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Abstract

Agriculture contributes to a significant proportion of global emissions of greenhouse gases (GHG) but can also participate in climate change mitigation. The introduction of legumes in crop rotations reduces the dependence on N fertilizers and may mitigate the carbon (C) footprint of cropping systems. The aim of this study was to quantify the C footprint of six low-input arable cropping systems resulting from the combination of three levels of grain legumes introduction in a 3-yr rotation (GL0: no grain legumes, GL1: 1 grain legume, GL2: 2 grain legumes) and the use of cover crops (CC) or bare fallow (BF) between cash crops, covering two rotation cycles (6 years). The approach considered external emissions, on-site emissions and soil organic carbon (SOC) stock changes, and rioritized (i) field observations and (ii) simulation of non-measured variables with the STICS model, rather than default emission factors. As expected, fertilizers accounted for 80–90% of external emissions, being reduced by 50% and 102% with grain legumes introduction in GL1-BF and GL2-BF, compared to the cereal-based rotation (GL0-BF). Cover crops management increased machinery emissions by 24–35% compared to BF. Soil nitrous oxide (N2O) emissions were low, ranging between 205 and 333 kg CO2 eq. ha−1 yr−1 in GL1-BF and GL0-BF, respectively. Nitrate leaching represented the indirect emission of 11.6 to 27.2 kg CO2 eq. ha−1 yr−1 in the BF treatments and 8.2 to 10.7 kg CO2 eq. ha−1 yr−1 in the CC treatments. Indirect emissions due to ammonia volatilization ranged between 8.4 and 41.8 kg CO2 eq. ha−1 yr−1. The introduction of grain legumes strongly influenced SOC changes and, consequently, the C footprint. In the BF systems, grain legumes introduction in the rotations led to a significant increase in the C footprint, because of higher SOC losses. Contrarily, the use of cover crops mitigated SOC losses, and lowered the C footprint. These results indicated the need of CC when increasing the number of grain legumes in cereal-based rotations. Despite the multiple known benefits of introducing grain legumes in cropping systems our research highlights the need to consider soil organic carbon changes in environmental assessments.

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... The detailed estimation of GHG emissions from the agricultural sector allows for the identification of hot-spots, which provide information about which input causes the most significant effect on climate change due to the release of GHG [10]. The amounts of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) emissions from various sources are converted to one unit, such as kilograms of CO 2 eq , emitted to the atmosphere and this is defined as the C footprint [11]. The C footprint can be quantified on a land-area basis as a spatial C footprint, on an output basis defined as per yield unit of produced biomass C footprint or on a produced energy basis [12,13]. ...
... Greenhouse gas emissions can be divided into external and on-farm emissions [11]. These emissions are a result of production processes and application of agricultural inputs, such as pesticides, fertilizers, seeds, and combustion of diesel oil during farm operations [8,19]. ...
... These emissions are a result of production processes and application of agricultural inputs, such as pesticides, fertilizers, seeds, and combustion of diesel oil during farm operations [8,19]. Production and application of fertilizers is a significant contributor to the emissions of GHG from arable crop production [11,12,20,21]. Crop production should take into account the C footprint of the whole biomass energy production chain, in particular at the farm stage. ...
Article
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Currently, little data are available on greenhouse gas (GHG) emissions from sweet sorghum production under temperate climate. Similarly, information on the effect of bio-based waste products use on the carbon (C) footprint of sorghum cultivation is rare in the literature. The aim of this study was to evaluate the agronomical and environmental effects of the application of biosolids as a nitrogen source in the production of sweet sorghum as a bioenergy crop. The yield of sorghum biomass was assessed and the GHG emissions arising from crop production were quantified. The present study focused on whether agricultural use of sewage sludge and digestate could be considered an option to improve the C footprint of sorghum production. Biosolids—sewage sludge and digestate—could be recognized as a nutrient substitute without crop yield losses. Nitrogen application had the greatest impact on the external GHG emissions and it was responsible for 54% of these emissions. CO2eq emissions decreased by 14 and 11%, respectively, when sewage sludge and digestate were applied. This fertilization practice represents a promising strategy for low C agriculture and could be recommended to provide sustainable sorghum production as a bioenergy crop to mitigate GHG emissions.
... 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. Plaza-Bonilla et al. (2018) and Kaye and Quemada (2017) performed more balances that were complete (including ISFM); the latter included an estimation of albedo change under several scenarios. Both approaches used values from models or global meta-analyses to calculate direct and indirect N 2 O emissions or SOC changes. ...
... The components which contributed most (on average) to the standard deviation (Fig. S1) were N fertilizer (34.9%) and SOC (34.1%), followed by GHG direct (11.7%) and N 2 O indirect (11.0%). The values obtained by Plaza-Bonilla et al. (2018) for their estimations using the STICS (Simulateur multidiscplinaire pour les cultures standard) model for the SW of France (Garonne valley) ranged from 977 (with the use of CCs and with no grain legumes in the rotation) to 4,015 (with bare fallow instead of CCs and grain legumes included in the rotation) kg CO 2 eq ha À1 y À1 . These values are higher than those of the present study, perhaps as a result of different management (e.g., crops) and edaphoclimatic conditions or the fact that albedo changes were not considered. ...
... This fact is crucial in a context of increasing worldwide population and controversial when adjusted N rates are employed in an optimized N fertilization scenario. The values obtained by Plaza-Bonilla et al. (2018) ranged from 411 to 2,458 g CO 2 eq kg grain À1 using durum wheat, soybean, sunflower, sorghum or winter/spring pea as cash crops. The mitigation effect of the legume CC is mainly due to the reduction of synthetic N inputs in the subsequent cash crop as well as a decrease in indirect N 2 O emissions from NO 3 À leaching and an increase in C sequestration. ...
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.
... Diversification of the current N-reliant cereals and oilseeds by introducing alternative crops such as N 2 -fixing legumes is a key strategy for reducing the carbon footprint of cropping systems ( Jensen et al., 2012;Tian et al., 2021). The decreased carbon footprint with legume-based systems is mainly due to reducing the N fertilizer need Plaza-Bonilla et al., 2018;Sinclair and Vadez, 2012). ...
... In another study in a similar area, Gan et al. (2011b) found a 34% carbon footprint reduction in the durum wheat grown following two consecutive pulse crops compared to a cereal monoculture. In a temperate area of southwest France, Plaza-Bonilla et al. (2018) assessed the carbon footprint of six low-input arable cropping systems combining three levels of grain legumes in a 3-year rotation (control without grain legumes, and one or two grain legumes) and the use of cover crops or bare fallow between cash crops, managed under conventional tillage. The introduction of legumes into the cropping systems under bare fallow between cash crops reduced emissions by 50% and 102% during the production and transport of inputs and the use of energy for irrigation water, respectively, compared to the system without grain legumes, leading to lowered carbon footprint. ...
... In the study, the wheat carbon footprint was a reverse function of the amount of SOC gains, with each kg of soil carbon gain lowering the carbon footprint values by 0.0003 units, and a legume-included rotation increased SOC the most and decreased the carbon footprint the most. In a study in southwest France, SOC decreased significantly when grain legumes replaced cover crops in the rotations (Plaza-Bonilla et al., 2018). However, the authors observed a lowered carbon footprint in the cropping systems that included grain legumes when SOC changes were excluded from the analysis. ...
... Diversification of the current N-reliant cereals and oilseeds by introducing alternative crops such as N 2 -fixing legumes is a key strategy for reducing the carbon footprint of cropping systems ( Jensen et al., 2012;Tian et al., 2021). The decreased carbon footprint with legume-based systems is mainly due to reducing the N fertilizer need Plaza-Bonilla et al., 2018;Sinclair and Vadez, 2012). ...
... In another study in a similar area, Gan et al. (2011b) found a 34% carbon footprint reduction in the durum wheat grown following two consecutive pulse crops compared to a cereal monoculture. In a temperate area of southwest France, Plaza-Bonilla et al. (2018) assessed the carbon footprint of six low-input arable cropping systems combining three levels of grain legumes in a 3-year rotation (control without grain legumes, and one or two grain legumes) and the use of cover crops or bare fallow between cash crops, managed under conventional tillage. The introduction of legumes into the cropping systems under bare fallow between cash crops reduced emissions by 50% and 102% during the production and transport of inputs and the use of energy for irrigation water, respectively, compared to the system without grain legumes, leading to lowered carbon footprint. ...
... In the study, the wheat carbon footprint was a reverse function of the amount of SOC gains, with each kg of soil carbon gain lowering the carbon footprint values by 0.0003 units, and a legume-included rotation increased SOC the most and decreased the carbon footprint the most. In a study in southwest France, SOC decreased significantly when grain legumes replaced cover crops in the rotations (Plaza-Bonilla et al., 2018). However, the authors observed a lowered carbon footprint in the cropping systems that included grain legumes when SOC changes were excluded from the analysis. ...
Article
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A significant challenge in our time is to produce sufficient agricultural products on limited farmable land to meet the needs for food, feed, fiber, and industrial uses in the face of a changing climate. Conventional cropping systems mostly rely on inputs, such as fertilizers and pesticides, to boost crop yields. However, excessive inputs increase production costs and entail more direct and indirect emissions of greenhouse gases to the atmosphere that negatively impact the environment. Finding sustainable ways to increase crop productivity with little or no impact on the environment is the primary goal of modern agriculture. This review reveals that temporal-spatial diversification of crop rotations is critically needed to advance toward this goal sustainably. We find that (i) intensified crop rotations enhance carbon conversion from atmospheric CO2 into plant biomass and thus sequester more carbon into soil; (ii) diversified crop mixtures improve system resilience, i.e., increased resistance to pest/disease incidence and weed infestation, and faster recovery after removal of the abiotic or biotic stress; (iii) diversifying crop rotations increases crop yields at the system level with improved water and fertilizer use efficiencies; (iv) legume-based crop rotations reduce the need for synthetic nitrogen fertilizers thus lowering N2O and CO2 emissions to the atmosphere; (v) crop diversity leads to soil microbiome diversity that optimizes soil microenvironment, improving soil health. We believe that developing and adopting of diversified cropping systems are key factors for agricultural policy setting and a top priority for on-farm decision-making to increase crop productivity and enhance soil health, while reducing negative environmental impacts.
... Brentrup et al. (2000) proposed Tier 1 and Tier 2 models to estimate the most important nitrogen emissions (NH 3 ,N 2 O, 3 ) related to agricultural production in LCA. Tier 2 models, for instance, SALCA (Nemecek et al. 2016) and AGRYBALYSE (Koch and Salou 2015), and Tier 3 models, such as DAYCENT in Kim and Dale (2005), DNDC in Goglio et al. (2014) and STICS in Plaza-Bonilla et al. (2018), have also been used to estimate nitrogen emissions in LCA. ...
... Tier 3 models are more common for the NO − 3 leaching estimations. The complexity of the estimate can vary Kim and Dale (2005), DNDC in Goglio et al. (2014), STICS in Plaza-Bonilla et al. (2018) and Daisy, as aforementioned. Tier 1 models represented by different rates or EF have also been applied, for example, 0.25 for summer maize (Wang et al. 2007) and 0.26 for rice in Xue et al. (2016). ...
... Usually, when authors use mechanistic models, all nitrogen emissions are estimated using the same model (Goglio et al. 2014;Kim and Dale 2005;Li et al. 2016;Plaza-Bonilla et al. 2018). The scientific advantage of using mechanistic models is the calibration performed, making the results more credible and appropriate to the system. ...
Article
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Purpose Several models are available in the literature to estimate agricultural emissions. From life cycle assessment (LCA) perspective, there is no standardized procedure for estimating emissions of nitrogen or other nutrients. This article aims to compare four agricultural models (PEF, SALCA, Daisy and Animo) with different complexity levels and test their suitability and sensitivity in LCA. Methods Required input data, obtained outputs, and main characteristics of the models are presented. Then, the performance of the models was evaluated according to their potential feasibility to be used in estimating nitrogen emissions in LCA using an adapted version of the criteria proposed by the United Nations Framework Convention on Climate Change (UNFCCC), and other relevant studies, to judge their suitability in LCA. Finally, nitrogen emissions from a case study of irrigated maize in Spain were estimated using the selected models and were tested in a full LCA to characterize the impacts. Results and discussion According to the set of criteria, the models scored, from best to worst: Daisy (77%), SALCA (74%), Animo (72%) and PEF (70%), being Daisy the most suitable model to LCA framework. Regarding the case study, the estimated emissions agreed to literature data for the irrigated corn crop in Spain and the Mediterranean, except N 2 O emissions. The impact characterization showed differences of up to 56% for the most relevant impact categories when considering nitrogen emissions. Additionally, an overview of the models used to estimate nitrogen emissions in LCA studies showed that many models have been used, but not always in a suitable or justified manner. Conclusions Although mechanistic models are more laborious, mainly due to the amount of input data required, this study shows that Daisy could be a suitable model to estimate emissions when fertilizer application is relevant for the environmental study. In addition, and due to LCA urgently needing a solid methodology to estimate nitrogen emissions, mechanistic models such as Daisy could be used to estimate default values for different archetype scenarios.
... Augseku secībai jālieto labākie kultūraugu pārvaldības nosacījumi (N mēslošanas ātrums un laiks, augsnes apstrāde, ravēšana, apūdeņošana). Lauksaimnieki ievērojami nesamazina N mēslošanas līdzekļu izmantošanu pēc pākšaugu kultūrām, tādēļ rodas slāpekļa noplūžu risks(Plaza-Bonilla et al., 2017).Augsnes apstrāde ar dažādu pākšaugu kultūrām ir efektīvs ilgtermiņa pasākums SOC uzglabāšanai un iespējamai globālās sasilšanas mazināšanai(Plaza-Bonilla et al., 2018). Dziļi iesakņojušies pākšaugi, piemēram, cūku zirņu (Cajanus cajan) un hiacinšu pupas (Lablab purpureus), palīdz veidot augsnes struktūru un bioporas, kas uzlabo drenāžu un aerāciju augsnē(FAO, 2016).Faba pupiņu un kviešu rotācijas sistēmas rezultātā kviešu raža var tikt palielināta līdz 70%, vienlaikus samazinot vajadzību pēc slāpekļa mēslojuma(FAO, 2016). ...
... Pākšaugi spēj ficksēt N no 124-279 kg no hektāra. Audzējot kukurūzu pēc pākšaugiem, ražas palielinājums bija 0.5 t no ha, salīdzinot ar kukurūzu pēc kukurūzas(Plaza-Bonilla et al., 2018).EļļaugiRapsis ir izplatītākā eļļas augu kultūra Latvijā. Kultivētās platības ir palielinājušās, sākot ar 2004.Gadu. ...
Technical Report
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Pētījuma mērķis ir pilnveidot aramzemju un ilggadīgo zālāju apsaimniekošanas radīto SEG emisiju un CO₂ piesaistes uzskaites sistēmu un pilnveidot, kā arī izstrādāt jaunus metodiskos risinājumus SEG emisiju un CO₂ piesaistes aprēķiniem. Pētījumā izstrādātos risinājumus paredzēts izmantot nacionālās SEG inventarizācijas pilnveidošanai, novērtējot augsnes oglekļa uzkrājuma izmaiņas un SEG emisijas lauksaimniecībā izmantojamās zemēs. Pētnieciskie uzdevumi: 1. Pilnveidot aramzemju un ilggadīgo zālāju apsaimniekošanas radīto SEG emisiju un CO₂ piesaistes uzskaites un ziņošanas sistēmu. 2. Raksturot minimālas augsnes apstrādes ietekmi uz SEG emisijām LLU mācību pētījumu saimniecībā "Pēterlauki". 3. Pilnveidot minerālaugšņu oglekļa uzkrājumu modelēšanas instrumentu Yasso. 4. Iegūt galveno lauksaimniecības kultūru biomasas datus un izstrādāt biomasas pārrēķinu vienādojumus.
... To reduce carbon dioxide (CO 2 ) losses, different solutions have been proposed, ranging from paludiculture to wet extensive pasture, and to complete rewetting to a natural state [20]. Other conservation practices may also help reduce the negative environmental impacts of using peatlands for agricultural purposes, such as reducing tillage [21,22], cultivating cover crops [23], or raising the water table [24,25], which reduces the mineralization of organic matter [26][27][28]. ...
Article
Full-text available
Drained cultivated peatlands have been an essential agricultural resource for many years. To slow and reduce the degradation of these soils, which increases with drainage, the use of plant-based amendments (straw, wood chips, and biochar) has been proposed. Literature on the effects of such amendments in cultivated peatlands is scarce, and questions have been raised regarding the impact of this practice on nutrient cycling, particularly nitrogen (N) dynamics. By means of a six-month incubation experiment, this study assessed the effects of four plant-based amendments (biochar, a forest mix, willow, and miscanthus) on the release kinetics of water-soluble N pools (mineral and organic) in two histosols of differing degrees of decomposition (Haplosaprist and Haplohemist). The amendment rate was set at 15 Mg ha−1 on a dry weight basis. The N release kinetics were significantly impacted by soil type and amendment. Miscanthus and willow were the amendments that most reduced the release of soluble organic N (SON) and mineral N (minN). The addition of plant-based amendments reduced the total amount of released N pools during the incubation (cumulative N pools) by 50.3 to 355.2 mg kg−1, depending on the soil type, the N pool, and the type of amendment. A significant relationship was found between microbial biomass N, urease activity, and the cumulative N at the end of the incubation. The results showed that the input of plant-based amendments in cultivated peatland decreases N release, which could have a beneficial impact by decreasing N leaching; however, it could also restrict crop growth. Further research is needed to fully assess the impact of such amendments used in cultivated peatlands on N and on C fluxes at the soil–plant and soil–atmosphere interfaces to determine if they constitute a long-term solution for more sustainable agriculture
... However, a possible trade-off of legume cultivation is higher rates of nitrate leaching (Nemecek et al. 2008;Watson et al. 2017). Overall, agricultural experiments and life cycle assessment (LCA) studies suggest that increasing legume production in Europe could be an effective strategy to improve protein security whilst reducing environmental impacts (Nemecek et al. 2008;Karlsson et al. 2015;Stoate et al. 2015;Plaza-Bonilla et al. 2018). ...
Article
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Purpose There is an imperative to accurately assess the environmental sustainability of crop system interventions in the context of food security and climate change. Previous studies have indicated that the incorporation of legumes into cereal rotations could reduce overall environmental burdens from cropping systems. However, most life cycle assessment (LCA) studies focus on individual crops and miss environmental consequences of inter-annual crop sequence and nutrient cycling effects. This review investigates state-of-the-art representation of inter-crop rotation effects within legume LCA studies. Methods A literature review was undertaken, starting with a search for all peer-reviewed articles with combinations of ‘LCA’, ‘legumes’ and ‘rotations’ or synonyms thereof. In total, 3180 articles were obtained. Articles were screened for compliance with all of the following requirements: (i) reporting results based on LCA or life cycle inventory methodology; (ii) inclusion of (a) legume(s); (iii) the legume(s) is/are analysed within the context of a wider cropping system (i.e. rotation or intercropping). Seventy articles satisfying these requirements were analysed. Results and discussion We identified three broad approaches to legume LCA. Most studies involved simple attributional LCA disregarding important interactions across years and crops in rotations. N-fertilizer reduction through legume residue N carryover is either disregarded or the benefit is attributed to the following crop in such studies, whilst N leaching burdens from residues are usually attributed to the legume crop. Some studies applied robust allocation approaches and/or complex functional units to enable analysis of entire rotation sequences, accounting for nutrient cycling and break crop effects. Finally, a few studies applied consequential LCA to identify downstream substitution effects, though these studies did not simultaneously account for agronomic effects of rotational sequence changes. Conclusions We recommend that LCA studies for legume cropping systems should (i) evaluate entire rotations; (ii) represent nitrogen and ideally carbon cycling; (iii) for attributional studies, define at least two functional units, where one should encompass the multifunctional outputs of an entire rotation and the other should enable product footprints to be calculated; (iv) for CLCA studies, account for both agronomic changes in rotations and markets effects; (v) include impact categories that reflect hotspots for agricultural production.
... To reduce CO 2 losses, different management practices can be adopted, for example reducing tillage [Buragienė et al., 2019, Rutkowska et al., 2018 and cultivating cover crops [Plaza-Bonilla et al., 2018]. In addition to these methods, organic soils can be better preserved if the water table is elevated [Ferré et al., 2019, Joosten et al., 2012, Kløve et al., 2017 which reduces organic matter oxidation and release of CO 2 [Berglund and Berglund, 2011, Regina et al., 2015, Taft et al., 2018. ...
Thesis
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The goal of the experiment was to expose two types of organic soils incubated at two temperatures with five different plant-based amendments at two different dosage to see what was the impact of the different amendments on the release of nitrogen species as well as phosphorus and carbon.
... Analyzing whole rotation sequences from cradle-to-gate introduces the challenge of selecting an appropriate functional unit (FU) to represent multiple crop outputs. Previous rotation LCA studies have often related environmental burdens to highly simplified FU such as tons of dry matter or ha.yr (hectare per year) cultivated (e.g., Plaza-Bonilla et al., 2018). Such FU can be misleading, through disregard for the nutritional value of different crops and via the implication that less agricultural activity (and thus potentially productivity) per unit area is always environmentally favorable (Brankatschk, 2018). ...
Article
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Introducing legumes to crop rotations could contribute toward healthy and sustainable diet transitions, but the current evidence base is fragmented across studies that evaluate specific aspects of sustainability and nutrition in isolation. Few previous studies have accounted for interactions among crops, or the aggregate nutritional output of rotations, to benchmark the efficiency of modified cropping sequences. We applied life cycle assessment to compare the environmental efficiency of ten rotations across three European climatic zones in terms of delivery of human and livestock nutrition. The introduction of grain legumes into conventional cereal and oilseed rotations delivered human nutrition at lower environmental cost for most of the 16 impact categories studied. In Scotland, the introduction of a legume crop into the typical rotation reduced external nitrogen requirements by almost half to achieve the same human nutrition potential. In terms of livestock nutrition, legume-modified rotations also delivered more digestible protein at lower environmental cost compared with conventional rotations. However, legume-modified rotations delivered less metabolisable energy for livestock per hectare-year in two out of the three zones, and at intermediate environmental cost for one zone. Our results show that choice of functional unit has an important influence on the apparent efficiency of different crop rotations, and highlight a need for more research to develop functional units representing multiple nutritional attributes of crops for livestock feed. Nonetheless, results point to an important role for increased legume cultivation in Europe to contribute to the farm and diet sustainability goals of the European Union's Farm to Fork strategy.
... Aguilera et al., 2015;Fuentes et al., 2006;Gustafson, 2017), while others have included a broader range of impact categories (Abeliotis et al., 2013;MacWilliam et al., 2018;Nemecek, 2005). Some LCA studies have evaluated the role of pulses in crop rotations (MacWilliam et al., 2014;Plaza-Bonilla et al., 2018). Only a few studies have covered major parts or the entire supply chain, including packaging, processing and transport (Del Borghi et al., 2018;Fuentes et al., 2006). ...
Article
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Pulses are important components in sustainable diets and cropping systems. This study evaluated the environmental impact of cultivation of five Swedish pulses (yellow peas, grey peas, faba beans, common beans and lentils) in a life-cycle perspective. The impact of selected Swedish pulses (conventional or organic) was then compared with that of imported pulses in Sweden, including contributions from processing, packaging and transport. The influence of origin and transportation mode and differences between home cooking and canned pulses (Tetra Recart) were considered. The impact of cultivation differed considerably between the Swedish pulses, ranging between 1.6-3.3 MJ, 0.18-0.44 kg CO2e and 3.1-5.9 m² land use per kg dry product. In general, pulses with higher yield had lower cultivation impact. However, intercropping pulses and cereals showed potential to reduce environmental pressures, despite low per-hectare yield of the pulse crop. When processing, packaging and transport were included, the variation in impact was even greater, illustrating the importance of including post-farm activities in the assessment when comparing pulses. Emissions of greenhouse gases per kg cooked product ranged from 0.1 kg CO2e for Swedish pulses purchased dry to 0.8 kg CO2e for canned beans. Long transport distances contributed considerably to energy use and climate impact, particularly when the pulses were processed and packaged far from the final destination, due to high moisture content of the product. Origin affected also biodiversity impact, since the risk of species losses differs widely between ecoregions. Pesticide use is reported to be high in many countries, and residues are commonly found in many pulses. However, lack of data prevented comparisons of ecotoxicity or pesticide use for different imported pulses. The important role of origin and post-farm activities, in particular transport, for the environmental impact of pulses calls for increasing awareness and action among purchasers, food industries, and consumers to achieve more sustainable sourcing of pulses.
... While knowledge of soil erosivity and wind erodibility can be used to counter soil erosion (Blanco & Lal, 2010;Lal & Elliot, 2017), reducing and compensating for the carbon lost through the oxidation of organic matter can be more challenging. Soil management practices such as reduced tillage (Rutkowska, Szulc, Sosulski, Skowrońska, & Szczepaniak, 2018;Šarauskis et al., 2019), traffic control (Antille, Chamen, Tullberg, & Lal, 2015) and the use of cover crops (Plaza-Bonilla, Nogué-Serra, Raffaillac, Cantero-Martínez, & Justes, 2018) have been found to reduce soil CO 2 emissions. Using straw as a soil amendment has produced mixed results, as the balance between carbon priming and sequestration remains unclear (Fang, Nazaries, Singh, & Singh, 2018;Shahbaz et al., 2017b;Shahbaz, Kuzyakov, & Heitkamp, 2017a;Wu et al., 2019). ...
Article
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Peatlands are known to perform essential economical, societal and regulating functions. Once they are drained to provide optimal crop growth conditions, however, a series of degradation processes is generated. Wind and water erosion, subsidence and soil organic matter oxidation are the main causes of degradation observed in cultivated histosols. This study evaluated the decomposition dynamics and chemical changes of three biomass crops during an in‐situ incubation in a cultivated histosol. The decomposition dynamics characterized in the field study were then used in a simulation to determine if sustainability could be reached by using biomass crops as a soil amendment. The results showed that an exponential decay fitting curve best represented the weight loss of sorghum (Sorghum bicolor (L.) Moench) in the in‐situ bags over time, while a logistic fitting curve best represented that of miscanthus (Miscanthus X giganteus) and willow (Salix miyabeana). The quality of the crop determined the initial and overall decomposition dynamics observed. The loss of carbon from the crushed biomass crop was much more important in sorghum than in miscanthus and willow. The long‐term simulation of histosol amendment revealed that using miscanthus and willow at input rates of 7.5 and 10 T of carbon per year, respectively, would be sufficient to ensure sustainability. Improving knowledge on carbon loss in cultivated histosols as related to soil and crop management would help in developing a soil amendment program at the farm scale. In addition, more knowledge is needed to determine the impact of long‐term and successive amendment with biomass crops on the physical and biochemical properties of histosols.
... It is made available under a France with a legume in the rotation was associated with the lowest per kg oil emissions, despite very low levels of N having been applied. Lower N inputs were required due to the presence of residual soil N following legume cultivation 29 . ...
Preprint
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Sunflower (Helianthus annuus L.) is the largest source of vegetable oil in Europe and the fourth largest globally. Intensive cultivation and post-harvest steps contribute to global food-systems greenhouse gas (GHG) emissions. However, variation between production systems and reporting disparity have resulted in discordance in previous emissions estimates. To assess systems-wide GHG implications of meeting increasing edible oil demand using sunflower, we performed a unified re-analysis of primary life cycle inventory data, representing 995 farms in 11 countries, from a saturating search of published literature. Total GHG emissions varied from 1.1 to 4.2 kg CO2-equivalent per kg oil across systems, 62% of which originated from cultivation. Major emissions sources included diesel- and fertiliser-use, with irrigation electricity contributing most to between-systems variation. Our harmonised, cross-study re-analysis not only enabled robust comparisons and identification of mitigation opportunities across sunflower oil production systems, but also lays the groundwork for comparisons between alternative oil crops.
... This was due to differences in input and management practices adopted, as CF and energy input were positively related to each other (Zhang et al., 2016). An increase in the number of crops in crop rotation significantly increased the CF over M-F rotation (Plaza-Bonilla et al., 2018). Prechsl et al. (2017) also reported slightly higher GWP due to higher energy demand in intensified cropping systems compared to crop fallow systems. ...
Article
Achieving a circular economic model in agriculture and meeting the food requirement of the growing population is a global challenge. The task is much more daunting in the Eastern Himalaya where low productive maize–fallow is a predominant production system. To enhance system productivity and energy use efficiency while maintaining environmental sustainability and economic profitability, therefore, energy-efficient, low carbon footprint (CF; CO2-e) and profitable short duration crops must be made an integral part of the maize fallow system. Thus, six cropping systems viz., maize–fallow, maize–French bean, maize–soybean, maize–black gram, maize–green gram, and maize–toria were evaluated for seven consecutive years (2011–2018) to assess their energy requirement and efficiency, carbon footprint (CF; CO2-e), economic returns and eco-efficiency. The results revealed that the maize–French bean system had the highest system productivity (11.4 Mg ha⁻¹), energy productivity (17.9), energy profitability (15.9) and non-renewable energy use efficiency (9.97). The maize–French bean system had also the highest net profit (US$ 3764.5 ha⁻¹) and benefit to cost ratio (2.54). The energy consumed under different inputs/activities across the cropping systems for chemical fertilizers, diesel and machinery ranged from 50.0–62.7%, 17.3–20.8% and 4.6–15.4%, respectively. The maize–fallow system had the highest CF (0.34 kg CO2 e per kg grain) while, the maize–French bean system had the lowest CF (0.19 kg CO2 e per kg grain). The maize–French bean system had also considerably increased eco-efficiency both in terms of energy use (US$ 0.23 MJ⁻¹) and (US$ 1.78 per kg CO2 e) over maize–fallow system. Thus, the study has suggested that maize–French bean system is energy-efficient, economically viable and environmentally safer systems to utilize maize fallow and improve food security, may help in achieving green/circular economy.
... Reduction in fertiliser use, reduced tillage intensity and introduction of crop rotation may reduce GHG emissions from agricultural land (Oertel et al. 2016). By sowing legumes in rotation with cereals, crop rotation can reduce GHG emissions (Plaza-Bonilla et al. 2018) while also improving carbon (C) sequestration (Poeplau et al. 2015). For instance, the demand for N fertiliser decreases without reducing yield or grain quality (Plaza-Bonilla et al. 2017). ...
... In order to study such innovative CS and highlight their potential benefits, new indicators should be taken into account, considering an economic value of the ecosystem services provided by diversification. For example, the strong decrease of N-fertilizer amount in VLI systems (Fig.1D) suggests that they could have a reduced environmental impact compared to LI systems or the REF considering both greenhouse gases emissions and water pollution, as ever demonstrated (Plaza-Bonilla et al. 2018). For this reason, agroecological CS able to deliver on reduce N-fertilizer inputs would require reward. ...
Conference Paper
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Spatial and temporal diversification of cropping systems (CS) is recognized as a relevant alternative to move towards sustainable agriculture. It could be achieved by several agronomic levers, and more particularly by lengthening and diversifying crop rotations notably by the introduction of legumes, crop mixtures and multi-services cover crops (CC) during fallow periods. In this study, we assumed that diversified CS could reduce the use of pesticides and N fertilizers in South-West France context, while maintaining the economic profit and improving the overall performances of CS in terms of ecosystem services. After designing CS varying by their degree of agro-ecologization, our objective was to illustrate their strengths and weaknesses and discuss the possible way to improve their performances for favoring their adoption by farmers in the future.
... At the same time, agricultural practices are also responsible for the mitigation of various greenhouse gases. In this line, the inclusion of legumes in the cropping system provides numerous benefits including decreased dependence on nitrogenous fertilizers along with the mitigation of carbon footprints (Plaza-Bonilla et al. 2018;Meena et al. 2018b). ...
Chapter
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The climatic variations and swiftly increasing the world’s population are crucial drivers of universal famines and lead to the stern food insecurity. These factors affect all the magnitudes of food collateral, such as food accessibility, consumption, reliability, and constancy, and also strengthen additional calamities allied with health concerns of plants, animals, and environment. Although applications of agrochemicals to the soil largely contributed to increased food production, extensive use of these leads to the nutrient disparity and environmental hazards resulting in considerable economic losses. Consequently, it is utmost important to manage the application of agrochemicals with the aim of increased food production in environmental as well as economical unthreatened manner. Legumes have a great potential to enhance crop diversity as well as productivity and to reduce dependence on exterior inputs as legumes are well known for their illustrious capabilities such as nitrogen (N) fixation by biological means, increase in soil organic matter (SOM), efficient roles in nutrient and water retention, and improvement in soil properties which contribute to recover soil health. These manifold abilities of legumes make them potential candidates for management of agriculture in a sustainable way. The upshots of sustainable agriculture can be optimistic for higher food production and to ensure future food availability in an eco-friendly manner by reducing the usage of agrochemicals and maintaining the nutrient balances in the soil.
... At the same time, agricultural practices are also responsible for the mitigation of various greenhouse gases. In this line, the inclusion of legumes in the cropping system provides numerous benefits including decreased dependence on nitrogenous fertilizers along with the mitigation of carbon footprints (Plaza-Bonilla et al. 2018;. ...
Book
Fertilizers have been used extensively around the globe since the Green Revolution, due to the high subsidies. However, extensive fertilizer use exacerbates soil degradation and causes yield stagnation, and as a result threatens food security and soil sustainability, especially in developing countries. This means that sustainable soil and environmental management are vital to provide food and nutritional security for present and future generations. This has led to the International Union of Soil Science (IUSS) declaring 2015-2024 the International Decade of Soils. This book focuses on the impact of sustainable management of soil and environment on improving the functioning of soil-ecosystems and agronomic productivity, and also discusses food security, nutrient cycling, recent advances in INM technologies, eco-friendly cultivation, agricultural practices to reduce greenhouse gas (GHG) emissions, as well as conservation agriculture and its effects, and strategies for soil sustainability. Offering a comprehensive overview of management in the context of the sustainability of soil and the agroecosystems that it supports, it demonstrates the options available and provides insights into restoring soil health and matching soil nutrient supply with crop demand to ensure nutritional security in an eco-friendly environment.
... de Jesus Pereira et al. (2021 found that the CF to produce 1 kg of intercropped vegetables was approximately five times lower than that in monocultures. In addition, a case study indicated that the use of cover crops mitigated SOC losses and lowered the CF in diverse rotation -Bonilla et al., 2018). ...
Article
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Introducing cover crops into crop rotation systems is widely practiced to enhance the sustainability of agricultural production, but comprehensive evaluations of farmlands in cover crop-maize rotations on the North China Plain (NCP) from environmental, economic and net ecosystem economic benefits (NEEB) perspectives have rarely been performed. Therefore, a field experiment was conducted to compare economic benefits (EB), greenhouse gas (GHG) emissions, reactive nitrogen (Nr) losses, soil nutrient cycling values (SNV) and NEEB in three farming systems. The farming systems included a conventional wheat-maize (WM) rotation system, a government-promoted monoculture maize (MM) system and an innovative Orychophragmus violaceus (O. violaceus)-maize (OvM) rotation system. The OvM rotation system achieved more EBs from the maize season but lower annual profits than the WM system, with 68.29% lower GHG emissions and 39.33% lower Nr losses. In addition, the highest SNV was achieved in the OvM rotation system, which was 700.18% and 116.97% higher than those in the WM and MM systems, respectively. Furthermore, the NEEB of the OvM rotation system was 61.92% and 29.31% higher than those of the WM and MM systems, respectively. In conclusion, the OvM rotation is recommended as a sustainable and cleaner maize production farming system for the NCP and other regions with similar ecological conditions because it led to lower annual GHG emissions and Nr losses, as well as higher SNV and NEEB than the other farming systems.
... Organic and locally produced chickpea presents two main benefits compared to similarly produced barley: It is richer in protein, so it can help meet the animals' protein requirement according to the organic standards, and fixes atmospheric nitrogen, so contributing to reduced N 2 O emissions and mitigating the carbon footprint of cropping systems [40]. In this study, we aimed to demonstrate the benefits of using chickpea as energy-protein feed in diets for native bulls in terms of growth performance and economic return. ...
Article
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We assessed the effects of inclusion of chickpea from 24 to 21%, as feed basis, in diets for organically reared bulls. Sixteen young bulls (270 ± 6.4 days of age; 246 ± 0.13 kg in weight) belonging to a native Italian breed (Maremmana) were randomly assigned to two dietary treatments. The control diets were based on mixed grass hay, maize meal, and barley meal. In the experimental diets, barley was equally substituted by locally produced chickpea. Animals were weighed every 2 weeks until the prefixed slaughtering weight (630 kg). Plasma metabolites were measured at the 1st, 7th, and 14th month of the experiment. Chemical composition, colour, shear force, and water holding capacity of meat were assessed on Longissimus thoracis et lumborum 7 days after slaughter. The chickpea-fed animals showed a significantly greater average daily gain (1064 vs. 1168 kg/day), a shorter growing phase (364 vs. 335 days), and a better carcass conformation. Plasma metabolites and meat quality were not influenced by the treatments. The better growth performance and carcass quality of the chickpea fed bulls resulted in a higher economic profit for the chickpea-based diets. Results suggest that chickpea may allow sustainable performance improvement of native breeds within their traditional farming systems.
... The boundaries were established to measure CF at field level (Plaza-Bonilla et al., 2018). For estimation of the greenhouse gases (GHGs) emissions, a boundary was established from the production to application of different farming practices (fertilizers, pesticides, irrigation, tillage, planting, and harvesting) (Gan et al., 2011a) (Fig. 1). ...
Article
Improving agriculture intensity implies desirable crop productivity at a noteworthy environmental cost. A comprehensive comparative analysis of carbon footprint (CF) and greenhouse gases emissions (GHGs) of the two major and contrasting cropping systems is of paramount importance, which is rarely done. The life-cycle assessment (LCA) was performed to assess the alleviating potential, and differences in CF of wheat and maize crops within irrigated and rain-fed cropping systems. The two 25-year experiments included a winter wheat-summer maize cropping under irrigated conditions with five treatments: Control without fertilization (CK), combination of nitrogen and phosphorus (NP), NP plus potassium (NPK), NPK plus crop straw (S) (SNPK), and dairy manure (M) integrated with NPK (MNPK); and a winter wheat-summer fallow system under rain-fed conditions with four treatments as stated above except SNPK. Results showed that high N input increased total GHG emission and CF across cropping systems in question. The mean GHGs’ emissions ranged from 2000.9 to 7586.7 kg ha⁻¹ for irrigated cropping system, and 192.5–1834.6 kg ha⁻¹ for rain-fed cropping system. Over the 25 years, without considering SOC gain, the mean CF values for irrigated and rainfed cropping systems ranged from 0.51 to 0.62 and 0.16–0.50 kg CO2 kg⁻¹ of grain, respectively. When SOC gains were involved in, the mean CF values for the two investigated cropping systems ranged from 0.22 to 0.42 and −0.26 to 0.29 kg CO2 kg⁻¹ of grain, respectively (in exclusion of SNPK). SOC sequestration played an important part in mitigation of CF. Our research may provide valuable information to promote the optimization of agricultural practices and guide the design/choice of future farming systems in the region and where with similar environmental conditions.
... The contribution of the agriculture sector towards total GHGs production is substantially high, amounting to around 13.5% of the total GHGs CO 2equivalents (eq.) (IPCC, 2007). Use of petroleum products for performing on-farm operations, elevated soil N 2 O flux from sites where high nitrogenous fertilizers are applied asynchronously with plant N uptake and changes in land use pattern are some of the major reasons behind the GHGs production from arable crop production (Jensen et al., 2012;Plaza-Bonilla et al., 2018;Dahiya et al., 2018). The consumption of fertilizer chemicals (major fertilizer nutrients viz., nitrogen (N), phosphorus (P), and potassium (K) have increased worldwide after the inception of the green revolution to a record high of 192 million tons ( (Bajiya et al., 2017;Behera et al., 2020). ...
Chapter
The ever-increasing population has intensified farming practices resulting in excessive use of farm inputs including fossil fuels and agrochemicals. Agriculture has proven to be one of the significant contributors, contributing 13.5% to the global greenhouse gases (GHGs) pool while still being a potent climate change mitigating option. Sustainable crop production keeping into account the pace of climate change will be a mammoth task to execute in the years to come. Apart from being a major source of dietary protein for humans and feed for animals, legumes play a major role in fixing atmospheric nitrogen (N), enhancing soil water retention and nutrient cycling. Legumes offer a wide array of functions including reducing dependence on N2 fertilizer, their strong influence soil organic carbon content and lowering agricultural born greenhouse gas emissions reduce ecological foot print of non-legume based cropping systems. They play pivotal roles in the food system, production system and cropping system levels. Therefore, it might be worthwhile to introduce legumes into crop rotations for the development of agroecosystem diversity, provide environmental and socio-economic benefits.
... At the same time, agricultural practices are also responsible for the mitigation of various greenhouse gases. In this line, the inclusion of legumes in the cropping system provides numerous benefits including decreased dependence on nitrogenous fertilizers along with the mitigation of carbon footprints (Plaza-Bonilla et al., 2018). ...
Article
Full-text available
Development was conventionally driven by one particular need, without fully considering the wider or future impacts. This kind of approach has now been considered to be responsible for the economic and environmental catastrophes that humans are facing: from large scale financial crises caused by irresponsible banking to the changes in global climate resulting from our dependence on fossil fuel based energy sources. Soils provide essential ecosystem services such as primary production, regulation of biogeochemical cycles (with consequences for the climate), water filtration, resistance to diseases and pests, and regulation of above-ground biodiversity. Changing of the climate systems is unequivocal. Adaptation to global climate change through improved soil quality by adoption of improved management practices is key to maintaining sustainable agricultural production. A holistic approach to soil management as the engine for increasing productivity by increasing resource use efficiency and making agriculture environmentally compatible is more important than ever before. Strategies of greenhouse gas emission reduction include those that increase the use efficiency of inputs. Herein, we discussed how management and protection of soil resources can contribute to sustainable intensification throug
... To comprehensively and integrally assess the environmental impacts caused by both the production system and the resources consumed, Life Cycle Assessment (LCA) (IS0 14040, 2006) is applied as a methodology to evaluate environmental impacts of agricultural systems (González-García et al., 2016Noya et al., 2018;Vásquez-Ibarra et al., 2021a, 2021bWeidema, 2019). The state of the art in farming systems indicates that increased legume production in Europe could represent an effective strategy to improve protein security and reduce environmental impacts (Costa et al., 2020;Karlsson et al., 2015;Plaza-Bonilla et al., 2018). ...
Article
Crop diversification, as a sustainable land management practice, is a potential strategy to face soil degradation, climate change and food security, being the incorporation of legumes in cereal rotation systems, a strategy that improves soil nutrient levels. In a context of sustainable agriculture, this manuscript aims to evaluate the effect of lupin cultivation from an environmental and economic perspective in Galician winter wheat-based rotation systems. The life cycle analysis (LCA) methodology was applied for three rotation systems over a six-year period: lupin + wheat + oilseed rape (RA1), lupin + potato + wheat (RA2), and lupin + wheat + oilseed rape + maize (RA3). The general approach of this study was to collect primary data associated with the rotation crops to quantify their environmental impacts and economic benefits and to identify their advantages or disadvantages. Comparing and contrasting the environmental profiles based on three functional units: hectare land (ha), financial indicator (gross margin, €) and yield production (kg of wheat grain) allows a robust evaluation of each crop rotation system. Relating to rotations without lupin, the results indicate that for the impact categories evaluated, the introduction of lupin proved to be favourable with notable reductions of 64% and 30% in the environmental categories of Global Warming and Marine Eutrophication, respectively. Moreover, favourable economic consequences were evident in rotations RA1 and RA2 with a 19% and 51% increase in financial indicators, respectively, but with a marginal reduction of 2% in gross margin in RA3. This study motivates stakeholders to understand the environmental impacts of diversification strategies in agricultural systems and serves as a baseline to address the assessment of the social aspects of these systems for a complete sustainability perspective.
... Similarly, conservation-effective production systems have improved the resilience of ecosystem services under different climatic conditions across the globe [36,107]. Conservation-effective farm practices reduce carbon footprint [30,72,48], increase economic output [25,6], resource use efficiency [26,107], and energy productivity [50,48]. Various studies have quantified the GHG emission in terms of carbon footprints of different crops [30,50], energy use patterns in different cropping and soil management scenarios [30,109,44] across the world. ...
Article
The conventional agricultural production systems are facing multiple challenges of yield plateauing, low farm profitability, energy intensiveness, unemployment, and environmental unsustainability. Hence, four production scenarios viz., integrated organic management, integrated crop management, conservation agriculture, and conventional system and three cropping system viz., maize-mustard, maize + cowpea-mustard, and pigeon pea-wheat were tested to examine their energy, carbon, and economic feasibility for the development of environmentally clean production system. The integrated crop management system recorded significantly higher system productivity (12621 kg ha⁻¹), net energy (471632 MJ ha⁻¹), and economic returns (US$ 2079 ha⁻¹). However, the integrated organic management system resulted in the highest energy productivity (0.83 kg MJ⁻¹), eco-efficiency (0.18 US$ MJ⁻¹ha⁻¹), carbon economic efficiency (2.47 US$ ha⁻¹CO2-eq), and carbon sustainability index (37.5), and the lowest greenhouse gas intensity (0.06 kg grain kg⁻¹CO2eq). Among the cropping systems, maize + cowpea-mustard produced 32.6% higher net energy and 31.1% higher energy use efficiency over the maize-mustard system, respectively. However, the pigeonpea –wheat system recorded the highest carbon economic efficiency (1.41 US$ kg⁻¹ CO2eq), and carbon sustainability index (24.4). The greenhouse gases intensity was positively (+) correlated with specific energy but negatively (-) correlated with carbon ecological efficiency, C-gain, and carbon sustainability index. Thus, the study suggested that the intensified cropping is profitable and environmentally clean systems either in integrated crop management or in integrated organic management scenarios.
... The effect of cover cropping on N 2 O emissions has been evaluated under different environmental conditions and management practices Pimentel et al., 2015;Plaza-Bonilla et al., 2018). Some meta-analyses show that cover crops (particularly legumes) increase N 2 O emissions (Basche et al., 2014;Kaye & Quemada, 2017). ...
Article
Full-text available
Cover cropping is an approach used to improve soil quality and increase N inputs in agricultural systems, but also may enhance greenhouse gases (GHG) emissions. Here, a 47‐d incubation study was conducted to track the decomposition process and evaluate GHG emissions and its drivers, as well to calculate the C costs of residue‐derived N released following the addition of residues from cover crops (pigeon pea, cowpea, lablab bean, vetch, and black oat) and maize under two water‐filled pore space levels (40 and 70% WFPS). For both WFPS levels, the increase in cumulative CO2 fluxes in plots which received residues is mainly related with the increment of potentially mineralizable C. Crop residues increased the global warming potential (GWP) under both WFPS levels, with CO2 emissions accounting to at least 98% of the GWP at 40% WFPS. For 70% WFPS, the GPW increment was driven by a notable increase in N2O emissions. The contribution of CH4 in the GWP emissions was negligible for all the crop residues evaluated. Principal component analysis highlighted that the optimal conditions for production and release are specific for each GHG. The cleaner N source was cowpea at 40% WFPS, which produced only 17.7 kg CO2‐eq kg–1 N mineralized, compared to vetch residues which produced 233 kg CO2‐eq kg–1 N mineralized. To integrate agronomic and climate change mitigation perspectives, we suggest considering the C costs of the residue‐N released when choosing a cover crop. This article is protected by copyright. All rights reserved
... all direct and indirect emissions of GHG) of innovative crop 3-year rotations based on the introduction of grain legumes in comparison to the traditional rotation based on cereals and sunflower in south-west France.The authors observed a greater C footprint of the rotations, including grain legumes, when cover crops were not used as a result of SOC losses. However, as stated, that process is finite until SOC reaches a new equilibrium while significant amounts of GHG emissions are avoided thanks to the N-fertilizer savings when adopting legumes(Plaza-Bonilla et al., 2018). ...
... Future research should broaden the geographic coverage of the assessment with the CS framework to other regions across Europe. In areas where the CS framework has not yet been applied, such as in south-western Europe, the impacts of integrating legumes into CS could be different, as indicated for example by contrasting findings about higher carbon footprints and N leaching in south-western France (Plaza-Bonilla et al., 2018). The framework could be further modified to integrate cover crops along with additional environmental indicators such as carbon sequestration and yield stability. ...
Thesis
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Legumes provide high quality protein for food and feed as well as other ecosystem services, but it is still challenging to use them to meet the growing global demand for protein, partly because European farmers consider their cultivation unprofitable and risky. This thesis aims to design legume-supported cropping systems and assess their environmental and economic impacts along with their production risks in European agriculture. The approaches used included (i) the development of a framework to design cropping systems and to assess impacts of management, (ii) modelling the impact of integrating legumes into cropping systems and assess trade-offs, (iii) the development of a statistical method to quantify crop yield stability independent of the mean yield, (iv) assessing grain legume yield stability statistically compared to other crops using data from long-term experiments, and (v) participatory methods to re-design legume-supported cropping systems. The framework consists of a rule-based rotation generator and algorithms to calculate impact indicators, following a three-step approach: (i) generate rotations, (ii) evaluate crop production, and (iii) assess cropping systems. It was used to design and assess legume-supported cropping systems in five case study regions in Europe and to identify trade-offs between economic and environmental impacts. On average, the generated cropping systems with legumes reduced N2O emissions by 18 % and 33 % and N fertilizer use by 24 % and 38 % in arable and forage systems, respectively, compared to systems without legumes. Grain legumes increased gross margins in two of five regions and forage legumes in all three study regions. A scale-adjusted coefficient of variation was developed as a stability measure that accounts for mean yield differences. Using data from five long-term experiments in northern Europe, this method showed that yield instability of grain legumes (30 %) was higher (P < 0.001) than that of autumn-sown cereals (19 %), but lower (P < 0.001) than that of other spring-sown broad-leaved crops (35 %), and only slightly greater (P = 0.042) than spring-sown cereals (27 %). The combination of on-station and on-farm trials with crop rotation modelling was useful when re-designing cropping systems. Nine agronomic practices were identified for improving grain legume production at the farm level. In this thesis, it is shown that legumes can provide both economic and environmental benefits, the instability of yields is similar to other spring crops and that cropping systems can be re-designed effectively in a co-learning process with farmers.
... Life Cycle Assessment (LCA) principles are taken into account in CF calculations throughout the production process, e.g., production inputs, transport, distribution, and productscraps disposal. CFs are used in agriculture, especially when growing crops such as beans and grains (rice, wheat, and corn) [6][7][8][9][10], potatoes and sugarcane [11], and organic vegetables [12,13]. In previous studies, however, CF calculation was not applied to horticulture because of the long production time and harvest periods involved. ...
Article
Full-text available
The study of the carbon footprint (CF) of agricultural crops provides important information that can help achieve low-carbon agriculture, but there are still very few studies on CF for farmed fruit. This research emphasized CF calculation for mangosteen crops at the farm level. The study was carried out on 55 mangosteen farms that belong to the Tambol Troknong Community Enterprise in the Khlung District of Chanthaburi Province, Thailand. The findings revealed that the product CF average was 1.71  1.38 kg CO 2 eq/kg, and the farm CF was 15,623.41  16,981.27 kg CO 2 eq/ha. The total CF was determined from six sources, including the application of substances such as fertilizers (organic and inorganic), pesticide and herbicide, as well as from the use of electricity and fuel. We found that most of the CF was direct emissions from electricity usage, which accounted for as much as 85.33% of the total CF. Thus, this research provides important information on the CF and level of production inputs. We developed guidelines for reducing greenhouse gas emissions from mangosteen production in the area.
... Soil disturbance stimulates carbon losses, even shallow tillage and hoeing to control weeds can have negative impacts that might partly counteract the positive effects of significant carbon inputs, e.g., green manure and crop residues. For instance, introducing grain legumes without cover crops showed higher carbon losses than when only having cover crops without the grain legumes (Plaza-Bonilla et al., 2018). The combination of crop patterns and diversity may be an effective way to restore soil functioning. ...
Article
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Diversification of cropping and farming systems is a central agroecological principle, which may improve resource use efficiency, reduce pests and diseases, diversify income sources, and enhance the resilience of the production. The main objective of this study was to identify challenges related to the sustainability of organic cropping systems that were diversified according to one or several of the following practices: diverse crop rotation, integration of cover crops, and intercropping. The sustainability assessments were made using a multi-criteria decision aid method (MCDA) and a framework based on the FAO Sustainability Assessment of Food and Agricultural Systems (SAFA) guidelines. Social, economic and environmental aspects were integrated in the sustainability assessments and combined with semi-structured interviews to identify and discuss farmer's perceptions of barriers to crop diversification and sustainability transition. The results showed that diversified organic cropping systems could achieve high overall sustainability, especially in the environmental dimension thanks to non-inputs of pesticides or mineral fertilizers and efficient use of resources. On the other hand, social and economic dimensions were more variable, with challenges of lower sustainability in profitability and management complexity for several of the diversified cropping systems. Limited access to knowledge, technology and markets for minor crops, and concerns about the consistency of policies were highlighted by farmers as barriers for crop diversification. We discuss how the identified challenges can be overcome and argue that fostering collaboration among stakeholders may increase investment capacity and improve access to new or alternative markets, thereby stimulating transitions toward more diversified and sustainable cropping systems.
Article
Crop rotations and residue management contributes to the sustainability of the soil and environment and reduction of fertiliser use. However, appropriate crop and residue level combinations have yet to be determined to maximise productivity, while ensuring the preservation of soil resources in different agricultural production systems. The experiment evaluated production and soil chemical properties in bean after three preceding crops (bread wheat, durum wheat, and corn) with four residue incorporation levels (0%, 50%, 100%, and 200%) under irrigation conditions in volcanic soil in south central Chile. A split plot design with four replicates was used. Results indicated that the production of grain and crop residue of bean were higher after corn and durum wheat. The preceding crop also affected some soil chemical properties, especially after the corn crop. The production parameters were not affected by the different residue levels; these had a positive effect on the concentrations of N, K, and Mg and an effect that was directly proportional to the residue level being used. Correlations between soil chemical properties were also established, consistently highlighting the increase in the concentration of the nutrients N, K, Ca, and Mg associated with increases in organic matter content.
Article
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Identification of the appropriate tillage production system having lower energy use and carbon-emission, and better crop productivity is becoming increasingly important to maintain the environmental sustainability. In the present study, a comprehensive system analysis was performed for four consecutive years (2016 to 2019) in three major agroecosystems of eastern India: eastern Indo-Gangetic plain, coastal agroecosystem, and hill & plateau region. Six rice-based production systems with different levels of farm mechanization viz., a) fully mechanized tillage, b) partly mechanized tillage and c) traditional tillage were considered in the analysis. The main aim was to assess the energy flow and carbon-balance of diverse tillage production systems. Among different sources of total input energy, chemical fertilizer accounted for highest energy used in partly mechanized tillage (44%) and mechanized tillage (38%) followed by diesel, irrigation water, plant protection chemical, seed and electricity. Seed, human, animal energy and farmyard manure accounted for 21, 20, 16 and 16%, respectively, of the total energy input in traditional tillage. Maximum energy input (52161 MJ ha⁻¹) was noted in mechanized tillage and minimum with traditional tillage (16879 MJ ha⁻¹). Cropping systems followed in eastern Indo-Gangetic plain were more energy-intensive (50908 MJ ha⁻¹) compared to coastal-ecosystem (27459 MJ ha⁻¹). On average, the total energy output in mechanized tillage (395245 MJ ha⁻¹) were 0.3 and 2.4 times higher over partly mechanized and traditional tillage, respectively. Overall, the present results indicated that partly mechanized tillage and coastal agroecosystem were the most energy-efficient with an energy ratio of 8.88 and 9.81, respectively. Mechanized tillage was 0.24 and 1.66 times more carbon-intensive in comparison to partly mechanized and traditional tillage system. Mechanized tillage had higher carbon efficiency (3.75), carbon-sustainability index (2.75), carbon-footprint in spatial scales (4342 kg CO2eq. ha⁻¹), but had 34% less carbon-footprint in yield scales compared to traditional tillage. Mechanized tillage showed 22 and 73% higher system productivity compared to partly mechanized and traditional tillage, respectively. Partly mechanized tillage had a 23% lower cultivation cost than mechanized tillage. Thus, the present study suggests that partly mechanize tillage was the most appropriate energy and carbon-efficient production system in eastern India.
Article
The article examines the structure of the cultivated areas of the Khabarovsk Territory, reveals the predominance of soybeans. For the rational use of natural resources in the Far East, the varieties of spring oats Express, Tigrovy, Premier, Marshal, Cardinal, Peredovik have been created, which are distinguished by high productivity - 4.4-6.7 t / ha. It has been established that the yield of spring wheat and spring triticale under the conditions of the Khabarovsk Territory is realized practically equally - 2.6 t/ha. It is noted that the need for heat in the sprouting-tillering phase in spring wheat and spring triticale is opposite, which indicates the need to use both crops in agrocenoses of the Far Eastern region.
Article
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Agricultural intensification increased crop productivity but simplified production with lower diversity of cropping systems, higher genetic uniformity, and a higher uniformity of agricultural landscapes. Associated detrimental effects on the environment and biodiversity as well as the resilience and adaptability of cropping systems to climate change are of growing concern. Crop diversification may stabilize productivity of cropping systems and reduce negative environmental impacts and loss of biodiversity, but a shared understanding of crop diversification including approaches towards a more systematic research is lacking. Here, we review the use of ‘crop diversification’ measures in agricultural research. We (i) analyse changes in crop diversification studies over time; (ii) identify diversification practices based on empirical studies; (iii) differentiate their use by country, crop species and experimental setup and (iv) identify target parameters to assess the success of diversification. Our main findings are that (1) less than 5% of the selected studies on crop diversification refer to our search term ‘diversification’; (2) more than half of the studies focused on rice, corn or wheat; (3) 76% of the experiments were conducted in India, USA, Canada, Brazil or China; (4) almost any arable crop was tested on its suitability for diversification; (5) in 72% of the studies on crop diversification, at least one additional agronomic measure was tested and (6) only 45% of the studies analysed agronomic, economic and ecological target variables. Our findings show the high variability of approaches to crop diversification and the lack of a consistent theoretical concept. For better comparability and ability to generalise the results of the different primary studies, we suggest a novel conceptual framework. It consists of five elements, (i) definition of the problem of existing farming practices and the potential need for diversification, (ii) characterisation of the baseline system to be diversified, (iii) definition of the scale and target area, (iv) description of the experimental design and target variables and (v) definition of the expected impacts. Applying this framework will contribute to utilizing the benefits of crop diversification more efficiently.
Article
The carbon-nutrient-water cycles of farmland ecosystem not only provides support for crop production, but also has an impact on the environment. Comprehensively quantifying the impact of crop production on the environment can provide a basis for crop sustainable production. A series of environmental footprint approaches, including carbon footprint (CF), nitrogen footprint (NF) and water footprint (WF), were optimized to evaluate greenhouse gas (GHG) emissions, reactive nitrogen (Nr) loss and water resource consumption in crop production, and a comprehensive footprint method based on Endpoint modeling was proposed to evaluate the overall environmental impact of crop production in China. The CF, NF and WF of 28 forms of crop production varied from 1206.29 kg CO2 equivalent (CO2-eq) ha-1 of oil crops to 7326.37 kg CO2-eq ha-1 of fiber crops, 16.07 kg Nr-eq ha-1 of oil crops to 60.70 kg Nr-eq ha-1 of sugar crops, and 4032.04 m3 ha-1 oil crops to 12,476.28 m3 ha-1 of sugar crops, respectively. The contribution of each component to footprints varied greatly among different crops, and fertilizer manufacture, NH3 volatilization and green WF were generally the main contributors of CF, NF and WF, respectively. The total GHG emissions, Nr loss and water consumption were estimated to be 670.11 Tg CO2-eq, 5.50 Tg Nr-eq and 837.06 G m3 for all crop production of China. The greenhouse vegetable with the highest area-scaled comprehensive footprint was 4.5 times that of the oil crops which had the lowest one. The contribution of crop production to the corresponding environmental impact in China was as low as 3.7%, of which NH3 volatilization contributed 48% and grain production contributed 72%. Mineral N fertilization was the main driver of the variation of comprehensive footprint between provinces, with reduction of N fertilizer application as an important way to reduce the environmental impact of crop production.
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A significant challenge in our time is to produce sufficient agricultural products on limited farmable land to meet the needs for food, feed, fiber, and industrial uses in the face of a changing climate. Conventional cropping systems mostly rely on inputs, such as fertilizers and pesticides, to boost crop yields. However, excessive inputs increase production costs and entail more direct and indirect emissions of greenhouse gases to the atmosphere that negatively impact the environment. Finding sustainable ways to increase crop productivity with little or no impact on the environment is the primary goal of modern agriculture. This review reveals that temporal-spatial diversification of crop rotations is critically needed to advance toward this goal sustainably. We find that (i) intensified crop rotations enhance carbon conversion from atmospheric CO2 into plant biomass and thus sequester more carbon into soil; (ii) diversified crop mixtures improve system resilience, i.e., increased resistance to pest/disease incidence and weed infestation, and faster recovery after removal of the abiotic or biotic stress; (iii) diversifying crop rotations increases crop yields at the system level with improved water and fertilizer use efficiencies; (iv) legume-based crop rotations reduce the need for synthetic nitrogen fertilizers thus lowering N2O and CO2 emissions to the atmosphere; (v) crop diversity leads to soil microbiome diversity that optimizes soil microenvironment, improving soil health. We believe that developing and adopting of diversified cropping systems are key factors for agricultural policy setting and a top priority for on-farm decision-making to increase crop productivity and enhance soil health, while reducing negative environmental impacts.
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A number of challenges will face the world in the years to come, including food security, climate change risks, and increasing demand for energy. Therefore, agriculture and food systems are increasingly focused on producing sustainably. By delivering multiple services in line with sustainability principles, legume crops could play a significant role in this context. In addition, legumes are also potentially competitive crops, which are useful for increasing crop diversity and reducing the use of external inputs in modern cropping systems due to their environmental and socioeconomic benefits. In a cropping system involving legumes most important aspect is N balance which summarizes the complex N inflow and outflow of the system. Legumes hold potential to variegate cropping systems, restore inter-related biodiversity, and assist break-crops. The key part of the residual N is obtained from rhizodeposition and recoverable debris which become part of the active soil organic matter pool that derives the N pool in soil for the long term. The ability of legumes to fix atmospheric nitrogen as well as produce biomass and sequester carbon (C) is a crucial factor in reducing greenhouse gases emissions. Therefore, legumes have been envisioned as a solution for decreasing nitrous oxide (N2O) emissions. The foremost goal of writing this review article is to have an enhanced interpretation of nitrogen dynamics, its residual effect, increase its use efficiency under diverse agroclimatic conditions, its influence on C stabilization, climate change, and enhance soil health by stimulating microbial activity and biomass. In fact, legumes are expected to play an increasingly critical role over the coming decades.
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This study aims to evaluate the medium-term effect of two biannual rotations and four residue rate incorporation on durum wheat production and its nutritional composition and nutrient extraction. The effects of two biannual rotations of canola (Brassica napus L.) durum wheat (Triticum turgidum L.) and bean (Phaseolus vulgaris L.)-durum wheat and four incorporation rates (0%, 50%, 100%, and 200%) of residues of each preceding crop were evaluated after four seasons on durum wheat production and on its nutritional composition and nutrient extraction, in a volcanic soil in south-central Chile. Results indicated that the highest grain yield and residue production of durum wheat was obtained after bean (7.40 and 7.92 Mg ha−1, respectively). In the grain were obtained lower N and P concentrations after bean, and higher K, Ca, and Mg concentrations in the residue. The extraction of most durum wheat grain and residue nutrients was higher after bean. Nutrient distribution in the durum wheat plant concentrated in the grain was 79.9 to 80.7% N, 91.3 to 92.1% P, 27.1 to 27.4% K, 16.8 to 18.8% Ca, 68.3 to 70.4% Mg, and 56.3 to 57.4% S. In the residue, nutrient distribution was 19.3 to 20.4% N, 7.9 to 8.7% P, 72.6 to 72.9% K, 81.2 to 83.2%, Ca, 29.6 to 31.7% Mg, and 42.6 to 43.7% S. The highest grain and residue production of durum wheat was obtained after bean crop and also the extraction of most nutrients.
Thesis
La méthanisation agricole des effluents animaux est une pratique en fort développement en France. Elle produit de l’énergie renouvelable (biogaz). La valorisation des digestats au champ, comme celle des effluents non méthanisés, permet le retour au sol de nutriments et de matière organique, ce qui diminue le besoin en engrais minéraux et entretient les stocks de C des sols. Le traitement et l’épandage de ces produits peut aussi induire l’émission de gaz à effet de serre et de contaminants. La méthanisation agricole influence ces impacts : pour les maitriser, il faut comprendre comment la digestion des effluents avec des déchets importés modifie les cycles du C et du N à l’échelle de la ferme. Cette question a été traitée en s’appuyant sur un cas d’étude à l’INRAE de Nouzilly (Centre – Val de Loire) : une exploitation agricole avec un méthaniseur traitant les effluents de son élevage bovin et divers déchets organiques. Lors de l’essai au champ MétaMétha, nous avons comparé les flux d’azote au cours d’une rotation culturale fertilisée avec des engrais minéraux, des lisiers et fumiers bovins, ou des digestats issus de ces effluents. Les digestats se substituent bien aux engrais minéraux, mais ils sont sensibles à la volatilisation d’ammoniac (NH3). Les vers de terre peuvent être négativement impactés juste après l’épandage de digestat ou de lisier, mais les effets sont similairement positifs après 2 ans d’apports de matière organique. Nous avons ensuite évalué les modèles STICS et SYS-Metha pour simuler respectivement l’essai au champ et le traitement des digestats. Ces modèles ont été couplés pour simuler les flux de C et N à l’échelle de la ferme. Avec de forts imports de déchets, la méthanisation favorise la substitution des engrais minéraux, le stockage de C dans les sols, mais aussi les émissions de NH3. Ce travail permet de mieux évaluer les conséquences de l’introduction d’un méthaniseur dans une exploitation agricole et ainsi d’optimiser la filière.
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Decomposition and nutrient release patterns of prunings of three woody agroforestry plant species (Acioa barteri, Gliricidia sepium and Leucaena leucocephala), maize (Zea mays) stover and rice (Oryza sativa) straw, were investigated under field conditions in the humid tropics, using litterbags of three mesh sizes (0.5, 2 and 7 mm) which allowed differential access of soil fauna. The decomposition rate constants ranged from 0.01 to 0.26 week−1, decreasing in the following order; Gliricidia prunings >Leucaena prunings > rice straw > maize stover >Acioa prunings. Negative correlations were observed between decomposition rate constants and C:N ratio (P < 0.004), percent lignin (P < 0.014) and polyphenol content (P < 0.053) of plant residues. A positive correlation was observed between decomposition rate constant and mesh-size of litterbag (P < 0.057). These results indicate that both the chemical composition of plant residues and nature of the decomposer played an important role in plant residue decomposition.Nutrient release differed with quality of plant residues and litterbag mesh-size. Total N, P, Ca and Mg contents of plant residues decreased with time for Gliricidia and Leucaena prunings, maize stover, and rice straw, and increased with time for Acioa prunings. There was some indication of N immobilization in maize stover and rice straw; P immobilization in Leucaena prunings and rice straw; and Ca immobilization in maize stover, rice straw and Gliricidia and Leucaena prunings. Acioa prunings immobilized N, P, Ca and Mg. All plant residues released K rapidly. Nutrient release increased with increasing mesh-size of litterbags, suggesting that soil faunal activities enhanced nutrient mobilization.
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Systems approaches to research can be used to study characteristics of agricultural systems that cannot be addressed using conventional factorial experiments. The goal of a factorial experiment is to break down a complex system in order to isolate and study specific components and identify cause-effect relationships. In contrast, systems experiments aim to understand how a complex system functions as a whole and thus requires that intact systems be studied. Two approaches have been successfully applied to agricultural systems research: 1) field station experiments where simulated cropping systems are established in replicated plots and 2) studies of intact agroecosystems using commercial farms as study sites. These two approaches have complementary strengths and limitations and have made significant contributions to our understanding of ecological processes in agricultural systems. The development of sustainable agroecosystems will be best accomplished using an integrated research approach combining systems experiments with appropriately designed factorial experiments.
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All references to energy for pesticide production in agriculture can be traced back to the original data of Green (1987). The most common method used to derive values for current chemicals is to use the average of each category of active ingredient. However a comparison of the mean and standard deviation of the categories provides little justification for using anything other than the overall average for agrochemicals, both for the total energy used and the breakdown into the different sources of inherent and process energy. However it is likely that using energy requirements derived directly from Green, such as the mean or maximum will generally underestimate for chemicals introduced since 1985. Of the methods tested to derive improved estimates, the only practical and effective one is to use a linear regression on the year of discovery. From these data, the total pesticide energy input to each type of crop by category of pesticides can be calculated. This is 1681 MJ/ha for wheat. It seems reasonable that 1130 is a minimum and 3280 is a maximum value for wheat. Table 1 lists the appropriate values for each crop per hectare and the weighted average pesticide production energies per unit mass of the different types of pesticide – overall 370 MJ/kg active ingredient. A factor of 0.069 kg CO2 equivalent per MJ pesticide energy can be used to convert these to the Global Warming Potential (100 years). The pesticide energy input of 1364 MJ/ha thus corresponds to a weighted average greenhouse gas emission of 94 kg CO2 equivalent per hectare of arable crop. The results show that pesticide manufacturing represents about 9% of the energy use of arable crops – less for spring crops and more for potatoes. The amount represents about 100-200 MJ/t of crop. Given the above maxima and minima, the range is no lower than 6% and no higher than 16%. Pesticide manufacturing represents about 3% of the 100-year Global Warming Potential (GWP) from crops. This lower value is because about 50% of the GWP from arable crops is due to the field emissions of nitrous oxide from the soil which has a very large GWP. The above values come with a very wide range of uncertainty. There would thus be considerable benefit to more detailed information on the energy required for the manufacture of some current pesticides. This may be possible by repeating the method of analysis of Green using patent data on modern pesticides, in conjunction with an industrial organic chemist, but actual plant data would be preferable. Indeed the latter is essential for use in a procedure for “carbon footprinting”, such as that being sponsored by the Carbon Trust and Defra in the BSI’s Publicly Available Specification PAS2050. Corporate Environmental data published by Monsanto suggest that energy consumption in their chemical plants may have reduced by up to 47% in the last 20 years.
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World population is projected to reach over nine billion by the year 2050, and ensuring food security while mitigating environmental impacts represents a major agricultural challenge. Thus, higher productivity must be reached through sustainable production by taking into account climate change, resources rarefaction like phosphorus and water, and losses of fertile lands. Enhancing crop diversity is increasingly recognized as a crucial lever for sustainable agro-ecological development. Growing legumes, a major biological nitrogen source, is also a powerful option to reduce synthetic nitrogen fertilizers use and associated fossil energy consumption. Organic farming, which does not allow the use of chemical, is also regarded as one prototype to enhance the sustainability of modern agriculture while decreasing environmental impacts. Here, we review the potential advantages of eco-functional intensification in organic farming by intercropping cereal and grain legume species sown and harvested together. Our review is based on a literature analysis reinforced with integration of an original dataset of 58 field experiments conducted since 2001 in contrasted pedo-climatic European conditions in order to generalize the findings and draw up common guidelines. The major points are that intercropping lead to: (i) higher and more stable grain yield than the mean sole crops (0.33 versus 0.27 kg m −2), (ii) higher cereal protein concentration than in sole crop (11.1 versus 9.8 %), (iii) higher and more stable gross margin than the mean sole crops (702 versus 577€ha −1) and (iv) improved use of abiotic resources according to species complementarities for light interception and use of both soil mineral nitrogen and atmospheric N 2. Intercropping is particularly suited for low-nitrogen availability systems but further mechanistic understanding is required to propose generic crop management procedures. Also, development of this practice must be achieved with the collaboration of value chain actors such as breeders to select cultivars suited to intercropping.
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Humans are currently confronted by many global challenges. These include achieving food security for a rapidly expanding population, lowering the risk of climate change by reducing the net release of greenhouse gases into the atmosphere due to human activity, and meeting the increasing demand for energy in the face of dwindling reserves of fossil energy and uncertainties about future reliability of supply. Legumes deliver several important services to societies. They provide important sources of oil, fiber, and protein-rich food and feed while supplying nitrogen (N) to agro-ecosystems via their unique ability to fix atmospheric N-2 in symbiosis with the soil bacteria rhizobia, increasing soil carbon content, and stimulating the productivity of the crops that follow. However, the role of legumes has rarely been considered in the context of their potential to contribute to the mitigation of climate change by reducing fossil fuel use or by providing feedstock for the emerging biobased economies where fossil sources of energy and industrial raw materials are replaced in part by sustainable and renewable biomass resources. The aim of this review was to collate the current knowledge regarding the capacity of legumes to (1) lower the emissions of the key greenhouse gases carbon dioxide (CO2) and nitrous oxide (N2O) compared to N-fertilized systems, (2) reduce the fossil energy used in the production of food and forage, (3) contribute to the sequestration of carbon (C) in soils, and (4) provide a viable source of biomass for the generation of biofuels and other materials in future biorefinery concepts. We estimated that globally between 350 and 500 Tg CO2 could be emitted as a result of the 33 to 46 Tg N that is biologically fixed by agricultural legumes each year. This compares to around 300 Tg CO2 released annually from the manufacture of 100 Tg fertilizer N. The main difference is that the CO2 respired from the nodulated roots of N-2-fixing legumes originated from photosynthesis and will not represent a net contribution to atmospheric concentrations of CO2, whereas the CO2 generated during the synthesis of N fertilizer was derived from fossil fuels. Experimental measures of total N2O fluxes from legumes and N-fertilized systems were found to vary enormously (0.03-7.09 and 0.09-18.16 kg N2O-N ha(-1), respectively). This reflected the data being collated from a diverse range of studies using different rates of N inputs, as well as the large number of climatic, soil, and management variables known to influence denitrification and the portion of the total N lost as N2O. Averages across 71 site-years of data, soils under legumes emitted a total of 1.29 kg N2O-N ha(-1) during a growing season. This compared to a mean of 3.22 kg N2O-N ha(-1) from 67 site-years of N-fertilized crops and pastures, and 1.20 kg N2O-N ha(-1) from 33 site-years of data collected from unplanted soils or unfertilized non-legumes. It was concluded that there was little evidence that biological N-2 fixation substantially contributed to total N2O emissions, and that losses of N2O from legume soil were generally lower than N-fertilized systems, especially when commercial rates of N fertilizer were applied. Elevated rates of N2O losses can occur following the termination of legume-based pastures, or where legumes had been green- or brown-manured and there was a rapid build-up of high concentrations of nitrate in soil. Legume crops and legume-based pastures use 35% to 60% less fossil energy than N-fertilized cereals or grasslands, and the inclusion of legumes in cropping sequences reduced the average annual energy usage over a rotation by 12% to 34%. The reduced energy use was primarily due to the removal of the need to apply N fertilizer and the subsequently lower N fertilizer requirements for crops grown following legumes. Life cycle energy balances of legume-based rotations were also assisted by a lower use of agrichemicals for crop protection as diversification of cropping sequences reduce the incidence of cereal pathogens and pests and assisted weed control, although it was noted that differences in fossil energy use between legumes and N-fertilized systems were greatly diminished if energy use was expressed per unit of biomass or grain produced. For a change in land use to result in a net increase C sequestration in soil, the inputs of C remaining in plant residues need to exceed the CO2 respired by soil microbes during the decomposition of plant residues or soil organic C, and the C lost through wind or water erosion. The net N-balance of the system was a key driver of changes in soil C stocks in many environments, and data collected from pasture, cropping, and agroforestry systems all indicated that legumes played a pivotal role in providing the additional organic N required to encourage the accumulation of soil C at rates greater than can be achieved by cereals or grasses even when they were supplied with N fertilizer. Legumes contain a range of compounds, which could be refined to produce raw industrial materials currently manufactured from petroleum-based sources, pharmaceuticals, surfactants, or food additives as valuable by-products if legume biomass was to be used to generate biodiesel, bioethanol, biojet A1 fuel, or biogas. The attraction of using leguminous material feedstock is that they do not need the inputs of N fertilizer that would otherwise be necessary to support the production of high grain yields or large amounts of plant biomass since it is the high fossil energy use in the synthesis, transport, and application of N fertilizers that often negates much of the net C benefits of many other bioenergy sources. The use of legume biomass for biorefineries needs careful thought as there will be significant trade-offs with the current role of legumes in contributing to the organic fertility of soils. Agricultural systems will require novel management and plant breeding solutions to provide the range of options that will be required to mitigate climate change. Given their array of ecosystem services and their ability to reduce greenhouse gas emissions, lower the use of fossil energy, accelerate rates of C sequestration in soil, and provide a valuable source of feedstock for biorefineries, legumes should be considered as important components in the development of future agroecosystems.
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Growing interest in environmental quality has provided a strong incentive to examine how farming practices affect agricultural products’ carbon footprints (CF), an environmental quality indicator. This study determined (i) the CF of spring wheat (Triticum aestivum L.) grown in different cropping systems over 25 years, and (ii) the effect of soil organic carbon (SOC) changes over years on wheat CF. Wheat was grown in four cropping systems: (a) fallow-wheat (FW), (b) fallow-wheat-wheat (FWW), (c) fallow-wheat-wheat-wheat-wheat-wheat (FWWWWW), and (d) continuous wheat (ContW), in replicated field plots in Saskatchewan, Canada. Wheat CF was calculated at a system level with measured variables coupled with modeling approaches. Over the 25-year period, the soil under the ContW system gained organic C of 1340 kg CO2 eq ha−1 annually, or 38%, 55%, and 127% more than those gained in the FWWWWW, FWW, and FW systems, respectively. The SOC gain more than offset the greenhouse gas (GHG) emissions occurred during wheat production, leading to negative emission values at −742 kg CO2 eq ha−1 annually for ContW, and −459, −404, and −191 kg CO2 eq ha−1 for FWWWWW, FWW, and FW systems, respectively. Wheat in the ContW system produced the highest grain yield and gained highest SOC over the years, leading to the smallest (more negative) CF value at −0.441 kg CO2 eq kg−1 of grain, significantly lower than the CF values from the three other systems (−0.102 to −0.116 kg CO2 eq kg−1 of grain). Without considering the SOC gain in the calculation, wheat CF averaged 0.343 kg CO2 eq kg−1 of grain and which did not differ among cropping systems. Wheat is the largest agricultural commodity in Saskatchewan, and the way the crop is produced has significant impacts on environmental quality, reflected by its carbon footprint. Cropping systems with decreased fallow frequency was shown to significantly enhance soil carbon gains over the years, increase annualized crop yields, and effectively lower the carbon footprint of this important commodity.
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Many current organic arable agriculture systems are challenged by a dependency on imported livestock manure from conventional agriculture. At the same time organic agriculture aims at being climate friendly. A life cycle assessment is used in this paper to compare the carbon footprints of different organic arable crop rotations with different sources of N supply. Data from long-term field experiments at three different locations in Denmark were used to analyse three different organic cropping systems (‘Slurry’, ‘Biogas’ and ‘Mulching’), one conventional cropping system (‘Conventional’) and a “No input” system as reference systems. The ‘Slurry’ and ‘Conventional’ rotations received slurry and mineral fertilizer, respectively, whereas the ‘No input’ was unfertilized. The ‘Mulching’ and ‘Biogas’ rotations had one year of grass-clover instead of a faba bean crop. The grass-clover biomass was incorporated in the soil in the ‘Mulching’ rotation and removed and used for biogas production in the ‘Biogas’ rotation (and residues from biogas production were simulated to be returned to the field). A method was suggested for allocating effects of fertility building crops in life cycle assessments. The results showed significantly lower carbon footprint of the crops from the ‘Biogas’ rotation (assuming that biogas replaces fossil gas) whereas the remaining crop rotations had comparable carbon footprints per kg cash crop. The study showed considerable contributions caused by the green manure crop (grass-clover) and highlights the importance of analysing the whole crop rotation and including soil carbon changes when estimating carbon footprints of organic crops especially where green manure crops are included.
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In agricultural systems, optimization of carbon and nitrogen cycling through soil organic matter can improve soil fertility and yields while reducing negative environmental impact. A basic tenet that has guided the management of soil organic matter for decades has been that equilibrium levels of carbon and nitrogen are controlled by their net input and that qualitative differences in these inputs are relatively unimportant. This contrasts with natural ecosystems in which there are significant effects of species composition and litter quality on carbon and nitrogen cycling,. Here we report the net balances of carbon and nitrogen from a 15-year study in which three distinct maize/soybean agroecosystems are compared. Quantitative differences in net primary productivity and nitrogen balance across agroecosystems do not account for the observed changes in soil carbon and nitrogen. We suggest that the use of low carbon-to-nitrogen organic residues to maintain soil fertility, combined with greater temporal diversity in cropping sequences, significantly increases the retention of soil carbon and nitrogen, which has important implications for regional and global carbon and nitrogen budgets, sustained production, and environmental quality.
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Although it is well established that soils are the dominating source for atmospheric nitrous oxide (N2O), we are still struggling to fully understand the complexity of the underlying microbial production and consumption processes and the links to biotic (e.g. inter- and intraspecies competition, food webs, plant-microbe interaction) and abiotic (e.g. soil climate, physics and chemistry) factors. Recent work shows that a better understanding of the composition and diversity of the microbial community across a variety of soils in different climates and under different land use, as well as plant-microbe interactions in the rhizosphere, may provide a key to better understand the variability of N2O fluxes at the soil-atmosphere interface. Moreover, recent insights into the regulation of the reduction of N2O to dinitrogen (N2) have increased our understanding of N2O exchange. This improved process understanding, building on the increased use of isotope tracing techniques and metagenomics, needs to go along with improvements in measurement techniques for N2O (and N2) emission in order to obtain robust field and laboratory datasets for different ecosystem types. Advances in both fields are currently used to improve process descriptions in biogeochemical models, which may eventually be used not only to test our current process understanding from the microsite to the field level, but also used as tools for up-scaling emissions to landscapes and regions and to explore feedbacks of soil N2O emissions to changes in environmental conditions, land management and land use.
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Soil nitrogen (N) budgets are used in a global, distributed flow-path model with 0.5° × 0.5° resolution, representing denitrification and N2O emissions from soils, groundwater and riparian zones for the period 1900-2000 and scenarios for the period 2000-2050 based on the Millennium Ecosystem Assessment. Total agricultural and natural N inputs from N fertilizers, animal manure, biological N2 fixation and atmospheric N deposition increased from 155 to 345 Tg N yr(-1) (Tg = teragram; 1 Tg = 10(12) g) between 1900 and 2000. Depending on the scenario, inputs are estimated to further increase to 408-510 Tg N yr(-1) by 2050. In the period 1900-2000, the soil N budget surplus (inputs minus withdrawal by plants) increased from 118 to 202 Tg yr(-1), and this may remain stable or further increase to 275 Tg yr(-1) by 2050, depending on the scenario. N2 production from denitrification increased from 52 to 96 Tg yr(-1) between 1900 and 2000, and N2O-N emissions from 10 to 12 Tg N yr(-1). The scenarios foresee a further increase to 142 Tg N2-N and 16 Tg N2O-N yr(-1) by 2050. Our results indicate that riparian buffer zones are an important source of N2O contributing an estimated 0.9 Tg N2O-N yr(-1) in 2000. Soils are key sites for denitrification and are much more important than groundwater and riparian zones in controlling the N flow to rivers and the oceans.
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The processes of N mineralization and immobilization which can occur in agricultural soils during decomposition of plant residues are briefly reviewed in this paper. Results from different incubation studies have indicated that the amounts of N immobilized can be very important and that the intensity and kinetics of N immobilization and subsequent remineralization depend on the nature of plant residues and the type of decomposers associated. However, most of the available literature on these processes refer to incubations where large amounts of mineral N were present in soil. Incubations carried out at low mineral N concentrations have shown that the decomposition rate of plant residues is decreased but not stopped. The immobilization intensity, expressed per unit of mineralized C, is reduced and N remineralization is delayed. Nitrogen availability in soil can therefore strongly modify the MIT kinetics (mineralization-immobilization turnover) by a feed-back effect. The mineralization and immobilization kinetics have been determined in a two-years field experiment in bare soil with or without wheat straw. Mineralization in plots without straw seemed to be realistically predicted by accounting for variations in soil temperature and moisture. Immobilization associated with straw decomposition was clearly shown. It was increased markedly by the addition of mineral N throughout decomposition. It is concluded that mineral N availability is an important factor controlling plant residues decomposition under field conditions. A better prediction of the evolution of mineral N in soil may therefore require description and modelling of the respective localization of both organic matter and mineral N in soil aggregates.
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Nitrogen catch crops are grown to absorb nitrogen from the rooting zone during autumn and winter. The uptake of N (Nupt) from the soil inorganic N pool (Nmin) to a pool of catch crop nitrogen, will protect the nitrogen against leaching. After incorporation, a fraction (m) of the catch crop nitrogen is mineralized and becomes available again. However, not all available nitrogen present in the soil in the autumn is lost by leaching during winter. A fraction (r) of the nitrogen absorbed by the catch crop would, without a catch crop, have been retained within the rooting zone. The first year nitrogen beneficial effect (Neff) of a catch crop may then be expressed b N eff = m*N upt - r* N upt The soil-plant simulation model DAISY was evaluated for its ability to simulate the effects of catch crops on spring Nmin and Neff. Based on incubation studies, parameter values were assigned to a number of catch crop materials, and these parameter values were then used to simulate spring Nmin. The model was able to predict much of the vairiation in the measured spring Nmin (r2 = 0.48***) and there was good agreement between the measured and the simulated effect of winter precipitation on spring Nmin and Neff.Scenarios including variable soil and climate conditions, and variable root depth of the succeeding crop were simulated. It is illustrated that the effect of catch crops on nitrogen availability for the succeeding crop depends strongly on the rooting depth of the succeeding crop. If the succeeding crop is deep rooted and the leaching intensity is low, there is a high risk that a catch crop will have a negative effect on nitrogen availability. The simulations showed that the strategy for the growing of catch crops should be adapted to the actual situation, especially to the expected leaching intensity and to the rooting depth of the succeeding crop.
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Concerns with rising atmospheric levels of CO2 have stimulated interest in C flow in terrestrial ecosystems and the potential for increased soil C sequestration. Our objectives were to assess land management effects on soil organic carbon (SOC) dynamics and SOC sequestration for long-term studies in the tallgrass prairie region of the US. Major losses of SOC following conversion of native prairie to arable agriculture at Sanborn Field and the Morrow Plots were rapid (20 to 40 yr), occurred in response to greatly reduced C inputs and accelerated C decay rates, and had largely abated by the mid-1900s. Losses of SOC occurred mainly in easily decomposable, labile C fractions. At Sanborn Field, modeled labile SOC was reduced to 4% of native prairie levels for treatments with low C inputs. A large capacity for soil C sequestration likely exists in the tallgrass prairie region, if labile C pools can be replenished. This agroecosystem has a strong C decomposition regime and increased sequestration of labile C will rely on management practices that increase C inputs (i.e., fertilization, returning crop residues) and stabilize labile C (i.e., perennial cropping, reduced tillage). The capacity for soil C sequestration, however, will vary considerably among sites and be dependent on initial levels of labile SOC and the ability of management practices to stabilize greater inputs of labile C.
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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±228gCm−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±239gCm−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-eqm−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.
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Increasing greenhouse gaseous concentration in the atmosphere is perturbing the environment to cause grievous global warming and associated consequences. Following the rule that only measurable is manageable, mensuration of greenhouse gas intensiveness of different products, bodies, and processes is going on worldwide, expressed as their carbon footprints. The methodologies for carbon footprint calculations are still evolving and it is emerging as an important tool for greenhouse gas management. The concept of carbon footprinting has permeated and is being commercialized in all the areas of life and economy, but there is little coherence in definitions and calculations of carbon footprints among the studies. There are disagreements in the selection of gases, and the order of emissions to be covered in footprint calculations. Standards of greenhouse gas accounting are the common resources used in footprint calculations, although there is no mandatory provision of footprint verification. Carbon footprinting is intended to be a tool to guide the relevant emission cuts and verifications, its standardization at international level are therefore necessary. Present review describes the prevailing carbon footprinting methods and raises the related issues.
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STICS (Simulateur mulTIdiscplinaire pour les Cultures Standard) is a crop model constructed as a simulation tool capable of working under agricultural conditions. Outputs comprise the production (amount and quality) and the environment. Inputs take into account the climate, the soil and the cropping system. STICS is presented as a model exhibiting the following qualities: robustness, an easy access to inputs and an uncomplicated future evolution thanks to a modular (easy adaptation to various types of plant) nature and generic. However, STICS is not an entirely new model since most parts use classic formalisms or stem from existing models. The main simulated processes are the growth, the development of the crop and the water and nitrogenous balance of the soil-crop system. The seven modules of STICS development, shoot growth, yield components, root growth, water balance, thermal environment and nitrogen balance are presented in turn with a discussion about the theoretical choices in comparison to other models. These choices should render the model capable of exhibiting the announced qualities in classic environmental contexts. However, because some processes (e.g, ammoniac volatilization, drought resistance, etc.) are not taken into account, the use of STICS is presently limited to several cropping systems. ((C) Inra/Elsevier, Paris.).
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This manuscript is a synthesis of the available information on energy use in farm operations, and its conversion into carbon equivalent (CE). A principal advantage of expressing energy use in terms of carbon (C) emission as kg CE lies in its direct relation to the rate of enrichment of atmospheric concentration of CO2. Synthesis of the data shows that estimates of emissions in kg CE/ha are 2-20 for different tillage operations, 1-1.4 for spraying chemicals, 2-4 for drilling or seeding and 6-12 for combine harvesting. Similarly, estimates of C emissions in kg CE/kg for different fertilizer nutrients are 0.9-1.8 for N, 0.1-0.3 for P2O5, 0.1-0.2 for K20 and 0.03-0.23 for lime. Estimates of C emission in kg CE/kg of active ingredient (a.i.) of different pesticides are 6.3 for herbicides, 5.1 for insecticides and 3.9 for fungicides. Irrigation, lifting water from deep wells and using sprinkling systems, emits 129+/-98 kg CE for applying 25 cm of water and 258+/-195 for 50 cm of water. Emission for different tillage methods are 35.3 kg CE/ha for conventional till, 7.9 kg CE/ha for chisel till or minimum till, and 5.8 kg CE/ha for no-till method of seedbed preparation. In view of the high C costs of major inputs, sustainable management of agricultural ecosystems implies that an output/input ratio, expressed either as gross or net output of C, must be >1 and has an increasing trend over time.
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Measurement of the change in soil carbon that accompanies a change in land use (e.g., forest to agriculture) or management (e.g., conventional tillage to no-till) can be complex and expensive, may require reference plots, and is subject to the variability of statistical sampling and short-term variability in weather. In this paper, we develop Carbon Management Response (CMR) curves that could be used as an alternative to in situ measurements. The CMR curves developed here are based on quantitative reviews of existing global analyses and field observations of changes in soil carbon. The curves show mean annual rates of soil carbon change, estimated time to maximum rates of change, and estimated time to a new soil carbon steady state following the initial change in management. We illustrate how CMR curves could be used in a carbon accounting framework while effectively addressing a number of potential policy issues commonly associated with carbon accounting. We find that CMR curves provide a transparent means to account for changes in soil carbon accumulation and loss rates over time, and also provide empirical relationships that might be used in the development or validation of ecological or Earth systems models.
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With anthropogenic nutrient inputs to ecosystems increasing globally, there are long-standing, fundamental questions about the role of nutrients in the decomposition of organic matter. We tested the effects of exogenous nitrogen and phosphorus inputs on litter decomposition across a broad suite of litter and soil types. In one experiment, C mineralization was compared across a wide array of plants individually added to a single soil, while in the second, C mineralization from a single substrate was compared across 50 soils. Counter to basic stoichiometric decomposition theory, low N availability can increase litter decomposition as microbes use labile substrates to acquire N from recalcitrant organic matter. This "microbial nitrogen mining" is consistently suppressed by high soil N supply or substrate N concentrations. There is no evidence for phosphorus mining as P fertilization increases short- and long-term mineralization. These results suggest that basic stoichiometric decomposition theory needs to be revised and ecosystem models restructured accordingly in order to predict ecosystem carbon storage responses to anthropogenic changes in nutrient availability.
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The term “carbon footprint” has evolved as an important expression of greenhouse gas (GHG) intensity for diverse activities and products. Widespread public acceptance and the ease of conveying information about GHG intensity with this term has also attracted scientists and policy makers to review and refine its calculations. Standard methods for carbon footprinting have been prepared, and sector-specific standards are under development. These standards direct the procedures to carry out carbon footprinting through life cycle assessment in conjunction with GHG accounting, classifes activities into three tiers based on the order of emissions. Agriculture is the largest contributor to anthropogenic emissions of greenhouse gases, so the quantification of different agricultural practices is essential for identification of more sustainable practices. Carbon footprinting has potential as a tool for assessing and comparing GHG performances of different agricultural products along with identification of points to improve environmental efficiencies. Case studies on the application of carbon footprinting to cultivation practices are increasing in the scientific literature, but the majority of studies do not comply with the standard three-tier methodology. This leads to nonuniformity among different studies and their comparisons. Hence, a standard guideline addressing carbon footprinting specifically for agriculture is essential for the effective application of this tool in the quantification of GHG intensity, mitigation of global warming, and adaptation against future climate change scenarios.
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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.
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Increasing atmospheric concentrations of greenhouse gases has caused grievous global warming and associated consequences. Lowering carbon footprint to promote the development of cleaner production demands the immediate attention. In this study, the carbon footprint calculations were performed on five cropping systems in North China Plain from 2003 to 2010. The five cropping systems included sweet potato → cotton → sweet potato → winter wheat–summer maize (SpCSpWS, 4-year cycle), ryegrass–cotton → peanut → winter wheat–summer maize (RCPWS, 3-year cycle), peanut → winter wheat–summer maize (PWS, 2-year cycle), winter wheat–summer maize (WS, 1-year cycle), and continuous cotton (Cont C), established in a randomized complete-block design with three replicates. We used a modified carbon footprint calculation with localized greenhouse gas emissions parameters to analyze the carbon footprint of each cropping system per unit area, per kg biomass, and per unit economic output. Results showed that the lowest annual carbon footprint values were observed in SpCSpWS among the five cropping systems, which were only 27.9%, 28.2% and 25.0% of those in WS rotation system (the highest carbon footprint) in terms of per unit area, per unit biomass, and per unit economic output, respectively. The five cropping systems showed the order of SpCSpWS < Cont C < RCPWS < PWS < WS sorting by their annual carbon footprint calculated by all the three metrics above-mentioned. Results revealed that appropriate diversified crop rotation systems could contribute to decreased carbon footprint compared with conventional intensive crop production system in North China Plain.
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Introducing cover crops (CC) interspersed with intensively fertilized crops in rotation has the potential to reduce nitrate leaching. This paper evaluates various strategies involving CC between maize and compares the economic and environmental results with respect to a typical maize-fallow rotation. The comparison is performed through stochastic (Monte-Carlo) simulation models of farms' profits using probability distribution functions (pdfs) of yield and N fertilizer saving fitted with data collected from various field trials and pdfs of crop prices and the cost of fertilizer fitted from statistical sources. Stochastic dominance relationships are obtained to rank the most profitable strategies from a farm financial perspective. A two-criterion comparison scheme is proposed to rank alternative strategies based on farm profit and nitrate leaching levels, taking the baseline scenario as the maize-fallow rotation. The results show that when CC biomass is sold as forage instead of keeping it in the soil, greater profit and less leaching of nitrates are achieved than in the baseline scenario. While the fertilizer saving will be lower if CC is sold than if it is kept in the soil, the revenue obtained from the sale of the CC compensates for the reduced fertilizer savings. The results show that CC would perhaps provide a double dividend of greater profit and reduced nitrate leaching in intensive irrigated cropping systems in Mediterranean regions. (c) 2013 Elsevier Ltd. All rights reserved.
Article
We conducted a meta-analysis of previously published empirical studies that have examined the effects of nitrogen (N) enrichment on litter decomposition. Our objective was to provide a synthesis of existing data that comprehensively and quantitatively evaluates how environmental and experimental factors interact with N additions to influence litter mass loss. Nitrogen enrichment, when averaged across all studies, had no statistically significant effect on litter decay. However, we observed significant effects of fertilization rate, site-specific ambient N-deposition level, and litter quality. Litter decomposition was inhibited by N additions when fertilization rates were 2–20 times the anthropogenic N-deposition level, when ambient N deposition was 5–10 kg N·ha−1·yr−1, or when litter quality was low (typically high-lignin litters). Decomposition was stimulated at field sites exposed to low ambient N deposition (<5 kg N·ha−1·yr−1) and for high-quality (low-lignin) litters. Fertilizer type, litterbag mesh size, and climate did not influence the litter decay response to N additions.
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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
The Intergovernmental Panel on Climate Change (IPCC) standard methodology to conduct national inventories of soil N2O emissions is based on default (or Tier I) emission factors for various sources. The objective of our study was to summarize recent N2O flux data from agricultural legume crops to assess the emission factor associated with rhizobial nitrogen fixation. Average N2O emissions from legumes are 1.0 kg N ha−1 for annual crops, 1.8 kg N ha−1 for pure forage crops and 0.4 kg N ha−1 for grass legume mixes. These values are only slightly greater than background emissions from agricultural crops and are much lower that those predicted using 1996 IPCC methodology. These field flux measurements and other process-level studies offer little support for the use of an emission factor for biological N fixation (BNF) by legume crops equal to that for fertiliser N. We conclude that much of the increase in soil N2O emissions in legume crops may be attributable to the N release from root exudates during the growing season and from decomposition of crop residues after harvest, rather than from BNF per se. Consequently, we propose that the biological fixation process itself be removed from the IPCC N2O inventory methodology, and that N2O emissions induced by the growth of legume crops be estimated solely as a function of crop residue decomposition using an estimate of above- and below-ground residue inputs, modified as necessary to reflect recent findings on N allocation.
Article
Summary(1) N added to decomposing organic matter often has no effect or a negative effect on microbial activity, at least in the long term. More than 60 papers are cited in support of this statement.(2) The negative effect of N is mainly found with recalcitrant organic matter with a high C/N ratio (straw, wood, etc.), whereas a positive effect of N is common for easily degradable organic material with low C/N ratio.(3) The negative effect of N could be explained by: (i) N disturbs the outcome of competition between potent and less potent decomposers; (ii) through ‘ammonia metabolite repression’, N blocks production of certain enzymes, at least in basidiomycetes, and enhances breakdown of the most available cellulose, whereby recalcitrant lignocellulose accumulates; (iii) amino compounds condense with polyphenols and other decomposition products, forming ‘browning precursors’ which are toxic or inhibitory.(4) The effect of adding N may depend on the microflora present.(5) There are indications that some microorganisms have a ‘luxury uptake’ of N when it is present in sufficient amounts, thereby delaying N mineralization.(6) The addition of N seems to increase the formation of water-soluble, brown, recalcitrant compounds, but to decrease the amount of humus formed.
Article
Emissions of nitrogen compounds from heavily fertilized and irrigated maize fields have been studied in the Southwest of France, over an annual cultivation cycle. Strong nitrous oxide emissions from denitrification were observed after application of nitrogen fertilizer. Flux intensity appears to be stimulated by rain or irrigation. Emission algorithms, taking into account both nitrogen input and soil water content were established on the basis of the experimental data set. They allowed us to estimate annual nitrogen loss in the form of nitrous oxide modulated by rainfall. Production of methane is observed at the level of the water table under anoxic conditions. Nevertheless, the net flux between soil and atmosphere is negative for most of the time. When methane is produced, fluxes were very low due to methane oxidation in the soil surface layer.
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Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional plow tillage to no-till can increase soil C by an estimated 16±3%, whereas increasing rotation intensity can increase soil C by an estimated 6±3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly longer period (26yr) than that for tillage cessation (21yr). Sequestration strategies for grasslands have, on average, longer sequestration durations (33yr) than for croplands. Estimates for sequestration rates and durations are mean values and can differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C steady state is reached. However, soils could potentially sequester additional C following additional changes in management until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes in land management.