.g. reducing nitrogen leaching, storing carbon in soils) during fallow periods, but it can be challenging to successfully establish them in summer, when water availability may be low. Thus, it is crucial to better quantify, understand and predict the emergence date of a variety of cover crops from multiple contexts in impact assessment studies. The objectives of this study were to 1) analyze variability in emergence dynamics among cover crops grown in fields, 2) identify variables that influence emergence the most and use them to develop a simple model to predict emergence date and 3) calibrate the STICS model to improve its predictions of cover crop emergence. STICS was chosen because it is a dynamic soil-plant model widely validated in the literature for simulating the production of cover crop services. We analyzed emergence dynamics of ten cover crop species sown under a variety of soil, climate and sowing conditions from 18 experimental sites across France. We developed and independently evaluated a static model based on these data to predict the number of days until emergence. We then calibrated STICS using the same data. Results revealed a mean emergence duration of 12 days for all species, but with high variability among experimental sites and years. The simple static model contained only three variables, with the number of consecutive days without significant water input after sowing the most significant. Overall, both the model and STICS predicted emergence date well in the calibration and validation datasets. Accurate prediction of soil moisture in the seedbed and soil water balance is a key factor to accurately predict cover crop emergence. Accurately predicting emergence of cover crops in crop models will help to assess the former's ability to provide ecosystem services in cropping systems in current and future climates.
Article
Soil water-holding capacity is an important component of the water and energy balances of the terrestrial biosphere. It controls the rate of evapotranspiration, and is a key to crop production. It is widely accepted that the available water capacity in soil can be improved by increasing organic matter content. However, the increase in amount of water that is available to plants with an increase in organic matter is still uncertain and may be overestimated. To clarify this issue, we carried out a meta-analysis from 60 published studies and analysed large databases (more than 50 000 measurements globally) to seek relations between organic carbon (OC) and water content at saturation, field capacity, wilting point and available water capacity. We show that the increase in organic carbon in soil has a small effect on soil water content. A 1% mass increase in soil OC (or 10 g C kg⁻¹ soil mineral), on average, increases water content at saturation, field capacity, wilting point and available water capacity by: 2.95, 1.61, 0.17 and 1.16 mm H2O 100 mm soil⁻¹, respectively. The increase is larger in sandy soils, followed by loams and is least in clays. Overall the increase in available water capacity is very small; 75% of the studies reported had values between 0.7 and 2 mm 100 mm⁻¹ with an increase of 10 g C kg⁻¹ soil. Compared with reported annual rates of carbon sequestration after the adoption of conservation agricultural systems, the effect on soil available water is negligible. Thus, arguments for sequestering carbon to increase water storage are questionable. Conversely, global warming may cause losses in soil carbon, but the effects on soil water storage and its consequent impact on hydrological cycling might be less than thought previously.
Article
Over the last decade, efforts have been carried on to develop and evaluate versions of global terrestrial ecosystem models (GTEM) in which crop specificities are represented. The goal of this study is to evaluate the ability of the ORCHIDEE-STICS (Organising Carbon and Hydrology In Dynamic EcosystEms—Simulateur mulTIdisciplinaire pour les Cultures Standard) GTEM in simulating the observed seasonal variations and annual budgets of net ecosystem exchange (NEE), gross primary production (GPP) and total ecosystem respiration (TER) fluxes over seven wheat sites spanning a large climate gradient in Europe. Overall, the seasonal variations of GPP are well represented by the model, with 5 sites out of 7 exhibiting a correlation coefficient (R) value higher than 0.9 and a normalized standard deviation (NSTD) between 0.8 and 1.2. In comparison, the model performances for catching the seasonal variations of TER are lower, especially in terms of NSTD. Regarding the annual budgets, mean simulated deviations averaged over all sites do not exceed 10% and 15% of the observed annual mean budget, for GPP and TER, respectively. For NEE, the model capacity at estimating annual budgets is low, its mean deviation corresponding to ∼35% of the observed mean value. This clearly shows that more accurate model estimates of GPP and especially TER are required for estimating NEE annual budgets. In this respect, past land-use and land-management changes are probably the most crucial processes to add, for getting soil carbon disequilibrium and more accurate NEE annual budgets.
Article
To determine the effects of crop rotation, crop residue management, and N fertilization, changes in microbial biomass C and N and populations of several soil microbial groups were measured in long-term (58-yr) plots under different winter wheat. Total soil and microbial biomass C and N contents were significantly greater in annual-crop than wheat-fallow rotations, except when manure was applied. Microbial biomass C in annual-crop and wheat-fallow rotations averaged 50 and 25%, respectively, of that in grass pasture. Residue management significantly influenced the level of microbial biomass C. Both microbial counts and microbial biomass were higher in early spring than other seasons. Annual cropping significantly reduced declines in soil organic matter and soil microbial biomass. -from Authors
Article
A promising option to sequester carbon in agricultural soils is the inclusion of cover crops in cropping systems. The advantage of cover crops as compared to other management practices that increase soil organic carbon (SOC) is that they neither cause a decline in yields, like extensification, nor carbon losses in other systems, like organic manure applications may do. However, the effect of cover crop green manuring on SOC stocks is widely overlooked. We therefore conducted a meta-analysis to derive a carbon response function describing SOC stock changes as a function of time. Data from 139 plots at 37 different sites were compiled. In total, the cover crop treatments had a significantly higher SOC stock than the reference croplands. The time since introduction of cover crops in crop rotations was linearly correlated with SOC stock change (R2 = 0.19) with an annual change rate of 0.32 +/- 0.08 Mg ha-1 yr-1 in a mean soil depth of 22 cm and during the observed period of up to 54 years. Elevation above sea level of the plot and sampling depth could be used as explanatory variables to improve the model fit. Assuming that the observed linear SOC accumulation would not proceed indefinitely, we modeled the average SOC stock change with the carbon turnover model RothC. The predicted new steady state was reached after 155 years of cover crop cultivation with a total mean SOC stock accumulation of 16.7 +/-1.5 Mg ha-1 for a soil depth of 22 cm. Thus, the C input driven SOC sequestration with the introduction of cover crops proved to be highly efficient. We estimated a potential global SOC sequestration of 0.12 +/-0.03 Pg C yr-1, which would compensate for 8% of the direct annual greenhouse gas emissions from agriculture. However, altered N2O emissions and albedo due to cover crop cultivation have not been taken into account here. Data on those processes, which are most likely species-specific, would be needed for reliable greenhouse gas budgets.
Article
In Northern Europe, cover crops are traditionally established before spring crops by undersowing, but some cover crops might also have an effect if preharvest sown before spring crops and even winter crops. The effects of cover crop sowing date, sowing technique and succeeding main crop on biomass production, N uptake, nitrate leaching and soil inorganic N were tested in lysimeters and in the field. Cruciferous cover crops (oil radish, white mustard) were sown preharvest by broadcasting into winter wheat in July and were allowed to grow until a following winter wheat was established in September. Other preharvest cover crops were left in place until late autumn. For comparison, the same cruciferous cover crops were established postharvest after light harrowing. Perennial ryegrass undersown in spring barley was also included. Aboveground N uptake in preharvest cover crops amounted to a maximum of 24 kg N/ha in September before sowing winter wheat. When left until late autumn, preharvest oil radish took up a maximum of 66 kg N/ha, and ryegrass and postharvest cover crops 35 kg N/ha. Preharvest establishment of cruciferous cover crops before a spring-sown crop thus seems promising. The soil was depleted of inorganic N to the same extent in late autumn irrespective of cover crop type, sowing time and technique within winter wheat or spring barley. However, the reduction in nitrate leaching of preharvest cover crops incorporated after 2 months and followed by winter wheat was only half of that achieved by cover crops left until late autumn or spring.
Article
Adopting mixtures between legumes and non legumes can be an efficient tool to merge the advantages of the single species in the fall-sown cover crop practice. Nevertheless there is a lack of information on how the species proportion may affect N accumulation and C/N of the cover crops and how this can influence the N uptake and N status of different subsequent summer cash crops.In this study the N effect of barley (Hordeum vulgare L.) and hairy vetch (Vicia villosa Roth.) grown in pure stands or in mixtures with different sowing proportion was tested on maize (Zea Mays L.) and processing tomato (Lycopersicon esculentum Mill.). Cover crop N accumulation and C/N ratio were monitored during the whole growing cycle, and CO2 flux from the soil was measured after their incorporation into the soil. N status of the following cash crops was evaluated by comparing the observed data with the appropriate critical N dilution curves.The results highlight the effectiveness of mixtures for the management of the winter cover crop practice. In the two considered years, the species proportion influences the aboveground biomass (ranging from 2.90 to 5.94 Mg ha−1) and N accumulation (ranging from 73.8 to 183.2 kg ha−1) of the mixtures. The legume component, even at low proportion, increased the N accumulation of the cover crop of 148% (in 2006) and 134% (in 2007) compared to pure stand barley. Also the biomass quality of the cover crops was greatly affected by species proportion (e.g. C/N ranging from 12.0 to 18.9) and this aspect showed a clear effect on the N availability for the subsequent crop. N effect (Neff) of the different cover crop mixtures (especially those with high barley proportions) brought tomato much closer to the critical N value than they did with maize. The basis of the relationship between cover crop C/N and Neff was confirmed, so mixtures can be used to adjust the extent and timing of mineralisation of the incorporated biomass to the subsequent cash crop requirements. Prediction of the cash crops N status on the cover crop C/N appears to be a useful approach, but, it may be important to take the characteristics of the following cash crop into account.
Article
Ecophysiological models are widely used to forecast potential impacts of climate change on future agricultural productivity and to examine options for adaptation by local stakeholders and policy makers. However, protocols followed in such assessments vary to such an extent that they constrain cross-study syntheses and increase the potential for bias in projected impacts. We reviewed 221 peer-reviewed papers that used crop simulation models to examine diverse aspects of how climate change might affect agricultural systems. Six subject areas were examined: target crops and regions; the crop model(s) used and their characteristics; sources and application of data on [CO2] and climate; impact parameters evaluated; assessment of variability or risk; and adaptation strategies. Wheat, maize, soybean and rice were considered in approximately 170 papers. The USA (55 papers) and Europe (64 papers) were the dominant regions studied. The most frequent approach used to simulate response to CO2 involved adjusting daily radiation use efficiency (RUE) and transpiration, precluding consideration of the interacting effects of CO2, stomatal conductance and canopy temperature, which are expected to exacerbate effects of global warming. The assumed baseline [CO2] typically corresponded to conditions 10–30 years earlier than the date the paper was accepted, exaggerating the relative impacts of increased [CO2]. Due in part to the diverse scenarios for increases in greenhouse gas emissions, assumed future [CO2] also varied greatly, further complicating comparisons among studies. Papers considering adaptation predominantly examined changes in planting dates and cultivars; only 20 papers tested different tillage practices or crop rotations. Risk was quantified in over half the papers, mainly in relation to variability in yield or effects of water deficits, but the limited consideration of other factors affecting risk beside climate change per se suggests that impacts of climate change were overestimated relative to background variability. A coordinated crop, climate and soil data resource would allow researchers to focus on underlying science. More extensive model intercomparison, facilitated by modular software, should strengthen the biological realism of predictions and clarify the limits of our ability to forecast agricultural impacts of climate change on crop production and associated food security as well as to evaluate potential for adaptation.
Article
A 24-yr-old permanent field trial with spring-sown crops was used in a nitrate N leaching study to determine (i) the effect of long-term cover crop use compared with the introduction of perennial ryegrass (Lolium perenne L.) as a cover crop on plots with a history of no previous cover crop use and (ii) the effect of discontinuing long-term use of ryegrass as a cover crop compared with no previous cover crop use. The cover crop (seed rate 8-0 kg ha -1) was undersown in spring wheat (Triticum aestivum L.). The field trial was conducted on a coarse sand (Orthic Haplohumod) under temperate coastal climate conditions in Denmark. From 1993 to 1997, nitrate leaching was estimated by use of soil water samples from ceramic cups in four treatments: cover crop since 1968, cover crop since 1993, no cover crop, and cover crop until 1993. Each treatment was carried out at two N rates: 60 and 120 kg N ha -1 yr -1. As an average of 4 yr and two N rates, leaching was 14 kg N ha -1 yr -1 or 29% higher in plots with long-term previous cover crop use than in plots without. The effect of previous long-term use of ryegrass as a cover crop lasted at least 4 yr. Thus, if the higher N mineralization due to long-term use of cover crop is not taken into consideration by adjusting the cropping system, the reduction in nitrate leaching caused by the cover crop may not be as significant in the long- term.
Article
An evaluation of a generic crop growth model, STICS, described in Brisson et al. [11], is presented, based on an agronomic database which combines various wheat crop and maize crop situations in France. Emphasis is placed on the need to use standard references for parameterising varieties, particularly concerning the development stages. The validation was carried out for the model's output variables, defined as being the final variables of agronomic interest (yield and components, above-ground biomass, flowering and maturity dates, nitrogen contents in the plant and grain, water and nitrogen contents in the soil) using several mathematical criteria (square errors, mean deviation, efficiency). Results indicated that the two crops behave quite similarly with square errors of 1.6 t.ha(-1) for wheat yield and 2.4 t.ha(-1) for maize yield. The two yield components, grain number and grain weight, were simulated less successfully, as was the case for the simulations concerning nitrogen both in the plant and soil, which were systematically biased. However, the water content in the soil was simulated accurately. An analysis of the dynamics of the main state variables in the system, such as leaf area index or nitrogen nutrition index, which in some cases were extracted from the database, made it possible to reveal the shortcomings in the model and propose ways of modifying it. The results we will retain include the introduction of a relationship between grain number and maximal grain weight, which makes the "grain number" variable dependent on the variety, the consideration of leaf senescence due to environmental stress, and the end of nitrogen absorption at the onset of grain filling. These modifications help to improve modelling results of yield components and soil and plant nitrogen contents. They have little effect on biomass and yield, for which errors remain at levels of approximately 15%; the impossibility of reducing the error concerning biomass, and consequently that concerning yield, illustrates the model's robustness.
Article
Cover cropping is a common agro-environmental tool for soil and groundwater protection. In water limited environments, knowledge about additional water extraction by cover crop plants compared to a bare soil is required for a sustainable management strategy. Estimates obtained by the FAO dual crop coefficient method, compared to water balance-based data of actual evapotranspiration, were used to assess the risk of soil water depletion by four cover crop species (phacelia, hairy vetch, rye, mustard) compared to a fallow control. A water stress compensation function was developed for this model to account for additional water uptake from deeper soil layers under dry conditions. The average deviation of modelled cumulative evapotranspiration from the measured values was 1.4% under wet conditions in 2004 and 6.7% under dry conditions in 2005. Water stress compensation was suggested for rye and mustard, improving substantially the model estimates. Dry conditions during full cover crop growth resulted in water losses exceeding fallow by a maximum of +15.8% for rye, while no substantially higher water losses to the atmosphere were found in case of evenly distributed rainfall during the plant vegetation period with evaporation and transpiration concentrated in the upper soil layer. Generally the potential of cover crop induced water storage depletion was limited due to the low evaporative demand when plants achieved maximum growth. These results in a transpiration efficiency being highest for phacelia (5.1gm−2mm−1) and vetch (5.4gm−2mm−1) and substantially lower for rye (2.9gm−2mm−1) and mustard (2.8gm−2mm−1). Taking into account total evapotranspiration losses, mustard performed substantially better. The integration of stress compensation into the FAO crop coefficient approach provided reliable estimates of water losses under dry conditions. Cover crop species reducing the high evaporation potential from a bare soil surface in late summer by a fast canopy coverage during early development stages were considered most suitable in a sustainable cover crop management for water limited environments.
Article
A new integrated hydrological and nitrogen model, called TNT2 (topography-based nitrogen transfer and transformation), has been developed to study nitrogen fluxes in small catchments. This model, process-based and spatially distributed in order to take spatial interactions into account, has been kept as simple as possible. Here, only the hydrological module is discussed. The two main hypotheses of the hydrological model are taken from the TOPMODEL concept (constant hydraulic gradient equal to slope and hydraulic conductivity decreasing exponentially with depth). The model is based on a daily water balance for each cell of a regular square grid and computes an explicit cell-to-cell routing. Transfer through the vadose zone is simulated using a conceptual, layer-based algorithm analogous to the Burns model, except that a drainage water reservoir has been added to simulate mobile/immobile water processes and variations of the water table within the soil. The crop growth and nitrogen transformations are simulated using the equations of a generic plant-soil model, STICS. As an example, a preliminary study of the effect of the catchment geomorphology on denitrification is presented. The study was performed on theoretical catchments with contrasted slope shapes and pathway patterns. Results show that the whole-catchment denitrification depends on catchment geomorphology, although not directly through the extent of saturated areas. It is concluded that TNT2 seems to be a powerful tool to explore catchment processes, both by application to actual cases and by exploration on simple scenarios.
Article
Human production of food and energy is the dominant continental process that breaks the triple bond in molecular nitrogen (N2) and creates reactive nitrogen (Nr) species. Circulation of anthropogenic Nr in Earth’s atmosphere, hydrosphere, and biosphere has a wide variety of consequences, which are magnified with time as Nr moves along its biogeochemical pathway. The same atom of Nr can cause multiple effects in the atmosphere, in terrestrial ecosystems, in freshwater and marine systems, and on human health. We call this sequence of effects the nitrogen cascade. As the cascade progresses, the origin of Nr becomes unimportant. Reactive nitrogen does not cascade at the same rate through all environmental systems; some systems have the ability to accumulate Nr, which leads to lag times in the continuation of the cascade. These lags slow the cascade and result in Nr accumulation in certain reservoirs, which in turn can enhance the effects of Nr on that environment. The only way to eliminate Nr accumulation and stop the cascade is to convert Nr back to nonreactive N2.
Article
The long term effects of repeated catch crops on N dynamics in arable farming were assessed using mid-term experiments and long-term simulations. The soil-crop model STICS (v6.9) was tested against a database provided by three experiments (13–17 years) carried out in Northern France, including treatments with or without repeated catch crops. STICS performance was checked for crop biomass, N uptake, soil water content and mineral N at harvest of main crops, drained water, N leaching and mineralization rates. The model satisfactorily reproduced these variables, except for soil mineral N and N leached at one site. N leached was predicted with a slight bias, between −3 and +7kgNha−1yr−1, and soil N mineralized was simulated with a bias lower than 7kgNha−1yr−1. The model simulated correctly the N uptake by catch crops and the kinetics of extra N mineralization due to catch crops. Seven scenarios varying in the presence of catch crops, fertilization rate and climate were simulated on long-term (60 years); their effects on N uptake, soil N storage, N mineralization and nitrate leaching were compared by difference with a control scenario. Repeated catch crops lead to reduce N leaching, sequester organic N and increase N mineralization. The model indicated that the sequestered N reached a maximum of 430–750kgNha−1 after 23–45 years depending on site. The extra-mineralization due to catch crops progressively increased up to 38–65kgNha−1yr−1. A strategy of constant N fertilizer rate resulted in raising the N uptake of main crops and slowing down the abatement of nitrate leaching. Conversely, when N fertilization rates were reduced by 20–24kgNha−1yr−1, crop production remained stable and catch crops reduced N leaching on the long term by 33–55%. Therefore catch crop is a promising technique for controlling the N cascade.
Article
Land-use changes (LUC) influence the balance of soil organic carbon (SOC) and hence may cause CO2 emissions or sequestration. In Europe there is a side by side of LUC types that lead to SOC loss or SOC accumulation. However, there is a lack of studies covering all major LUC types to investigate qualitative and quantitative LUC effects on SOC. In this study we sampled 24 paired sites in Europe to a depth of 80 cm, covering a wide range of pedo-climatic conditions and comprising the major European LUC types cropland to grassland, grassland to cropland, cropland to forest and grassland to forest. To assess qualitative changes and the sensitivity of different functional SOC pools with distinct turnover times, we conducted a fractionation to isolate five different fractions of SOC. The mean SOC stock changes after LUC were 18±11 Mg ha−1 (cropland to grassland), 21±13 Mg ha−1 (cropland to forest), −19±7 Mg ha−1 (grassland to cropland) and −10±7 Mg ha−1 (grassland to forest) with the main changes occurring in the topsoil (0–30 cm depth). However, subsoil carbon stocks (>30 cm depth) were also affected by LUC, at 19 out of 24 sites in the same direction as the topsoil. LUC promoting subsoil SOC accumulation might be a sustainable C sink. Particulate organic matter (POM) was found to be most sensitive to LUC. After cropland afforestation, POM accounted for 50% (9.1±2.3 Mg ha−1) of the sequestered carbon in 0–30 cm: after grassland afforestation POM increased on average by 5±2.3 Mg ha−1, while all other fractions depleted. Thus, afforestations shift SOC from stable to labile pools. The resistant fraction comprising the so‐called inert carbon was found to be only slightly less sensitive than the total SOC pool, suggesting that an inert carbon pool was not chemically extracted with NaOCl oxidation, if there is any inert carbon.
Article
The greenhouse gas budgets of 15 European crop sites covering a large climatic gradient and corresponding to 41 site-years were estimated. The sites included a wide range of management practices (organic and/or mineral fertilisation, tillage or ploughing, with or without straw removal, with or without irrigation, etc.) and were cultivated with 15 representative crop species common to Europe. At all sites, carbon inputs (organic fertilisation and seeds), carbon exports (harvest or fire) and net ecosystem production (NEP), measured with the eddy covariance technique, were calculated. The variability of the different terms and their relative contributions to the net ecosystem carbon budget (NECB) were analysed for all site-years, and the effect of management on NECB was assessed. To account for greenhouse gas (GHG) fluxes that were not directly measured on site, we estimated the emissions caused by field operations (EFO) for each site using emission factors from the literature. The EFO were added to the NECB to calculate the total GHG budget (GHGB) for a range of cropping systems and management regimes. N2O emissions were calculated following the IPCC (2007) guidelines, and CH4 emissions were estimated from the literature for the rice crop site only. At the other sites, CH4 emissions/oxidation were assumed to be negligible compared to other contributions to the net GHGB. Finally, we evaluated crop efficiencies (CE) in relation to global warming potential as the ratio of C exported from the field (yield) to the total GHGB. On average, NEP was negative (−284 ± 228 g C m−2 year−1), and most cropping systems behaved as atmospheric sinks, with sink strength generally increasing with the number of days of active vegetation. The NECB was, on average, 138 ± 239 g C m−2 year−1, corresponding to an annual loss of about 2.6 ± 4.5% of the soil organic C content, but with high uncertainty. Management strongly influenced the NECB, with organic fertilisation tending to lower the ecosystem carbon budget. On average, emissions caused by fertilisers (manufacturing, packaging, transport, storage and associated N2O emissions) represented close to 76% of EFO. The operation of machinery (use and maintenance) and the use of pesticides represented 9.7 and 1.6% of EFO, respectively. On average, the NEP (through uptake of CO2) represented 88% of the negative radiative forcing, and exported C represented 88% of the positive radiative forcing of a mean total GHGB of 203 ± 253 g C-eq m−2 year−1. Finally, CE differed considerably among crops and according to management practices within a single crop. Because the CE was highly variable, it is not suitable at this stage for use as an emission factor for management recommendations, and more studies are needed to assess the effects of management on crop efficiency.Graphical abstractResearch highlights▶ Mean NEP was −284 ± 228 g C m−2 year−1 and most crops behaved as atmospheric sinks. ▶ Mean crop carbon budget was 138 ± 239 g C m−2 year−1, corresponding to a carbon loss. ▶ Management strongly influenced crop carbon budget. ▶ Field operations represented 32% of the GHG budget. ▶ Mean total GHG budget was 203 ± 253 g C-eq m−2 year−1.
Article
The soil water and N dynamics have been studied during two long fallow periods (between wheat or oilseed rape and a spring crop) in a field experiment in Chlons-en-Champagne (eastern France, 4850 N, 215 E). The experiment involved frequent measurements of soil water, soil mineral N, dry matter and N uptake by cover crops. Water and N budgets were established using Ritchie''s model for calculating evapotranspiration in cropped soils and a model (LIXIM) for calculating water drainage, N leaching and N mineralisation in bare soils. During the first autumn and winter, a radish cover crop (grown from September 1994 to January 1995) was compared to a bare soil. During the second period (July 1995 to April 1996), a comparison was carried out between (i) oilseed rape volunteers, (ii) bare soil with two types of oilseed rape residues incorporated into the soil (R0 and R270 residues) and (iii) bare soil without residues incorporation. R0 and R270 residues came from two preceding oilseed rape crops which received two rates of N fertilizer (0 and 270 kg N ha-1).Soil mineral N content was markedly reduced by the presence of radish cover crop or oilseed rape volunteers during autumn. The calculated actual evapotranspiration (AET) did not differ much between treatments, meaning that the transpiration by the cover crop or volunteers was relatively low (100–150 L kg-1 of dry matter). Consequently, nitrate leaching was reduced during the rest of the winter and spring as well as nitrate concentration in the percolating water: 45 vs. 91 mg NO3 - L-1 for radish cover crop and bare soil, respectively. The incorporation of oilseed rape residues to soil also exerted a beneficial but smaller action on reducing the nitrate content in the soil. This effect was due to extra N immobilisation which reached a maximum of about 20 kg N ha-1 in mid-autumn for both types of residues. Nine months after the incorporation of the oilseed rape residues, and comparing to the control soil without residues incorporation, N rich residues induced a significant positive N net effect (+ 9 kg N ha-1) corresponding to 10% of N added whereas for N poor residues no net effect was still obtained at the end of experiment (–3 kg N ha-1, not significantly different from 0).To reduce nitrate leaching during long fallow periods, it is necessary to promote techniques leading to decrease mineral-N contents in the soil during autumn before the drainage period, such as (i) residue incorporation after harvest (without fertiliser-N) and (ii) allowing volunteers to grow or sowing a cover crop just after the harvest of the last main crop.
Article
During the last decades a lot of research have been made on the use of cover crops. Cover crops are grown for many purposes, but most of the resent interest have focused on their effects on nitrogen. Studies have been made on catch crops grown to catch N from the soil and prevent leaching losses to the environment and on legume green manure crops grown to improve the N supply for succeeding crops. Many of the experiments have been agronomic studies, where choise of plant species or management strategies have been tested to identify the optimal way to grow cover crops in a specific situation. Other experiments have aimed at gaining more basic understanding of the effects of catch crops or green manure crops on N dynamics. These studies include subjects as catch crop growth, root growth, N uptake and soil depletion, kill-date, N mineralisation and pre-emptive competition, and how these factors interact with soil, climatic conditions, and the main crops in the cropping system, both in the short term and in the longer term. Together, the results from these studies have given a more comprehensive understanding of the mechanisms by which a catch crop or a green manure affect N leaching losses and N supply for succeeding crops. The principles governing the effect of catch crops on N supply for succeeding crops have been found to differ basically from the effects N effects of added organic matter. This is mainly due to the fact that a catch crop do not add N to the soil, the N which is incorporated with the catch crop has first been taken from the soil.
Article
Cereal straw, which is most often returned to the soil in arable cropping systems, is of renewed interest as a potential source of bioenergy. However, the sustainability of this practice which implies systematic removal of aerial biomass of cereal crops is a controversial issue, particularly in soils having a low soil organic carbon (SOC) content. This study aims at evaluating a simple model (AMG) to predict the consequences of straw export on SOC evolution in various cropping and pedoclimatic conditions. The model was tested on nine long-term field experiments (18–35 yr) dominated by cereal crops and differing in climate, soil type and carbon inputs. The model was able to provide satisfactory simulations of the evolution of SOC in most experiments with a unique set of parameters. The sensitivity analysis indicated that the quality of fit was very sensitive to humification coefficient, moderately sensitive to the size of the stable SOC pool and weakly affected by the ratio of belowground: aerial C input. The dependence of model parameters (humification and mineralization rates) on pedoclimatic conditions (soil clay content and temperature) was analyzed and compared to those proposed in other models (DAISY, CENTURY, ROTHC, CN-SIM) since they vary widely between models. AMG functions provided the best fit in seven out of nine experiments. More generally, the best fit was obtained by assuming that clay content had a small or no effect on humification coefficient and a marked effect on mineralization rate, in accordance with incubation studies in literature. The AMG model was used to simulate the impact of a straw export scenario in nine experiments considering a systematic straw removal one year out of two. With this scenario, straw removal vs. incorporation would reduce carbon stocks by 2.5–10.9% of the initial SOC after 50 yr, depending primarily on the experiment (soil, climate, productivity) and secondarily on the size of the stable C pool (varying from 10% to 65%).
Article
The long-term effects of undersowing a ryegrass catch crop in cereals was analysed with the FASSET simulation model. The model was tested on a 28-year field experiment with ryegrass catch crops in spring barley. The experiment included treatments with nitrogen (N) fertiliser rates, catch crop use and timing of tillage. The modelled effects of these treatments generally agreed with observations on crop production, soil carbon, soil nitrogen and nitrate leaching. Both the observations and the simulations predicted a yield increase of 7 kg N ha−1 and an increase in nitrate leaching of 13 kg N ha−1 due to a prehistory of 24 years with continuous use of catch crops compared to a prehistory without catch crops.A range of scenarios was constructed to evaluate the fate of the reduced nitrate leaching on crop N uptake, N leaching, gaseous emissions and change in soil organic N, and how this fate interacts with soils and climate and management. These scenarios showed that 22–30% of the reduced nitrate leaching was subsequently leached during the following decades after termination of catch crop use. Between 35 and 40% of the reduced nitrate leaching was harvested in cereals. The exact distribution depended primarily on the soil texture. The scenarios showed that effects of catch crops should be evaluated on the long-term rather than consider short-term effects only.
Article
This study was designed to test whether the cultivation of cover crops between tree rows in short-rotation woody crop (SRWC) plantations could reduce erosion. Sweetgum (Liquidambar styraciflua L.) seedlings were planted as the SRWC at a 1.5×3 m spacing. Four cover crops, annual ryegrass (Lolium multiflorum L. a winter annual grass); tall fescue (Festuca arundinacea L. a cool-season perennial grass); crimson clover (Trifolium incarnatum L. a winter annual legume); and Interstate sericea lespedeza [Lespedeza cuneata (Dumont) G. Don. a summer growing-perennial legume], were tested at two different strip widths (1.22 and 2.44 m) in comparison with complete competition control. Erosion was measured from 1 August, 1995 to 8 March, 1997 (585 days) by sediment accumulation near the fence where 72 PVC pipes were inserted into soil on a 4.65 m2 (50 ft3) grid area of each plot. The total rainfall recorded during this period was 2422.91 mm (95.3 in.). All cover crops reduced erosion over the complete competition free plot (control), although tall fescue performed poorly at the narrow strip width. There were no significant differences between grasses and legumes for erosion control. Winter annual crops provided significantly more erosion protection than summer growing-perennials. With the exception of tall fescue, narrow strip widths performed as well as wider strip widths. The results indicate that cover crops ryegrass, crimson clover, lespedeza and tall fescue controlled about 64, 61, 51 and 37% soil erosion respectively as compared to the control during the critical early years of stand development in SRWC hardwood plantations.
Article
Soil moisture is a key variable of the climate system. It constrains plant transpiration and photosynthesis in several regions of the world, with consequent impacts on the water, energy and biogeochemical cycles. Moreover it is a storage component for precipitation and radiation anomalies, inducing persistence in the climate system. Finally, it is involved in a number of feedbacks at the local, regional and global scales, and plays a major role in climate-change projections. In this review, we provide a synthesis of past research on the role of soil moisture for the climate system, based both on modelling and observational studies. We focus on soil moisture–temperature and soil moisture–precipitation feedbacks, and their possible modifications with climate change. We also highlight further impacts of soil moisture on climate, and the state of research regarding the validation of the relevant processes.There are promises for major advances in this research field in coming years thanks to the development of new validation datasets and multi-model initiatives. However, the availability of ground observations continues to be critical in limiting progress and should therefore strongly be fostered at the international level. Exchanges across disciplines will also be essential for bridging current knowledge gaps in this field. This is of key importance given the manifold impacts of soil moisture on climate, and their relevance for climate-change projections. A better understanding and quantification of the relevant processes would significantly help to reduce uncertainties in future-climate scenarios, in particular with regard to changes in climate variability and extreme events, as well as ecosystem and agricultural impacts.
Article
We have been making year-round measurements of mass and energy exchange in three cropping systems: (a) irrigated continuous maize, (b) irrigated maize–soybean rotation, and (c) rainfed maize–soybean rotation in eastern Nebraska since 2001. In this paper, we present results on evapotranspiration (ET) of these crops for the first 5 years of our study. Growing season ET in the irrigated and rainfed maize averaged 548 and 482 mm, respectively. In irrigated and rainfed soybean, the average growing season ET was 452 and 431 mm, respectively. On average, the maize ET was higher than the soybean ET by 18% for irrigated crops and by 11% for rainfed crops. The mid-season crop coefficient Kc (=ET/ET0 and ET0 is the reference ET) for irrigated maize was 1.03 ± 0.07. For rainfed maize, significant dry-down conditions prevailed and mid-season Kc was 0.84 ± 0.20. For irrigated soybean, the mid-season Kc was 0.98 ± 0.02. The mid-season dry down in rainfed soybean years was not severe and the Kc (0.90 ± 0.13) was only slightly lower than the values for the irrigated fields. Non-growing season evaporation ranged from 100 to 172 mm and contributed about 16–28% of the annual ET in irrigated/rainfed maize and 24–26% in irrigated/rainfed soybean. The amount of surface mulch biomass explained 71% of the variability in non-growing season evaporation totals. Water use efficiency (or biomass transpiration efficiency), defined as the ratio of total plant biomass (YDM) to growing season transpiration (T) was 5.20 ± 0.34 and 5.22 ± 0.36 g kg−1, respectively for irrigated and rainfed maize crops. Similarly, the biomass transpiration efficiency for irrigated and rainfed soybean crops was 3.21 ± 0.35 and 2.96 ± 0.30 g kg−1. Thus, the respective biomass transpiration efficiency of these crops was nearly constant regardless of rainfall and irrigation.