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Evapotranspiration partitioning and water use efficiency of switchgrass and biomass sorghum managed for biofuel
Abstract
Switchgrass (Panicum virgatum L.) and biomass sorghum (Sorghum bicolor L. Moench) are two candidate bioenergy crops for the US Southern Great Plains region. In this water-limited region, there is a need to partition evapotranspiration (ET) and to determine the water use efficiency (WUE) of these potential feedstocks. Both crops were grown in a field plot experiment at Stillwater, OK. Soil water content measurements were made by neutron probe every two weeks to a depth of 2.0 m in 0.2-m intervals over the course of three growing seasons. Growing season ET was estimated as the difference between growing season precipitation and change in root zone soil water storage. Evapotranspiration was partitioned by measuring canopy interception using interception trays and estimating soil evaporation using the FAO-56 dual crop coefficient method. Transpiration was calculated as ET minus soil evaporation and canopy interception. Transpiration was the largest component of ET; however, soil evaporation and canopy interception accounted for 28% of growing season ET for switchgrass and 42% for biomass sorghum. Although the non-productive losses were greater from biomass sorghum, WUE values of 9–49 kg ha−1 mm−1 based on ET and 22–83 kg ha−1 mm−1 based on transpiration were observed for biomass sorghum, which were greater than the WUE values of switchgrass, 8–21 kg ha−1 mm−1 based on ET and 12–28 kg ha−1 mm−1 based on transpiration. These results demonstrate that biomass sorghum is a candidate feedstock with potential to achieve greater WUE than switchgrass at this location; however, other factors such as economics and ecosystem services should also be considered.
... A 4-year yield trial of biomass sorghum varieties reported average biomass yields of 15-25 Mg ha −1 across the field sites, with the highest average yields at sites in the southern US (Gill et al., 2014;Lee et al., 2018). Olson et al. (2012) measured yields as high as 49.5 Mg ha −1 under irrigated conditions in Texas, and other studies done in the southern US have reported yields of >30 Mg ha −1 (Rocateli et al., 2012;Yimam et al., 2015). In Illinois, average biomass yields of 30.1 Mg ha −1 were achieved with sufficient nitrogen (N) and moisture (Maughan et al., 2012), and biomass sorghum yields have been reported by Roby et al. (2017) to be higher than corn biomass yields under the same environmental conditions in Iowa. ...
... Other studies, however, have found that biomass sorghum yields decreased substantially under drought conditions. Oklahoma experienced major droughts in 2011 and 2012 (D4 and D3, respectively, USDM), with respective yields of 4.4 Mg ha −1 in 2011 and 12.9 Mg ha −1 in 2012; with ample moisture in 2013, biomass sorghum yields reached 32.5 Mg ha −1 (Yimam et al., 2015). However, during a major drought in Missouri in 2012 (D3, USDM), there were no substantial yield declines observed in corn or biomass sorghum (Maw et al., 2017a). ...
... Therefore, the growing period will be longer in the south and thus higher yields can be achieved. The yield trial results mapped on Figure 7 indicate that average yields are highest in the southeastern sites, with yields of ~30 Mg ha −1 measured in non-drought years in this and other experiments in southeastern locations (Olson et al., 2012;Rocateli et al., 2012;Yimam et al., 2015). Therefore, we are confident that our results are representative of potential biomass sorghum production. ...
Biomass sorghum (Sorghum bicolor L. Moench) is an annual C4 grass that has emerged as a candidate bioenergy crop but has not been widely grown in the United States. Corn (Zea mays L.), another annual C4 grass, has been produced on a large scale in the United States for biofuels. Iowa leads the nation in both corn and ethanol production. The high productivity of corn in Iowa creates the research question: could biomass sorghum be as or more productive than corn in the state in terms of bioenergy? Efforts to use crop models to fill the gaps left by field experimentation on biomass sorghum have also been limited thus far. To address our research question, we collected biophysical data on biomass sorghum grown in Iowa for two growing seasons, used them to develop a biomass sorghum module in an agroecosystem model (Agro‐IBIS), and predict the potential performance of biomass sorghum across Iowa compared to maize. Despite dry conditions in 2019 and 2020, average biomass sorghum yields were 17.20 Mg ha⁻¹. By comparison, average corn aboveground biomass was higher in 2020 (22.02 Mg ha⁻¹). Soil cores indicated average belowground biomass of 1.46 Mg ha⁻¹, with roots concentrated near the surface (73% of biomass above 50 cm in a 1 m core). When biomass sorghum model parameters were calibrated with measured values, model output was in close agreement with measured biomass (slope = 0.932, R² = 0.91) and evapotranspiration (slope = 0.757, R² = 0.64). Subsequent regional simulations revealed a notable latitudinal gradient in biomass sorghum yield, with a strong linear relationship between yield and seasonal growing degree‐days (R² = 0.89). When these yields were compared to simulated corn aboveground biomass yields, only 3.4% of the state had biomass sorghum yields that were significantly higher than corn. This number was reduced to 0.3% when comparing the crops in terms of energy ethanol yield. Thus, we conclude biomass sorghum must be improved to be competitive with corn as an annual biofuel crop in Iowa. This study provides a baseline against which to compare advancements in sorghum breeding for biomass and stress tolerance in Iowa.
... You can see that development of improved methods for measuring soil water content has been a major focus in soil physics and related disciplines, and you can understand why soil water 3.1 Soil Water Content | 55 content data are becoming increasingly available around the world [13]. One of the great opportunities for researchers today is to find creative ways to use these data for societal benefit whether for improved drought monitoring, more accurate streamflow forecasting, increased wildfire preparedness, or a host of other potential applications [14][15][16]. ...
... We sometimes have measurements of soil hydraulic conductivity at saturation and perhaps at one or two water contents below saturation, but we often need a mathematical function to allow calculation of hydraulic conductivity for all other values of water content. For this reason, soil hydraulic conductivity functions have been developed corresponding to each of the soil water retention functions presented in Chapter 3. The hydraulic conductivity function of Brooks and Corey [15], is defined by: ...
... mays L.), 35% in soybean [Glycine max (L.) Merr.], 25-31% in switchgrass (Panicum virgatum L.), and 27-45% in forage sorghum (Sorghum bicolor L. Moench)[13][14][15]. Interception also occurs during sprinkler irrigation and accounted for approximately 8% of applied water for a maize crop irrigated with a center pivot system in western Kansas, USA[16]. ...
... Recent reports of biomass sorghum (Sorghum bicolor spp.) indicate that it has potential to produce similar yields to perennial grasses in the Midwest region of the United States. Yimam et al. (2015) reported that yields for biomass sorghum were similar to or higher than switchgrass for a 3-yr study in Oklahoma. Biomass sorghum yields of 10.1-26.1 Mg ha −1 were reported by Wang et al. (2017a) for the NC Piedmont, whereas (Heitman et al., 2017) reported yields of 15.7 ± 5.1 Mg ha −1 in the NC Coastal Plain, which suggests that biomass sorghum grown in NC could produce high biomass yields as seen in other areas of the United States. ...
... Mg ha −1 for dryland sorghum, indicating that sorghum can be influenced by water availability. Yimam et al. (2015) reported that the yields of rainfed biomass sorghum were strongly influenced by seasonal water supply when comparing growing seasons with drought to growing seasons with adequate rainfall. ...
... These curves were calculated using the K c values presented in Table 3. Fescue had the highest cumulative ET c of all perennial crops. The cumulative ET c for switchgrass was higher than what was reported in Oklahoma and Illinois (Hickman et al., 2010;Yimam et al., 2015). This is likely explained by the longer growing season observed in our study. ...
Crops grown for bioenergy purposes are a potential alternative to traditional row crops and pasture–hay systems in the North Carolina (NC) Piedmont, but there is limited information available about their biomass yields and water requirements in this region. The goal of this study was to evaluate biomass yield and water‐use efficiency of switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus × giganteus Greef et Deu.), biomass sorghum (Sorghum bicolor spp.), silage corn (Zea mays L.) and tall fescue (Lolium arundinacea Schreb.). The perennial systems were established in 2012 while annuals were planted each spring. Crop water use was evaluated for the 2016 and 2017 growing seasons using a water balance approach. Giant miscanthus had the highest 2‐yr average biomass yield (29.1 ± 0.8 Mg ha–1) followed by corn (23.6 ± 0.6 Mg ha–1) and biomass sorghum (22.0 ± 1.8 Mg ha–1). Switchgrass and tall fescue had the lowest biomass yields, 14.2 ± 1.9 and 12.5 ± 1.2 Mg ha–1, respectively. Fescue had the highest season‐long water use in both years of the study. Perennial grasses giant miscanthus and switchgrass had similar seasonal water use, but giant miscanthus had higher water‐use efficiency due to greater biomass yields. The annual crops corn and sorghum used less water than the perennial systems because of their shorter growing season, and, consequently, had higher water‐use efficiencies. This information can aid growers when making management decisions about converting land into bioenergy crops.
... Esta característica corrobora os resultados de maior produção de biomassa da parte aérea na ILP (PEZZOPANE et al., 2017), além de maior quantidade de raízes finas no início dos períodos secos de 2015 e 2016 dessa área, quando comparada a área de pastagem extensiva com Urochloa decumbens (Figura 3.12 C). Assim, na estação seca desses anos a ILP produziu mais raízes (Tabela 3.3), e conteve uma maior taxa de lotação animal, sendo todos esses fatores supracitados favoráveis à uma maior extração e evapotranspiração de água nesse sistema intensivo (YIMAM;OCHSNER;KAKANI, 2015;PEREYRA et al., 2017). ...
... Esta característica corrobora os resultados de maior produção de biomassa da parte aérea na ILP (PEZZOPANE et al., 2017), além de maior quantidade de raízes finas no início dos períodos secos de 2015 e 2016 dessa área, quando comparada a área de pastagem extensiva com Urochloa decumbens (Figura 3.12 C). Assim, na estação seca desses anos a ILP produziu mais raízes (Tabela 3.3), e conteve uma maior taxa de lotação animal, sendo todos esses fatores supracitados favoráveis à uma maior extração e evapotranspiração de água nesse sistema intensivo (YIMAM;OCHSNER;KAKANI, 2015;PEREYRA et al., 2017). ...
... Esta característica corrobora os resultados de maior produção de biomassa da parte aérea na ILP (PEZZOPANE et al., 2017), além de maior quantidade de raízes finas no início dos períodos secos de 2015 e 2016 dessa área, quando comparada a área de pastagem extensiva com Urochloa decumbens (Figura 3.12 C). Assim, na estação seca desses anos a ILP produziu mais raízes (Tabela 3.3), e conteve uma maior taxa de lotação animal, sendo todos esses fatores supracitados favoráveis à uma maior extração e evapotranspiração de água nesse sistema intensivo (YIMAM;OCHSNER;KAKANI, 2015;PEREYRA et al., 2017). ...
Integrated farming systems (IS) diversify and intensify rural production, although there are still gaps in advancing and detailing of the processes and mechanisms involved in the soil-plant-atmosphere relations, which are essential to adapt and model these systems for the different eco-regions and edafoclimatic conditions. This study investigated the effects of the intensification of IS on the quantity, quality and origin of soil organic matter (SOM) and on root growth and decomposition dynamics of plant species during cropping and grazing periods. The experiment was conducted at Embrapa Pecuária Sudeste, state of São Paulo, southeast region of Brazil. Two IS were evaluated: integrated crop-livestock system (ICL) and integrated crop-livestock-forest system (ICLF). Two references areas were used: extensive grazing (not degraded) and a semideciduous seasonal forest (only for SOM evaluations). Two evaluation periods were considered: cropping (summer of 2014/15) and grazing period (winter of 2015 and summer and winter of 2015/16). The quantity (C and N contents and stocks), quality (C management indexes, light, particulate and mineral SOM fractions) and the origin (?13C and ?15N) of SOM in the 0-0.40 m layer, and the growth and decomposition of the root systems of the plant species and water flow in the soil profile (0-0.7 m) were evaluated during cropping and grazing periods. In addition, in ICLF also these parameters of plants and soils were evaluated at three distances of eucalyptus rows (1.9, 4.5 and 7.3 m). The conversion of extensive grazing to ICL system resulted in: (i) increased availability of nutrients (Ca, Mg, K and P) in the soil; (ii) increases in C and N stocks, as well as labile fractions of SOM; (iii) maintenance of greater water content in the soil; and (iv) cycling of C and N, with higher root production and decomposition, even in deeper layers of the soil. Implementing the ICLF under the area used for ICL promoted the following effects: (i) reduction in soil water content; (iii) limitations in the root production in the cropping season (mainly in places near the trees) and increases in the root decomposition, resulting in higher cycling rates of the roots in the soil; (iv) increases in C and N cycling; and, (v) occurrence of symbiotic associations with the roots, such as ectomycorrhizal fungi, which were perceptible by the technique of root analysis using minirhizotrons. According to the results, it is suggested that the arrangement of the trees in the ICLF system need to be restructured after the fourth year of age, when they limited the root growth and the amount of labile organic matter, besides reducing the contents of water in the soil. However, farming intensification is recommended under tropical conditions, as the SOM quantity and quality, and the productivity and deepening of the root system were increased during cultivations in the IS, especially in the ICL system.
... Since bioenergy cropping is almost negligible in the North China Plain, the selection of experimental bioenergy crops for cellulosic ethanol production was based on experiences in the Great Plains (USA) that has a similar climate. Switchgrass (Panicum virgatum L.) (a C4 perennial grass; (Mclaughlin et al., 2002)) and biomass sorghum (Sorghum bicolor (L.) Moench) (a highly productive annual; (Rooney et al., 2010)) are considered as the most productive bioenergy crops (Yimam et al., 2015). Switchgrass is a North-American native perennial warmseason grass that can be used as feedstock for cellulosic biofuel production under the US Renewable Fuel Standard ( Schnepf and Yacobucci, 2013). ...
... Le et al. (2011) in the Midwestern USA found a similar switchgrass evapotranspiration rate of 498 mm. Yimam et al. (2015) in Oklahoma reported a higher growing season ET a of switchgrass from 521 to 786 mm under rainfed conditions from 2011 to 2013, with rainfall varying between 572 mm and 918 mm (ratios 1.10-1.16). The annual average ET a of our WM rotation was 715 mm (Fig. 5A, Table 3), which is consistent with previous observations of irrigated systems in the North China Plain ( Liu et al., 2001;Sun et al., 2010;Zhang et al., 2011;Yang et al., 2015bYang et al., , 2017. ...
... Our growing season ET a of sweet sorghum was 528 ± 57 mm with a ratio of precipitation to ET a of 0.75 (Fig. 5B), which was similar to Yimam et al. (2015) in Oklahoma with a ratio of 0.70 and ( Garofalo and Rinaldi, 2013) in southern Italy with a ratio of about 0.80 under similar conditions. Less irrigation water applied will reduce evaporation losses ( Hao et al., 2014;Enciso et al., 2015). ...
... Since water availability appears to underpin differences in crop growth and water dynamics between maize and biomass sorghum, it is important to evaluate these species in a variety of moisture environments. However, previous studies on biomass sorghum water dynamics have largely focused on irrigated systems (Steduto et al., 1997;Farré and Faci, 2006;Narayanan et al., 2013;Garofalo and Rinaldi, 2013;Mullet et al., 2014;Hao et al., 2014;Oikawa et al., 2014;Yimam et al., 2015) or on grain-yielding sorghum varieties (Steduto and Albrizio, 2005;Farré and Faci, 2006). While data are available for irrigated systems, they are limited for sorghum grown specifically for biomass production in rain-fed systems (Yimam et al., 2015). ...
... However, previous studies on biomass sorghum water dynamics have largely focused on irrigated systems (Steduto et al., 1997;Farré and Faci, 2006;Narayanan et al., 2013;Garofalo and Rinaldi, 2013;Mullet et al., 2014;Hao et al., 2014;Oikawa et al., 2014;Yimam et al., 2015) or on grain-yielding sorghum varieties (Steduto and Albrizio, 2005;Farré and Faci, 2006). While data are available for irrigated systems, they are limited for sorghum grown specifically for biomass production in rain-fed systems (Yimam et al., 2015). ...
... Contrasting LAI among species may have also influenced species differences in water availability and the efficiency of water use. The larger observed LAI of biomass sorghum may have increased canopy interception of precipitation, which has been shown to be the largest non-productive ET loss in biomass sorghum agroecosystems (Yimam et al., 2015), relative to maize. However, since LAI also influences the relative amount of water lost through transpiration and evaporation, higher late season LAI in biomass sorghum may have led to more efficient (productive) water use in biomass sorghum than maize. ...
Biomass sorghum (Sorghum bicolor L. Moench) is a candidate bioenergy feedstock for the U.S. Midwest. Research suggests that biomass sorghum is more drought tolerant and has higher water-use-efficiency (WUE) than maize (Zea mays L.) in water-limiting environments, but most species comparisons of the seasonal evapotranspiration (total ET) and WUE have focused on irrigated systems (WUE defined as the ratio of cumulative dry biomass production (dry matter; DM) to total evapotranspiration (mm); g DM (mm H2O)⁻¹). Since comparative data for the rain-fed Midwest are scarce, we conducted a side-by-side evaluation of the total ET and WUE of maize and biomass sorghum in central Iowa—a site within the U.S. Corn Belt. Total ET was estimated using a micrometeorological method, and aboveground plant biomass was determined using destructive hand harvests. Similar mean WUE was determined for maize (3.51 ± 0.26 g DM (mm H2O)⁻¹) and biomass sorghum (3.47 ± 0.22 g DM (mm H2O)⁻¹) over two non-drought growing seasons with total ET of 567 ± 26 mm and 600 ± 20 mm, respectively. Even though total ET and WUE were not statistically different between species (P > 0.1), maize had significantly greater theoretical ethanol yield (EY; L ethanol m⁻²) and lower ethanol water requirement (EWR; L water L ethanol⁻¹), relative to biomass sorghum (P < 0.1). We observed differences in water dynamics between species and growing seasons that were related to biophysical properties and the pattern of canopy development of maize and biomass sorghum. Our two main findings suggest that these C4 grasses may not be intrinsically different in how they use water, unless prolonged water limitation induces contrasting biophysical responses to drought. However, considering that drought conditions did not occur in 2014 and 2015, our results do not capture the response of total ET and WUE to the full range of climate variability in the Midwest U.S.
... The southern Great Plains has great potential to produce biofuel feedstock, with most efforts focusing on switchgrass (Panicum virgatum) cultivation. Switchgrass is an important component of the native tallgrass prairie ecosystem and can be cultivated on marginal lands without irrigation (Wagle et al., 2016) to produce yields in excess of 13 Mg ha −1 year −1 under moderate drought (Yimam et al., 2015) and 20 Mg ha −1 year −1 with fertilization (Thomason et al., 2005). In addition to switchgrass, the region contains existing sources of biofuel feedstock such as native tallgrass prairie, encroaching woody plants, and native oak-dominated forest. ...
... Average annual temperature is 15°C with an average monthly minimum of −3.2°C in January and an average monthly maximum of 33.3°C in July. The long-term annual average precipitation was 880 mm (Yimam et al., 2015). The Cross Timbers Experimental Range sits along the ecotone between the eastern deciduous forest and the southern Great Plains. ...
The southern Great Plains of the USA has great potential to produce biofuel feedstock while minimizing the dual stresses of woody plant encroachment and climate change. Switchgrass (Panicum virgatum) cultivation, woody biomass captured during removal of the encroaching eastern redcedar (Juniperus virginiana) to restore grasslands and thinning of the native oak forest can provide an integrated source of feedstock and improve ecosystem services. In north‐central Oklahoma, we quantified productivity and ecosystem water use of switchgrass stands and degraded ecosystems encroached by eastern redcedar and compared these to native oak forest and tallgrass prairie ecosystems. We measured aboveground net primary productivity (ANPP) using allometric equations (trees) and clip plots (herbaceous), and evapotranspiration (ET) using a water balance approach from gauged watersheds, and calculated water use efficiency (WUE = ANPP/ ET) from 2016 to 2019. Among vegetation cover types, ANPP averaged 5.1, 5.4, 6.0, and 7.8 Mg ha‐1 y‐1 for the prairie, oak, eastern redcedar, and switchgrass watersheds and was significantly greater for switchgrass in 2018 and 2019 (two and three years post‐establishment) when it reached 8.6 Mg ha‐1 y‐1. Averaged across 2017‐2019, ET was significantly greater in the forested watersheds than the grassland watersheds (1,022 mm y‐1 for eastern redcedar, 1,025 mm y‐1 for oak, 874 mm y‐1 for prairie, and 828 mm y‐1 for switchgrass). The mean WUE was significantly greater (9.47 kg ha‐1 mm‐1) for switchgrass than for the prairie, eastern redcedar, and oak cover types (6.03, 6.02, and 5.31 kg ha‐1 mm‐1). Switchgrass offered benefits of greater ANPP, less ET, and greater WUE. Our findings indicate that an integrated biofuel feedstock system that includes converting eastern redcedar encroached areas to switchgrass and thinning the oak forest can increase productivity, increase runoff to streams, and improve ecosystem services.
... In this context ADM, canopy cover (CC), iPAR and Tr collected on daily basis, would represent the optimal dataset, but technical, human or environmental constrains could not allow for daily sampling. In the light of that, most of the researches to estimate RUE and/or TUE relied on time-spaced samples or even on the data collected at harvest Kemanian et al., 2004;Kiniry et al., 2005, Garofalo andYimam et al., 2015;Liu and Stützel, 2004). ...
... Rainfall plus water supply indicated a total water consumption (soil evaporation, drainage and crop, drainage and crop transpiration) equal to 475 mm (Fig. 4 a), in line with the finding (489 mm-517 mm) reported by Hao et al. (2014), or (446 mm-683 mm) indicated by Yimam et al. (2015) both calculated under well-watered regimes. It should be pointed out that to account for the effect of closed canopy on rainfall interception, a 22% reduction of water amount from precipitation in calculating WU (Kozak et al., 2007) was applied after CC reached 0.9. ...
In this experimental-modelling research, the potential biomass achievable by sorghum to be converted in bioethanol was assessed and then formalized into the radiation use efficiency (RUE) and transpiration use efficiency (TUE). Dry above-ground biomass (harvested at the flowering stage) ranged between 22.6 t ha-1 and 28.34 t ha-1 over two growing seasons with a total water consumption of 382 mm and 504 mm, respectively. Starting from sampling measurements, the empirical framework allowed to reproduce daily data of dry biomass, canopy development, intercepted pho-tosynthetically active radiation and transpiration related efficiencies. RUE and TUE resulted 4.98 g MJ-1 and 7.45 kg m-3, respectively. Their robustness (as stable param-eters) was assessed through the validation process. Finally, the multiple linear regres-sion approach, was applied to screen among limiting factors. It was pointed out that although sorghum was grown under irrigated regime, water demand resulted not fully fulfilled to achieve the full performance of the crop.
... Evapotranspiration is used as an indicator of plant growth and yield, and it includes losses of water that are not associated with biomass production like evaporation from the soil surface, external plant surfaces, and residues, as well as productive transpiration through plant stomata [86]. A few studies considered the relation between evapotranspiration and biofuel production, for example, estimation of evapotranspiration partitioning and water use efficiency of different crops produced for biofuel production [87,88]. Yimam et al. [87] compared between switchgrass and biomass sorghum in terms of evapotranspiration efficiency, and recommended biomass sorghum as a more efficient crop in water use than switchgrass. ...
... A few studies considered the relation between evapotranspiration and biofuel production, for example, estimation of evapotranspiration partitioning and water use efficiency of different crops produced for biofuel production [87,88]. Yimam et al. [87] compared between switchgrass and biomass sorghum in terms of evapotranspiration efficiency, and recommended biomass sorghum as a more efficient crop in water use than switchgrass. Abraha et al. [88] compared rain-fed cellulosic and grain biofuel crops produced in the United States and suggested that in humid temperate, water consumption of grain biofuel crops was similar to normal consumption of grain crops. ...
Renewable energy production from biomass sources and related bio-based economy is gaining more and more attention nowadays. Research related to biomass and bio-based fuels is an important part of the strategic agenda of many countries in Europe and Asia. Furthermore, upscaling investigation in the area is undergoing in many other countries around the globe like United States, China, and India. The expansion of the biofuels usage raises concerns related to their production sustainability, including several environmental, economic, and social aspects. The aim of this chapter is to present in detail the evaluation of different climate matrices used in global biomass energy research. A strategic framework for production of biofuels and their utilization is also presented. This strategic framework merges the different environmental indicators and conversion technologies in order to achieve a sustainable circular bio-based economy.
... Sorghum bicolor (L.) Moench is highly productive C4 crop that is mainly utilized for animal feed, fodder, forage, and human food. Sorghum demonstrates several advantageous characteristics, including high water and N-use efficiencies [1][2][3] and drought tolerance [4], and exhibits limited flood tolerance [5,6]. Sorghum is also an important source of fiber and feedstock for biofuel production [7][8][9]. ...
To achieve sustainable and profitable production of sorghum for energy purposes, it is crucial to ensure the efficient use of the nutrients necessary for its growth and development. This research investigates the influence of diverse management practices on biomass production, nutrient use efficiency, and nitrogen balance in two sorghum hybrids cultivated for bioenergy applications. A comprehensive field study was conducted over two growing seasons, evaluating the effects of fertilization methods and crop rotation strategies. Results indicate that high nitrogen (HN) fertilization increased dry biomass production (up to 20.7 Mg ha−1) and nutrient removal (up to 343.5 kg K ha−1) in both sorghum hybrids. The H128 hybrid showed higher nutrient use efficiency, especially for phosphorus, while the nitrogen balance was positive under HN but varied under low nitrogen (LN), with the H133 hybrid experiencing a net nitrogen loss at LN. These findings contribute valuable insights into sustainable sorghum cultivation for bioenergy production, highlighting the importance of tailored management practices in achieving optimal crop performance.
... Precision irrigation is widely employed and is commonly defined as precise water delivery to crop at the right time, at the right place, with the right amount and the right manner (Abioye et al., 2020, Fernández et al., 2018, Khriji et al., 2014. In fact, a precise estimate of crop water requirements, also known as crop evapotranspiration (ETc), can be used to quantify the appropriate amount of irrigation, thereby helping to better manage irrigation and increase water use efficiency throughout the growing season (Ait Hssaine et al., 2021, Allen et al., 2011, Amazirh et al., 2017Elfarkh et al., 2022 ;Er-Raki et al., 2007;Kharrou et al., 2013;Pereira et al., 2015;Rozenstein et al., 2023;Yimam et al., 2015). ...
Olives constitute a frequently grown crop in semi-arid areas. Therefore, accurate quantification of evapotrans-piration (ET) within olive groves is crucial to enhance agricultural water productivity and promote their resilience to water scarcity and future climate scenarios. In the present work, we assessed the accuracy of 3 versions of the Two-Source-Energy-Balance (TSEB) model, the first one "TSEB-SPT" using a standard Priestley-Taylor coefficient (αPT) to estimate the transpiration, the second one called "TSEB-CPT" constrained by a computed αPT using measured ET along with the equilibrium term, and the third one "TSEB-SM" where soil moisture is used as an additional constraint to improve the soil evaporation. The 3 models were applied over an irrigated olive orchard in the Tensift basin (Morocco) during two growing periods of 2003 and 2004. The comparison with ground-based flux measurements from Eddy-Covariance tower and sap flow data revealed that the TSEB-SPT model overestimates ET with an average relative error of 87% and a percentage bias of-78% during the two growing seasons. Conversely, TSEB-SM and TSEB-CPT improved ET estimates as compared to TSEB-SPT, with mean relative errors of 31% and 24% and an average percentage bias of 0.6% and-7.4%, respectively. For ET partitioning, TSEB-SM appears to be less effective in estimating transpiration, while the simulated transpiration by TSEB-CPT fits well the actual one with a root mean square error of 0.27 mm, mainly during the summer of 2003. These results open a path for future improvements: by reviewing the calibration procedure of αPT, and implementing alternative formulas to compute the evaporation, the TSEB-SM could be potentially a robust tool for monitoring the seasonal variation of ET and its partitioning over a heterogeneous canopy cover.
... The enhanced soil C stock in rotational and perennial cropping systems was mainly attributed to the huge root biomass and substantially higher cumulative belowground C input than in continuous monoculture (Yimam et al., 2015;Fig. 3A). ...
Multipurpose cropping is promoted to provide biomass to meet the growing demand for biorefining, but excessive biomass removal may decrease soil C stocks and ecosystem multifunctionality. Here, soil C stocks across 0-200 cm depth and soil ecosystem multifunctionality at 0-40 cm were evaluated based on a 19-year field experiment, including three multipurpose cropping systems as continuous cotton (CC), ryegrass-sweet sorghum double cropping (RS) and perennial switchgrass (SG). Compared to CC, RS and SG increased the soil C stocks by 19% and 28%, and N stocks by 19% and 23% at 0-200 cm, respectively. The soil C stocks were positively correlated with belowground C input and negatively associated with C mineralization. RS and SG increased soil ecosystem multifunctionality by 16.8 and 15.7 folds at 0-20 cm and 0.34 and 0.61 folds at 20-40 cm relative to CC, respectively. The benefit of soil C stocks and ecosystem multifunctionality was more pronounced in SG than in RS due to the deeper root system. In conclusion, relative to continuous monoculture, rotational and perennial cropping can enhance soil C sequestration, maintain soil function, and provide feedstock for bioenergy.
... Their study analyzes differences and uncertainties in water use estimates for different types of power generation. Some works have investigated the relationship between water usage and biomass for energy purposes using the concept of water footprint for a different kind of biomass ( [79][80][81][82][83]). In this context, several works have investigated water usage in H 2 production processes ( [84][85][86][87][88]). ...
Renewable fuels contribute to net zero emissions by replacing fossil fuels in the transportation sector. Nevertheless, there are significant environmental concerns associated with renewable energy development, including land and water usage. This research explores the use of land and water related to large-scale renewable fuel production. We develop a multi-objective mathematical model to determine the optimal supply chain design for the EU's future renewable fuel demand in the transportation sector. We propose a flexible, multi-period, and multi-stage supply chain design that can accommodate multiple feedstocks and multiple products and that takes the seasonality of the resources into account. We consider economic and environmental impacts by minimizing total system costs, land use, and water use. Based on the analysis of the results, we gain insights into conflicting objective functions and the associated trade-offs and synergies to assist decision-makers in selecting an appropriate framework and gaining a better understanding of future opportunities and impacts of renewable fuel production. The outcome demonstrates that, despite not being a desirable alternative in terms of water and land usage, the utilization of energy crops as raw material has economic benefits. As shown by the results, the burden of such a supply chain lies with renewable electricity requirements that could be the capacity bottleneck and require investments. We find that we could achieve a nearly optimal value of land use and water use by increasing total cost by only 10%.
... Therefore, T/ET estimates were further evaluated against the published findings in terms of land cover types as indicated in Table 5 due to the lack of observed T/ET dataset. For croplands, the OPTREF-based T/ ET values were very close to results estimated by a crop coefficient method (Yimam et al., 2015) and to reports found by a Priestley Taylor-based ecosystem conductance model (Nguyen et al., 2021). For grasslands, the OPTREF-based T/ET results were consistently within the range synthesized from 81 ET partitioning studies (Schlesinger and Jasechko, 2014) and were similar to T/ET estimates from Nguyen et al. (2021) and from Ma et al. (2020) that used a dataset of empirical measurements in the same region as this study. ...
Drought is one of the globally extreme events and is physically defined as an extended imbalance between moisture supply and demand, which might severely affect crop growth and water preservation. More specifically, agricultural and meteorological droughts are manifest as the deficits in actual evapotranspiration (ET) and a surplus in atmospheric evaporative demand ET0 (sometimes referred to as potential ET). Therefore, the accurate estimations and reliable information regarding to ET might enhance the drought monitoring and provide better agricultural management policies. However, ET estimations and its components remain many challenges. For example, as three ET contributors are soil evaporation (ETsoil), plant transpiration (ETveg), and vegetation interception evaporation (ETic), current ET models tend to ignore the ETic and consider it as residual of two others. This leads to the uncertainties and incomprehensive reflection of ET. Additionally, ET models-based flux measurement might produce good accurate results, but they have limitations of spatial coverage. With the rapid development of remote sensing platforms, the models-based remote sensing are able to cover a large and regional scale, but they remain higher uncertainties due to the low spatial resolution, complexities in processing, requirements of many input data. Currently, the optical Sentinel-2 is a newly launched product with the Multi Spectral Instruments that might provide 10, 20, and 60-m spatial resolution, which potentially supports to design and improve ET models with superior performance. To overcome these mentioned disadvantages of ET models, the main objectives of this study are to propose a simple and objective method using only optical Sentinel-2 dataset to improve the accuracy of ET estimation; and to project the enhanced ET partitioning as feasible method for further monitoring the agricultural drought. This study might bridge the gap in knowledge and applicability of ET in monitoring the hydrological disasters under severe climate change context.
Key words: Evapotranspiration partitioning, Agricultural drought, Sentinel-2, Optical model
... Therefore, T/ET estimates were further evaluated against the published findings in terms of land cover types as indicated in Table 5 due to the lack of observed T/ET dataset. For croplands, the OPTREF-based T/ ET values were very close to results estimated by a crop coefficient method (Yimam et al., 2015) and to reports found by a Priestley Taylor-based ecosystem conductance model (Nguyen et al., 2021). For grasslands, the OPTREF-based T/ET results were consistently within the range synthesized from 81 ET partitioning studies (Schlesinger and Jasechko, 2014) and were similar to T/ET estimates from Nguyen et al. (2021) and from Ma et al. (2020) that used a dataset of empirical measurements in the same region as this study. ...
The Optical Trapezoidal method is a recently proposed method using solely optical remote sensing data with promising potential in hydroclimatic applications; however, its application in evapotranspiration (ET) parti- tioning is still questionable. This study therefore improved an Optical Trapezoidal-based Evaporative Fraction (OPTREF) model reliant on the physical association between soil surface properties and shortwave infrared transformed reflectance (STR). The proposed model was parameterized using trapezoidal shapes formed by STR and Normalized Difference Vegetation Index (NDVI) retrieved from Sentinel-2 to compute contribution of transpiration to ET (T/ET) in the Central Valley region of California, United States. Results indicated that the OPTREF model efficiently captured regional plant characteristics and seasonal variation of T/ET for three typical land cover types in study region (cropland, grassland, and savanna), particularly T/ET discrepancies rising from alternative cropping systems in cropland. Importantly, predicted T/ET values were in good agreement with previous modelling and empirical reports; for example, T/ET ranges in [0.37-0.75] for cropland, [0.30-0.82] for grassland, and [0.39-0.77] for savanna. In addition, applicability of the OPTREF approach was investigated in tracking agricultural drought using evaporative drought index (EDI), together with analysis of physiological response of T/ET to drought. The OPTREF-based EDI consistently reflected the same drought patterns indicated by records of vegetation health index and drought area percentages data from NOAA. Also, our findings un- covered that under extreme drought, the T/ET ratio is likely to increase and might be approximately equal to 1.0 in areas covered by drought-tolerant plants. Overall, this OPTREF approach offers novelty, simplicity, and versatility to satellite-based remote sensing of ET partitioning and identifying agricultural drought, especially in the context of rapid climate variation.
1.
... GEP can be regulated by climate change-induced shifts of limiting resources, as well as variation in species composition because plant species differ in their WUE (Roman et al., 2015). ET is routinely partitioned into vegetation transpiration and soil evaporation, these two components are likely to respond differently to changing environment (Hu et al., 2009;Niu et al., 2011;Yimam et al., 2015;Li et al., 2016;Medlyn et al., 2017). ...
Precipitation amount and seasonality can profoundly impact ecosystem carbon (C) and water fluxes. Water use efficiency (WUE), which measures the amount of C assimilation relative to the amount of water loss, is an important metric linking ecosystem C and water cycles. However, how increasing precipitation at different points in the growing season affects ecosystem WUE remains unclear. A manipulative experiment simulating increasing first half (FP+) and/or second half (SP+) of growing-season precipitation was conducted for 4 years (2015-2018) in a temperate steppe in the Mongolian Plateau. Gross ecosystem productivity (GEP) and evapotranspiration (ET) were measured to figure out ecosystem WUE (WUE = GEP/ET). Across the four years, FP+ showed no considerable impact on ecosystem WUE or its two components, GEP and ET, whereas SP+ stimulated GEP but showed little impact on ET, causing a positive response of WUE to FP+. The increased WUE was mainly due to higher soil water content that maintained high aboveground plant growth and community cover while ET was stable during the second half of growing season. These results illustrate that second half of growing-season precipitation is more important in regulating ecosystem productivity in semiarid grasslands and highlight how precipitation seasonality affects ecosystem productivity in the temperate steppe ecosystem.
... Previous studies have extensively investigated canopy interception in land covers other than turfgrass. For example, a forage sorghum (Sorghum bicolor L. Moench) canopy in a humid subtropical climate in Oklahoma, US intercepted 27-45% of the growing season rainfall [12]. In a tallgrass prairie dominated by big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparium), and Indiangrass (Sorghastrum nutans) in the Flint Hills region in Kansas, US, mean canopy interception throughout a two-year study accounted for 38% of annual rainfall [13]. ...
Turfgrass management relies on frequent watering events from natural precipitation or irrigation. However, most irrigation scheduling strategies in turfgrass ignore the magnitude of canopy interception. Interception is the process by which precipitation or irrigation water is intercepted by and evaporated from plant canopies or plant residue. The objective of this study was to quantify the magnitude of precipitation interception and throughfall in ‘Meyer’ zoysiagrass (Zoysia japonica L.) and ‘007’ creeping bentgrass (Agrostis stolonifera L.). We used a new method consisting of co-located pluviometers with and without circular turfgrass patches to measure interception and throughfall. The resulting dataset includes 15 storms and 25 individual rainfall events ranging in precipitation totals from 0.3 mm to 42.4 mm throughout the research study. Throughfall amount resulted in a strong (r = 0.98) positive linear relationship with precipitation totals. On average, zoysiagrass and creeping bentgrass canopies intercepted a minimum of 4.4 mm before throughfall occurred. This indicates that, on average, no precipitation reaches the soil surface for precipitation events <4.4 mm. After the point of throughfall, 16% of each additional millimeter of precipitation or irrigation is lost due to interception. Nearly, 45% of the area of the contiguous U.S. could result in >50% of the annual precipitation being intercepted by canopies of zoysiagrass and bentgrass. This study provides detailed insights to understanding the interception dynamics in turfgrass and highlights the inefficient nature of small precipitation and irrigation events in turfgrass systems.
... As an opportunity crop, sorghum (predominantly for grain) is mainly grown under nonirrigated conditions (<38% of the area under irrigation; USDA NASS, 2021b) mostly in Texas (Ciampitti et al., 2019). Field experiments have demonstrated that irrigation can increase energy biomass production in several water-limited regions of the United States such as the Southern Great Plains (Yimam et al., 2015), the Midwest (Roby et al., 2017), and the Southeast (Rocateli et al., 2012). Huntington et al. (2020) recently projected irrigated biomass production to 2099 using machine learning algorithms based on climate variables. ...
Regional scale estimations of sorghum biomass production allow identification of optimum genotype × environment × management (G×E×M) combinations for bioenergy generation. The objective of this study was to determine the degree of contributions of G, E and M toward variability in sorghum biomass in the USA. Using the Agricultural Production Systems sIMulator in a grid computing platform, biomass was simulated for irrigated and rainfed conditions for 30 years across the USA for four sorghum varietal types (grain-GS, sudangrass-SS, photosensitive-PS and photo insensitive-PI). Simulated biomass was assessed by environments clustered using the sum of intercepted solar radiation (ir), mean of temperature stress factor (tp) and water stress factor (sw). Simulated biomass ranged from 5.8 t ha-1 (GS-rainfed) to 27.5 t ha-1 (PI-irrigated). Under high-temperature environments (mean annual temperature=25°C), rainfed biomass between 40 and 80 days after planting (DAP) was strongly correlated with sw (r=0.64-0.86) and irrigated biomass with ir (r=0.68-0.81). Under low-temperature environments (mean annual temperature=18°C) after 40DAP, tp and ir had greater effects than sw (r=0.55-0.82). Biomass variance was mainly explained by varietal type (50-76%) in all environments × irrigation combinations, except in the high- and mid-temperature environments under rainfed conditions where rainfall had the major effect (25-45%). However, when mean temperature during the growing season decreased from 25°C (high-environments) to 18°C (low-environments), the contribution of mean temperature to biomass variance increased from 7% to 34% (rainfed) and from 4% to 36% (irrigated). Varietal type had the larger interactions with other factors independently of the environment and irrigation. We demonstrated a need to quantify (i) the main G×E×M drivers of biomass variability based on environmental stress factors and (ii) the variance contribution of these drivers on sorghum biomass. Our regional-scale estimations are key inputs for future robust biomass projections of energy sorghum genotypes integrating G×E×M under climate change scenarios.
... This is due to the fact that the ET lawn included the transpiration of the grass and the evaporation of the canopy and soil. Evaporation could count for 28% [75], 64% [76], and 12-27% [77] of the ET lawn in previous studies. In Huanjiang, Guangxi, which also experiences a subtropical humid climate, the evaporation contributed 36% of the ET lawn in the growing season [78]. ...
Urban evapotranspiration (ET) is an effective way to mitigate ecological challenges resulting from rapid urbanization. However, the characteristics of urban vegetation ET, especially how they respond to meteorological factors and soil water, remains unclear, which is crucial for urban ET regulation. Therefore, this study measured the actual ET rate of an urban lawn (ETlawn) using the Bowen ratio system and an urban tree (Ttree) by a sap flow system in the hot summer of a subtropical megacity, Shenzhen. The results showed that the daily ETlawn was more restricted by energy (Rs) and diffusion conditions (vapor pressure deficit, VPD), while the daily Ttree was more restricted by VPD and relative extractable water (REW) in the urban area. The daily Ttree decreased when the REW was lower than 0.18, while the daily ETlawn started to decrease when it was lower than 0.14. When REW was lower than 0.11, the Ttree stayed at a relatively low level. The impacts of VPD was more evident on the diurnal Ttree than on the diurnal ETlawn. Wind speed had a scarce impact as it was relatively low in urban areas. This study clarifies the different responses of ETlawn and Ttree to meteorological factors and soil water based on actual ET. The results are of great significance for the knowledge of urban forestry and urban hydrology.
... However, average simulated biomass was 33% lower in dry years (4.25 ± 0.9 Mg ha −1 ; precipitation < 536 mm) and 28% higher in wet years (8.17 ± 0.6 Mg ha −1 ; precipitation >785). Precipitation during the growing season drives crop development in semi-arid regions such as the Texas Rolling Plains (Yimam et al., 2015). Intermittent drought and scanty precipitation during the growing season can significantly reduce biomass yield (Hao et al., 2015;Maw et al., 2017). ...
The Decision Support System for Agrotechnology Transfer for sugarcane (DSSAT‐CANEGRO) was evaluated for simulating the growth of energy cane (Saccharum spp. hybrid), a perennial biofuel feedstock crop. Plant growth data collected from a field experiment conducted in the semi‐arid Texas Rolling Plains was used for model calibration and validation. All model performance indicators showed good agreement between simulated and measured biomass accumulation. After calibration, model was used for simulating plant cane and ratoon biomass yield using long‐term (i.e., 33‐year) historic weather data under rainfed and two irrigation levels. The irrigated treatments were a) 300 mm seasonal supplementary irrigation and b) auto‐irrigation to replenish soil water in the profile to field capacity. The long‐term average biomass yield of plant cane (6.4 ± 0.47 Mg ha–1) and ratoon (14.4 ± 0.92 Mg ha–1) were the lowest when simulated under rainfed conditions. Supplemental irrigation with 300 mm irrigation water significantly increased yield of both crops (14.6 ± 0.53 Mg ha–1 for plant cane and 29.5 ± 1.33 Mg ha–1 for ratoon). The auto‐irrigation option substantially increased the amount of water applied and resulted in an average biomass of 16.7 ± 0.24 Mg ha–1 for plant cane and 44.4 ± 0.36 Mg ha–1 for ratoon. Biomass water use efficiency was the highest for ratoon due to its longer growing season. This modeling study showed reasonable performance of DSSAT‐CANEGRO for simulating energy cane growth. Irrigation experiments using historical data showed energy cane as a competitive biomass crop in the Texas Rolling Plains region.
... The accurate quantification of ETc at local and regional scales can aid in water resource-based policy and decision making and help manage our water resources. ETc is an energy-driven process and an important component of water budget [2] and is an essential component of irrigation water requirement quantification, irrigation planning and design, soil, and hydrological modeling [3], water use efficiency [4], and carbon flux [5], amongst others. ...
The regional-scale estimation of crop evapotranspiration (ETc) over a heterogeneous surface is an important tool for the decision-makers in managing and allocating water resources. This is especially critical in the arid to semi-arid regions that require supplemental water due to insufficient precipitation, soil moisture, or groundwater. Over the years, various remote sensing-based surface energy balance (SEB) models have been developed to accurately estimate ETc over a regional scale. However, it is important to carry out the SEB model assessment for a particular geographical setting to ensure the suitability of a model. Thus, in this study, four commonly used and contrasting remote sensing models viz. METRIC (mapping evapotranspiration at high resolution with internalized calibration), SEBAL (surface energy balance algorithm for land), S-SEBI (simplified surface energy balance index), and SEBS (surface energy balance system) were compared and used to quantify and map the spatio-temporal variation of ETc in the semi-arid to arid inter-mountain region of Big Horn Basin, Wyoming (Landsat Path/Row: 37/29). Model estimates from 19 cloud-free Landsat 7 and 8 images were compared with the Bowen ratio energy balance system (BREBS) flux stationed in a center pivot irrigated field during 2017 (sugar beet), 2018 (dry bean), and 2019 (barley) growing seasons. The results indicated that all SEB models are effective in capturing the variation of ETc with R2 ranging in between 0.06 to 0.95 and RMSD between 0.07 to 0.15 mm h−1. Pooled data over three vegetative surfaces for three years under irrigated conditions revealed that METRIC (NSE = 0.9) performed better across all land cover types, followed by SEBS (NSE = 0.76), S-SEBI (NSE = 0.73), and SEBAL (NSE = 0.65). In general, all SEB models substantially overestimated ETc and underestimated sensible heat (H) fluxes under dry conditions when only crop residue was available at the surface. A mid-season density plot and absolute difference maps at image scale between the models showed that models involving METRIC, SEBAL, and S-SEBI are close in their estimates of daily crop evapotranspiration (ET24) with pixel-wise RMSD ranged from 0.54 to 0.76 mm d−1 and an average absolute difference across the study area ranged from 0.47 to 0.56 mm d−1. Likewise, all the SEB models underestimated the seasonal ETc, except SEBS.
... maize plants (Zhang et al., 2016;Fan et al., 2018). Partitioning ET into I c , E s and T p is desirable to improve the understanding of soil water loss processes and then to increase crop production through maximizing transpiration and reducing evaporation (Yimam et al., 2015). ...
Soil mulching can effectively modify crop growth environments and increase crop productivity in rainfed agriculture, and the knowledge about water fluxes within the soil-crop-atmosphere ecosystem is essential for improving water productivity (WP) in water-limited regions such as Northwest China. This study systematically investigated seasonal and inter-annual dynamics of evapotranspiration (ET) partitioning into canopy interception (Ic), soil evaporation (Es) and plant transpiration (Tp) in rainfed maize fields under four mulching conditions (NM: non-mulching, SM: straw mulching, RPBF: plastic-mulched ridge with bare furrow, and RPSF: plastic-mulched ridge with straw-mulched furrow) from June to October in 2015, 2016 and 2017 characterized by various seasonal rainfall distributions. The results showed that seasonal ET was slightly higher under mulching conditions compared with NM during each growing season, but the difference was not statistically significant. Soil mulching decreased Es/ET (22.0–29.8 %, 14.3–19.5 % and 11.3–15.1 % under SM, RPBF and RPSF, respectively) relative to NM (27.6–34.5 %), while it increased Tp/ET (55.8–63.7 %, 63.0–71.0 % and 65.6–73.2 %, respectively) and Ic/ET (13.2–16.0 %, 14.7–17.4 % and 15.4–19.3 %, respectively) relative to NM (52.4–58.7 % and 13.0–15.7 %, respectively). Differences in ET partitioning under contrasting mulching conditions were related largely to variations in leaf area index and soil water stress. Although seasonal ET under various mulching conditions varied among the three seasons (264.8–286.6 mm in 2015, 241.2–242.5 mm in 2016 and 296.6–324.4 mm in 2017), the proportions of Ic (13.0–15.4 %, 13.3–19.3 % and 15.7–17.7 %), Es (11.3–28.3 %, 15.1–34.5 % and 11.4–27.6 %) and Tp (58.7–73.2 %, 52.4–65.6 % and 56.7–70.9 %) to total ET were similar. Soil mulching greatly enhanced maize yield by 9.5–26.1 %, 27.0–186.5 % and 30.8–209.7 % under SM, RPBF and RPSF compared with NM, respectively, resulting in 1.5–15.8 %, 19.0–184.7 % and 20.8–214.8 % higher WP, respectively. It was concluded that soil mulching largely promoted Tp and restrained Es in spite of slight increase in Ic, thereby improving maize yield and WP during the three seasons. The present study gives a better understanding of rainwater cycle and crop water use, which is critical to sustainable management of rainfed agriculture.
... When the SDI and SSDI methods are compared, it is noteworthy that a water saving of 27.2 mm in 2017 and 21.1 mm in 2018 has been achieved in terms of full irrigation (I 100 ) level. Sorghum ET were reported to vary from 200.0 to 683.0 mm (Mastrorilli et al., 1995b;Dercas et al., 2001;Sakellariou-Makrantonaki et al., 2007;Lamm et al., 2010;Klocke et al., 2012;Hao et al., 2014;Yimam et al., 2015;Mengistu et al., 2016;Wagle et al., 2016). El-Awady et al. (2003) K. Aydinsakir, et al. ...
The objective of the present study was to determine the effects of different irrigation levels applied with surface drip irrigation (SDI) and subsurface drip irrigation (SSDI) method on yield and bioethanol productivity of sorghum (Sorghum bicolor L. cv. Early Sumac) in the West Mediterranean Region of Turkey. Field study was conducted in Batı Akdeniz Agricultural Research Institute in Antalya during the growing seasons of 2017−2018. Five different irrigation levels designated as full irrigation (I100) with no water stress and slight (I75), mild (I50), severe water stress (I25) and no irrigation (I0) treatments were applied. The results showed that different irrigation levels applied had statistically significant effect on yield and yield components such as plant height, leaf number, leaf area index, chlorophyll context, brix, sucrose, glucose, fructose and bioethanol. In both of the drip irrigation methods, water deficit stress significantly (P ≤ 0.01) decreased bioethanol yield. The maximum bioethanol yield was obtained from SSDI method under full irrigation, slight, mild, severe and full water deficit stress as much as 2085, 2045, 1684, 1569 and 1407 L ha⁻¹, respectively, in 2017 and 2390, 2266, 1954, 1901 and 1493 L ha⁻¹, respectively, in 2018. The highest water consumption was observed in I100 treatment as 553.6 mm for SDI in 2017, while the lowest was found in I0 treatment as 198.5 mm for SDI in 2018. The highest water productivity was found in I0 as 6.0 kg ha⁻¹ mm⁻¹ for SSDI method in 2018, and the lowest one was found in I25 as 2.9 kg ha⁻¹ mm⁻¹ for SDI in 2017. The results of the present study showed that an average water saving of 24.0 mm compared with the SDI method was achieved without any decrease in efficiency in the SSDI method.
... Although increase in cultivated land was accompanied by a corresponding increase in the evaporative index, the decreasing ET trajectory could be linked to stomata closure to optimise water use under conditions of moisture deficit as recognised by Hernandez et al. (2015) with respect to maize (Zea mays) in water limited environments. Yimam et al. (2015) also reported higher water use efficiency of sorghum compared to switch grass. It should be noted that in the study area, maize and sorghum are the main cultivated crops. ...
ABSTRACT
It is imperative to understand the strong coupling between the carbon capture process and water use to sustainably manage rangelands. Woody encroachment is undermining rangelands grass production. Evapotranspiration (ET) highlights the links between ecosystem carbon capture process and water use. It forms the biggest flux of the hydrological cycle after precipitation yet it is not well understood. The Grassland and the Albany Thicket (AT) biomes in the Eastern Cape, South Africa, provide an interesting space to study the dynamics in rangelands biomass production and the associated water use. Therefore, the main purpose of this study was to contribute towards management of rangelands by understanding the dynamics in rangeland grass production and water use. To achieve this aim, the impact of Acacia mearnsii, an invasive alien plant, on soil chemical properties and rangelands grass production was investigated. This was achieved by analysing the biophysical attributes of A. mearnsii as they related to grass production. Secondly, selected soil variables that could be used as a prognosis for landscape recovery or deterioration were evaluated. In addition, aboveground grass biomass was measured in areas cleared of A. mearnsii and regression equations were prepared to help model aboveground grass biomass in areas cleared of A. mearnsi. The thesis also explored dynamics in water vapour and energy fluxes in these two biomes using an eddy covariance system. Consequently, water vapour and energy fluxes were evaluated in order to understand landscape water use and energy partitioning in the landscape. The study also tested the application of Penman-Monteith equation based algorithms for estimating ET with micrometeorological techniques used for validation. Pursuant to this, the Penman-Monteith-Leuning (PML) and Penman-Monteith-Palmer (PMP) equations were applied. In addition, some effort was devoted to improving the estimates of ET from the PMP by incorporating a direct soil evaporation component. Finally, the influence of local changes in catchment characteristics on ET was explored through the application of a variant of the Budyko framework and investigating dynamics in the evaporative index as well as applying tests for trends and shifts on ET and rainfall data to detect changes in mean quaternary catchment rainfall and ET. Results revealed that A. mearnsii affected soil chemical properties and impaired grass production in rangelands. Hence, thinning of canopies provided an optimal solution for enhanced landscape water use to sequestrate carbon, provide shade, grazing, and also wood fuel. It was also shown that across sites, ET was water limited since differences between reference ET and actual ET were large. ET was largely sensitive to vapour pressure deficit and surface conductance than to net radiation, indicating that the canopies were strongly coupled with the boundary layer. Rangeland ET was successfully simulated and evaporation from the soil was the dominant flux, hence there is scope for reducing the so-called ‘unproductive’ water use. Further, it was shown that the PML was better able to simulate ET compared to the PMP model as revealed by different model evaluation metrics such as the root mean square error, absolute mean square error and the root mean square observations standard deviation ratio. The incorporation of a soil evaporation component in the PMP model improved estimates of ET as revealed by the root mean square error. The results also indicated that both the catchment parameter (w) and the evaporative index were important in highlighting the impacts of land cover change on ET. It was also shown that, despite changes in the local environment such as catchment characteristics, global forces also affected ET at a local scale. Overall, the study demonstrated that combining remote sensing and ground based observations was important to better understand rangeland grass production and water use dynamics.
... It is important to mention that differences between baseline conditions and scenario results depend on the selection of model parameters to represent land use changes. Parameter modifications to represent land use changes were based on information reported by several studies: Baron et al. (1993) Yimam et al. (2018). The results presented are highly dependent on the applicability of the information reported in the literature for our CCW and model assumptions. ...
... The use of irrigation in the sorghum crop also shows high biomass yields, due to its high efficiency in water use and competition, being a crop with high potential for the Brazilian Semi-arid (Yimam et al., 2015;Campi et al., 2016). In intercrop with the forage cactus, the productive benefits of the production system are even greater (Farias et al., 2000;Amorim et al., 2017;Diniz et al., 2017), since there is an increase in yield, in quality and in forage intake by animals, reducing spending on concentrated foods (Lopes et al., 2017). ...
In arid and semi-arid regions, climatic conditions and salinization of soil and water lead to declines in forage production and compromise the yield of herds. Therefore, the use of adapted forage species and of high nutritional value becomes an alternative to maintain the availability of food in seasonal periods. Among these species, forage
cactus is a recommended food for ruminants, due to the high-water content in its structures, good acceptability and low production cost. Sorghum cultivation also has high forage potential, high dry matter production, low water demand, and adaptability to intercropping, helping in the improvement of the production in arid and semi-arid environments. The use of intercropped systems added to irrigation is of great relevance for the sustainable management of local livestock, since this type of system maximizes the forage yield of the productive areas. Thus, the aim of this review was to emphasize the importance of studies related to the forage cactus-sorghum intercropping under irrigated conditions in the semi-arid region to subsidize policies for continuous forage production. The information compiled in this review encourages research in agricultural area planning in neglected environments under semi-arid conditions with the forage cactus sorghum intercropping for the forage production.
... The use of irrigation in the sorghum crop also shows high biomass yields, due to its high efficiency in water use and competition, being a crop with high potential for the Brazilian Semi-arid (Yimam et al., 2015;Campi et al., 2016). In intercrop with the forage cactus, the productive benefits of the production system are even greater (Farias et al., 2000;Amorim et al., 2017;Diniz et al., 2017), since there is an increase in yield, in quality and in forage intake by animals, reducing spending on concentrated foods (Lopes et al., 2017). ...
In arid and semi-arid regions, climatic conditions and salinization of soil and water lead to declines in forage production and compromise the yield of herds. Therefore, the use of adapted forage species and of high nutritional value becomes an alternative to maintain the availability of food in seasonal periods. Among these species, forage cactus is a recommended food for ruminants, due to the high-water content in its structures, good acceptability and low production cost. Sorghum cultivation also has high forage potential, high dry matter production, low water demand, and adaptability to intercropping, helping in the improvement of the production in arid and semi-arid environments. The use of intercropped systems added to irrigation is of great relevance for the sustainable management of local livestock, since this type of system maximizes the forage yield of the productive areas. Thus, the aim of this review was to emphasize the importance of studies related to the forage cactus-sorghum intercropping under irrigated conditions in the semi-arid region to subsidize policies for continuous forage production. The information compiled in this review encourages research in agricultural area planning in neglected environments under semi-arid conditions with the forage cactus sorghum intercropping for the forage production.
... Modifications to baseline model parameters to represent land use changes (e.g. native vegetation and cover crops/no-till) were based on information reported by several studies: Baschle, (2017); Mohamoud, (1991); VanLoocke et al., (2012);Kang et al. (2003);Baron et al. (1993),Bharati et al. (2002);Yimam et al. (2015),and Cronshey, (1986). ...
Each one of Iowa's 99 counties has been impacted by flooding events that exceeded the state's capacity to respond and that ultimately led to flood-related presidential disaster declarations (FRDD). In the last three decades, the total number of FRDD in Iowa counties has exceeded 900 making flooding one of the most prominent environmental challenges that Iowa faces. Physically-based watershed modeling was used to evaluate the flood reduction benefits expected from both nature-based and structural mitigation strategies. Model baseline conditions were determined using a 15-year continuous simulation. The model was forced with hourly climatological data and simulated streamflow hydrographs were compared against measurements taken at USGS stations. The model was able to reproduce satisfactorily the measured hydrographs as well as seasonal and annual trends. Model baseline parameters were modified to simulate implementation of cover crops and native vegetation (e.g. tall-grass prairie) in the study area. In addition, the watershed model was used to evaluate the flood reduction benefits associated to a system of distributed storage built with ponds located in the watershed's headwater catchments. This work presents quantifications of changes in watershed's hydrology as well annual peak flow reductions.
... En la actualidad, se requiere un entendimiento claro de la dependencia de los cultivos a la disponibilidad de agua y los posibles impactos de los sistemas agrícolas en la hidrología de una región (Yimam et al., 2015). El conocimiento de la evapotranspiración es esencial para los responsables de la planif icación y manejo del agua en el sector agrícola, especialmente en las regiones áridas y semiáridas donde la demanda de agua de los cultivos supera la precipitación y se requiere la aplicación a través del riego. ...
Estimating evapotranspiration (ETc) is essential for water planning and management in agricultural areas, particularly in arid and semi-arid regions; ETc partitioning into soil evaporation (E) and plant transpiration (T) would allow the use of more eff icient water management strategies. The aims of the present study were to estimate daily evapotranspiration of sorghum and its components, using the FAO-56 method with the dual crop coeff icient (dual Kc) approach and scintillometer method, and to determine the single crop coeff icient (Kc) and basal crop coeff icient (Kcb) values for different development seasons. Results have shown that using the dual Kc approach allows reasonable simulation of ETc in comparison to values estimated using the scintillometer method. ETc estimated with both methods was 413.8 and 406.3 mm, respectively, resulting in a 1.8% overestimation for FAO-56. Root mean square error (RMSE) was 0.584 mm d-1 and Willmott’s agreement coeff icient (d) was 0.91. Evaporation estimated with FAO-56 was 17.1% of ETc, while with the scintillometer it was 21.6% of ETc. The RMSE of the estimated E values was 0.397 mm d-1 and d = 0.94, while, when comparing T, calculated RMSE was 0.371 mm d-1 and d = 0.98. Kc values estimated with the FAO-56 method were 0.68, 1.06 and 0.4 for initial, middle and end season of the crop, while for the scintillometer, values were 0.75, 0.94 and 0.41, respectively.
... En la actualidad, se requiere un entendimiento claro de la dependencia de los cultivos a la disponibilidad de agua y los posibles impactos de los sistemas agrícolas en la hidrología de una región (Yimam et al., 2015). El conocimiento de la evapotranspiración es esencial para los responsables de la planif icación y manejo del agua en el sector agrícola, especialmente en las regiones áridas y semiáridas donde la demanda de agua de los cultivos supera la precipitación y se requiere la aplicación a través del riego. ...
SUMMARY
Estimating evapotranspiration (ETc) is essential for water planning and management in agricultural areas, particularly in arid and semi-arid regions; ETc partitioning into soil evaporation (E) and plant transpiration (T) would allow the use of more eff icient water management strategies. The aims of the present study were to estimate daily evapotranspiration of sorghum and its components, using the FAO-56 method with the dual crop coeff icient (dual Kc) approach and scintillometer method, and to determine the single crop coeff icient (Kc) and basal crop coeff icient (Kcb) values for different development seasons.
... The NSE value for LAI was 0.86 with a corresponding R 2 and PBIAS values of 0.88 and 5.2% for the DeKalb 52-59 at the LIRF (Fig. 4). A good match of simulated LAI with the observed data is important for obtaining reasonable partitioning of ET to transpiration and evaporation and accurate simulation of crop growth stages (Chen et al., 2018;Yimam et al., 2015). It is also crucial to obtain good corn growth simulations for the full irrigation scenarios using adequate plant growth parameterization so that meaningful evaluations of the plant stress algorithms can be performed using the deficit irrigation treatments. ...
Core Ideas
SWAT simulated corn LAI and yield of full irrigation matched measured data well.
Stress algorithms adjusted corn LAI and yield unsatisfactory for limited irrigation.
Stress algorithms only consider dominant stress factors such as water and temperature.
Stress algorithms only adjust LAI and biomass rather than crop growth parameters.
Long‐term measured field data are needed to develop new stress algorithms.
ABSTRACT
Decreased groundwater levels of the Ogallala Aquifer have increased interest in simulating crop responses to deficit irrigation strategies to evaluate the sustainable irrigation management for profitable crop production. However, the ability of widely used simulation models to accurately represent crop responses to deficit irrigation is not thoroughly evaluated. Therefore, the objective of this research was to evaluate the efficacy of the plant stress algorithms in Soil and Water Assessment Tool (SWAT) to simulate corn (Zea mays L.) responses to deficit irrigation treatments. Results showed simulated corn leaf area index (LAI), biomass, and yield under full irrigation scenarios matched measured data reasonably well at two study sites. However, clear reductions in model performance statistics for corn LAI simulations were found under the deficit irrigation scenarios for both sites (Nash‐Sutcliffe efficiency [NSE] <0.49; percent bias [PBIAS] >14%). Additionally, considerable overestimation of yield occurred in the deficit irrigation scenarios for both sites (PBIAS >30% in most years). The unsatisfactory results from simulations of both LAI and yield under the deficit irrigation scenarios suggested potential deficiencies of the plant stress algorithms in SWAT. Two apparent limitations of the plant stress algorithms were (i) the equation for computing actual plant growth factor using a singular stress factor, determined by the maximum value of four plant stress factors of water, temperature, nitrogen, and phosphorus, and (ii) the computed actual plant growth factor only adjusting potential daily accumulations of LAI rather than modifying the shape of the LAI development by adjusting related parameters.
... Although increase in cultivated land was accompanied by a corresponding increase in the evaporative index, the decreasing AET trajectory could be linked to stomata closure to optimise water use under conditions of moisture deficit as recognised by Hernández et al. (2015) with respect to maize (Zea mays) in water limited environments. Yimam et al. (2015) also reported higher water use efficiency of sorghum compared to switch grass. It should be noted that in the study area, maize and sorghum are the main cultivated crops and hence there is a distinct possibility for optimal water use leading to reduced AET relative to carbon accumulated. ...
Land cover change is a pervasive force and it influences the relationship between precipitation (P) and actual evapotranspiration (AET). The study sought to determine variations in catchment scale AET attributable to land cover change over a grassland in the Eastern Cape, South Africa. Remotely sensed rainfall and AET data were used. Land cover maps for the study area were used to extract annual AET from the MOD16 ET product. The method of cumulative residuals was applied to link dynamics in AET with land cover change to enable the application of an appropriate map for retrieving AET. Rainfall and AET were subjected to the Mann- Kendall and Pettitt's tests. Grassland and built-up cover classes AET showed step changes (p < 0.05) indicating sudden changes. Forest cover revealed a marginal trend (p < 0.1), since forest cover change was a slow process. Changes in the evaporative index suggest that land cover influenced AET and this was confirmed by dynamics in the catchment parameter (w). Average w (1.88) indicated that the catchment had a low water retention capacity and this suggests that the hydrological response was sensitive to land cover change. Management interventions are required to improve water retention in the catchment.
... Many studies analysed water use efficiency (WUE) as the relationship between biomass or grain yield and evapotranspiration (ET) (Dagdelen et al., 2006;Fischer, 1979;Garafolo and Rinaldi, 2013;Kresovic et al., 2016;Suyker and Verna, 2009;Tolk et al., 1998;Yimam et al., 2015). Separating the components of ET, soil evaporation (E) and crop transpiration (T) (Cooper et al., 1987;de Wit, 1958): ...
... K c values reported by Guidi et al. (2008) for unfertilized willow and poplar ranged from 0.6 to 1.2 during the growing season. Faced with a lack of K c estimates for biomass sorghum and switchgrass in the literature, Yimam et al. (2015) approximated them using FAO K c values for sweet sorghum (1.05 midseason, 1.2 late season) and sudan grass (0.5 early season, 1.15 mid-season, 1.1 late season), respectively, as surrogates. For biomass crops, PRISM-ELM K c was set to single values between 1.0 and 1.3, with refinements made which gave the best fit to the yield data. ...
Several crops have recently been identified as potential dedicated bioenergy feedstocks for the production of power, fuels, and bioproducts. Despite being identified as early as the 1980s, no systematic work has been undertaken to characterize the spatial distribution of their long-term production potentials in the US. Such information is a starting point for planners and economic modelers, and there is a need for this spatial information to be developed in a consistent manner for a variety of crops, so that their production potentials can be inter-compared to support crop selection decisions. As part of the Sun Grant Regional Feedstock Partnership, an approach to mapping these potential biomass resources was developed to take advantage of the informational synergy realized when bringing together coordinated field trials, close interaction with expert agronomists, and spatial modeling into a single, collaborative effort. A modeling and mapping system called PRISM-ELM was designed to answer a basic question: how do climate and soil characteristics affect the spatial distribution and long term production patterns of a given crop? This empirical/mechanistic/biogeographical hybrid model employs a limiting factor approach, where productivity is determined by the most limiting of the factors addressed in sub-models that simulate water balance, winter low temperature response, summer high temperature response, and soil pH, salinity, and drainage. Yield maps are developed through linear regressions relating soil and climate attributes to reported yield data. The model was parameterized and validated using grain yield data for winter wheat and maize, which served as benchmarks for parameterizing the model for upland and lowland switchgrass, CRP grasses, Miscanthus, biomass sorghum, energycane, willow, and poplar. The resulting maps served as potential production inputs to analyses comparing the viability of biomass crops under various economic scenarios. The modeling and parameterization framework can be expanded to include other biomass crops.
... A graphical comparison showed that SWAT simulated LAI after calibration matched the observed data well (Fig. 3). A good fit of simulated LAI is beneficial for achieving reasonable partitioning of transpiration and evaporation, which in turn, contribute to the accurate simulations of both the hydrologic cycle and plant growth (Yimam et al., 2015). In this study, it is of primary importance to obtain good LAI simulation agreement due to the development of FAO-MADs for the schedule by date option. ...
Decreasing groundwater availability in the Texas High Plains has resulted in the widespread adoption of management allowed depletion (MAD) irrigation scheduling. Modeling of such practices and their effects on water balance components can be a cost-effective and time-saving alternative to field-based research. However, studies have identified deficiencies in the auto-irrigation algorithms in the Soil and Water Assessment Tool (SWAT) including the continuation of irrigation during the non-growing season and an inability to simulate growth stage-specific irrigation. Consequently, new and representative auto-irrigation algorithms were developed using 1) a uniform, single season MAD and 2) a growth stage-specific MAD with options for seasonal growth stage partitioning based on scheduled date and accumulated heat units. Comparisons with observed data from an irrigated lysimeter field showed improved model performance for simulations of irrigation amount and frequency and actual evapotranspiration. Minimal differences in leaf area index and yield were observed with the non-water stressed management.
... Agricultural uses of the data continued to be strong, especially for research on improving management of resources such as cattle (Scasta et al. 2015), crops (Lollato & Edwards 2015), and timber (Bendixsen, Hallgren & Frazier 2015). Increased attention to potential energy resources, such as biofuels (Yimam, Ochsner & Kakani 2015), solar (McGovern et al. 2015), and wind (Stadler, Dryden & Green 2015) also drew upon Mesonet sensor data for economic and technical model building. ...
This pilot study of 110 scientific papers utilizing environmental sensor data from the Oklahoma Mesonet during its first two decades of operations demonstrates the diversity of potential purposes in scientific research for a robust, rigorously maintained, accessible source of environmental sensor data, as well as the challenges involved in identifying uses of that data within scientific papers. The study authors selected three publication years (1995, 2005, 2015) from an extensive corpus of peer-reviewed journal publications, identified each paper’s specific citation of and uses of the Mesonet’s environmental sensor data, and derived a typology of those usages (assimilation, experimentation, observation, simulation, utilization, validation) found to be most common. The rapid increase in data assimilation research projects today is discussed in terms of the difficulty and importance of correct attribution to individual data sources in these complex research projects. The study examines the possible role played by highly-cited papers that describe the quality assurance procedures in sensor data sources, which may serve as surrogates to signal the quality of the data provided by such sources, and which may also provide a useful contribution towards understanding data citation as a special form of scholarly citation.
... Overall, the field was supplied with 400 mm of irrigation water in 2013 (12 irrigations) and 2014 (13 irrigations), and 267 mm of irrigation water in 2015 (7 irrigations). The field was harvested at physiological maturity for seed on 8 October in 2013 (DOY 282), 11 October in 2014 (DOY 285), and 1 October in 2015 (DOY 275). The growing season was 140, 147, and 119 days long in 2013, 2014, and 2015, respectively. ...
The eddy covariance method was used to investigate carbon fluxes and evapotranspiration (ET) from a high biomass forage sorghum (Sorghum bicolor L.) field in the Southern U.S. Great Plains for three growing seasons (2013–2015). Above normal precipitation and narrow row spacing (50 cm) led to higher biomass production (25 Mg ha⁻¹) and leaf area index (LAI = 7.2) development in 2014. This also resulted in higher carbon uptake or net ecosystem production (NEP) and ET during that year. Early and late season precipitation enhanced ecosystem respiration (Reco) resulting in lower NEP in 2015. Shorter growing season (119 days) also contributed to lower cumulative NEP in 2015. Estimated gross primary production (GPP) in 2014 (1780 g m⁻²) was 10% higher than the GPP in 2013 (1591 g m⁻²) and 24% higher than the GPP in 2015 (1353 g m⁻²). During all growing seasons, the site was a source of carbon (negative NEP) at the beginning and transitioned to a sink (positive NEP) later in the season. Biomass-GPP relationship indicated that approximately 65% of total GPP was allocated to above ground biomass (AGB). Average monthly ecosystem WUE (expressed as gross carbon gain per unit of ET) ranged from 1.7 g mm⁻¹ to 4.2 g mm⁻¹. Results from our study indicate that weather conditions, growing season length and crop management are important factors in determining the magnitude of carbon uptake and release, and ET of this cellulosic biofuel feedstock crop in the Southern U.S. Great Plains.
The water footprint of a crop (WF) is a common metric for assessing agricultural water consumption and productivity. To provide an update and methodological enhancement of existing WF datasets, we apply a global process-based crop model to quantify consumptive WFs of 175 individual crops at a 5 arcminute resolution over the 1990–2019 period. This model simulates the daily crop growth and vertical water balance considering local environmental conditions, crop characteristics, and farm management. We partition WFs into green (water from precipitation) and blue (from irrigation or capillary rise), and differentiate between rainfed and irrigated production systems. The outputs include gridded datasets and national averages for unit water footprints (expressed in m³ t⁻¹ yr⁻¹), water footprints of production (m³ yr⁻¹), and crop water use (mm yr⁻¹). We compare our estimates to other global studies covering different historical periods and methodological approaches. Provided outputs can offer insights into spatial and temporal patterns of agricultural water consumption and serve as inputs for further virtual water trade studies, life cycle and water footprint assessments.
The water requirements of the wheat crop are represented by the actual evapotranspiration, which depends on the meteorological data of the study area and the amount of water consumed during the season. Estimation of crop coefficients (KC) and evapotranspiration (ETc) using remote sensing data is essential for decision-making regarding water management in irrigated areas in arid and semi-arid large-scale areas. This research aims to estimate the crop coefficient calculated from remote sensing data and the actual evapotranspiration values (ETc) for the crop. The FAO Penman-Monteith equation has been used to estimate the reference evapotranspiration (ETo) from meteorological data. Linear regression analysis was applied by developing prediction equations for the crop coefficient (KC) for different growth stages of comparing with the vegetation cover index (NDVI). The results showed that (R^2=0.98 ) between field crop coefficient and crop coefficient predicted from (Kc=2.0114 NDVI-0.147) in addition to (RMSE = 0.92 and (d= 0.97).
Partitioning evapotranspiration (ET) into soil evaporation (Esoil), canopy interception evaporation (Eic), and transpiration (T) yields both comprehensive insight into hydrological processes and better water management, but it is challenging. This study proposes a modified ecosystem conductance-based Priestley-Taylor (MEC-PT) algorithm for ET partitioning based on the total ecosystem conductance (GTotal) fractions of soil, interception, and canopy. Datasets from 24 flux towers around the world were used to estimate GTotal by coupling aerodynamic conductance and surface conductance (Gs). Results from the MEC-PT model were compared with those from an original best-fit ecosystem-level conductance (m-order) model that only partitions Gs into soil and canopy domains. The superior performance of the MEC-PT model, with the inclusion of an intercepted contributor and ability to fill the data gap associated with the m-order during wet conditions, describes the robustness of this approach for partitioning ET. The MEC-PT model results might reflect dew formation that produces minimal Eic volume under non-rainfall conditions with support from the diurnal temperature (DT) presence. The ratio of T to total ET (T/ET) was found highest in forest with 0.72 (±0.17 of standard deviation), followed by savanna (0.57 ± 0.11), cropland (0.48 ± 0.10), and grassland (0.39 ± 0.17). Also, sensitivity analysis was conducted with main input variables of the MEC-PT and m-order models over four land cover types and the whole study period of each site used in this study. The results demonstrated that, in general conditions, net radiation was the key driver controlling T/ET variations, whereas air temperature and wind speed indirectly and slightly affected T/ET. This study underlines that the inclusion of Eic might bridge the gap in knowledge about ET and its components regarding canopy dynamics and ecosystem behaviors in the context of climate change.
Carbon capture and sequestration (CCS) is an important technology to reduce fossil CO2 emissions and remove CO2 from the atmosphere. Scenarios for CCS deployment consistent with global climate goals involve gigatonne-scale deployment of CCS within the next several decades. CCS technologies typically involve large water consumption during their energy-intensive capture process. Despite potential concerns, the water footprint of large-scale CCS adoption consistent with stringent climate change mitigation has not yet been explored. This study presents the water footprints (m³ water per tonne CO2 captured) of four prominent CCS technologies: Post-combustion CCS, Pre-combustion CCS, Direct Air CCS, and Bioenergy with CCS. Depending on technology, the water footprint of CCS ranges from 0.74 to 575 m³ H2O/tonne CO2. Bioenergy with CCS is the technology that has the highest water footprint per tonne CO2 captured, largely due to the high water requirements associated with transpiration. The widespread deployment of CCS to meet the 1.5 °C climate target would almost double anthropogenic water footprint. Consequently, this would likely exacerbate and create green and blue water scarcity conditions in many regions worldwide. Climate mitigation scenarios with a diversified portfolio of CCS technologies have lower impacts on water resources than scenarios relying mainly on one of them. The water footprint assessment of CCS is a crucial factor in evaluating these technologies. Water-scarce regions should prioritize water-efficient CCS technologies in their mitigation goals. In conclusion, the most water-efficient way to stabilize the Earth's climate is to rapidly decarbonize our energy systems and improve energy efficiency.
The concept of ecosystem services (ES) has risen to prominence based on its promise to vastly improve environmental decision‐making and to represent nature's many benefits to people. Yet the field has continued to be plagued by fundamental concerns, leading some to believe that the field of ES must mature or be replaced.
In this paper, we quantitatively survey a stratified random sample of more than 1,000 articles addressing ES across three decades of scholarship. Our purpose is to examine the field's attention to common critiques regarding insufficient credible valuations of realistic changes to services; an unjustified preoccupation with monetary valuation; and too little social and policy research (e.g. questions of access to and demand for services).
We found that very little of the ES literature includes valuation of biophysical change (2.4%), despite many biophysical studies of services (24%). An initially small but substantially rising number of papers address crucial policy (14%) and social dimensions, including access, demand and the social consequences of change (5.8%). As well, recent years have seen a significant increase in non‐monetary valuation (from 0% to 2.5%).
Ecosystem service research has, we summarize, evolved in meaningful ways. But some of its goals remain unmet, despite the promise to improve environmental decisions, in part because of a continued pre‐occupation with numerical valuation often without appropriate biophysical grounding. Here we call for a next generation of research: Integrative biophysical‐social research that characterizes ES change, and is coupled with multi‐metric and qualitative valuation, and context‐appropriate decision‐making.
A free Plain Language Summary can be found within the Supporting Information of this article.
High biomass sorghum (HBS) (Sorghum bicolor (L.) Moench) is an emerging biofuel feedstock that can produce high yields in the Midwestern U.S. and is known for high nitrogen (N) use efficiency at low N fertilizer input. This two-year study examined the effect of five N fertilization treatments (0, 56, 112, 168, 224 kg N ha⁻¹) on the uptake of 11 macro- and micronutrients by photoperiod sensitive HBS. Leaf, stem, and shoot nutrient concentrations and contents were determined and nutrient relationships examined. Few consistent relationships existed across all nutrients, but concentrations were generally greater in the drier and shorter growing season with less dry matter (DM) accumulation, and, when present, N treatment response often resulted in decreased concentrations with increasing N. Inversely, the amount of nutrients present in the shoot generally were associated with greater DM production in the wetter year with longer growing season. Content of nutrients in the shoot did not increase beyond the 56 kg N ha⁻¹ treatment in the wetter year, but there was a nutrient uptake response to higher N rates in the drier crop year. This suggests more so than other nutrients that N was more of a limitation that year. Even though shoot mineral nutrient removal is often similar at higher N treatments, applying a minimal N fertilizer rate results in minimized tissue mineral concentrations, thereby creating an optimal crop management balance of targeting high crop yield, low concentrations to optimize conversion efficiency, and sustainable agronomic management.
In drylands, evapotranspiration (ET) is the dominant ecohydrologic process. For this reason, partitioning of ET—determining the relative importance of interception (I), soil evaporation (E), and plant transpiration (T)—is critical, but remains a challenge. Recently, however, advances in measurement technologies and data availability have triggered an upsurge in in situ studies focused on quantifying T/ET. We carried out a meta-analysis of 38 datasets drawn from 31 studies done in drylands worldwide. This analysis showed that over the growing season, E and T are roughly equivalent for most natural ecosystems, whereas T/ET is higher in irrigated agro-ecosystems. With respect to factors controlling variations in T/ET, we found (1) no clear correlation for annual precipitation, soil texture, or ecosystem type; (2) leaf area index is a more significant controlling factor than fractional cover; and (3) T/ET varies most during dynamic wetting–drying episodes. We also found that controlling factors are different for E and T. Because these two processes differ in temporal dynamics, the factors controlling ET partitioning vary with temporal scale. Further, when interception and shallow groundwater are substantial, including these factors is essential for accurate T/ET quantification. The isotopic approach, especially using laser spectroscopy, is now indispensable for such studies. However, issues related to sampling protocols and quality assurance still must be resolved. We propose three promising areas for future studies in drylands: (1) isotopic sampling of vadose-zone water vapor using laser spectroscopy; (2) improved definition/identification of diffusive pathways; and (3) robust upscaling from incongruent hydrometric and isotopic measurements.
Oilseed rape (Brassica napus L.) is the major oil crop in Europe and Germany but its hydrological functioning is poorly understood. Studies on the interception processes in oilseed rape have been lacking until the present. The interception of rainfall by oilseed rape is expected to vary in response to substantial changes in canopy structure throughout the cropping cycle and fertilization treatment. To determine evaporation of intercepted water, field measurements of a winter oilseed rape crop were conducted for different stages of development and five treatments of fertilization (0, 60, 120, 180 and 240 kg N/ha). Precipitation (P) and throughfall (TF) were measured hourly, along with vegetation structure measurements of the leaf area index (LAI). A range of 0–21% for the percentage of stemflow (SF) of P was estimated from soil moisture measurements. For the vegetation period from March to June the cumulative P of 112mm was converted into 49 mm TF (44%). The inferred evaporation of intercepted water (I) was 63 mm (56%). There was a gradual and clear increase in I from 45% to 67%, reflecting the increasing fertilization treatments. Hence, less soil water was available with increasing amounts of fertilization, since the water fraction evaporating from the canopy increases. Plant architecture, LAI and meteorological conditions during the cropping cycle appeared to be the main factors determining I. For irrigation planning and water use, studies of the evaporation of intercepted water must be considered.
Evapotranspiration and transpiration measurements represent a tool for the assessment of crop water demand. The aim of this study was to compare sorghum and maize with respect to its potential for forage production in areas with insufficient precipitation in Central Europe. The values of the actual evapotranspiration (ETa, Bowen ratio balance method), transpiration (sap flow method), leaf area index (LAI) and biomass production of sorghum and maize were measured continuously in years 2010–2012. Sorghum stand provided higher ETa in comparison with maize in dry year 2012. Maize produced consistently more above-ground biomass yield and lower LAI over all evaluated years than sorghum. The sorghum provided similar or higher water use efficiency (WUE) than maize during the period of intensive prolongation growth, however, the higher WUE did not result in higher biomass production.
Interception of precipitation by grass canopies in annually burned and unburned tallgrass prairie was measured for individual precipitation events from 1983 to 1984. Seasonal patterns of interception closely reflected differences in grass canopy development throughout the growing season in burned but not unburned prairie. Mean interception for the study period was 38 and 19% for unburned and burned prairie, respectively, indicating that throughfall volume in burned prairie was approximately 1.3 times that of unburned prairie on an annual basis. Thus, water availability for plant uptake may be initially higher in burned prairie, especially early in the growing season.
Soil evaporation (E) was measured with mini-lysimeters 225 mm deep and 150 mm in diameter over the growing season in 1986 and 1987. Mini-lysimeters were placed in corn field plots under dryland, limited irrigation and full irrigation water regimes, with or without canopy shading and with or without straw mulch. Soil water content in the mini-lysimeters was periodically matched to that in the surrounding field. Mean daily E was calculated and the effects of canopy shading and straw mulch were analyzed. No significant differences in E between mini-lysimeters at different row positions under the corn canopy were observed. Shading by the corn canopy significantly reduced E 0.3 to 0.5 mm d-1 under dryland, 0.6 to 0.7 mm d-1 under limited irrigation, and 1.2 mm d-1 under full irrigation. The presence of a straw mulch significantly reduced E 0 to 0.1 mm d-1 under dryland, 0.5 mm d-1 under limited irrigation, and 0.9 to 1.1 mm d-1 under full irrigation. The crop canopy played a more important role in reducing soil E than straw mulch under dryland. Under limited or full irrigation the crop canopy and straw mulch contributed equally to E reduction. Combined reduction of mean daily E by the crop canopy and straw mulch was approximately 0.5, 1.0, and 2.0 mm d-1 for dryland, limited irrigation, and full irrigation wetting frequencies, respectively.
Water stress restricts crop yield in both the arid and semi-arid zones of the world. In particular, water stress is associated with low availability of water, as well as osmotic effects associated with salinity. The response of forage sorghum [Sorghum bicolor (L.) Moench] varieties to salinity and irrigation frequency were studied from December 2007 to December 2008. Speedfeed and KFS4 were grown under salinity levels of 0, 5, 10 and 15 dS m -1 and irrigated when the leaf water potential reached -1.0 (control), -1.5 and -2.0 MPa. The irrigation frequency was found to affect growth and yield of the forage sorghums. When irrigation was delayed in leaf water potential of -1.0 to -2.0 MPa, the yield and yield components were found to decrease. The maximum dry forage yields were 45.1, 38.9 and 38.5 g plant -1 for frequent, intermediate and infrequent irrigation regimes, respectively. Increased salinity significantly reduced forage dry yield from 44.09 g plant -1 in the control to 32.76 g plant -1 at salinity of 15 dS m -1 . For every one unit increase in salinity, the forage yield decreased by 5.2 units and for every one unit increase in water stress (irrigation frequency), the forage yield decreased by 3.6 units. The variety Speedfeed had higher total dry mass than KFS4 under well-watered conditions but KFS4 performed better than Speedfeed under water stress. For both varieties, infrequent watering reduced dry matter and biomass accumulation, but increased water use efficiency (WUEs) (6.88).
Interception, as a function of simulated rainfall intensity and duration, was determined for a midgrass [sideoats grama (Bouteloua curtipendula (Michx.) Torr.)] and a shortgrass [curleymesquite (Hilaria belangeri (Steud.) Nash)]. In addition, the redistribution of natural precipitation via plant interception was determined for live oak (Quercus virginiana Mill.) mottes. Interception storage capacity for sideoats grama and curleymesquite was 81 and 114% of dry weight, respectively. This difference was attributed to physical characteristics of the species and their respective growth forms. However, because sites dominated by sideoats grama had more standing biomass (3,640 kg ha-1) than sites dominated by curleymesquite (1,490 kg ha-1), it was estimated that a sideoats grama dominated site had an interception storage capacity of 1.8 mm compared to curleymesquite dominated site with an interception storage capacity of 1.0 mm. Based upon precipitation event size and distribution for the study site at the Texas Agricultural Experiment Station near Sonora, Texas, the estimated interception loss for curleymesquite dominated sites was 10.8% of annual precipitation, compared to 18.1% interception loss for sideoats grama dominated sites. Only 54% of the annual precipitation reached mineral soil beneath the oak mottes as throughfall or stemflow. The remainder of the precipitation was intercepted by the motte canopy or litter layer and evaporated. Due to the water concentrating effect of stemflow, soil near the base of trees received about 222% of annual precipitation. Soil at a distance greater than approximately 100 mm from a tree trunk received only 50.6% of annual rainfall. Individual tree canopy width, height and depth measurements were insignificant predictors of stemflow and throughfall. Interception, throughfall and stemflow, expressed as percent of storm precipitation, were well-defined curvilinear functions.
Mathematical crop simulation models are useful tools in predicting the potential yield of field crops in a specific environment. The main driving parameter used to estimate biomass accumulation in most of these models is radiation-use efficiency (RUE). Biomass sorghum (Sorghum bicolor L. Moench) is a crop that can be used for energy production (thermal and bioethanol chains) and a knowledge of its RUE in different water supply conditions can help to improve model simulations and evaluate crop diffusion.
Increasing water and radiation use efficiencies (WUE and RUE, respectively) are critical to enhance crop production. Exploring genetic variability in WUE and RUE is necessary to improve these traits. The objectives of this research were to evaluate eight sorghum [Sorghum bicolor (L.) Moench] genotypes for biomass production, WUE, and RUE and to test whether the differences in WUE among sorghum genotypes were associated with increased biomass production or decreased water use under field conditions. The WUE was estimated as the slope of the regression of aboveground biomass on cumulative water use for specified sampling intervals. The RUE was estimated as the slope of the regression of aboveground biomass on cumulative intercepted photosynthetically active radiation (IPAR). Sorghum genotypes showed significant differences in biomass production, WUE, and RUE. The WUE varied from 3.39 +/- 0.80 to 5.42 +/- 0.80 g kg(-1) in 2009 and from 4.04 +/- 0.58 to 7.63 +/- 0.58 g kg(-1) in 2010. Similarly, RUE varied from 2.13 +/- 0.33 to 3.53 +/- 0.31 g MJ(-1) IPAR in 2009 and from 2.08 +/- 0.35 to 3.83 +/- 0.33 g MJ(-1) IPAR in 2010. Among the eight sorghum genotypes tested in this study, IS 27111 and IS 27150 had the largest biomass production, WUE, and RUE. The WUE was more strongly correlated to biomass production than to water use. This result implies that it is possible to improve WUE without compromising biomass production. The sorghum genotypes evaluated for biomass production, WUE, and RUE in this study offer useful plant materials for identifying the mechanisms causing differences in these traits.
Perennial grass systems are being evaluated as a bioenergy feedstock in the northern Great Plains. Inter-annual and inter-seasonal precipitation variation in this region will require efficient water use to maintain sufficient yield production to support a mature bioenergy industry. Objectives were to evaluate the impact of a May–June (early season) and a July–August (late season) drought on the water use efficiency (WUE), amount of water used, and biomass production in monocultures of switchgrass (Panicum virgatum L.), western wheatgrass (Pascopyrum smithii (Rydb.) Á. Löve), and a western wheatgrass–alfalfa (Medicago sativa L.) mixture using an automated rainout shelter. WUE was strongly driven by biomass accumulation and ranged from 5.6 to 7.4 g biomass mm−1 water for switchgrass to 1.06 to 2.07 g biomass mm−1 water used with western wheatgrass. Timing of water stress affected WUE more in western wheatgrass and the western wheatgrass–alfalfa mixture than switchgrass. Water deficit for the western wheatgrass–alfalfa mixture was 23 % lower than western wheatgrass (P = 0.0045) and 31 % lower than switchgrass (P < 0.0001) under the May–June stress water treatment, while switchgrass had a 37 and 38 % greater water deficit than did western wheatgrass or western wheatgrass–alfalfa mixture, respectively (P < 0.001) under the July–August water stress treatment. Water depletion was always greatest in the upper 30 cm. Switchgrass had greater WUE but resulted in greater soil water depletion at the end of the growing season compared to western wheatgrass and a western wheatgrass–alfalfa mixture which may be a concern under multi-year drought conditions.
In this chapter, we review the physiology of switchgrass from seed dormancy till the effects of water and nutrients stress on grown plants. These characteristics are presented and discussed mainly at the canopy and whole-plant level with emphasis on the agro-physiology of the species in view of the possible contribution of crop physiology to agricultural development. Switchgrass is noted for the variable degrees of seed dormancy regulated by endogenous and exogenous factors that determine the successful seedling establishment. Plant growth rates are determined by temperature while the reproductive phase is controlled mainly by photoperiod. There is also evidence that some physiological attributes, such as photosynthesis, transpiration, and water use efficiency differ between tetraploid, hexaploid and octaploid ecotypes. But despite these differences, in general switchgrass combines important attributes of efficient use of nutrients and water with high yields thanks to its ability to acquire resources from extended soil volumes, especially at deep layers. Moreover at canopy level, resources capture and conservation are determined by morpho-physiological characteristics (Câ photosynthetic pathway, stomatal control of transpiration, high leaf area index, low light extinction coefficient) that enhance radiation use efficiency and reduce carbon losses. However, specific information on switchgrass physiology is still missing, in particular deeper understanding of physiological principles controlling the water and nutrients acquisition mechanisms and allocation under suboptimal growing conditions. The physiology of tillering and root respiration are also factors that need further investigation.
Two of the main plants currently being considered as potential biofuel feedstocks in the U.S. are switchgrass (Panicum virgatum L.) and maize (Zea mays L.). Recent expanded production of both has raised serious questions about natural resource utilization, notably, soil carbon, soil nutrients, and water. Water is often the limiting resource for crop and grass productivity. The objective of this study was to calculate and compare water use and water use efficiency of maize with current growth characteristics, switchgrass with current growth characteristics, and switchgrass with characteristics improved by normal plant breeding selection techniques. We used the calibrated and validated ALMANAC model for five sites representing the southern Great Plains (Stephenville, TX), the northern Great Plains (Mead, NE), and two locations in the Corn Belt (Ames, IA and Columbia, MO). Ten years of historical weather data were used. Mean values for water use and water use efficiency were calculated for maize, switchgrass with currently growth characteristics, and switchgrass with anticipated improved growth characteristics. These results show the relative impact of expanded maize production, expanded switchgrass production, and use of improved switchgrass varieties, on the water balance in these regions. The water use efficiency (WUE) of four switchgrass types showed means ranging from 3 to 5 mg g-1. Switchgrass WUE values were much greater than WUE of maize grain, but such was not always the case when
Production of forage species like switchgrass (Panicum virgatum L.) is often relegated to areas with minimal inputs of water and fertilizer, therefore, selection should be based on efficient use of these resources. This study examined genotypic variation in switchgrass transpiration efficiency (TE), defined as the weight of dry matter per unit of water transpired, under conditions of water and N stress. Since reports show TE to be correlated with specific leaf weight (SLW) and leaf ash, these easily measured traits were assessed for their potential as predictors of switchgrass TE. In one greenhouse experiment with nine cultivars and two outdoor experiments with two cultivars, plants were grown in closed containers in a soil–peat mix or solution culture and subjected to water or N deficit. Cultivars differed in TE; however, TE did not differ between water stressed and well‐watered conditions. With decreasing N in solution, TE also decreased. Cultivars differed in their values of TE when grown in nutrient solutions containing 10.0 and 1.0 mM N, but not at 0.3 mM N. Transpiration efficiency was positively correlated with SLW in each experiment and across all experiments (r=0.85) Correlation between TE and leaf ash was inconsistent, with a negative relationship in the water stress experiment and a positive relationship in the N experiment. The results show differences in TE among switchgrass cultivars and show that SLW is consistently predictive of TE.
A model is presented for calculating the daily evaporation rate from a
crop surface. It applies to a row crop canopy situation in which the
soil water supply to the plant roots is not limited and the crop has not
come into an advanced stage of maturation or senescence. The crop
evaporation rate is calculated by adding the soil surface and plant
surface components (each of these requiring daily numbers for the leaf
area index), the potential evaporation, the rainfall, and the net
radiation above the canopy. The evaporation from the soil surface
Es is calculated in two stages: (1) the constant rate stage
in which Es is limited only by the supply of energy to the
surface and (2) the falling rate stage in which water movement to the
evaporating sites near the surface is controlled by the hydraulic
properties of the soil. The evaporation from the plant surfaces
Ep is predicted by using an empirical relation based on local
data, which shows how Ep is related to Eo through
the leaf area index. The model was used to obtain the total evaporation
rate E = Es + Ep of a developing grain sorghum
(Sorghum bicolor L.) canopy in central Texas. The results agreed well
with values for E measured directly with a weighing lysimeter.
Fundamental to deriving a sustainable supply of cellulosic feedstock for an emerging biofuels industry is understanding how biomass yield varies as a function of crop management, climate, and soils. Here we focus on the perennial switchgrass (Panicum virgatum L.) and compile a database that contains 1190 observations of yield from 39 field trials conducted across the United States. Data include site location, stand age, plot size, cultivar, crop management, biomass yield, temperature, precipitation, and information on land quality. Statistical analysis revealed the major sources of variation in yield. Frequency distributions of yield for upland and lowland ecotypes were unimodal, with mean ({+-}SD) biomass yields of 8.7 {+-} 4.2 and 12.9 {+-} 5.9 Mg ha-1 for the two ecotypes, respectively. We looked for, but did not find, bias toward higher yields associated with small plots or preferential establishment of stands on high quality lands. A parametric yield model was fit to the data and accounted for one-third of the total observed variation in biomass yields, with an equal contribution of growing season precipitation, annual temperature, N fertilization, and ecotype. The model was used to predict yield across the continental United States. Mapped output was consistent with the natural range of switchgrass and, as expected, yields were shown to be limited by precipitation west of the Great Plains. Future studies should extend the geographic distribution of field trials and thus improve our understanding of biomass production as a function of soil, climate, and crop management for promising biofuels such as switchgrass.
Annual monitoring of water-budget components is useful for comparing the fate of water inputs among ecosystems. Land-use changes from natural prairies to managed agroecosystems alter water-budget components. Weekly hydrological budgets for a restored natural prairie and maize (Zea mays L.) agroecosystems (no-tillage and chisel-plow) were constructed for 132 consecutive wk between June 1995 and January 1998. Precipitation, drainage, sod water-storage changes, and snow-cover changes were measured on Plano silt loam soil (fine-silty, mixed, superactive, mesic Typic Argiudoll) at agricultural and prairie sites. Compared with the maize ecosystems, the prairie maintained greater soil water contents deeper in the soil profile (0.8-1.4 m), somewhat larger evapotranspiration (Et), and significantly less drainage because of considerable interception of precipitation by a residue layer. Soil water storage in the no-tillage maize setting was more similar to the prairie, while Et, net primary productivity, and drainage were more comparable to the chisel-plow agroecosystem. Total drainage measured with equilibrium-tension lysimeters was 199 mm of water (coefficient of variation [CV] = 5.7%) for the prairie ecosystem, 563 mm of water (CV = 13.6%) for the no-tillage maize ecosystem, and 793 mm of water (CV = 18.5%) for the chisel-plow maize ecosystem. Residue interception for the prairie was 477 mm, compared with 681 mm of precipitation during the growing season of 1997, which contributed to lower prairie drainage. The combination of similar productivity, higher soil water contents, and less drainage than the chisel-plow ecosystem suggests that a no-tillage ecosystem is more sustainable than the chisel-plow agroecosystem in terms of reducing potential adverse environmental impacts associated with soil water movement.
a b s t r a c t The production of cellulosic feedstocks for renewable fuels will increase over the coming decades. How-ever, it is uncertain which feedstocks will be best suited for bioenergy production. A key factor dictating feedstock selection for a given region is water use efficiency (WUE), the trade-off between evapotranspira-tion (ET) and carbon uptake or productivity. Using an ecosystem model, two of the top candidate cellulosic feedstocks, Miscanthus × giganteus (miscanthus) and Panicum virgatum (switchgrass) were compared to Zea mays L. (maize), the existing dominant bioenergy feedstock, with 0 and 25% residue removal for the Midwest US. We determined productivity in three ways: harvested yield (HY), net ecosystem productiv-ity (NEP) and net biome productivity (NBP). Evapotranspiration was compared against each of the three productivity metrics, respectively, to yield Harvest Water Use Efficiency (HWUE), Ecosystem Water Use Efficiency (EWUE) and Biome Water Use Efficiency (BWUE). Simulations indicated that, over the study domain, miscanthus had a significantly higher HWUE compared to switchgrass and maize, while maize and switchgrass were similar. When EWUE was compared miscanthus was higher than both maize and switchgrass, which were similar for most of the region. Biome WUE was similar for both of the perenni-als and higher compared to maize for most of the study domain with the exception of the driest regions where maize showed the highest BWUE. Removing 25% of maize residue slightly increased HWUE and greatly decreased BWUE throughout the domain, however only HWUE changes were statistically signif-icant. These results indicate that the feedstock with the highest WUE varied based on the productivity metric, but BWUE for maize was consistently lower than the perennials. Published by Elsevier B.V.
Established as a multipurpose network, the Oklahoma Mesonet operates more than 110 surface observing stations that send data every 5 min to an operations center for data quality assurance, product generation, and dissemination. Quality-assured data are available within 5 min of the observation time. Since 1994, the Oklahoma Mesonet has collected 3.5 billion weather and soil observations and produced millions of decision-making products for its customers.
The crop coefficient during the initial period K c ini varies with wetting frequency, evaporative demand, and water-holding capacity of the upper soil layer. It is possible to develop a semitheoretical integrated function to predict the average K c ini representing the initial period of a growing season when the soil is mostly bare and that incorporates these three factors. The function is based on a two-stage evaporation function as used in the Food and Agriculture Organization Irrigation and Drainage Paper No. 56 (FAO-56) dual crop coefficient method. Parameters in the integrated equation are soil based and can be calculated a priori without field measurements. The procedure can be used to produce graphical figures similar to that introduced in FAO-24 for K c ini . Similar to FAO-24, the function utilizes the mean time between wetting events and reference evapotranspiration. In this paper, the development of the procedure and figures for K c ini are described. Comparisons with measured evaporation and K c ini in southern California indicate relatively good perfor-mance by the function without calibration.
To meet emerging bioenergy demands, significant areas of the large-scale agricultural landscape of the Midwestern United States could be converted to second generation bioenergy crops such as miscanthus and switchgrass. The high biomass productivity of bioenergy crops in a longer growing season linked tightly to water use highlight the potential for significant impact on the hydrologic cycle in the region. This issue is further exacerbated by the uncertainty in the response of the vegetation under elevated CO(2) and temperature. We use a mechanistic multilayer canopy-root-soil model to (i) capture the eco-physiological acclimations of bioenergy crops under climate change, and (ii) predict how hydrologic fluxes are likely to be altered from their current magnitudes. Observed data and Monte Carlo simulations of weather for recent past and future scenarios are used to characterize the variability range of the predictions. Under present weather conditions, miscanthus and switchgrass utilized more water than maize for total seasonal evapotranspiration by approximately 58% and 36%, respectively. Projected higher concentrations of atmospheric CO(2) (550 ppm) is likely to decrease water used for evapotranspiration of miscanthus, switchgrass, and maize by 12%, 10%, and 11%, respectively. However, when climate change with projected increases in air temperature and reduced summer rainfall are also considered, there is a net increase in evapotranspiration for all crops, leading to significant reduction in soil-moisture storage and specific surface runoff. These results highlight the critical role of the warming climate in potentially altering the water cycle in the region under extensive conversion of existing maize cropping to support bioenergy demand.
Measuring percent occurrence of objects from digital images can save time and expense relative to conventional field measurements. However, the accuracy of image analysis had, until now, not reached the level of the best conventional field measurements. Additionally, most image-analysis software programs require advanced user training to successfully analyze images. Here we present a new software program, 'SamplePoint,' that provides the user a single-pixel sample point and the ability to view and identify the pixel context. We found SamplePoint to allow accuracy comparable with the most accurate field-methods for ground-cover measurements. Expert use of the program requires minimal training and its ease of use allows rapid measurements from image data. We recommend SamplePoint for calibrating the threshold-detection level of image-analysis software or for making direct measurements of percent occurrence from digital images.
Understanding soil water dynamics and evapotranspiration (ET) is imperative to predict the interactions between bioenergy cropping systems and water resources; yet measurements of these variables under bioenergy crops in the U. S. Southern Great Plains (SGP) are limited. The objectives of this study were to quantify and compare soil water dynamics and ET under switchgrass (Panicum virgatum L.), biomass sorghum [Sorghum bicolor (L.) Moench], and mixed perennial grasses managed for biofuel production. Soil water content was measured from 2011 through 2013 at Stillwater, OK, and from 2012 through 2013 at Chickasha, OK, and ET was estimated using the soil water balance approach. For these crops, soil water depletion occurred mainly above the 2.0-m depth, suggesting negligible root water uptake below 2.0 m. Growing season soil water depletion ranged from 4 to 287 mm and was greater (alpha = 0.10) for sorghum than switchgrass in 2 out of 5 site-yr, while mixed grasses exhibited the greatest soil water depletion in 1 out of 3 yr. Growing season soil water depletion was positively related to initial soil water content. Crop year ET ranged from 493 to 846 mm and was greater for switchgrass than sorghum in 2 out of 3 site-yr. At Stillwater, average crop year ET measured for 2 yr was 676 mm for switchgrass, 630 mm for sorghum, and 717 mm for mixed grasses. In the SGP, rainfed bioenergy production systems based on biomass sorghum may consume less water per unit land area than systems based on perennial grasses.
This presentation will highlight efforts on development of a new online WEPP GIS interface, targeted toward application in forested regions bordering the Great Lakes. The key components and algorithms of the online GIS system will be outlined. The general procedures used to provide input to the WEPP model and to display model output will be demonstrated.
The FAO-56 soil water evaporation model is a simple ‘slab’ model that has been found to produce good estimates of evaporation from bare soil over a range of conditions due to its adherence to conservation of mass and energy. The simplicity of the model makes it straightforward to apply and to parameterize. An enhancement is made to the original formulation to accommodate light wetting events that wet the soil ‘skin’ near the surface and evaporate relatively quickly, even when the underlying soil is dry. In effect, the evaporation process, when the soil skin is wetted, reverts temporarily into stage 1 evaporation. The enhancement utilizes the ‘readily evaporable water’ (REW) term of the original model so that no new parameters are required. The extended model performs similar to the original model in the absence of small precipitation events, but increases the evaporation rate when small events occur. The FAO-56 method with the skin evaporation enhancement is shown to compare well against simulations made using the HYDRUS 1D model that bases evaporation on the Richards equation. The enhanced model also closely followed evaporation recorded by weighing lysimeter for a silt loam soil at Kimberly, Idaho, with root mean square difference of 0.39 and 0.69mmd−1 for two wetting/drying sequences. Total cumulative evaporation during the longest and wettest sequence was estimated at 92% of the measured value.
Plant biomass accumulation, and consequently yield, was shown to be inextricably linked to transpiration. The ratio of plant productivity to water loss, water-use efficiency, was very conservative. Only a few variables are available for manipulating water-use efficiency, and these have already been exploited to a large degree.
Soil evaporation is often an important component of the total water loss from plant canopies, but is poorly estimated in many SVAT models. This paper reports the use of micrometeorological and lysimetric methods to measure soil evaporation (Es) in the canopy of a wheat crop over a period of 7 weeks as the crop matured and green leaf area index (L) declined from 3.8 to 0.2. Simultaneous measurements of total canopy evaporation (E) were made by eddy correlation. The within-canopy micrometeorological methods employed a variance ratio approach and an inverse Lagrangian analysis. The pooled micrometeorological and lysimetric data conformed very well to the relationship EsE = exp(−0.61L) with an r2 value of 0.95. The relationship should be a useful empirical means for estimating daily or weekly Es in SVAT studies.