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HighlightsSoil water depleted by the cover crop was quickly replenished by spring precipitation.Higher soil water was maintained during the cotton growing season under the cover crop treatment.Cover crops improved soil organic carbon under both irrigated and dryland conditions.Cover crops enhanced crop water productivity under both irrigated and dryland conditions.Abstract. Cover crops provide many soil health benefits to agricultural systems. An interest in growing cover crops in cotton (Gossypium hirsutum L.) production systems has been increasing in the Texas Rolling Plains (TRP) region. Due to limited rainfall and groundwater availability, producers in this semi-arid region are concerned that winter cover crops can reduce soil water availability for a subsequent cotton crop. In addition, the long-term effects of cover crops on soil organic carbon (SOC) are not well studied in this region. The overall goal of this study was to assess the long-term effects of growing a winter wheat (Triticum aestivum) cover crop on soil water, SOC, seed cotton yield, and crop water productivity (CWP) under irrigated and dryland cotton production systems using the Decision Support System for Agrotechnology Transfer (DSSAT) model. Measured data from cover crop experiments conducted at the Texas A&M AgriLife Research Station at Chillicothe from 2011 to 2020 were used to evaluate the CROPGRO-Cotton and CERES-Wheat modules in the DSSAT Cropping System Model. The average percent error (PE) between the simulated and measured seed cotton yield was 0.3% and -0.9%, and that between the simulated and measured aboveground wheat biomass was 1.4% and -3.4% during the calibration and evaluation periods, respectively. For the simulation of SOC, the PE was 8.5% and 7.6% during the calibration and evaluation periods, respectively. Long-term (2001 to 2020) simulations showed that soil water was reduced substantially by the winter wheat cover crop before its termination. However, depleted soil water was quickly replenished by spring precipitation and maintained at a higher level during the cotton growing season. Winter wheat cover crops can potentially improve SOC in irrigated and dryland cotton production systems. The CWP of cotton also improved with a winter wheat cover crop under both irrigated and dryland conditions. We concluded that cover crops could potentially improve soil health and provide a sustainable environment for TRP cotton production. Keywords: CERES-Wheat, CROPGRO-Cotton, DSSAT, Soil health, Texas Rolling Plains (TRP).

Parameters adjusted during the evaluation of CERES-Wheat and CROPGRO-Cotton modules of the DSSAT Cropping System Model; and Comparison of simulated and measured soil water and cover crop and no-cover-crop treatments.

HighlightsCotton yield was reduced significantly under projected future climate conditions for the Arizona low desert (ALD). Of all the weather variables, yield reduction was primarily due to projected increases in daily maximum and minimum air temperatures.Cotton reproductive stages were more susceptible to heat stress than vegetative stages. Projected increases in air temperature may result in a slight increase in cotton growth or biomass production; however, heat stress significantly reduced fruit retention, leading to lower boll number and yield.Although future increases in CO2 may improve plant growth and productivity, the potential benefit of CO2 fertilization on cotton growth and yield in the ALD was offset by the projected increase in air temperature.The projected average seasonal irrigation requirement increased by at least 10%. This suggests that greater demand for freshwater withdrawal for agriculture can be expected in the future. Therefore, given the projected change in future climate, cotton cultivars tolerant of longer periods of high air temperature, changes in planting dates, and improved management practices for higher water productivity are critical needs for sustainable cotton production in the ALD.Abstract. Cotton is an important crop in Arizona, with a total cash value of approximately $200 million for fiber and cottonseed in 2018. In recent years, heat stress from increasing air temperature has reduced cotton productivity in the Arizona low desert (ALD); however, the effects of future climate on ALD cotton production have not been studied. In this study, the DSSAT CSM-CROPGRO-Cotton model was used to simulate the effects of future climate on cotton growth, yield, and water use in the ALD area. Projected climate forcings for the ALD were obtained from nine global climate models under two representative concentration pathways (RCP 4.5 and 8.5). Cotton growth, yield, and water use were simulated for mid-century (2036 to 2065) and late century (2066 to 2095) and compared to the baseline (1980 to 2005). Results indicated that seed cotton yield was reduced by at least 40% and 51% by mid-century and late century, respectively, compared to the baseline. Of all the weather variables, the seasonal average maximum (R2 = 0.72) and minimum (R2 = 0.80) air temperatures were most correlated with yield reductions. Under the future climate conditions of the ALD, cotton growth or biomass accumulation slightly increased compared to the baseline. Irrigation requirements in the ALD increased by at least 10% and 14% by mid-century and late century, respectively. Increases in irrigation requirements were due to an increase in crop water use; hence, greater demand for freshwater withdrawal for agricultural purposes is anticipated in the future. Therefore, cotton cultivars that are tolerant of long periods of high air temperature and improved management practices that promote efficient crop water use are critical for future sustainability of cotton production in the ALD. Keywords: . Arid region, CSM-CROPGRO-Cotton, Future climate, Gossypium hirsutum L., Heat stress, Irrigation demand.

Highlights Over the last 40 years the amount of irrigation water used by cotton in the United States has decreased while yields have increased leading to a large increase in crop water productivity (CWP). Many factors have contributed to improved CWP, such as improvements in water delivery systems. Irrigation scheduling technologies have also contributed to improved CWP; however, farmer adoption of advanced scheduling technologies is still limited and there is significant room for improvement. Increased yields from improved cultivars without an increase in water requirements has also been important for CWP. Continued developments in sensor technologies and improved crop simulation models are two examples of future strategies that should allow the U.S. cotton industry to continue an upward trend in CWP. Abstract. Over the last 40 years the amount of irrigation water used by cotton in the United States has decreased while yields have increased. Factors contributing to higher water productivity and decreased irrigation water use include migration of cotton out of the far western U.S. states to the east where more water requirements are met by rainfall; improved irrigation delivery systems with considerable variation in types and adoption rates across the U.S.; improved irrigation scheduling tools; improved genetics and knowledge of cotton physiology, and improved crop models that can help evaluate new irrigation strategies rapidly and inexpensively. The considerable progress over the last 40 years along with the promise of emerging technologies suggest that this progress will continue. Keywords: Cotton, Crop water productivity, Irrigation, Sustainability, Water use efficiency.

HighlightsIrrigation water use efficiency was consistently higher under deficit irrigation as compared to full irrigation.Irrigation water use was always less than the annual allowable pumping limit under deficit irrigation.The first/second week of September was ideal for terminating irrigation under full/deficit irrigation in normal years.Ideal irrigation termination periods in wet/dry years were a week earlier/later than those in normal years.Abstract. Cotton ( L.) production in the Texas High Plains (THP) region relies heavily on irrigation with groundwater from the underlying Ogallala Aquifer. However, rapidly declining groundwater levels in the aquifer and increasing pumping costs pose challenges for sustainability of irrigated cotton production in this region. Adoption of efficient irrigation strategies, such as terminating irrigation at an appropriate time in the growing season, could enable producers to increase irrigation water use efficiency (IWUE) while maintaining desired yield goals. The objective of this study was to determine optimum irrigation termination periods for cotton production in the THP under full and deficit irrigation conditions using the Decision Support System for Agrotechnology Transfer (DSSAT) CROPGRO-Cotton model, which was evaluated in a prior study in the THP using measured data from an IWUE field experiment at Halfway, Texas. The treatment factors in the field experiment included irrigation capacities of 0 mm d-1 (low, L), 3.2 mm d-1 (medium, M), and 6.4 mm d-1 (high, H), applied during the vegetative, reproductive, and maturation growth stages. This study focused on a full irrigation (HHH) treatment and three deficit irrigation (LMH, LHM, and LMM) treatments. Eight irrigation termination dates with a one-week interval between 15 August and 30 September were simulated, and the impact of irrigation termination date on cotton IWUE and seed cotton yield were studied by dividing the 39-year (1978 to 2016) simulation period into dry, normal, and wet years based on the precipitation received from 1 April to the simulated irrigation termination date. Results indicated that the simulated IWUE was consistently higher under the LHM, LMH, and LMM treatments when compared to the HHH treatment. Based on the simulated average seed cotton yield and IWUE, optimum irrigation termination periods for cotton were found to be the first week of September (about 118 days after planting, DAP) for the HHH and LMH treatments and the second week of September (125 DAP) for the LHM and LMM treatments in normal years. In wet years, optimum irrigation termination periods were a week earlier than those in normal years and a week later in dry years for the HHH, LHM, and LMM treatments. For the LMH treatment, the optimum irrigation termination period in wet years was the same as that in normal years and two weeks later in dry years. The results from this study along with field-specific, late-season information will assist THP cotton producers in making appropriate irrigation termination decisions for improving economic productivity of the Ogallala Aquifer and thereby ensuring water security for agriculture. However, the recommendations from this study should be used with caution, as the optimum irrigation termination periods could potentially change with changes in cultivar characteristics, soil type, climate, and, crop management practices. Keywords: CROPGRO-Cotton, Deficit irrigation, DSSAT, Full irrigation, Irrigation water use efficiency, Seed cotton yield.

HighlightsReplacing either a winter wheat or corn system with a spring wheat system improved soil retention by more than 19%.When grown for bioenergy production instead of forage hay, switchgrass improved soil retention by 40%.Replacement of field cropping systems with grassland systems improved soil retention by over 70%.Incorporating the environmental merits and demerits of cropping systems during on-farm and policy decision-making may go a long way toward ensuring food, feed, and energy security and environmental sustainability.Abstract. While policies that take land out of production provide a quick fix to erosion, the sustainability of such approaches has been questioned, particularly with the increasing demand for arable land. Policies that reconcile the needs for food, feed, fuel, and healthy ecosystems provide a more sustainable alternative approach to soil erosion management in agricultural lands. This study evaluates the impacts of such a policy that prioritizes the implementation of cropping systems with relatively high environmental benefits. The effectiveness of three field cropping systems and three grassland systems in reducing soil erosion is examined on a 6.6 ha field plot in central Texas over a 20-year period. Soil loss rates under each system are estimated using the Agricultural Policy/Environmental eXtender (APEX) model. A relational comparison of the simulated soil losses and water budget components is undertaken to determine the impact of alternative cropping and grassland systems on the landscape’s hydrologic and erosion processes. The results revealed that replacing a winter wheat system and a corn cropping system with a spring wheat system improved soil retention by 19% and 25%, respectively. Growing switchgrass for bioenergy production instead of forage hay improved soil retention considerably (by 40%). Irrespective of the grassland system adopted (restoration to native prairie or growing switchgrass for hay or bioenergy), the replacement of corn or wheat cropping systems with grassland systems increased soil retention by over 70%. This study shows that there is an opportunity to alleviate concerns about conservation programs that take cropland out of production and those that use food crops as fuel and feedstocks, while considerably reducing soil loss from agricultural lands. Incorporating the merits and demerits of cropping systems and why one system should be preferred over another during on-farm and policy decision-making may go a long way toward ensuring food, feed, and energy security and environmental sustainability. Keywords: Cropping systems, Soil retention, Sustainability, Switchgrass.

HighlightsASABE and ISAE convened the Global Water Security Conference for Agriculture and Natural Resources in Hyderabad, India, in 2018.Recommendations represent collective contribution of attendees and presenters in seven key priorities.Continuation of a narrow focus on technical aspects will likely prevent the success of technical solutions.Scientists and engineers should work together across all disciplines and boundaries to ensure global water security. Keywords: Climate change, Crop water productivity, Food security, Irrigation efficiency, Natural resource policy, Wastewater reuse, Water resource infrastructure, Water scarcity.

HighlightsIrrigated grain sorghum yield and irrigation water use decreased under climate change.Increase in growing season temperature beyond 26°C resulted in a sharp decline in grain sorghum yield.Irrigating during early reproductive stages resulted in the most efficient use of limited water.Irrigating to replenish soil water to 80% of field capacity was found suitable for both current and future climates. Groundwater overdraft from the Ogallala Aquifer for irrigation use and anticipated climate change impacts pose major threats to the sustainability of agriculture in the Texas High Plains (THP) region. In this study, the DSSAT-CSM-CERES-Sorghum model was used to simulate climate change impacts on grain sorghum production under full and deficit irrigation strategies and suggest optimal deficit irrigation strategies. Two irrigation strategies were designed based on (1) crop growth stage and (2) soil water deficit. For the first strategy, seven deficit irrigation scenarios and one full irrigation scenario were simulated: three scenarios with a single 100 mm irrigation scheduled between panicle initiation and boot (T1), between boot and early grain filling (T2), and between early and late grain filling (T3) growth stages; three 200 mm irrigation treatments with combinations of T1 and T2 (T4), T1 and T3 (T5), and T2 and T3 (T6); one 300 mm irrigation scenario (T7) that was a combination of T1, T2, and T3; and a full irrigation scenario (T8) in which irrigation was applied throughout the growing season to maintain at least 50% of plant-available water in the top 30 cm soil profile. For the second strategy, the irrigation schedule obtained from auto-irrigation (T8) was mimicked to create a full irrigation scenario (I100) and six deficit irrigation scenarios. In the deficit irrigation scenarios, water was applied on the same dates as scenario I100; however, the irrigation amounts of scenario I100 were reduced by 10%, 20%, 30%, 40%, 50%, and 60% to create deficit irrigation scenarios I90, I80, I70, I60, I50, and I40, respectively. Projected climate forcings were drawn from nine global climate models (GCMs) and two representative concentration pathways (RCP 4.5 and RCP 8.5). Climate change analysis indicated that grain sorghum yield under full irrigation was expected to be reduced by 5% by mid-century (2036 to 2065) and by 15% by late-century (2066 to 2095) under RCP 8.5 compared to the baseline period (1976 to 2005). Simulated future irrigation water demand of grain sorghum was reduced due to the shorter growing season and improved dry matter- and yield-transpiration productivity, likely due to CO2 fertilization. Based on the simulated grain sorghum yield and irrigation water use efficiency, the most efficient use of limited irrigation was achieved by applying irrigation during the early reproductive stages of grain sorghum (panicle initiation through early grain filling). A 20% deficit irrigation scenario was found to be optimal for current and future conditions because it was more water use efficient than full irrigation with a minor yield reduction of

HighlightsWe provide context and perspectives on 13 articles in the Global Water Security collection.Limited irrigation, precision irrigation, and sustainable water resources management were critical themes.The collection emphasizes the need for adopting location-specific technologies to achieve global water security.Advances in data acquisition, data analysis, and modeling should be utilized to aid managing water resources. Abstract. This article introduces the Global Water Security collection in this issue of Transactions of the ASABE and issue 36(1) of Applied Engineering in Agriculture. Researchers, educators, industry partners, agricultural producers, and policymakers from 19 countries met at Hyderabad, India, to discuss critical issues and advancements at the Global Water Security Conference for Agriculture and Natural Resources. The conference was organized jointly by ASABE and the Indian Society of Agricultural Engineers (ISAE). This special collection consists of 13 articles selected from the 245 meeting presentations as well as invited articles. A perspectives article in this collection summarizes seven key priorities identified for action at the conference: reduce food waste, increase wastewater reuse, increase agricultural resiliency and efficiency, optimize irrigation efficiency and increase crop water productivity, improve water supply management, improve water resource infrastructure, and enhance water resource decision-making and policy formulation. The remaining 12 articles address a wide range of water security topics grouped by four themes: sustainable management of water resources (3 articles), limited irrigation for water conservation (5 articles), precision irrigation management (2 articles), and water management in hilly regions (2 articles). While these articles are not inclusive of all water security challenges in the agriculture and natural resources sectors, they highlight selected important challenges and potential solutions. The research presented in this special collection emphasizes the importance of developing and using appropriate location-specific technologies that increase water application efficiency and water use efficiency while maintaining adequate water supplies for natural resource functions and ecosystem services to ensure global water security. Keywords: Climate change, Crop water productivity, Food security, Irrigation efficiency, Natural resource policy, Wastewater reuse, Water resource infrastructure, Water scarcity.

Guar, [Cyamopsis tetragonoloba (L.) Taub] is an annual summer legume that is widely grown in arid and semi-arid regions. It is a diploid legume (2n = 2x = 14) with a genome size of approximately 560 Mb. Guar can fix atmospheric nitrogen via a symbiotic process with rhizobial bacteria, thus enhancing soil fertility and decreasing the need for the use of expensive nitrogen (N) fertilizers. Guar is a drought- and heat-tolerant crop and can be grown using minimal agricultural inputs. Guar can be used as vegetable, feed/fodder, or green manure. One of the primary driving factors for guar cultivation is galactomannan gum, known as guar gum, found in the seed endosperm. Guar gum has various industrial uses that range from cosmetic applications, food ingredients, to the oil industries. India is the lead guar production and accounts for more than 80% of the world production. The U.S. is the world largest guar market. This review discusses the status of genomic resources in guar, the progress made for germplasm evaluation of various agronomic traits, and the genetic engineering efforts in guar.

Old world bluestem cultivar WW-B Dahl [Bothriochloa bladhii (Retz.), S. T. Blake] is a non-native perennial C4 bunch grass with biofuel production potential grown predominantly in the Southern U.S. Great Plains. Although this is a popular introduced grass cultivar, data on carbon fluxes and evapotranspiration (ET) from this warm-season grass is rare. In this study, the eddy covariance method was used to measure CO2 and ET from an established stand of bluestem for three years (2013–2015). Year 2015 had the highest gross primary production (GPP; 1358 ± 143 g C m−2) followed by 2014 (1250 ± 31 g C m−2) and 2013 (1024 ± 91 g C m−2). The average loss of GPP as ecosystem respiration (Reco) was 76%. Annual NEE sums were -302 ± 15 g C m−2 in 2013, -265 ± 41 g C m-2 in 2014, and -287 ± 32 g C m−2 in 2015. Results from this study show that the NEE in grasslands in years with normal precipitation that is well distributed may not vary from years with above-normal precipitation. This is because precipitation enhances Reco along with carbon uptake, which may result in lower net carbon uptake in perennial grasslands in higher precipitation years than normal precipitation years. Gross primary production showed a linear relationship with ET (R2 = 0.90) and above ground biomass (R2 = 0.74). Only 26% of the GPP was allocated to above ground biomass indicating a higher allocation of carbon to below ground biomass. The water use efficiency of bluestem (2.9 g C kg-1 of water) matched well with that of native prairies and other dedicated biomass crops grown in the Southern Great Plains. As the demand for cellulosic biofuels is increasing, results from field experiments quantifying seasonal changes in carbon fluxes and ET could be important in understanding the contributions of large-scale production of novel biomass crops to regional carbon and hydrologic cycles.

The Texas High Plains (THP) is a productive agricultural region, and it relies heavily on the exhaustible Ogallala Aquifer for irrigation water for crop production. Efficient use of irrigation water is critical for the sustainability of agriculture in the THP. Grain sorghum is one of the major crops grown in the region, and it is known for its drought tolerance and lower water requirement compared to other cereal crops such as corn. In this study, the CERES-Sorghum and CROPGRO-Cotton modules of the Decision Support System for Agrotechnology Transfer (DSSAT) were evaluated using data from cotton-sorghum rotation experiments at Halfway, Texas over a period of nine years (2006–2014). The evaluated CERES-Sorghum model was then used to identify the optimum (i) initial soil moisture at planting (ISM); (ii) threshold to start irrigation (ITH); (iii) threshold to terminate irrigation; and iv) deficit/excess (DFI) irrigation strategy for grain sorghum production based on simulated sorghum yield, irrigation water use efficiency (IWUE), and grain water use efficiency (WUE). In addition, the effect of weather conditions on simulated strategies was elucidated by dividing the long-term (1977–2016) weather data into cold, warm, wet, dry, and normal climate variability classes based on the 33rd and 66th percentiles of growing season temperature and precipitation. The DSSAT model adequately simulated the grain sorghum and seed cotton yields during calibration (average Percent Error (PE) of 1.3% (sorghum) and 3.4% (cotton)) and evaluation (average PE of −2.2% (sorghum) and −10.5% (cotton)). The results from long-term simulations indicated that weather conditions played a key role in selecting appropriate irrigation management strategies. Under normal/cold/wet weather, ISM of 75% available water holding capacity (AWC), ITH of 50%, and DFI 85% were found to be adequate for irrigated grain sorghum production. However, in warm/dry weather, ISM of 75%, ITH 60%, and DFI at 100% reduced sorghum yield loss.

In the Texas High Plains (THP), diminishing irrigation well-capacities, and increasing costs of energy and equipment associated with groundwater extraction and application are contributing factors to a transition from irrigated to dryland agriculture. The primary goal of this modeling exercise was to investigate whether and to what extent hypothetical changes in factors putatively associated with soil health would affect dryland cotton (Gossypium hirsutum L.) yields. The factors selected were drainage, surface runoff, soil water holding capacity, soil organic carbon (SOC) and albedo. As a first analysis to evaluate these factors, we used the CROPGRO-Cotton module within the Decision Support System for Agrotechnology Transfer (DSSAT) cropping system model. Specifically, we evaluated the effects of reduced surface runoff, increased soil water holding capacity, and SOC, doubling of the soil albedo through stubble mulching, and of soil drainage by enhancing infiltration with no-tillage/cover crops on yield by adjusting related soil properties. In our analysis, we used mean yields simulated with soil properties of a Pullman clay loam soil at Halfway, TX on the THP as baseline, which were compared to values obtained with the adjusted factors using weather data from 2005 to 2019. Simulated mean yield increased by 27% when the soil water holding capacity was increased by 25 mm, 7% when the runoff curve number was decreased from 73 to 60, 16% when soil albedo was increased from 0.2 to 0.4, and by 58% when the soil drainage factor (fraction day−1) was doubled from 0.2. No significant statistical change in simulated mean yield was calculated when SOC was increased by 1%. Further, effects of a 50 mm pre-plant irrigation were also assessed, simulating limited irrigation in the transition to dryland agriculture that resulted in a statistically insignificant 12% increase in seed-cotton yield. Simultaneous implementation of the four statistically significant individual scenarios (increased water holding capacity, infiltration, albedo, and drainage) resulted in the highest increase (93%) in mean seed-cotton yield. An economic and risk analysis of simulated yields under different scenarios indicated that these factors could reduce revenue risk for dryland cotton producers, with most of the effect from soil drainage improvements.

Over semi-arid agricultural regions such as the U.S. Southern High Plains (SHP) producers of dryland crops need to know which management practices increase yields and decrease production risk. Here, a modeling approach is used to explore management options (MO) that increase dryland cotton yields and estimate those practice's yield risk effects under current SHP climate conditions. To simulate current dryland yield variability, dense distributions of lint yield outcomes were generated using the CROPGRO-Cotton crop model driven by weather inputs from 21 SHP weather stations during 2005–2016. Management effects were explored by repeating simulations over 32 MOs defined by 4 planting dates, 4 planting densities, and applying or not applying nitrogen. Both earlier planting date and decreased plant density increased median simulated yields, with earlier planting having the greatest positive yield effects. The simulated MO that produced the highest median lint yields planted on the earliest planting date (May 15), at the lowest density (3 plants m−1), and applied no nitrogen. Recent SHP field studies generally confirm the earlier planting date effect, but suggest insignificant yield effects for different seeding rates. Even so, negligible yield effects and lower input costs favor lower seeding densities from a profit standpoint. These crop simulations demonstrate a modeling-based method for climate-related agricultural risk management, and suggest mid-May planting dates and low plant densities as part of management practices that increase yields and profits in dryland SHP cotton production.

Sorghum's heat and drought tolerance make it, together with upland cotton, one of two crops produced profitably under dryland conditions in the U.S. Southern High Plains (SHP). Here, a simulation-based method evaluates management options that increase median (50th percentile) SHP dryland sorghum yields and estimates those practice's yield risk effects. This method generates climate-representative distributions of grain yields via a crop model driven by weather inputs from 21 SHP weather stations during 2005–2016. Optimal management practices for current SHP climate conditions were sought by generating yield distributions under 32 management options defined by four planting dates, four plant densities, and applied or no applied N. The highest median grain yields resulted from management options with the latest planting date (July 5) and the lowest plant density (24.7 K plants ha−1), while applied N had essentially no yield effect. Increased yields with later planting dates are consistent with sorghum's growth cycle and SHP summer rainfall climatology. Confirming the low plant density yield effect may require additional field studies, as supporting evidence of higher yields at lower densities from other SHP field and modeling studies is inconclusive. These crop simulations, however, suggest late June to early July planting as part of management practices that maximize yields in dryland SHP sorghum production.

Lack of adoption of soil health–promoting practices (SHPPs) leaves soil vulnerable to erosion, exacerbating flooding and contributing to high nutrient and sediment levels in surface waters. To aid in the adoption of SHPPs, changes in soil health need to be measured and related to things that both clearly and directly matter to farmers and stakeholders, yet soil scientists still grapple with which indicators to measure when assessing soil health. Useful indicators of soil health show changes in soil function resulting from changes in soil management, are measurable, and have clear and direct value to their target audience. These “linking indicators” need to be identified in context for successful promotion of SHPPs. We collected data from two focus groups of farmers in the Brazos River Watershed, TX, who had either adopted SHPPs or who had not. Content analysis of focus group transcripts revealed soil health was an important part of a farmer's stewardship ethic. Farmers perceived that water management, organic matter, yield, and biomass were meaningful indicators of soil health that benefited their enterprise. However, using yield and biomass alone has the potential to create a “false positive” for soil health. When farmers chose their management practices, two themes interacted with farmer concerns for soil health: profitability and social interactions. This work provides context and recommended linking indicators for soil scientists to use for communication with farmers. Researchers and policymakers should be aware of these interactions if efforts to promote SHPP adoption are to be successful.

Texas High Plains (THP), which is an important cotton (Gossypium hirsutum L.) growing region in the United States faces challenges from declining/deteriorating groundwater levels/quality, recurring droughts and severe wind erosion. Growing cover crops after harvesting cotton and/or changing land use from cotton to perennial bioenergy crops could not only address above challenges, but also assist in meeting the national biofuel target. The objective of this study is to assess the implications of changes in land use (replacing cotton with Alamo switchgrass (Panicum virgatum L.) and Miscanthus × giganteus) and crop management (growing winter wheat (Triticum aestivum L.) cover crop) on hydrology and wind erosion in the Double Mountain Fork Brazos Watershed using the Agricultural Policy/Environmental eXtender (APEX) model. Simulated average annual wind erosion, total nitrogen (TN) loss to surface water and nitrate-nitrogen (NO3-N) leaching to groundwater reduced by more than 37%, 43% and 73%, respectively, when winter wheat was grown as a cover crop under the 457 mm (18-inch) annual groundwater pumping limit setup by the High Plains Water District. In addition, winter wheat produced about 0.20–0.26 kg m−2 of biomass for biofuel purposes. Land use change from irrigated cotton to switchgrass and rainfed cotton to Miscanthus decreased the TN load, NO3-N leaching and soil loss by wind erosion by > 89% relative to the baseline scenario. Under the groundwater pumping restrictions, multiple harvests of perennial grasses were found to be better in terms of biomass production (>2 kg m−2), and protection of groundwater and soil.

Guar [Cyamopsis tetragonoloba (L.) Taub] is a legume grown worldwide, tolerant of hot, dry, and saline conditions. Phenotyping is a key bottleneck in guar improvement, with belowground root nodule phenes being largely overlooked. To address this bottleneck, a greenhouse study was conducted to evaluate phenotypic variability and associations in 14 nodule and plant growth parameters in 50 guar genotypes over 48 days. Nodule mass per plant differed among genotypes and had moderate heritability (P = 0.011, H2 = 0.40), while nodule number did not differ and had low heritability (P = 0.247, H2 = 0.14), and the parameters were not correlated. Nodule mass was correlated with total plant N (r = 0.56), plus most biomass parameters, indicating phenotypic links between plant capacity to support nodulation, N2 accumulation, and plant biomass production. Stem diameter may be useful as an indirect, high-throughput selection trait for increased nodulation in guar, as there was a positive association between stem diameter and nodule mass. Branch number and stem diameter, which have great agronomic significance, had wide phenotypic variability and were highly heritable. Reproductive development was delayed in branched genotypes, which may have implications in breeding guar for environments that differ in growing season length. Despite low heritability, there was a wide range in specific leaf area (SLA) that may be exploited by breeders to optimize drought tolerance and N use efficiency traits. These analyses give novel and confirmatory insights on the nature and associations of phenotypic character traits in guar, particularly nodule traits, providing added tools for breeders in developing desired and beneficial plant ideotypes.

The Texas High Plains (THP) is a major cotton-producing region in the United States. Sustaining cotton production under declining groundwater availability in the underlying Ogallala Aquifer and changing climate remains a key challenge for stakeholders in this region. The objectives of this study were to assess climate change impacts on cotton yield and irrigation water use, and evaluate six ideotypes for adaptation. In this study, we used the DSSAT-CSM-CROPGRO-Cotton model for simulating cotton production under 18 projected future climate scenarios and with six potential adaptation ideotypes at Bushland, Halfway and Lamesa in the northern, central, and southern parts of the THP region, respectively. Seed cotton yield and irrigation water use between baseline (1976–2005) and future periods (mid-century:2036–2065 and late-century: 2066–2095) were compared. The irrigated seed cotton yield is expected to increase by 12–21 % at cooler northern sites, and decrease by 2% at the warmer southern site, in the mid-century compared to the baseline. For the same period, seasonal irrigation water use is expected to increase by 6–11 % and dryland seed cotton yield is expected to change by +6 % to −11 % across the locations. The increases in irrigated seed cotton yield were attributed to increased vegetative growth under elevated CO2, while the decline in dryland seed cotton yield was due to poor boll retention at high growing season temperatures. Six potential climate change adaptive ideotypes with greater drought and heat tolerances, higher yield potential, and longer maturity were designed and compared to the reference cultivar. For irrigated conditions, increasing area of full leaf and enhancing partitioning of assimilates to reproductive growth (high yield potential) were preferred, because these characteristics increased seed cotton yield substantially (by 3–9 %) with a marginal change in irrigation water use (by −1 to 3 %). For dryland production, a long maturity ideotype with longer boll filling duration was the most effective ideotype with a substantial increase in seed cotton yield by 11–45 %. The results from this study will be useful to THP cotton producers and water managers in making appropriate decisions for adapting cotton production to projected changes in future climate and groundwater availability.

As the Ogallala Aquifer depletes there is a need to identify management options that might make un-irrigated cotton production sustainable over the U.S. Southern High Plains (SHP). To explore those options, the CSM-CROPGRO-Cotton model was used to simulate the effects of planting options and elevation effects on SHP dryland cotton production. Of the management variables that define the 56 planting options simulated, planting date and density account for the most variability in median SHP yields. Cooler SHP growing seasons have the effect of reducing median lint yields relative to those simulated over the lower elevations of the nearby Rolling Plains. This effect is not as evident in median Rolling Plains yields, which suggests it can be traced to the cooler growing environment of the higher SHP elevations. Also, at both higher and lower elevations lower planting densities maximize median yields, while higher densities result in the lowest yields. These results suggest that the yield suppressing effect of the SHP region’s cooler growing conditions might be compensated for by planting early whenever possible and planting at lower densities. The clear decreasing effect on median yields at higher elevation also suggests the possibility of SHP cotton production moving to the lower elevations of the nearby Rolling Plains as Ogallala Aquifer levels drop.

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 (R eco ) 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.

Assessing the impacts of biofuel-induced land use change on hydrology, water quality and crop yield under the current and future climate scenarios enables selection of appropriate land uses and associated best management practices under the changing climate. In this study, the impacts of land use change from cotton (Gossypium hirsutum L.) to perennial grasses in the Double Mountain Fork Brazos watershed in the Texas High Plains were assessed using the Soil and Water Assessment Tool (SWAT). While switchgrass (Panicum virgatum L.) was assumed to replace cotton in irrigated areas, dryland cotton was replaced by Miscanthus × giganteus under the hypothetical land use change scenarios. Climate change impacts were assessed based on the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate projections of 19 General Circulation Models (GCMs) under two Representative Concentration Pathway (RCP) emission scenarios of RCP4.5 and RCP8.5 during two 30-year periods of middle (2040–2069) and end (2070–2099) of the 21st century. Median irrigation water use of cotton was simulated to decrease by 41%–61% in the future when compared to historic (1994–2009) period based on projections by 19 GCMs. Under the future climate change scenarios, when compared to cotton, median annual irrigation water use by switchgrass reduced by 62%–89%. Simulated future median total nitrogen load decreased by 30%–40% under perennial grasses when compared to future cotton land use. The median irrigated switchgrass yield decreased by 16%–28%, but the median dryland Miscanthus yield increased by 32%–38% under the future climate change scenarios.

Inappropriate grazing management with high stocking rates can result in significantly higher levels of runoff, sediment and nutrient losses to surface water resources. An assessment of water quality effects of various grazing management practices enables the selection of appropriate management practices. The overall objective of this study was to assess the impacts of alternate grazing management practices including the heavy continuous (HC), light continuous (LC) and adaptive multi-paddock (MP) grazing, and no grazing (EX; exclosure) on water quality at the ranch and watershed scales in the rangeland-dominated (71% rangeland) Clear Creek Watershed (CCW) in north central Texas using the Soil and Water Assessment Tool (SWAT). The SWAT model was calibrated and validated for water quality predictions using the measured data on county-level crop yield (1980–2013), and monthly sediment (1994–2009), total nitrogen (TN) and total phosphorus (TP) loads (1986–2009) at the watershed outlet. The ranch-scale assessment results at two study ranches indicated that when the grazing management was changed from the baseline MP grazing to HC grazing, the simulated average (1980–2013) annual surface runoff, sediment, TN and TP losses increased within the ranges of 106%–117%, 6.0–8.1 ton ha−1, 8.3–11.5 kg ha−1, and 1.6–2.6 kg ha−1, respectively. At the watershed-scale, shifting grazing management from the baseline HC grazing to the improved MP grazing decreased surface runoff, sediment, TN and TP loads by 47.0%, 39.7%, 35.1% and 34.1%, respectively. Thus, adaptive MP grazing was found to be the best grazing management practice for the CCW in terms of water quality protection and improvement in ecosystem functions such as reduced soil erosion and increased nutrient retention at both ranch and watershed scales. However, the magnitudes of water quality benefits due to adoption of MP grazing vary according to the extent of grazing lands in a watershed.