Texas High Plains Research Articles

Deficit irrigation effects on yield and yield components of grain sorghum

Development of sustainable and efficient irrigation strategies is a priority for producers faced with water shortages. A promising management strategy for improving water use efficiency (WUE) is managed deficit irrigation (MDI), which attempts to optimize yield and WUE by synchronizing crop water use with the crop’s reproductive stages. In comparison, deficit irrigation (DI) is applied at a fraction of the full (FI) irrigation requirement. Soil water use and grain yield of grain sorghum [Sorghum bicolor (L.) Moench] were evaluated in the High Plains of Texas, USA under three irrigation strategies: FI, DI, and MDI from 2010 to 2012. Grain yields of FI sorghum averaged 3.7 Mg ha−1 greater (p < 0.001) than DI sorghum in all years. However, MDI yields averaged 1.6 Mg ha−1 more than DI yields, which was significant in 2010 and 2012 (p ≤ 0.006). The WUE of FI sorghum was significantly greater than MDI in 2012 (p = 0.003) and DI in 2010 and 2012 (p ≤ 0.001) demonstrating that limiting water did not reduce WUE in two of the three years. Results suggest that WUE’s of grain sorghum are not compromised under MDI compared with FI in most cropping seasons. While FI provides the greatest opportunity to reduce production risks through increased yield, if irrigation water is limiting, MDI provides less risk than DI due to its ability to maintain yield and WUE. Yield was stabilized in all years by increasing seed panicle−1 under MDI, which was supportive of concentrating irrigation water between growing point differentiation and half bloom to maintain ovules.

Implications of biofuel-induced changes in land use and crop management on sustainability of agriculture in the Texas High Plains

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.

Corn Yield and Soil Fertility with Combined Use of Raw or Composted Beef Manure and Inorganic Fertilizers on the Texas Northern High Plains

ABSTRACTAbout 7 million beef cattle are raised annually in the Texas High Plains, producing 16 million Mg of manure, which is land-applied as raw manure (RM) to crops. An interest in aerobic composting prompted a 2-year field study with the primary objective of evaluating corn (Zea mays L.) yield and soil fertility for RM as compared to composted manure (CM). The four treatments (TRT) consisted of low-rate composted manure (CM-L), high-rate composted manure (CM-H), RM, and inorganic fertilizer (IN). All four TRT received equal plant—available N by supplementing the RM and CM with IN. Yield was measured by both machine-harvesting and hand-harvesting methods. Machine-harvested yield was similar among TRT for both years. Hand-harvested yield was lower for IN than RM in the first year, with similar yields among TRT in the second year. Due to drought, yields were considerably lower in the second year for all TRT. After 2 years, CM-H had higher soil P, K, Zn, and organic carbon concentrations than IN, with no differences among TRT for soil NO3-N, pH, or electrical conductivity. Both CM and RM provided beneficial nutrients for corn production and improving soil fertility. Land application of CM and RM provides long-term benefits to soil health and sustainability in the Texas High Plains region.

Evaluating Within‐Plant Variability of Cotton Fiber Length and Maturity

Core Ideas Cultivars showed differences for the within‐plant fiber length and maturity.Some cultivars exhibited relatively stable within‐plant fiber length and maturity.Genetic component plays a significant role for the differences among the cultivars. Previous studies have indicated differences in fiber quality parameters including fiber length and maturity within the canopy of cotton (Gossypium hirsutum L) plants. A 3‐yr study was conducted to investigate the impact of within‐plant variability on fiber length and maturity of upland cotton cultivars widely grown on the High Plains of Texas. Twelve upland cotton cultivars were grown in a randomized complete block design with three field replications, in Lubbock, TX, during the 2012, 2013, and 2014 growing seasons. A box‐picking harvesting method was used to individualize samples so that the within‐plant variability of cotton fiber quality could be studied. Bolls harvested from different positions on the plants were ginned with a tabletop roller gin to minimize fiber damage. The lint from each fruiting position was blended with a supple needles laboratory blender to reduce within‐sample variability while minimizing fiber breakage. Each sample collected from a different fruiting position on the plant was tested on the Advanced Fiber Information System (AFIS) with three replications of 3000 fibers. The results indicated that cultivars such as FM 9170 B2F, NG 4111 RF, PHY 499 WRF, and FM 2484 B2F showed lower within‐plant variability, while DP 1044 B2RF, PHY 367 WRF, and ST 5458 B2F showed relatively high within‐plant variability for AFIS fiber length and fiber maturity. In conclusion, variations in within‐plant fiber length and maturity among upland cotton cultivars could be a potential source of variability for breeding programs aimed at improving fiber quality.

Lysimetric Evaluation of the APEX Model to Simulate Daily ET for Irrigated Crops in the Texas High Plains

Abstract. The NTT (Nutrient Tracking Tool) was designed to provide an opportunity for all users, including producers, to run complex simulation models, such as APEX (Agricultural Policy Environmental eXtender), with the associated required databases. The APEX model currently nested within NTT provides estimates of the changes in nitrogen (N), phosphorus (P), and sediment losses that are associated with management practices specified by the user. Five methods (Penman-Monteith, Penman, Priestley-Taylor, Hargreaves-Samani, and Baier-Robertson) for determining potential evapotranspiration (PET) are available as inputs for estimating actual ET. This study was conducted to evaluate the accuracy of the ET values obtained from the five PET equations currently available in APEX using both onsite measured climate data and data from the NTT standard databases. The mean daily, monthly, and annual ET values predicted by each of the equations in APEX for a lysimeter field at the USDA-ARS Conservation and Production Research Laboratory at Bushland, Texas, was compared to values measured for the 2001-2010 period. APEX generally underestimated ET with all PET methods (mostly during growing seasons) at both the daily and monthly levels but overpredicted for years when cotton was grown as the major cash crop due to overprediction of leaf area index during the senescing stage for cotton. The underprediction of ET in growing seasons was possibly from underprediction of rainfall due to estimation of rainfall for missing data. Overall, APEX was able to adequately (R2 = 0.82 and NSE = 0.80) predict mean monthly ET for major crops grown in the semi-arid Texas High Plains region. These results should reinforce confidence in APEX’s ability to simulate ET accurately for fully irrigated farms. ET predictions with the Hargreaves-Samani and Priestley-Taylor methods, which require limited data compared to the Penman and Penman-Monteith methods, were similar (p &amp;gt; 0.05, one-way ANOVA), with mean errors within 8.7% for measured weather data and 12.6% for NTT-generated weather data for both methods. This is encouraging because of the limited availability of measured climate data for the majority of locations in the world, including the U.S. Keywords: APEX, Evapotranspiration (ET), Irrigation, Lysimeters, NTT, Semiarid regions.

Modeling Evapotranspiration and Crop Growth of Irrigated and Non-Irrigated Corn in the Texas High Plains Using RZWQM

Abstract. Accurate quantification and management of crop evapotranspiration (ET) are critical to optimizing crop water productivity for both dryland and irrigated agriculture, especially in the semiarid regions of the world. In this study, four weighing lysimeters in Bushland, Texas, were planted to maize in 1994 with two fully irrigated and two non-irrigated for measuring crop ET. The Root Zone Water Quality Model (RZWQM2) was used to evaluate soil water balance and crop production with potential evapotranspiration (PET) estimated from either the Shuttleworth-Wallace method (PTSW) or the ASCE standardized alfalfa reference ET multiplied by crop coefficients (PTASCE). As a result, two water stress factors were defined from actual transpiration (AT) and were tested in the model against the lysimeter data, i.e., AT/PTSW and AT/PTASCE. For both water stress factors, the simulated daily ET values were reasonably close to the measured values, with underestimated ET during mid-growing stage in both non-irrigated lysimeters. Root mean squared deviations (RMSDs) and relative RMSDs (RMSD/observed mean) values for leaf area index, biomass, soil water content, and daily ET were within simulation errors reported earlier in the literature. For example, the RMSDs of simulated daily ET were less than 1.52 mm for all irrigated and non-irrigated lysimeters. Overall, ET was simulated within 3% of the measured data for both fully irrigated lysimeters and undersimulated by less than 11% using both stress factors for the non-irrigated lysimeters. Our results suggest that both methods are promising for simulating crop production and ET under irrigated conditions, but the methods need to be improved for dryland and non-irrigated conditions. Keywords: ET, RZWQM modeling, Stress factor, Weighing lysimeter.

Measurement of Cotton Transpiration

There are a few field methods available to directly measure water evapotranspiration (ET) along with its two components, evaporation from the soil (E) and from the crop (T). One such technique that measures T, uses sensors to calculate the sap flow (F) of water through the plant stem and is based on the conservation of mass and energy, i.e., the stem heat balance method. This instrument consists of a flexible heater that is wrapped around the plant stem with temperature sensors to measure the difference in temperature of F below and above the heater. This is a null method, where all inputs and outputs are known and the calculated F is a direct measure of T. This method has been used to measure T in a variety of crops, including cotton, grapes, olive trees, soybean, ornamental and horticultural crops. A new version of the EXO-SkinTM is the Stem Gauge Dual Channel Design (SGDCTM), which was commercially introduced and had a radically new design resulting in a different energy balance, compared to the original design, which needed experimental verification. An initial evaluation was done with potted cotton (Gossypium hirsutum, L.) plants in a greenhouse experiment showing that values of cotton-T measured with the new sensor were accurate; however, this comparison was limited to daily T T in the 2 - 7 mm/d range, representative of the semiarid Texas High Plains. For this purpose, cotton was planted on 12 June 2017 on a 1000 m2 plot in a soil classified in the Amarillo series at the facilities of the USDA-ARS, Lubbock, TX. For a period of 15 days, 2 to 16 Sep 2017, we measured hourly cotton-T with the new sensors and with portable growth chambers (0.75 m × 1 m cross-section, and 1 m height) where water vapor flux was measured at a 10 Hz frequency using an infrared gas analyzer. We used three chambers and, in each chamber, the new sensors were installed on four cotton plants. We used linear regression analysis to compare hourly and daily values of cotton-T measured with the sap flow gauges against T measured by the chambers. Using a t-test (p T for a wide range of environmental conditions.

Evaluation of the Sensory Profiles of Texas High Plains Tempranillo and Cabernet Sauvignon Wines

A trained panel was asked to evaluate the sensory profiles of Tempranillo and Cabernet Sauvignon varietal wines from the Texas High Plains American Viticultural Area. The panelists evaluated 20 different wines using a modified conventional descriptive analysis and a modified citation frequency-based method. Our study revealed a significant correlation between both methods in the distribution of wines. The two varietal wines could not be significantly distinguished by their average sensory profiles, although butter, caramel and lavender were significantly stronger in Tempranillo and black currant in Cabernet Sauvignon. Both average sensory profiles were mainly driven by their oak-related characteristics. Our results provide a better understanding of the sensory properties of wines made from Texas High Plains grapes and highlight the importance of the human factor in defining the terroir and identity of wines, illustrated by differences in the use of oak. To our knowledge, this study is the first conducted in this area and could suggest the development of a technical winemaking consensus to strengthen the identity of wines from the Texas High Plains.

Irrigated Corn Production and Management in the Texas High Plains

AbstractCorn is the major irrigated crop in the Texas High Plains (THP) and uses 53% of the total agricultural regional water resource budget. Currently, the declining water level of the Ogallala Aquifer, coupled with irrigation pumping restrictions by regional groundwater conservation districts, is challenging sustainable, high level corn production. The objective of this article is to review production levels and evaluate corn management practices in the THP with reduced or limited levels of irrigation. Long‐term field studies demonstrate that yield and water use efficiency (WUE) have increased significantly over the last forty years while seasonal corn evapotranspiration (ET) under full irrigation conditions has not increased. Among management practices, irrigation remains the single‐most important factor in corn production. With recent advances in corn breeding and genetics, irrigation requirements can be reduced by up to 25% in some years and result in similar yields as compared to irrigation amounts at the 100% ET level. Also, WUE is generally maximized at irrigation levels meeting 75–80% ET demand. Newly developed drought tolerant corn hybrids have been shown to provide yield benefits of 10–15% under limited (reduced) irrigation water levels. At the higher irrigation levels (75–100% ET requirement), corn yield increased as seeding rate increased initially but did not increase further when the seeding rate exceeded 94,000 seeds ha−1. Also, a multi‐year planting date study indicated that high corn yields can still be achieved with a long‐season hybrid when planted in the middle of May and early June. When the planting date is delayed to late June and early July, mid‐ and short‐ season hybrids showed a yield advantage over the long season hybrids.

Calibration and Validation of CSM‐CROPGRO‐Cotton Model Using Lysimeter Data in the Texas High Plains

AbstractTexas High Plains (THP), one of the most important food and fiber producing regions in the Ogallala Aquifer Region, currently faces rapid decline of groundwater levels. Predicted climate extremes and high temporal variability in growing season precipitation may require growers to pump more groundwater from the Ogallala Aquifer to meet higher crop water demand. The Decision Support System for Agrotechnology Transfer (DSSAT) Cropping System Model (CSM) is a widely used crop simulation tool for evaluating impacts of different water and crop management practices, including irrigation on crop yield and water use efficiency. In this study, CROPGRO‐Cotton module of the DSSAT was calibrated and validated using 2000, 2001, 2002, and 2010 irrigated lysimeter field data managed by the USDA‐ARS (United States Department of Agriculture ‐ Agricultural Research Service) Conservation and Production Research Laboratory at Bushland, TX. The lysimeter field consisted of four equal plots designated as NE, SE, NW, and SW. Crop growth characteristics including leaf area index (LAI), above ground biomass (AGB), evapotranspiration (ET), soil moisture, and lint yield of 2000‐NE, 2000‐SE, and 2001‐NE, were used for calibration and 2002‐NE, 2010‐NE, and 2010‐SE were used for validation. The calibrated and validated model was used to simulate the long term (1924–2012) crop yield and seasonal crop ET. During the calibration process, some of the cultivar and ecotype parameters that influence LAI, AGB, and lint yield were adjusted for better statistical results. Measured and simulated LAI, AGB, ET, soil moisture, and lint yield showed good agreement during calibration and validation as indicated by performance statistics such as r2 from 0.70 to 0.82, and percent error (PE) = −0.85 to 17.3% for LAI; r2 = 0.89 to 0.95, and PE = −7.36 to −13.66% for AGB; and r2= 0.90 to 0.94, and PE = 3.20 to 3.44% for ET during calibration and validation, respectively. The model underestimated ET during peak vegetative growth and development stage except in some circumstances. The calibrated and validated model was able to simulate lint yield and seasonal ET during a long term (1924–2012) historic period for Bushland, TX, under irrigated conditions. The calibrated model could be used to schedule ET based irrigation management practices in the THP and to estimate future ET for other modeling experiments.

Ogallala Aquifer Program: A Catalyst for Research and Education to Sustain the Ogallala Aquifer on the Southern High Plains (2003–2017)

AbstractThe Ogallala Aquifer Program (OAP) was created in 2003 with support from Congressmen from Kansas and Texas. The OAP is a research‐education consortium seeking solutions from problems arising from declining water availability from the Ogallala Aquifer in western Kansas and the Texas High Plains. The consortium is led by the Agricultural Research Service (ARS) laboratories in Bushland and Lubbock, TX, and the university partners are Kansas State University, Texas A&amp;M AgriLife Research and Extension Service, Texas Tech University, and West Texas A&amp;M University. The OAP has provided over $40 million to support research and education activities. About half of these funds were used to support permanent ARS scientists and ARS hired post‐docs. The other half were used by university scientists to supplement on‐going projects by providing support for supplies, sample analyses, temporary employees, etc. Initially, OAP activities were focused on seven priorities. In 2013, four objectives replaced the original seven priorities. A fifth priority was added in 2017. The current objectives are: 1) Develop and evaluate water management strategies and technologies that could reduce water withdrawals for irrigation by 20% in 2020 compared to 2012; 2) Develop and evaluate management strategies and technologies that would increase the productivity and profitability of dryland cropping systems; 3) Improve the understanding of hydrological and climatic factors that affect water use and agricultural profitability; 4) Determine the impacts of alternative water withdrawal/use policies on the economic viability of the agriculture industry of the Southern Ogallala Aquifer Region; and 5) Develop best management practices for production of high value and alternative crops for both dryland and irrigated systems. The objectives of the program and distribution of resources are decided by an executive committee with a member from each of the four universities, two from ARS, one from Bushland, and the other from Lubbock. Proposed projects that utilize resources from more than one participating institution, leverage existing resources, and address the stated objectives are more likely to be provided support. The impact of the OAP on research directed at agriculture on the High Plains has been recognized by three prestigious awards.

Assessing Irrigation Aquifer Depletion: Introduction

Assessing Irrigation Aquifer Depletion: Introduction

More Recent Wheat Cultivars Extract More Water from Greater Soil Profile Depths to Increase Yield in the Texas High Plains

Core Ideas We investigated the depth and amount of soil‐water extraction in TAM wheat cultivars. Yield was largely related to soil‐water extraction under dryland conditions. Relatively newer cultivars were able to extract more water from deeper soil profile. Drought is the most important factor limiting wheat (Triticum aestivum L.) yield in the U.S. southern High Plains (SHP). Adoption of suitable cultivars and crop management practices are crucial to reducing yield loss from drought in the area. We conducted a 5‐yr study to investigate the depth and amount of net soil water extraction (SWE) in four wheat cultivars at different growth stages. Plants were grown under dryland conditions and volumetric soil water content (SWC) was measured in 0.2‐m increments to the depth of 2.4 m at planting, jointing, anthesis, and maturity. There were large variations in grain yields (474–3685 kg ha−1) in dryland wheat across years and cultivars. Yield was largely determined by plant available soil water (PASW) at planting and seasonal precipitation. In a season with high yield (3548 kg ha−1 in 2016), net SWE occurred in the whole 0.0‐ to 2.4‐m profile. In contrast, in a season with very low yield (650 kg ha−1 in 2011), net SWE was limited to the upper 1.2 m. More recent cultivars (TAM 110, TAM 111, and TAM 112) were able to extract more water from deeper in the soil profile (particularly between jointing and maturity), and had higher evapotranspiration (ET), biomass, and yield than the legacy wheat cultivar (TAM 105), especially during the dry seasons of 2011 and 2012. This study demonstrated that effective use of soil water from greater soil depths is important for greater ET and yield under dryland conditions in a semiarid environment.

The Impacts of an Ethanol Plant Placement on Cotton Acreage in the Texas High Plains

This study examines the impacts of a sorghum-based ethanol plant established in a major cotton producing area on local sorghum basis and cotton acreage distribution using county-level panel data from 2002 to 2014. Spatial econometric models are employed to account for any spatial dependence. Our results support the conclusion sorghum basis and cotton acreage within a county depends on characteristics of its neighbors. Specifically, the findings indicate that the sorghum basis increased by 1.5 cents per bushel in the short-run resulting from hosting a 40-million-gallon ethanol plant, and a short-run increase by 0.2 percent in cotton acres over all counties.

Performance of Precision Mobile Drip Irrigation in the Texas High Plains Region

Mobile drip irrigation (MDI) technology adapts driplines to the drop hoses of moving sprinkler systems to apply water as the drip lines are pulled across the field. There is interest in this technology among farmers in the Texas High Plains region to help sustain irrigated agriculture. However, information on the performance of this system and its benefits relative to common sprinkler application technologies in the region are limited. A two-year study was conducted in 2015 and 2016 to compare grain yields, crop water use (ETc) and water use efficiency (WUE) of corn (Zea Mays L.) irrigated with MDI, low elevation spray application (LESA) and low energy precision application (LEPA) methods. Irrigation amounts for each application method were based on weekly neutron probe readings. In both years, grain yield and yield components were similar among application treatment methods. Although WUE was similar for the MDI treatment plots compared with LEPA and LESA during the wet growing season (2015), MDI demonstrated improved WUE during the drier year of 2016. Additional studies using crops with less than full canopy cover at maturity (sorghum and cotton) are needed to document the performance of MDI in the Texas High Plains region.

Improving SWAT auto-irrigation functions for simulating agricultural irrigation management using long-term lysimeter field data

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.

Arthropod Abundance and Community Structure in Adjacent Cotton and Alfalfa on the Texas High Plains

A study was designed to examine the community composition of canopydwelling arthropods in adjacent fields of cotton, Gossypium hirsutum L., and alfalfa, Medicago sativum L., at Texas A&M University AgriLife Research and Extension Center farm near Lubbock, TX, during the cotton-growing seasons of 2008 and 2009. Samples were collected from 61 row-meter sections of cotton (1.02-m row spacing) and 61 row-meter sections of alfalfa (0.51-m spacing) via a “Keep It Simple Sampler” (KISS). Six samples were collected on each of 11 weekly sampling dates during the cotton-growing seasons of both years. We found that specimens in the canopy-dwelling arthropod community in cotton and alfalfa were from the orders Araneae, Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Neuroptera, and Orthoptera, and in the orders, 41 families were identified. Members of Araneae, Coleoptera, and Hemiptera were most abundant in both crops. Overall, a greater number of arthropod taxa was found in alfalfa, but some arthropod taxa were unique to each crop. Analyses revealed a difference in temporal abundance of captured arthropods at the order (p ≤ 0.018) and family levels (p ≤ 0.021) during cotton squaring, flowering, and boll-development stages, with significantly greater abundance of arthropods at the order level in alfalfa compared to cotton in both years, except during the cotton-flowering period in 2008. Implications of arthropod community differences between alfalfa and cotton were discussed with respect to using alfalfa as a potential source of predators for adjacent cotton.

Registration of CA 4005 and CA 4006 Cotton Germplasm Lines with Partial Resistance to Feeding Injury from Thrips

Thrips (Thysanoptera: Thripidae) are common pests of cotton (Gossypium spp.) worldwide, typically causing economic damage within the first few weeks after planting of a cotton crop. With the loss of granular aldicarbs and resistance development to other insecticides in recent years, host plant resistance could play an important role in the integrated management of thrips. Two breeding lines originally developed for cold tolerance in the Texas A&amp;M AgriLife Research cotton improvement program at Lubbock, TX, exhibited characteristics associated with thrips tolerance. These G. hirsutum lines, CA 4005 (Reg. No. GP‐1023, PI 681593) and CA 4006 (Reg. No. GP‐1024, PI 681594), are germplasm lines that were subsequently evaluated for potential resistance to thrips feeding injury. Both lines were evaluated in field and greenhouse tests from 2012 to 2014. CA 4005 and CA 4006 consistently displayed greater resistance to thrips feeding injury than the commercial and susceptible checks at the field level. Greenhouse evaluations, however, revealed that these lines are only partially resistant and can be overcome at high thrips densities. Yield potential, high‐volume instrument (HVI) fiber quality, and other agronomic characteristics of CA 4005 and CA 4006 were comparable to the evaluated commercial checks. These germplasm lines exhibited improved thrips resistance and competitive agronomic potential for the Texas High Plains and would be valuable sources of partial thrips resistance in adapted G. hirsutum germplasm.

Using an integrated crop water stress index for irrigation scheduling of two corn hybrids in a semi-arid region

Different thermal-based plant feedback systems have been used for irrigation management of cotton and grain crops in the Texas High Plains region, producing yields that are similar or better than irrigation scheduling using the neutron probe. However, there are limited studies using plant feedback systems to actively scheduling irrigations for corn. In this 2-year study, a drought tolerant and a conventional hybrid were managed under a variable rate center pivot irrigation system. The main treatments were manual and plant feedback irrigation scheduling based on weekly neutron probe readings and an integrated crop water stress index (CWSI), respectively. In each main treatment, three irrigation treatment levels were established. Crop responses were compared between irrigation methods and levels. Results demonstrated that overall grain and biomass yields and grain WUE for the plant feedback-control plots were similar to those from the manual-control plots for both years. These results indicate that a plant feedback system using a CWSI could be used to manage corn in a semi-arid region and over a large-sized field. The plant feedback system could provide convenience and time savings to farmers who manage multiple center pivot fields.

Modeling the effects of land use change from cotton (Gossypium hirsutum L.) to perennial bioenergy grasses on watershed hydrology and water quality under changing climate

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.