Texas High Plains Research Articles

Potential climate change adaptation strategies for winter wheat production in the Texas High Plains

Winter wheat is one of the major crops in the Texas High Plains (THP) region, which is facing challenges from climate change (CC) and exhausting irrigation water supplies from the Ogallala Aquifer. The goal of this study was to assess the impacts of CC on winter wheat production in the THP and evaluate potential adaptation strategies using the Decision Support System for Agrotechnology Transfer (DSSAT) CERES-Wheat model. A thorough calibration of the model against field data resulted in a satisfactory simulation of phenology, leaf area index, grain yield (percent error, |PE| <4.7%), biomass (|PE| <7.1%), and evapotranspiration (|PE| <11.9%). The evaluated model was then used for: (i) predicting winter wheat yield and irrigation water use, and (ii) evaluating six potential winter wheat cultivars under CC at three sites in the THP. Mixed trends were found for irrigated yield in the future across the study sites due to differences in climate and soils. Irrigation water use of winter wheat is expected to decrease in the future due to improved water use efficiency at elevated atmospheric CO2 concentration and reduced growing season length due to temperature rise. Dryland yield is expected to increase due to improved crop water use efficiency. Among the virtual cultivars tested for CC adaptation, increasing potential number of grains and vigorous root system were found to be the most desirable traits, since these cultivars had higher yield and lower or comparable irrigation water use than the reference cultivar. Long-maturity and stay-green cultivars were found to be not advisable due to significantly higher irrigation water use than the reference cultivar. Overall, the results showed that winter wheat production in the THP could benefit from CC under milder climatic conditions (mean growing season temperature <13 °C). Enhancing yield potential traits and root architecture should be considered for screening cultivars for CC adaptation.

A Survey of the Insects of the Southern High Plains (Llano Estacado) of Texas, with Particular Reference to Pollinators and Other Anthophiles

The economic value of insect pollination to the world economy is tremendous, and pollination service is critical for our food supply and persistence of native plants. Little data are currently available on pollinator occurrence in the Southern High Plains (SHP) of Texas. Past studies on hybrid cottonseed production in the region documented high abundance of six species of Agapostemon and lower abundance of Diadasia spp., Melissodes spp., and Perdita spp. Historical records indicated the presence of Bombus fraternus and B. pensylvanicus which now have Endangered and Vulnerable IUCN status respectively. In 2013 and 2014, we used blue vane traps and targeted netting to collect insect pollinators and anthophiles on the three dominant land uses in the region; cropland, Conservation Reserve Program (CRP), and native grasslands. With capture methods combined, we collected 74,215 insect specimens; 63% of the specimens were Hymenoptera (289 taxa), 28.61% were Coleoptera (150 taxa), 4.48% were Diptera (115 taxa), 2.34% were Lepidoptera (60 taxa), and 1.61% were of other orders (15 taxa). Our capture included all previously documented bee genera, but we did not detect B. fraternus. Studies support that blue vane traps are an effective method of trapping bees and our results demonstrated that they are also effective in attracting some families of anthophilous Coleoptera and Diptera. However, we captured several species of Hymenoptera, Diptera, and Lepidoptera with aerial nets that we did not capture in blue vane traps. This study documents pollinator and anthophile species present in a highly altered landscape and is the most comprehensive list of pollinators and anthophiles in this region to date.

Temporal Variability of Soil Carbon and Nitrogen in Cotton Production on the Texas High Plains

Soil organic carbon (SOC) is a key indicator of soil health as it is important in essential soil functions related to nutrient cycling and soil productivity. Although, it can take several decades to increase SOC in semi‐arid ecoregions, it is possible that the low organic matter background in sandy soils typical of semi‐arid soils may show greater fluctuations compared to soils from other regions. This study was conducted to evaluate the temporal C and N dynamics of cotton (Gossypium hirsutum L.) cropping systems in a semi‐arid region. The effects of no‐tillage (NT) and cover crop use on SOC, potassium permanganate oxidizable carbon (POXC), inorganic nitrogen (Ninorg), and microbial respiration were investigated in a long‐term study (∼19 yr) at Lamesa, TX, comparing conventional tillage (CT), winter fallow, to no‐tillage rye cover (R‐NT), and no‐tillage mixed species cover (M‐NT) on an Amarillo fine sandy loam. Results showed SOC and POXC were greatest during periods of active cover crop and cotton root growth. Soil organic C and POXC were significantly correlated (R2 = 0.75; p &lt; 0.0001), but poorly correlated to microbial respiration (R2 = 0.41, p = 0.0001; and R2 = 0.02, p = 0.8781, respectively). Conservation management practices did not impact Ninorg. Soil organic C and POXC levels were more variable than previously reported and responded to active root growth in this semi‐arid, sandy soil.Core Ideas Soil organic C and K permanganate oxidizable C were more temporally variable than previously reported. Soil organic C and K permanganate oxidizable C were greatest during active cover than fallow periods. Long‐term conservation management did not significantly increase inorganic N.

‘TAM 204’ Wheat, Adapted to Grazing, Grain, and Graze‐out Production Systems in the Southern High Plains

‘TAM 204’ (Reg. no. CV‐1155, PI 686859), a hard red winter wheat (Triticum aestivum L.) cultivar with the experimental designation of TX06V7266, was developed and released by Texas A&amp;M AgriLife Research in 2014. TAM 204 is an F4–derived line from the cross ‘TAM 112’/TX01M5009 made at Vernon, TX, in 2001. TAM 204 is an apically awnletted, medium‐maturing, semidwarf wheat with red glumes. It was released primarily as a grain, dual‐purpose, and graze‐out wheat with high grain and forage yield potential. It has good acid soil tolerance, is resistant to Soil‐borne wheat mosaic virus, Wheat streak mosaic virus and its vector wheat curl mite, greenbug, stem rust and stripe rust, and it is moderately susceptible to leaf rust. TAM 204 has a high level of resistance to Hessian fly biotypes GP and vH9 and a moderate level of resistance to biotype vH13. Compared with ‘TAM 111’, which is currently the most widely grown cultivars in Texas, TAM 204 has significantly higher grain yield in the Texas High Plains under both irrigated and dryland environments. Compared with ‘TAM 401’ and ‘Weathermaster 135’, which are currently the two most popular apically awnletted cultivars in Texas, TAM 204 has similar forage yield but higher grain yield across a wide range of environments. TAM 204 could be a better option for wheat growers and cattle owners under grain‐only, dual‐purpose (grazing‐plus‐grain), and graze‐out production system in the southern US Great Plains.

Rye Cover Crop Impacts Soil Properties in a Long‐Term Cotton System

Core IdeasSoil nitrate was lower due to a cereal rye cover crop during the active growing season.Infiltration was greater for no‐till with rye cover crop than conventional tillage.After 17 years, no‐till with rye had greater soil organic C than conventional tillage in surface layers.Soil organic C did not differ between no‐till with rye and conventional tillage for subsurface layers.No‐till with rye has potential to alleviate resistance and compaction at subsurface layers.Adoption of conservation tillage in cotton cropping systems lags well behind other major crops in the United States. The Texas High Plains region is the largest cotton‐producing region in the United States and is in an area where soil and water conservation are of utmost importance. There is little information of the impacts of conservation tillage on soil function within this environment, and long‐term studies are critical to understanding potential impacts of implemented practices. As conservation tillage expands in use, understanding the impact of transitioning to such systems on nutrient cycling and soil compaction becomes paramount. Our objective was to quantify the impact of a long‐term no‐till cover crop system on soil chemical and physical properties in a continuous cotton system within a semiarid environment. Two systems implemented in 1998 were evaluated: (1) conventional tillage (CT); and (2) no‐till with a cereal rye cover crop (NT‐rye). Soil NO3–N was significantly lower due to NT‐rye treatments during the active cover crop growing season. However, NO3–N concentrations were not different between tillage treatments in the cotton growing season. Soil organic C (SOC) was significantly greater for NT‐rye in the upper 10 cm, and there were no significant differences for SOC between treatments to a depth of 90 cm. Bulk density and penetration resistance varied by sampling time and depth and infiltration was as much as 34% greater for NT‐rye. No‐till with a rye cover crop can increase surface SOC levels while improving infiltration and penetration resistance in semiarid continuous cotton cropping systems.

Emerging disparities in community resilience to drought hazard in south-central United States

In search of new insights into the dynamics of hazard resilience, this study assessed the temporal changes of community resilience to the drought hazard in the south-central U.S. The study hypothesized that over time counties with more affluent socioeconomic conditions and more diverse agriculture would improve their resilience while counties with poorer socioeconomic conditions and heavy reliance on agriculture decreased their resilience, thus widening the regional disparities in community resilience to the drought hazard. The study applied the Resilience Inference Measurement (RIM) framework to measure the resilience levels of the 503 counties of Arkansas, Louisiana, New Mexico, Oklahoma, and Texas. Using data of Year 2000, the RIM model selected 10 variables as resilience predictors with a 67.9% classification accuracy and assigned a resilience level to each county. The variables selected in the RIM model are related to the economic performance in the agricultural sector, socioeconomic well-being, and health. The derived discriminant functions from the RIM model were then used to estimate the resilience levels in 2005, 2010, and 2015. Over the 15-year period, 262 counties across the study area improved their resilience, whereas 48 counties, mostly in the Texas High Plains, experienced a decrease in their resilience level. The results support the hypothesis and suggest a widening gap in resilience levels among counties. These results increase our understanding of the complex process underlying communities’ response to the drought impacts.

Harvesting Regimes Affect Brown Midrib Sorghum-Sudangrass and Brown Midrib Pearl Millet Forage Production and Quality

As water levels in the Ogallala Aquifer continue to decline in the Texas High Plains, alternative forage crops that utilize less water must be identified to meet the forage demand of the livestock industry in this region. A two-year (2016 and 2017) study was conducted at West Texas A&amp;M University Nance Ranch near Canyon, TX to evaluate the forage production and quality of brown midrib (BMR) sorghum-sudangrass (SS) (Sorghum bicolor (L.) Moench ssp. Drummondii) and BMR pearl millet (PM) (Pennisetum glaucum (L.) Leeke)) harvested under three regimes (three 30-d, two 45-d, and one 90-d harvests). Sorghum-sudangrass consistently out yielded PM in total DM production in both tested years (yield range 3.96 to 6.28 Mg DM ha−1 vs. 5.38 to 11.19 Mg DM ha−1 in 2016 and 6.00 to 9.87 Mg DM ha−1 vs. 6.53 to 15.51 Mg DM ha−1 in 2017). Water use efficiency was higher in PM compared to SS. The 90-d harvesting regime maximized the water use efficiency and DM production compared to other regimes in both crops; however, some forage quality may be sacrificed. In general, the higher forage quality was achieved in shorter interval harvesting regimes (frequent cuttings). The selection of suitable forage crop and harvesting regime based on this research can be extremely beneficial to the producers of Texas High Plains to meet their individual forage needs and demand.

Determining water-use-efficient irrigation strategies for cotton using the DSSAT CSM CROPGRO-cotton model evaluated with in-season data

The Texas High Plains (THP) region, a vital part of U.S. grain and fiber production, is experiencing the effects of conflicting interests in the diminishing Ogallala Aquifer, making necessary the adoption of more efficient irrigation strategies. Decision Support System for Agrotechnology Transfer (DSSAT) is a process-based model that uses meteorological, soil, and crop management data to predict crop growth, development, and yield. A well-evaluated DSSAT model is useful for simulation of efficient crop and irrigation management strategies. This study details the evaluation of CROPGRO-Cotton module in the DSSAT model based on measured in-season biomass and canopy height, and crop yield data from a field study as well as the use of the evaluated model for determining the best irrigation strategy for cotton (Gossypium hirsutum L. var. hirsutum) in terms of crop yield and irrigation water use efficiency. Irrigation simulation experiments were conducted over a testing range for four separate irrigation scheduling strategies —Time Temperature Threshold (TTT)-5.5 h, TTT-7.5 h, Daily Irrigation (DI), and percent ET replacement —to determine the most efficient irrigation strategy that results in maximum yield with minimum irrigation water input. The DSSAT CROPGRO-Cotton model demonstrated potential to simulate the effects of various irrigation strategies on cotton yield and water use efficiency. The 12 mm, 7.5 h TTT strategy was found to be the best strategy to achieve a maximized yield with the greatest irrigation water use efficiency, with a modelled yield of 5887 kg ha−1 using 195 mm of irrigation throughout the season.

Soil Water Sensor Performance and Corrections with Multiple Installation Orientations and Depths under Three Agricultural Irrigation Treatments.

Performance evaluations and corrections of soil water sensors have not been studied using different installation orientations under various irrigation treatments in the Texas High Plains. This study evaluated the performance of four sensors using factory calibration and derived field corrections as compared to calibrated neutron moisture meters (NMMs). Sensor performance was assessed using horizontal insertion, laid horizontal placement, and vertical insertion at 15.2, 45.7, and 76.2 cm depths in a clay loam soil with three irrigation treatments. Results indicated the factory-calibrated Acclima 315 L performed satisfactorily using horizontal insertion as compared to NMM measurements at 45.7 and 76.2 cm depths with a ±2% mean difference (MD) and <3.5% root mean square error (RMSE). The factory-calibrated Acclima 315 L using horizontal insertion also performed satisfactorily across all irrigation treatments according to soil profile water storage (MD = 0.36% and RMSE = 3.25%). Generally, the factory-calibrated Decagon GS1 and Campbell Scientific 655 using vertical insertion agreed more closely with NMM measurements compared with other installation orientations. There was a significant underestimation of water storage (>60 mm) in the 0.9 m soil profile using the Watermark 200SS. In summary, field corrections are required for Decagon GS1, Campbell Scientific 655, and Watermark 200SS sensors.

Yeast species isolated from Texas High Plains vineyards and dynamics during spontaneous fermentations of Tempranillo grapes.

Vineyards and grape musts harbor complex locally specific microbial communities, among which yeast species can be responsible of spontaneous alcoholic fermentation. Although relying on indigenous yeast can be a risk for winemaking, local yeast diversity is associated with complexity and stronger identity of the wine produced, compared to inoculated alcoholic fermentation with commercial yeast strains. In this context, the main yeast species present on grapes, leaves and soils of Tempranillo and Cabernet Sauvignon vineyards in the hot semi-arid climate of the Texas High Plains area were investigated, as well as the presence and dynamics of yeast species during spontaneous fermentations of Tempranillo grapes from the same vineyards. Molecular characterization of yeast species was performed using culture-dependent 5.8S-ITS restriction fragment length polymorphism method and sequencing. Yeast species recovered from grapes, leaves, and soils were mainly dominated by Aureobasidium pullulans, Cryptococcus species, Filobasidium species and Naganishia species, typical members of the vineyard environment. One isolate of potential enological interest, Lachancea thermotolerans, a fermenting yeast with potential in must acidification, was recovered from the vineyard environment. However, spontaneous alcoholic fermentations revealed the presence of fermenting yeast species, including Saccharomyces cerevisiae, Lachancea thermotolerans and Hanseniaspora species. The presence of the three aforementioned species is of extreme interest for winemaking in the Texas High Plains area. Indeed, Saccharomyces cerevisiae is the model for alcoholic fermentation, Hanseniaspora species have been shown to improve palatability of wines, and Lachancea thermotolerans has become of increasing interest due to its potential to acidify musts and palatability. One of the main characteristics of grapes grown in the Texas High Plains area being the lack of acidity, focusing on these three yeast species could promote the development of locally oriented started cultures for the production of wines with a stronger local identity.

Cotton's northward expansion in the Plains comes with a learning curve

Cotton acres continue to increase and are being grown in northerly regions of the Plains that only a decade ago were considered unsuitable. With that management comes a learning curve. Because cotton production is still relatively new in parts of the Texas High Plains, Oklahoma, and Kansas, extension specialists say successful production practices in other regions may not necessarily be applicable. Earn 0.5 CEUs in Crop Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/686.

Dynamic Optimization of Nitrogen in Plateau Cotton Yield Functions with Nitrogen Carryover Considerations

AbstractThis study utilizes a dynamic programming decision model, considering an intertemporal nitrogen carryover function, combined with both linear stochastic and deterministic plateau response functions to evaluate optimal nitrogen fertilizer decision rules and net present values (NPVs) in Texas High Plains cotton production. Nitrogen recommendations and NPVs are influenced by response function choice and nitrogen-to-cotton price ratios. Results indicate the stochastic plateau function better describes the data; the optimum nitrogen recommendation is to apply approximately 40 lb. of nitrogen for each bale of cotton production when considering nitrogen carryover information.

Efficacy of 2,4-D Choline as Influenced by Weed Size in the Texas High Plains

Aim: Postemergence timing trials based on weed size were conducted near Lubbock, TX to assess the effectiveness of 2,4-D choline + glyphosate on control of Palmer amaranth (Amaranthus palmeri S. Wats.), Russian-thistle (Salsola tragus L.), and kochia (Kochia scoparia L.) at three growth stages (3 to 5 cm, 10 to 15 cm, and 20 to 30 cm).&#x0D; Study Design: All trials were arranged in a randomized complete block design with four replications.&#x0D; Place and Duration of Study: Field experiments were conducted in 2013, 2014, and 2015 in Lubbock, TX at the Texas A&amp;M AgriLife Research and Extension Center near Lubbock, TX.&#x0D; Methodology: Herbicide treatments consisted of a single postemergence application of 2,4-D choline + glyphosate at two rates, 2,4-D choline + glyphosate at two rates + glufosinate, 2,4-D choline + glyphosate + S-metolachlor, 2,4-D choline + glyphosate + acetochlor, 2,4-D choline + glufosinate, glyphosate, or glufosinate.&#x0D; Results: The greatest level of weed control for all three weed species was achieved at the 3 to 5 cm timing; however, weed size was most critical for Palmer amaranth and Russian-thistle compared to kochia. Averaged over all three years, Palmer amaranth control decreased from 93 to 74% when evaluated 21 days after treatment following applications that included 2,4-D choline when applied to plants 3 to 5 and 10 to 30 cm, respectively. For Russian-thistle, control decreased from 98 to 78% when evaluated 21 days after treatment following treatments that included 2,4-D choline when applied to plants 3 to 5 and 10 to 30 cm, respectively. For kochia, control decreased from 98 to 84% when evaluated 21 days after treatment following treatments that included 2,4-D choline when applied to plant 3 to 5 and 10 to 30 cm, respectively.

Yield determination of maize hybrids under limited irrigation

ABSTRACTHybrid adoption, irrigation, and planting density are important factors for maize (Zea mays L.) production in semiarid regions. For this study, a 2-yr field experiment was conducted in the Texas High Plains to investigate maize yield determination, seasonal evapotranspiration (ETc), and water-use efficiency (WUE) under limited irrigation. Two hybrids (N74R, a conventional hybrid, and N75H, a drought-tolerant (DT) hybrid) were planted at three water regimes (I100, I75, and I50, referring to 100%, 75%, and 50% of the evapotranspiration requirement) and three planting densities (PD 6, PD 8, and PD 10, referring to 6, 8, and 10 seeds m−2). At I50, drought stress reduced grain yield by 4.78 t/ha for the conventional hybrid but only 4.22 t/ha for the DT hybrid, when compared to I100. Although ETc decreased at I75 and I50, the highest WUE was found at I75. The DT hybrid did not yield more than the conventional hybrid but had greater yield stability at lower water regimes and extracted less soil water. Drought decreased biomass, harvest index, and kernel weight but did not affect kernel number. Higher planting densities increased biomass and kernel number but decreased kernel weight. Kernel number and kernel weight of the conventional hybrid were more sensitive to planting density than the DT hybrid. These data demonstrated that limited irrigation at I75 is an effective way to save water and maintain the maize yield in semiarid areas, and that DT hybrid shows a greater yield stability to plant density under water stress.

Assessing Economic Changes Due to an Expanding Dairy Industry in the Texas High Plains

AbstractThe dairy industry in the Texas High Plains has experienced rapid expansion in the past two decades. This study assesses the impact of the increased presence of dairies on overall water use, crop composition, and the local economy. The increase in water use related to the dairy industry from 2000 to 2015 was primarily due to an increase in demand for drinking by the cows (direct water) as well as an increased demand for silage (indirect water). However, a comparative analysis (dairy presence vs. no dairy presence) from a single year indicates minimal impacts on total water use due to dairies. During the same time period, the number, size, and employment of related local business establishments have increased economic activity in rural areas. Editor's note: This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.

Essential oil composition of ‘WW-B.Dahl’ old world bluestem (Bothriochloa bladhii) grown in the Texas High Plains

Bothriochloa spp. include aromatic grasses that produce essential oils. Some of these grasses are reported to repel economically important insects. Leaves, stems, and seedheads of ‘WW-B.Dahl’ old world bluestem [Bothriochloa bladhii (Retz) S.T. Blake] were sampled during 3 years. Quantitative analysis by GC and GC–MS methods revealed a total of 172 compounds from methylation method, and 105 compounds from steam distillation method. Acorenone-B [spiro[4.5]dec-6-en-8-one, 1,7-dimethyl-4-(1-methylethyl)-] was in greatest concentration in both methods; however, this compound was detected on only one date (12 August) out of three collection dates extracted by steam distillation. Twenty-two compounds were detected by simple solvent extraction, in which acorenone-B was in greatest concentration in seedheads and least in stems. Diethylhexyl adipate was in highest concentration in stems and least in seedheads among the oils extracted by simple solvent. Camphene and limonene were present in the samples that contained seedheads. Naphthalene, a known insect deterrent, was detected in oils extracted from all methods and in all plant parts. Old world bluestem grass contained measurable amounts of essential oils that may be associated with previously observed repellency of red imported fire ants (Solenopsis invicta Buren).

Rainwater use by cotton under subsurface drip and center pivot irrigation

To increase the efficiency by which agronomic crops use water from both irrigation and rain during the growing season requires quantifying the proportion of rainfall used by the crop for a rain event. The rainfall pattern in the Texas High Plains (THP) is characterized by isolated thunderstorms of high rates and of short duration, where <1% of the storms produce rain events>50 mm and 80% of total rain events are < than 13 mm. The primary source of irrigation-water in the THP is pumped from the Ogallala Aquifer (OA), which has a different isotopic (δ18O) signature compared to rainfall-captured water. Given this difference, it is feasible to quantify changes in the δ18O signature of the plant water as the plant uptakes the rain- and irrigation-water stored in the soil. To this end, cotton (Gossypium hirsutum L.) was grown and irrigated with subsurface drip and center pivot and under dryland conditions. The irrigation-water was pumped from the OA and rainfall was collected in a rain gauge with mineral oil to prevent evaporation. Additionally, plant and soil samples were collected before and after each rain event. Thereafter, water was extracted from the collected soil and plant samples using cryogenic vacuum distillation and analyzed for δ18O (‰) using a Liquid-Water Isotope Analyzer. The difference in isotope concentrations in the extracts showed a change δ18O (‰) of the cotton petiole water toward that of the rainwater signature of 17% for sub-surface drip, 32% for dryland, and 63% for center pivot irrigation. These results imply that the application of irrigation-water with a sprinkler center pivot results in increased rainwater use in cotton compared to that of sub-surface drip.

Simulating the Impacts of Irrigation Levels on Soybean Production in Texas High Plains to Manage Diminishing Groundwater Levels

AbstractThere is an increasing need to strategize and plan irrigation systems under varied climatic conditions to support efficient irrigation practices while maintaining and improving the sustainability of groundwater systems. This study was undertaken to simulate the growth and production of soybean [Glycine max (L.)] under different irrigation scenarios. The objectives of this study were to calibrate and validate the CROPGRO‐Soybean model under Texas High Plains’ (THP) climatic conditions and to apply the calibrated model to simulate the impacts of different irrigation levels and triggers on soybean production. The methodology involved combining short‐term experimental data with long‐term historical weather data (1951–2012), and use of mechanistic crop growth simulation algorithms to determine optimum irrigation management strategies. Irrigation was scheduled based on five different plant extractable water levels (irrigation threshold [ITHR]) set at 20%, 35%, 50%, 65%, and 80%. The calibrated model was able to satisfactorily reproduce measured leaf area index, biomass, and evapotranspiration for soybean, indicating it can be used for investigating different strategies for irrigating soybean in the THP. Calculations of crop water productivity for biomass and yield along with irrigation water use efficiency indicated soybean can be irrigated at ITHR set at 50% or 65% with minimal yield loss as compared to 80% ITHR, thus conserving water and contributing toward lower groundwater withdrawals. Editor's note: This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.

Simulation of efficient irrigation management strategies for grain sorghum production over different climate variability classes

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.

Carbon dioxide mitigation potential of conservation agriculture in a semi-arid agricultural region

The Texas High Plains (THP) region is one of the largest upland cotton (Gossypium hirsutum L.) producing regions in the world. Cotton is a versatile crop with uses for both food and fiber products. Conservation management practices such as no-tillage and cover crops have been used to reduce wind erosion on the THP but are also associated with mitigating and reducing greenhouse gas (GHG) emissions from soil. Although row-crop agriculture has been linked to GHG emissions across the world, cotton production in the THP ecoregion has not been thoroughly evaluated for its contribution to GHG production. This research quantified the soil flux of carbon dioxide (CO2-C) from continuous cotton production systems on the THP after implementing three tillage practices: (1) no-till with a winter wheat cover crop (NTW); (2) no-till winter fallow (NT); and (3) conventional tillage winter fallow (CT). In addition, the timing of nitrogen fertilizer application was evaluated within each tillage system. Five N treatments were implemented: (1) an unfertilized control; (2) 100% pre-plant (PP); (3) 100% side-dressed (SD); (4) 40% PP 60% SD; and (5) 100% PP with a nitrogen stabilizer product (STB). Tillage practice affected CO2-C flux rates in spring 2016 and 2017 with the NTW system having greater CO2-C flux than the NT and CT systems. In summer 2017, the NTW system had a greater flux of CO2-C than the NT or CT systems. In fall/winter 2016, the NTW and CT systems had a greater CO2-C flux than the NT system. Cumulative emissions of CO2-C were affected by N treatment in 2016, with later season applications of N fertilizer increasing emissions compared to the STB treatment and the control. In 2017, cumulative emissions of CO2-C were greater in the NTW system than in the NT and CT system. However, a greater amount of CO2-C was assimilated by the wheat cover crop from the atmosphere than was lost from the soil which reduced net C losses from the system. With continued use of no-tillage and a cover crop, lower net soil CO2-C losses should result in a greater rate of soil organic C gain, positively impacting the sustainability of cotton production in the THP.