Location: Soil and Water Management Research2022 Annual Report
1. Develop tools for evapotranspiration (ET) yield and crop water productivity determinations, and management in irrigated, dryland and mixed precipitation dependent/irrigated cropping systems. Sub-objective 1A: Improved determinations of ET. Sub-objective 1B: Development and Application of Crop Coefficients. Sub-objective 1C: Managing crop water productivity using MDI. Sub-objective 1D: Develop management practices to improve marginally irrigated and dryland cropping systems. Sub-objective 1.E: Develop dryland cropping practices that are resilient and improve performance. 2. Develop sensors, technologies, and models that facilitate site-specific irrigation management. Sub-objective 2A: Develop new plant sensors to facilitate site-specific irrigation. Sub-objective 2B. Develop and evaluate energy and SW balance models. 3. Develop water management decision support tools and databases to facilitate better water allocation and irrigation scheduling decisions under limited irrigation. Sub-objective 3A: Provide long-term high-quality weather, ET, management, and crop development data. Sub-objective 3B: Conduct Sensitivity Analyses on ET Related Models and Decision Support Systems. Sub-objective 3C: Develop and Evaluate Crop and Hydrologic Models for Water Management Decision Support Systems.
To meet the nutritional, fiber and energy needs of a growing world population, global agricultural productivity needs to increase. While American agriculture has been a key contributor to feeding the world, further increases in agricultural production from much of the Great Plains region may not be able to keep up with anticipated increases in demand because of an inability to meet the water needs of future crops. Mean annual precipitation provides 40% to 80% of crop water demand. The balance of crop water demand is usually supplied by irrigation from the Ogallala Aquifer (OA); unfortunately, groundwater depletion has occurred in much of the aquifer. Over 80% of the newly permitted wells on the Texas High Plains have pumping rates that are insufficient to irrigate a 50 ha-pivot of corn. Because of the severity of aquifer depletion, water management strategies such as shifting to less water-intensive crops, allocating water among sectors within a pivot, conversion to dryland, etc. are being evaluated for their economic feasibility and effectiveness in prolonging the life of irrigated agriculture on the Southern High Plains. This research project seeks knowledge and technologies to decrease the impact of aquifer depletion on crop production by better matching irrigation water supply to targeted yields that tend to be less than maximum. An additional factor challenging crop production on the Southern High Plains is that the severity of multi-year droughts has increased in the past 120 years, which can threaten both irrigated and dryland crop production. Thus, this project also seeks management practices that increase the resilience and sustainability of dryland crop production.
Research project 3090-13000-016-00D entitled “Dryland and Irrigated Crop Management Under Limited Water Availability and Drought” was started in January 2022 after successfully completing the peer review process. A headquarter funded postdoc was hired midway through fiscal year (FY) 2022. One of two of the vacant scientific support positions was filled in FY2022. The drought that started on the Texas High Plains (THP) during the summer of 2021 has persisted at least through July 2022. Since August 2021, monthly rainfall has been less than the long-term average. Most of the wheat that was planted in the fall of 2021 did very poorly. Only the wheat planted just before a timely fall rain shower yielded over 10 bushels per acre. Because of the on-going drought, no dryland sorghum or cotton was planted during the summer of 2022. Four to 5.5 inches of rain fell from July 28, 2022 to August 4, 2022. It is not known at this time if this rainy period signals a return to more normal rainfall or just a brief interruption to a prolonged drought. Despite challenges from the weather, researchers attained fully met or substantially met for all milestones for FY2022. Progress Towards Objective 1. Sensors of the unit’s eddy covariance (EC) systems have been inspected and either re-calibrated or replaced where needed. Data from EC systems have been cross checked and are ready for deployment next year. Data from the large weighing lysimeters (LWL) from prior years continues to be complied and checked for quality. In FY2022 three data bases have been published at National Agricultural Library's’s Ag Data Commons: 1) weather; 2) evapotranspiration (ET) from corn; and 3) ET from alfalfa. After several years of cotton, corn is being grown on the LWL in FY2022 and the data will be used for further refinement of the two-source energy balance model (TWEB). The resulting data will compare crop coefficients for corn grown under mid-elevation sprinkler irrigation and subsurface drip irrigation (SDI). Mobile drip irrigation (MDI) technology has been installed on one of the location’s three spans center pivot irrigation systems. Therefore, two tests were conducted in FY2022 comparing MDI to low elevation sprinkler irrigation using watermelons and cotton as subject of investigations. Data from these two experiments and another being conducted in cooperation with Texas A&M AgriLIfe on vegetables common to the THP will provide data on the applicability of the project’s irrigation scheduling software to these crops and irrigation systems. Long-term (since 1960) dryland cropping experiments continued in FY2022. The drought mentioned above prevented the planting of sorghum on those plots this year. An experiment in which corn and cotton are grown under the same linear move irrigation was started in FY2022. Results from this experiment will provide additional support for the water allocation framework that project scientists have been working on in cooperation with researchers in Spain. Progress Towards Objective 2. Development of a low-cost, low-power durable hardware for sensing plant water stress and soil moisture and means to gather and transmit such data continued in FY2022. Preliminary results from the summer 2022 indicate that the most recent versions are operating as expected. Discussions with potential research partners have not yielded a new agreement yet. Corn data from the LWL and cotton data the 6 span center pivot were collected and will be used to create new prescription maps for scheduling irrigation. These efforts will also lead to in season prescription maps to meet target crop yields. Progress towards Objective 3. As mentioned under Objective 1, three data bases from the LWL were published so far in FY2022. The corn data base has been used by others in a cooperative study to better understanding ET. Data have been organized for use in ET and crop growth modeling using Decision Support System for Agrotechnology Transfer (DSSAT). Experiments under controlled conditions have been conducted to better understand soil water flow between layers in the Pullman clay loam common to the THP. Research being conducted in association with Binational Agricultural Research and Development (BARD), Irrigation Innovation Consortium (Colorado State University), and specialty crops grants proceeded as planned in FY2022.
1. Infrared thermometers on center pivots or stationary in the field yielded comparable results that were different from those from a drone. Crop canopy temperatures as measured by infrared thermometers on center pivots or stationary were different from those from a drone. Freshwater available for irrigation is decreasing, especially in regions where water for irrigation is from aquifers with limited recharge like the Ogallala; therefore, there is a need to maximize the efficient use of irrigation water. There is growing interest in using feedback from plant sensors to monitor crop canopy temperature to aid irrigation scheduling, primarily via the use of infrared thermometers (IRTs). However, sensors located on a center pivot are not widely practiced and there is some skepticism about the practicality of ground-based platforms relative to satellite or aerial platforms. In this study, researchers at ARS Bushland, Texas, and the University of Nebraska compared measurements of canopy temperature from IRTs mounted on the sprinkler lateral with measurements of IRTs that were stationary in the field, and with measurements from a thermal camera mounted on an unmanned aerial system (UAS). Results showed that canopy temperature measurements from the IRTs mounted on the sprinkler lateral were similar to those from stationary IRTs in the field. Canopy temperature measurements from the UAS disagreed with those from the IRTs by approximately 7 F. These results should instill confidence in researchers and others to utilize a moving sprinkler system as a platform for IRTs for the purpose of monitoring crop canopy temperature and bring into question the use of IRTs mounted on drones.
2. Corn growing on the Texas High Plains gets the vast majority of its water from the top 2.5 feet of soil. Producers often experience sizable yield losses in corn because irrigation cannot meet demand. This has become a common occurrence in the semiarid Texas High Plains where irrigation supply from the Ogallala Aquifer is in decline. Drought tolerant corn hybrids may reduce yield losses during periods of water stress by using soil water so that it is more available during sensitive growth periods. However, little is known from where in the soil profile do these drought tolerant corn hybrids take up their water. Therefore, scientists from ARS (Bushland, Texas) and Texas A&M AgriLife studied the effects of irrigation level and planting rate on soil water use by three maize hybrids, two of which were considered drought tolerant. Only 4% of the seasonal water use of the crop was extracted below a soil depth of 2.6 feet. Water use during the growing season did not differ among hybrids. Two conclusions can be derived from these results: 1) irrigation on the Texas High Plains needs to be managed to prevent significant accumulation of soil moisture below 2.6 feet; 2) development of corn hybrids that extract water from deeper in the soil profile may promote drought tolerance or avoidance.
3. New equations for predicting soil water holding capacity from soil organic content. There are growing concerns that as climate changes, the frequency of drought in many areas of the world may increase. The impact of drought can be decreased by increasing the water holding capacity of soils. Some studies suggest that water holding capacity (WHC) can be increased substantially by increasing soil organic carbon (SOC), but more data are needed to support this conclusion. ARS scientists from multiple locations and scientists from the Soil Health Institute's North America Project to Evaluate Soil Health Measurements participated in a project to relate changes in SOC to the measured soil water content. New functions improved WHC predictions over previous functions and showed that WHC increased as SOC increased, averaging 3% increase in WHC for every 1% increase in SOC across all soil texture classes. These new functions may help incentivize adoption of management practices that increase SOC and build drought resilience.
4. Use of a water allocation framework boosts crop water productivity and net returns. Reduced water availability for agriculture and increased energy costs make it necessary to improve crop water productivity. Under water-scarce conditions, crop water requirements often cannot be met throughout the growing season, which can occur frequently in semi-arid regions like the Texas High Plains and interior of Spain. Scientists from ARS (Bushland, Texas), Texas A&M AgriLife Research, and University of Castilla La Mancha (Spain) have developed a strategy to allocate a limited volume irrigation water to one or more crops to maximize crop water productivity, not necessarily crop yields. This year, these researchers reported on studies to maximum crop productivity for garlic production in Spain and for corn and cotton production on the Texas High Plains. Crop water productivity was greatest when the volume of water applied was approximately 70% of full irrigation. Concentrating irrigation water tended to support greater crop water productivity and thus higher returns. These results demonstrate the benefits of this framework by which water resources can be allocated to different crops to maximize returns from applied irrigation water, and thus, are of interest to stakeholders in other areas facing water scarcity issues, including the Texas High Plains.
5. Zebra chip infected potatoes use irrigation water poorly. Zebra chip (ZC) virus is a relatively new disease that has a devastating impact on potato production in the western United States. Reduction in tuber yield and crop water productivity have gone unreported and it is unknown if irrigation level influences disease severity. In a two-year study, ARS (Bushland, Texas) and Texas A&M AgriLife scientists investigated the effects of three irrigation levels on ZC diseased plants and non-diseased potato plants by comparing tuber yield, seasonal crop water use, crop water use efficiency (WUE), and irrigation water use efficiency. It was determined that ZC disease significantly reduced tuber yield and WUE by 20-55% depending on the year. Irrigation level did not lessen disease severity. This information indicates that once areas of ZC diseased potatoes are detected within in a field, irrigations should be withheld over these areas to prevent water wastage.
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