1a. Objectives (from AD-416):
Obj 1: Quantify the environmental factors that affect the degree of crop drought stress. Sub-obj 1A Assess the effects of rising atmospheric CO2 concentration on crop coefficients used in deficit irrigation scheduling systems. Sub-obj 1B Relate seasonal plant stress and water use efficiency responses of crop plants to irrigation scheduling techniques using stable carbon isotope discrimination. Sub-obj 1C Identify active root areas under sub-surface irrigation to determine optimal cultivar for dryland management. Obj 2: Develop crop management strategies that enhance water use efficiency. Sub-obj 2A Quantify the effects of wind speed, tillage management, and irradiance on surface water evaporation. Sub-obj 2B Identify changes in microbial and chemical characteristics that may impact water availability and productivity in dryland production. Obj 3 Develop a framework of methods and models for quantifying and studying the risks associated with water from rainfall for dryland agriculture over the Southern High Plains and other dryland agricultural regions. Sub-obj 3A Evaluate the ability of current weather generator configurations to reproduce the distributional characteristics of Southern High Plains summer weather variability. Sub-obj 3B Run calibrated and validated cotton and sorghum crop models with both observed and stochastically generated weather inputs to generate simulated dryland yield outcomes. Sub-obj 3C Convert modeled yield outcomes generated with simulated weather data into net profit outcomes to form corresponding profit distributions for dryland cotton and sorghum production. Obj 4: Evaluate management practices that prevent soil degradation by soil erosion in semiarid cropping and rangeland systems. Sub-obj 4A Investigate soil redistribution & dust emissions from agro-ecosystems including rangelands & native plant communities under the stressors resulting from climate change. Sub-obj 4B Evaluate management systems in terms of multi-decadal erosion rates estimated from radioisotope inventories. Obj 5: Evaluate management practices to increase soil water availability and contribute to higher water and nutrient use efficiencies. Sub-obj 5A Partitioning of evapotranspiration to water evaporation from soil & crop surfaces for dryland & irrigated cropping systems across different N fertilizer management strategies. Sub-obj 5B Investigate changes in groundwater quantity & quality that may affect cropland production in semiarid & arid regions. Obj 6: Develop management practices that contribute to maintaining microbial diversity and functions needed to improve soil health, ensure ecosystem sustainability, and maintain crop productivity under a changing climate. Sub-obj 6A Compare the effects of different management practices in semiarid regions on soil health indicators including the microbial community size, diversity & functions. Sub-obj 6B Characterize the effects of climatic events on soil health & the effects of future climate change (CO2, temperature and rainfall) on agro-ecosystems by measuring root biomass, soil microbial diversity & soil organic matter pools.
1b. Approach (from AD-416):
Sustainable agriculture, with emphasis on conservation of natural resources, is a challenge in the semiarid climate of the Southern High Plains (SHP). Of concern is developing cropping systems that cope with climate change, depletion of aquifers used for irrigation, and growing seasons characterized by frequent droughts and erratic rainfall. Climate change is expected to impose general global challenges but, clearly, solutions to these problems will be site specific. Within a framework to quantify and study the risks associated with dryland agriculture, we need sustainable agricultural systems that optimize productivity, conserve water, control soil erosion and improve soil health for agricultural production in semiarid regions and in a changing climate. We will continue long-term research that identifies management practices that impact water availability in dryland farming vs. lands in the Conservation Reserve Program. Our goal is to provide agricultural producers with tools to manage limited water resources in the semi-arid environment of the SHP. New technologies for exposing crops in the field to elevated levels of atmospheric CO2 concentration will be used to monitor hourly and daily whole canopy water use efficiency by simultaneously measuring the ratio of net CO2 assimilation to evapotranspiration. Optimum irrigation scheduling techniques will be determined from stable carbon isotope discrimination while optimal cultivars for dryland agriculture will be selected by identifying and comparing active rooting areas. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted.
3. Progress Report:
For a second year, ARS scientists working in Lubbock, Texas, made significant progress to develop management strategies for regions of lower rainfall and of diminishing irrigation-water to improve water conservation and develop soil biological indices to evaluate soil health. Studies were completed to quantify environmental factors that affect the degree of crop drought stress. Two growing seasons studying the effects of elevated CO2 concentration interactions with periodic drought stress on peanut were completed and a manuscript is under preparation. Different solvent-extraction methods for a stable C isotope technique to extract oil from cottonseeds was tested and were equally efficient, a result that will be reported in a short communication. An extraction method for a small numbers of seeds using microscale Soxhlet extractors was developed and is being characterized. A new instrument to quantify root-water uptake of crop cultivars grown in dryland conditions was evaluated using a 0.3 m diameter polyvinyl chloride pots, with holes in the bottom to drain water and vertical strips of bolts, 5 cm apart to measure conductance. Given the rapid movement of water through the fritted clay, standard soil sampling techniques were not useful and thus a method was developed, whereby filter papers could be inserted, extracted and replaced with a new filter paper and thereby multiple samples of the soil water could be sealed in glass tubes and frozen for later analysis. This is information needed to evaluate what cultivars are more efficient in using rainwater under dryland conditions. Capital expenditures were made to modify an available structure for experiments requiring climate control. We continue to install heaters and partitions needed for the experiment, which is scheduled for winter months due to the requirement of high ambient vapor pressure deficits. This year, ample spring rain broke a multi-year drought and provided sufficient soil water to extract soil monoliths needed for the experiment. Extraction equipment was readied for monolith collection and the monolith shells modified to accommodate the required instrumentation. We continued our soil sampling measuring changes in soil microbial community that when coupled with stable isotopes of the rainwater infiltrating the soil could lead to understand mechanisms to increase soil water storage. The crop growth (CROPGRO) simulation applied to sorghum modeling and statistical evaluation of measured and simulated crop yields was conducted. Crop yield database containing modeled cotton (lint) and sorghum (grain) yields was completed. After calibration, based on four years of sorghum field trials, the Decision Support System for Agrotechnology Transfer (DSSAT) CERES-Sorghum model was used to simulate rainfed sorghum production at numerous Southern High Plains production sites during 2005–2016. These simulations were repeated under 32 management options to evaluate the effects of planting date, plant density, and nitrogen (N) application on crop yield. The resulting sorghum yields completed the yield database required for a 36-month study comparing dryland cotton and sorghum profitability. An associated manuscript has been submitted to Frontiers in Sustainable Food Systems. During FY 2019 data from 11 years of May- and June-planted irrigated variety trials conducted at Texas A&M AgriLife Research Center in Lubbock was used to study the effects of planting date on cotton lint yield and fiber quality. These results were reported on a manuscript submitted to Agriculture that was accepted for publication. During FY 2019 collaborative research efforts begun focusing on the effects of soil organic matter on soil water capacity and dryland cotton lint yields, ambient temperature and humidity effects on cattle mortality in Southern High Plains feedlots, and on an R-based analysis of cotton genetic sequences. Studies evaluating management practices that prevent soil erosion in semiarid cropping and rangeland systems were advanced. Dust emissivity data collected during a field campaign testing the soil surfaces of cropped fields and native plant communities were analyzed. Also, soil samples collected at the time of dust emissivity were analyzed for particle diameter distribution, and a manuscript with these results is being written. Horizontal mass flux data from climax black grama grasslands and nearby shrublands on the Sevilleta National Wildlife Refuge in New Mexico were collected and the data analyzed. The shrubland sampler mast array was removed and reinstalled to the pattern used by the National Wind Erosion Research Network (NWERN). The three plots in the grassland were removed in preparation for a controlled burn in April that was cancelled and rescheduled for the late summer to early fall of 2019. The grassland samplers will be reinstalled post-burn in a NWERN pattern. Equipment was constructed that will allow periodic removal and reinstallation of sampler masts used in the NWERN sites in Big Spring and other remote plots. Finally, work has begun to develop an instrument that measures the strength of soil crusts that resist shear forces present during wind events. Through a non-funded cooperative agreement with the Department of Chemistry at Northern Arizona University, more than 300 soil extracts were prepared for 239+240Pu quantification by Magnetic Sector Inductively Coupled Plasma / Mass Spectrometry (ICP/MS). This data will identify the boundaries of the region in which fallout from the Trinity Site detonation in July of 1945 would render the radio-isotopic technique models as they currently exist invalid. Other samples including sample splits previously counted for 137Cs inventory from Bushland, Texas and organic soils from Michigan and Florida are scheduled for Magnetic Sector ICP/MS quantification this summer. Soil samples were collected at research stations in Big Spring, Texas, Akron, Colorado, and Moccasin, Montana to investigate several soil properties and their change since 1947, when archived samples were collected. The 239+240Pu analysis will quantify changes attributable to soil redistribution since the sampling date. An existing rainfall simulator (RFS) to be transported with a commercial cargo trailer was modified by cutting out the floor under the RFS and by removing the axles and replacing them with bilateral wheel hubs. Additionally, a remote control trailer mover rated for 1500 kg was purchased. The final result was a portable and mobile RFS that can be moved to fields using a hitch and can be operated by 50 % less people, from 4 to 2. The trailer and RFS were built and a manuscript is in preparation. An engineering computer-aided design (CAD) program will provide a detailed construction and of parts needed to build the RFS. An ARS scientist will use the RFS to collect data on rainfall rates and amount on major soil types and subsequent runoff and infiltration. These results will be merged with the energy and water balance (ENWATBAL) model to evaluate the components of the water balance. To model management practices for water use efficiency, several inputs must be measured including rainwater infiltration, ponding and runoff. The mobile RFS was finished and we are currently testing and calibrating the system for deployment to fields across the Texas High Plains and New Mexico. Field data obtained with the RFS will be combined with laboratory measurement to measure saturated hydraulic conductivity, bulk density, and soil water retention curves on undisturbed soil samples. The plan is to create a library of measured soil hydraulic properties for the Pullman, Amarillo and Brownfield soil series. These data are required for simulation models, e.g., ENWATBAL and DSSAT-CERES that we use in our research. Studies to investigate changes in groundwater quantity and quality that may affect cropland production in arid regions are on schedule. To date, a total of 21 well sites located on the Southern High Plains were sampled over the last couple of years. Samples were collected, when weather permitted, from all sites every two weeks. Depth to water measurements were obtained using a commercial water level meter whenever the wells were not operating. When the wells were in operation, water samples were obtained from faucets on the well. If a well was off then pencil bailers were lowered into the well to obtain water samples, which were tested for pH and electrical conductance. In FY 2019, we expanded our study to include other sources of water such as rainfall, springs, and surface water sources such as streams and ponds. We continued our progress in the evaluation of different management, including drought tolerant crops/forages, that sustain microbial diversity and functions to improve soil health, ensure ecosystem productivity, and reduce irrigation-water from the Ogallala aquifer. The area office post-doc awarded to this project is evaluating data for several soil health indicators and functions collected over 5 years that experienced record high and low rainfall. Discussions from a joint meeting of producers with Texas Tech and ARS scientists at Lubbock indicated interest in applying manure in combination with conservation tillage practices for dryland cotton production. Their interest is to evaluate how this approach impacts soil health. The response of soil microbial community and their functions including soil productivity and nutrient cycling due to increases in CO2 levels using portable growth chambers continues to be evaluated.
1. Assay of multiple enzyme activities (EAs) in a soil sample as a new soil biology-health index. Current protocols used to measure EAs are time-consuming and each assay requires a soil sample. This limits routine measurements of EAs by commercial laboratories and their use for large-scale soil health assessments due to the associated high cost. To alleviate this problem, ARS scientists in Lubbock, Texas, and Morris, Minnesota, developed an assay to simultaneously measure multiple EAs on the same soil sample. This simplified protocol is adaptable for a wide range of applications to evaluate soil health for a variety of cropping systems options and soil types. This approach reduces time and minimizes chemical waste generated from assaying individual EAs on several soil samples. Our expectation is that a single EA value derived from this combined enzyme assay will contribute to the adoption of EAs for producer-oriented soil health assessments in commercial laboratories. Further, it will facilitate meta-analyses and our understanding of trends and thresholds related to biogeochemical cycling potential across regions at large spatial scales.
2. Alternative forages for livestock production increased soil health and drought tolerance. Scientists from Texas Tech University and USDA-ARS in Lubbock, Texas, previously found improvements in soil health indicators (e.g., microbial community, organic matter, and enzyme activities of nutrient cycling) with the introduction of Old World bluestem (OWB) grass for livestock-cotton production in the Southern High Plains. The system also reduced tillage and irrigation (36 %) compared to monoculture cotton. Soil health was further compared under other forages more drought tolerant than OWB, which included OWB-alfalfa, alfalfa, and native mixed-grass pastures. The OWB-alfalfa system offered suppression of pestiferous ants, desirable cattle productivity when grazed, eliminated fertilizer requirements due to N fixation and enhanced soil health indicators, i.e., greatest fungal and bacterial populations and their enzyme activities. The forage system with alfalfa can provide a desirable forage for producers in a semi-arid region with a declining irrigation-water supply.
3. Seed size and uniformity affect crop value and harvest efficiency. Uniform seed size leads to easier harvesting, cleaning, and processing. It has long been thought that increasing seed numbers in plants would increase crop yield. Molecular biologists and breeders seldom look closely at seed size and usually characterize seeds with qualitative terms such as small or large, or simply weigh a hundred seeds and measure the average weight. A scientist from ARS in Lubbock, Texas, developed a method to quantitatively measure the volume differences of thousands of seeds resulting from differences in development. We showed that this approach is capable of clearly revealing differences in grain development in two types of sorghum. This approach can be used to select for uniformity of seed size in germplasm improvement and to examine efficiency of seed cleaning operations.
4. Sustainable agriculture depends upon maintaining production while reducing or even eliminating dependence on non-renewable resources. Although, molecular biologists have developed plants with traits such as those associated with resistance to insect damage or herbicide resistance, no single gene has been identified that is associated with drought tolerance. Maintaining yield under drought stress is important because precipitation is seldom optimal in the southwestern U.S. and irrigation water resources are being depleted. Scientists from ARS, Lubbock, Texas, Texas Tech University, Tohoku University (Japan), and the Volcani Center (Israel) inserted a gene from tomatoes into cotton plants. Cotton plants altered with the tomato gene continued to use sunlight to function under conditions where the normal plants had stopped functioning. Over the course of a preliminary small-scale pilot study, cotton yield was increased by 80%. These results suggested that this approach could result in traits to sustain or even improve cotton yield under mild droughty conditions typical of the southwestern U.S.
5. Planting date effects on cotton lint yield and fiber quality in the U.S. Southern High Plains. The U.S. Southern High Plains (SHP) is a leading U.S. cotton production region, but its high altitude and short growing season can reduce yields and fiber quality. To study the effects of SHP cotton planting dates in a field setting, ARS researchers at Lubbock, Texas, evaluated planting date effects on lint yield and fiber quality in 11 years of May- and June- planted irrigated variety trials. May planting increased lint yields in 8 of 10 years that comparisons could be made, and improved fiber fineness and maturity in 7 of 11 years. These effects, and analysis of SHP temperature data, show that late-April to early-May planting dates may increase lint yield and improve fiber quality. Although this practice may be best for the cool SHP summer growing environment it may also require high-vigor seed and pre-planting irrigation.
6. Irrigation system better suited to capture more rainfall in the Texas High Plains. In the Texas High Plains, the majority of the soils in cultivation are in three soil series: Olton, Pullman, and Amarillo, and soils tend to be sandier in the southern region and finer-textured soils more common in the northern region. The distribution of dryland and irrigated crop production is about 60% dryland and 40% irrigated. However, the amount of dryland production continues to increase every year due to the decline of the aquifer’s water table. Regardless of the cropping system in place the capture and use of rainfall is imperative. Further, what irrigation system (sprinkler vs. buried drip) makes better use of rainfall? Our hypothesis was that for the rainfall frequency and distribution of this region, crops would use more rain when irrigated with a sprinkler system compared to a buried drip. ARS scientists in Lubbock, Texas, tested the hypothesis using stable isotopes of water, given that rain- and irrigation-water have different isotopic signatures, and our hypothesis was shown to be correct. This result is explained by how rainfall frequency and amount affects the root distribution in the soil profile. For example, a sprinkler system promotes surface roots; whereas, a buried drip system tends to concentrate roots around the buried emitter. Thus a crop irrigated with a sprinkler system will likely have a root distribution adept to use water from rain events of 10-15 mm and a crop irrigated with a buried drip will not have the roots to use this water and as a result a larger proportion would be lost to evaporation.
7. Measurement of crop transpiration (T) under field conditions. In first analysis, the primary objective of irrigation is to replace the quantity of water transpired (T) by the crop. This is a simple premise but it is complicated by the fact that the measurement of crop T is difficult to obtain and as result measurements are replaced by calculations of evapotranspiration (ET), which requires estimates of soil water evaporation (E). For this purpose engineers have introduced a myriad of methods to calculate ET and of coefficients to empirically estimate T and E. Conversely, a null method to measure T was introduced by a Japanese scientist in the early 1980’s known as the stem heat balance method (SHBM). Scientists from ARS in Lubbock, Texas, evaluated a commercial version of the SHBM on cotton plants and we compared these measurements to values of cotton T measured with portable growth chambers on the same plants. Our results showed that the two values of cotton T measured with the SHBM and the chambers were statistically the same. The commercial sensor to measure cotton T provides a practical method that can be used to manage the irrigation of a crop.
8. Well sampling and salinity profile investigations. Scientists from ARS in Lubbock, Texas, samplings from groundwater at several locations across the Texas High Plains showed that while wells are active, the water quality can change; however, it is not always increasing in salinity. Salinity profile measurements have shown that, in most cases, groundwater is more saline towards the bottom of a well. As a result, when a well becomes active the more saline water is mixed from below into the upper portion of the profile and the entire water column becomes more uniform and generally more saline. With regard to the rainfall study, preliminary results suggest that there is a surprisingly weak statistical correlation between rainfall chemistry and atmospheric conditions, such as wind speed or direction. Further analysis of rainfall samples did, however, show a significant inverse relationship between salinity and the amount of rainfall collected in the rain gauge.
Acosta Martinez, V., Perez-Guzman, L., Johnson, J.M. 2019. Simultaneous determination of ß-glucosidase, ß-glucosaminidase, acid phosphomonoesterase, and arylsulfatase in a soil sample for a biogeochemical cycling index. Applied Soil Ecology. 142:72-80. https://doi.org/10.1016/j.apsoil.2019.05.001.
Bhandari, K., West, C.P., Acosta Martinez, V., Cotton, J.E., Cano, A. 2018. Soil health indicators as affected by diverse forage species and mixtures in semi-arid pastures. Applied Soil Ecology. 132:179-186.
Mauget, S.A., Ulloa, M., Dever, J. 2019. Planting date effects on cotton lint yield and fiber quality in the U.S. Southern High Plains. Agriculture. 9(4):82. https://doi.org/10.3390/agriculture9040082.
Lascano, R.J., Baker, J.T., Payton, P.R., Gitz, D.C., Mahan, J.R., Goebel, T. 2018. Measurement of cotton transpiration. Agricultural Sciences. https://doi.org/10.4236/as.2018.910091
Gitz, D.C., Baker, J.T., Payton, P.R., Xin, Z., Lascano, R.J. 2018. Analysis of grain size distribution through image analysis. American Journal of Plant Sciences. 9:2339-2346.
Stout, J.E. 2019. On the observed inverse relationship between rainfall amount and dissolved mineral content. Journal of Hydrometeorology. 20:1235-1240. https://doi.org/10.1175/JHM-D-18-0204.1.