Location: Soil and Water Management Research2017 Annual Report
Objective 1: Develop improved methods and sensor systems for determining crop water use and stress, and integrate these into systems for water management. Sub-objective 1.1: Improve understanding of soil water status and sensing. Sub-objective 1.2: Improve determinations of evapotranspiration (ET). Sub-objective 1.3: Improve water management decisions at multiple scales by incorporating a better understanding of ET into hydrological models. Objective 2: Develop irrigation and sensor technologies, and best management practices for different irrigation application systems and technologies. Sub-objective 2.1: Compare crop water use efficiency (WUE) and partitioning of water use between evaporation (E) and transpiration (T) between subsurface drip (SDI) and sprinkler irrigation systems. Sub-objective 2.2: Develop sensors and algorithms to improve decision support for an irrigation scheduling supervisory control and data acquisition (ISSCADA) system to spatially optimize crop yields and WUE. Sub-objective 2.3: Develop irrigation application strategies that vary water application temporally for improved cotton lint yields. Objective 3: Develop and determine best management practices to maximize WUE, and long-term profitability using multi-year rotations of different crops and cropping practices, including both dryland and intermittent irrigation practices. Sub-objective 3.1: Determine if long-term weather predictions can be used to optimize irrigation strategies for increased WUE and yield. Sub-objective 3.2. Determine the effects of different conservation tillage practices on precipitation capture and harvest in relation to crop rotation phase. Sub-objective 3.3: Evaluate crop yield response to varying levels of deficit irrigation and water stress under differing management (Genetics x Environment x Management, G x E x M).
The Ogallala Aquifer region of the U.S. is one of the primary crop production areas in the country, in part because it overlays one of the country’s largest fresh water aquifers. But water availability from the aquifer has decreased significantly since the beginning of wide-spread irrigation in the 1950s, with the greatest impact on the Southern and Central High Plains of western Kansas and Texas. Responding to this will require both more efficient water use by irrigation and increased productivity with lower risk from dryland farming. Cropping practices such as rotation with fallow period for soil water recharge and irrigation practices that avoid evaporation address many of the unique needs of the Central and Southern Great Plains. However the need remains for more efficient water use in these semi-arid regions. Therefore this project will research three areas. First, a better understanding of soil water movement and evaporation, and evapotranspiration. Second, sensors that monitor soil water and crop water stress will be developed to effectively and efficiently use the remaining groundwater for irrigated crop production. Finally, the project will develop best management practices for using water more efficiently under dryland and marginal irrigation regimes. These results will enable the region to remain a competitive area for crop production, sustain farm based communities, and maintain the strength of American agriculture in world markets. Research will be conducted in laboratory and field situations from scales of small plots to regions where crop related data is extracted from remotely sensed images. New plant and soil water stresses will be developed in the laboratory, and once refined, field tested. Data will be integrated into prescriptions for dynamic site specific irrigation scheduling that account for well capacities. These will be tested under field conditions. Understanding of methods to measure evapotranspiration, like eddy covariance, COSMOS, etc., will be enhanced by comparing values from large weighing lysimeters and accurate water balance derived from neutron probe measurements for the soil profile. Measurements from microlysimeters and soil heat flux plates will be used in the field to provide better separation of measures of evaporation and transpiration components of evapotranspiration. A better understanding of evapotranspiration will be used to guide the development of best management practices for crop production and those practices will be tested under field conditions. Data will be used to refine existing hydrologic models, including AcrSWAT, Aquacrop, etc. Data bases of crop water use will be developed and made available to other scientists. This research project also leads the Ogallala Aquifer Program, a research-education consortium addressing solutions arising from decreasing water availability from the Ogallala Aquifer in western Kansa and the Texas High Plains. The consortium includes the ARS NP211 projects at Bushland and Lubbock, Texas, Kansas State University, Texas A&M AgriLife Research and Extension Service, Texas Tech University and West Texas A&M University.
In FY2017, the former NP211, 3090-13000-014-00D, research project was replaced with NP211 project, 3090-13000-015-00D. This project continues a long standing record of soil and crop water management research. Significant hail storms struck the Bushland, Texas research location on July 2 and 3, 2017. Cotton and soybean crops were not salvageable. The corn crop had extensive defoliation but the growing point was close enough to the ground that continued crop growth occurred after the hail. However, maximum yields may be depressed. Despite damage from the hail storm only one of 11 milestones were not met. Thus, significant progress has been made regarding Objectives 1-3. In September 2016, the American Society of Agronomy and Crop Science Society of America published an update to their sorghum monograph called Sorghum: State of the Art and Future Perspectives, Agronomy Monograph 58. The monograph was edited by two scientists in the Ogallala Aquifer Program from Kansas State University. The topics include genetic improvements, development of new hybrids, biotechnology, and physiological modifications, water and nutrient management, rotations, pest control, final end uses, sorghum as a bioenergy crop, markets, and the future of sorghum are presented. Nine of the 16 chapters have participants from Ogallala Aquifer Program as authors. The information in these chapters are related to progress in Objectives 2 and 3.
1. Irrigation requirements for rotations defined for Texas High Plains. Groundwater resources on the Southern High Plains are finite and becoming increasingly scarce. Crop water use is the major use of rain and irrigation water. However, crop rotation strategies that minimize groundwater use will help to extend these resources. Thus, researchers from USDA-ARS Bushland, Texas and Texas A&M AgriLife Research used the Soil Water Assessment Tool (SWAT) model and long-term weather data to characterize irrigation requirements of several crop rotations used in the Texas High Plains. Results may serve as a decision tool for producers considering alternate crop rotation strategies by providing irrigation requirements for comparison to known irrigation capacities.
2. Forecast of an El Nino predicts higher wheat yields for the Texas High Plains. As water for irrigation from the Ogallala Aquifer declines, dryland farming will become a more prevalent land use practice. Adapting practices to long term climate forecasts may enable farmers to realize higher yields. Equatorial Pacific sea surface temperatures cause predictable El Nino and La Nina weather patterns in much of North America. However, crop management protocols that take into account a forecast for either El Nino or La Nina have not been developed. ARS scientists from Bushland and Lubbock, Texas compared effects on crop growth and yield in a dryland wheat-sorghum-fallow rotation over 58 years according to El Nino and La Nina periods. Wheat growing-season rain and grain yields were greater for El Nino phases years than La Nina phase years. These results are of interest to farmers and crop consultants as an aid to making strategic decisions regarding future crop practices.
3. Method to determine leaf canopy size from simple measurements. Leaf area index (LAI), plant leaf area per unit ground area, is a very important indicator of the productivity of the agricultural systems, but is difficult to measure directly. LAI can be estimated indirectly using other plant measurements, such as individual leaf length and width, but such data are also often impractical to obtain. Therefore, ARS scientists at Bushland, Texas developed a new method to estimate LAI for row crops. The method uses growing degree days, canopy height, and plant population, which are easily obtained and more widely available. The scientists tested the method using existing LAI measurements of corn, cotton, grain sorghum, and soybean and the method could estimate LAI with good accuracy. The method will make LAI estimates more practical and widely available compared with previous methods, and this will enhance the usefulness of large agricultural and ecological datasets.
4. Wireless plant leaf temperature measurements makes irrigation scheduling easier. The freshwater resources available for agriculture are diminishing due to reduced supplies and competition for other uses. Freshwater resources can be used more efficiently in agriculture by knowing when to irrigate crops. One method that can quickly tell farmers when to irrigate is measurement of plant leaf temperature. However, measuring plant leaf temperature in entire fields was not practical previously. Therefore, ARS scientists at Bushland, Texas developed a wireless sensor system that can measure plant leaf temperature over entire fields and the system was mounted to center pivot irrigation system. Results showed that crop water use calculated from plant leaf temperature using the sensor system could be a viable alternative to estimating crop water use by soil water measurements. Because over half of the irrigated area in the U.S. is now by center pivot, estimates of crop water use by sensors aboard center pivots will provide an unprecedented opportunity to conserve water.
5. Popular crop model overpredicts corn growth under limited water. Water scarcity due to drought and groundwater depletion has led to an increased number of modeling studies aimed at evaluating crop response to limited irrigation. The Decision Support System for Agrotechnology Transfer (DSSAT) is a widely used crop growth model. However, the ability of DSSAT to represent crop response and water balance under limited irrigation is not well studied. Therefore, ARS scientists from Bushland, Texas and Texas A&M AgriLife compared simulated and measured plant growth values for corn grown in the Texas Panhandle under full and limited irrigation. Results showed that DSSAT overestimated corn growth, yield, and crop water use (evapotranspiration) under limited irrigation. These results are of interest to agronomist, plant physiologists and crop modelers because they demonstrated the weakness of the current model to simulate corn growth under less than ideal growing conditions.
6. Soil water assessment tool does not mimic current irrigation practices. Water scarcity due to drought and groundwater depletion has led to an increased emphasis on irrigation strategies for extending limited water resources. Models are commonly used to assess the impacts of such strategies. The Soil and Water Assessment Tool (SWAT), a widely used hydrologic model, is increasingly being used to evaluate the impacts of irrigation strategies at both field and watershed scales. However, concerns about the ability of the auto-irrigate function in SWAT to simulate actual irrigation practices have tempered results. ARS scientists from Bushland, Texas along with scientists from Texas A&M AgriLife compared simulated irrigation, crop water use (ET), plant growth, and yield to measured values for crops grown in the Texas High Plains. Results showed that the auto-irrigate function was unable to represent irrigation practices of the region, prompting the need for revision of the auto-irrigation algorithm in SWAT. These results are of interest to SWAT users, other modeler and water policy makers using such information.
7. Effectiveness of water conservation policies affected by discount rates, and crop prices. Agriculture plays a vital role in the growth and development of the High Plains region of the United States. With the development and adoption of irrigation technology, this region was transformed into one of the most agriculturally productive regions in the world. The primary source of irrigation water in this region is the Ogallala Aquifer. Currently, water from the aquifer is being used at a much faster rate than natural recharge can occur, resulting in a high rate of depletion from this finite resource. However, depletion of scarce water resources will have a significant economic impact on the long-term sustainability of the region. Therefore, scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from West Texas A&M University and Kansas State University evaluated the impact alternative prices and discount rates have on groundwater policy recommendations. As indicated by results of this study, alternative prices, costs, and discount rates utilized in the study have an effect on policy effectiveness. These results are of interest to water policy makers and demonstrate the importance of economic assumptions in the outcome.
8. Future value of groundwater too low to prevent its current use. Irrigation water from the Ogallala Aquifer has had an influential role on the Texas High Plain in making it an agriculturally significant region. However, withdrawals for irrigation have greatly exceeded recharge, resulting in a decreasing water resource. Scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Texas Tech University have attempt to quantify the shadow price of an additional inch of groundwater resource left in situ for the Southern Ogallala Aquifer. We arrive at a marginal user cost for an additional acre-inch of water which is relatively low. Because this cost is so low, farmers are unlikely to conserve water based on economic considerations. These results are of interest to water policymakers and indicate that value of groundwater left in the aquifer is only slightly different from its value for present withdrawals.
9. Protein that helps confer salt tolerance identified. As water is removed from the Ogallala Aquifer there are concerns that the quality of the remaining water will be degraded. In general crops are not very tolerant of water with poor quality that is high salt content. Crops that are tolerant of high salt maybe needed for the Southern Ogallala Aquifer region. Unfortunately there are multiple avenues to breed crops for greater salt tolerance and few approaches have been attempted. Scientists have previously associated a specific plant protein with tolerance to salt. Therefore, scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Texas Tech University and Zhejiang Academy of Agricultural Sciences (China) investigated the role of root growth under salt stress. Loss of this protein through mutations decreased salt tolerance while over production improved salt tolerance. These data indicate that this specific protein affects salt tolerance. These results are of interest to plant physiologist, plant molecular biologists and plant breeders.
10. Switching to highly efficient irrigation systems requires increases in yields to recover cost. Crop yields have not decreased as water availability for irrigation from the Ogallala Aquifer has declined because of advancements in irrigation technology. However, producers can be reluctant to convert to a more efficient irrigation system when the initial investment costs are high. Therefore, scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from West Texas A&M University and Texas A&M AgriLife Research and Extension Service examined the economic feasibility of replacing low energy precision application (LEPA) center pivot sprinkler with subsurface drip irrigation (SDI). The increase in water efficiency from LEPA to SDI was estimated to be only 2%. Further analyses demonstrated that the return from investment from switching from LEPA to SDI was only possible with high value crops that had an increase in yield after the conversion. Corn was at the top of this list among typically grown row crops. These results are of interest to water policy makers, especially when making decisions regarding cost share for water conversing irrigation equipment.
11. Use of animal waste on crop land requires balancing applications with crop requirements. Application of cattle manure and swine effluent to cropland builds nutrient pools, affects soil quality, and increases crop productivity. However, application of animal waste in excess of crop nutrient requirements may lead to build up of soil nutrients that may have adverse environmental effects. Scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Kansas State University evaluated the rate of change in soil nutrient concentration and soil chemical properties in response cattle manure and swine effluent applications over a ten year period. A significant build up in soil nutrients of phosphorus and nitrate occurred when cattle and swine nutrient applications were supplied to meet or exceed the crop’s nitrogen requirement. These results indicate that farmers need to balance nutrient additions to crop requirements to avoid building up soil levels of these nutrients.
12. Improvements to beef slaughter procedure saves water. Water availability from the Ogallala Aquifer is declining. Beef slaughter is water intensive due to stringent food safety requirements. However, water use by slaughter facilities are high value use. Therefore, scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from West Texas A&M University conducted a study at a commercial beef processor to demonstrate water conservation by modifying the mechanical head wash. The modified mechanical washer cleaned beef heads as well as the standard washer but used 48% less water. These results are of interest to beef slaughter plants using water from the aquifer.
13. New design practices for efficient subsurface drip irrigation (SDI). As water availability from the Ogallala Aquifer for irrigation decreases, farmers are looking at installing the most water efficient irrigation systems. Yields per unit of applied water tends to be highest with SDI compared to other irrigation systems. However, SDI is a relatively new irrigation technology and design features are still evolving. Therefore, scientists in the ARS-Bushland, Texas Ogallala Aquifer Program from Kansas State University examined the applicability of fluid equations to the design of flushlines. The authors recommend that these modified equations be used with a standard fluid model to ensure reliability of improved flushline design for SDI systems.
14. Wheat does best with 4 inches of irrigation. Water availability from the Ogallala Aquifer for irrigation is decreasing, the occurrence of limited irrigation will increase on the Southern High Plains. Increasing irrigated wheat yields is important to the profitability of limited-irrigation cropping systems in the region. Scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Kansas State University examined the response of various wheat varieties to limited irrigation. Results indicated that, on average, an irrigation allocation of 4 inches increased wheat yield by 14% to 46% compared to rainfed production. Application of an additional 4 inches of irrigation did not improve wheat yield substantially. Applications at booting and heading resulted in the highest yields. This study demonstrates that limited irrigation targeted at sensitive growth stages could enhance wheat yields and improve water productivity of water-limited cropping systems, and are of interest to farmers.
15. Developing education programs for water management. Natural resource management and education, including those related to groundwater, must account for both the natural and human components of a very complex interactive system. However, examples of such interdisciplinary approaches are rare, and therefore guidelines for successful natural resource education programs are poorly defined. Scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Kansas State University, Auburn University and University of Minnesota developed a graduate seminar on water management. While the seminar was successful in terms of educating students on complexity of water management, several challenges remain when implementing such courses. These challenges include not only the organization and assessment of course deliverables, but also fitting such courses into the administrative structure of the university when represented disciplines are located in several colleges across campus. These results are of interest to other universities developing similar courses.
16. Late planted sorghum best for irrigation water efficiency. Many wells on the Southern High Plains drilled into the Ogallala Aquifer can no longer meet full crop water requirements due to declines in water levels. However, these sites are capable of contributing to the regional agricultural economy under appropriate management protocols. Therefore, scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Kansas State University conducted a study to determine optimum limited irrigation strategies for grain sorghum with varying planting dates. Highest grain yields were achieved with a late planting date in a wet season. Late planting was associated with lower irrigation requirements. Fluctuations in grain sorghum prices had a substantial impact on economic water productivity. Overall planting grain sorghum under optimum conditions combined with deficit irrigation improved water productivity. However the presence of sugar cane aphids may negate the advantages of late planted sorghum.
17. Increases in crop yields will help offset decreased irrigation water availability. The continued decline in the availability of water from the Ogallala Aquifer in the Texas Panhandle has led to an increased interest in conservation practices to extend the life of the aquifer and sustain rural economies. However, water policy makers need information on the effectiveness of conservation practices to conserve water in the aquifer while simultaneously considering the economic costs to producers. Scientists in the ARS-Bushland, Texas led Ogallala aquifer Program from West Texas A&M University, the University of Tennessee at Martin, Clarendon College and Fatima Jinnah Women University (Rawalpindi, Pakistan) evaluated the effectiveness of five policies in terms of changes in the saturated thickness, crop mix, water use per acre, and the net present value of farm profits over a 60-year planning horizon. Results indicate that the policy scenarios of biotechnology adoption (germplasm with 3% annual increase in yield) and a water use restriction will conserve the most water. In terms of economic returns, the biotechnology adoption policy by far provided the greatest benefit to producers. These comparisons will aid policy makers in determining the most effective strategy to conserve water while simultaneously considering the economic costs to producers. In addition, the results of this study can be applied to other areas facing similar conditions, either currently or in the future, throughout the Texas Panhandle.
18. Possibility of groundwater restrictions may increase short-term aquifer depletion. Concerns about the high rate of depletion of the Ogallala Aquifer in the Southern High Plains of Texas (Texas High Plains) in recent years have led to the enactment of policies designed to slow down water extraction and increase the usable life of the aquifer. However, policy implementation has not been uniform across the aquifer, leaving some farmers in portions of the aquifer with no effective groundwater extraction restrictions only a short distance away from areas where farmers face regulatory limits. Therefore, scientists in the ARS-Bushland, Texas led Ogallala Aquifer Program from Texas Tech University investigated the effects of policy implementation uncertainty on the extraction of groundwater. Producers, in their concern about the implementation of policies to slow down groundwater extraction, increase their use of water in the short-run in order to maximize profits before groundwater use restriction policies are enforced. These results are of interest to water policy makers.
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