1a. Objectives (from AD-416):
1. Develop new tools and a knowledge base that will enable decision makers to more effectively manage and conserve water resources. 1.a Design and test sensors that will quantify the level of plant water stress in growing crops and can be used to make irrigation decisions. 1.b Determine the relationship between crop productivity and applied water as a function of environmental factors so that irrigation can be managed for optimal use of all available water. 2. Develop and evaluate techniques and methodologies that maintain efficient agricultural production under deficit irrigation and dryland production. 2.a Design and evaluate water management strategies that optimize water use and crop production with limited well capacity. 2.b Define and evaluate crop management systems to facilitate the transition from irrigated to dryland cropping, considering crop species and varieties, cultural practices, and that incorporate long range weather prediction. 3. Identify changes in soil microbial, chemical, and physical properties affecting soil water availability and develop management practices that impact soil properties to sustain and improve crop production where water supply is in transition from limited irrigation to rainfed production. 4. Develop Best Management Practices based on a growing region's climate variability. 4.a Develop optimal planting strategies that integrate seasonal climate forecast information into agricultural managment. 4.b Develop software tools that provide detailed knowledge of precipitation, temperature stress, and evapotranspiration and demand to producers and plant breeders.
1b. Approach (from AD-416):
Develop and evaluate techniques and methodologies that utilize limited water resources efficiently to maintain economically viable deficit irrigated and dryland agricultural production systems. Develop new approaches, including acoustic detection of xylem cavitation and portable chamber technologies, to quantify the degree of crop drought stress and evaluate new and existing deficit irrigation strategies. Examine irrigation quantity and application rate effects on water use efficiency using the BIOTIC protocol for irrigation scheduling. Explore the efficiency of subsurface drip irrigation for storing water from low capacity wells in the soil during the fallow season. Determine the feasibility of enhancing water infiltration with adapted grasses and use water stored in playa lakes for forage production. Evaluate new crop species and cultural practices for facilitating the transition from irrigated to dryland cropping systems. Determine the effects of crop rotations and residue management systems on soil microbial, chemical, and physical properties including effects on soil water availability, infiltration, and rainfall capture efficiency. Assess the influence of row spacing and planting patterns on water use efficiency of different cropping systems. Use seasonal climate forecasts to develop optimal planting strategies and software tools to provide detailed predictions of precipitation, temperature stress, and evapotranspiration demand for producers and plant breeders. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources especially in arid and semi-arid regions where ground water resources are being depleted.
3. Progress Report:
As water is lost from leaves it is pulled up from the soil through the roots and stems to replace that which was lost from the leaves. The water in stems is under considerable tension and has an upper tensile strength of very fine copper wire. When the tensile strength of the water columns is exceeded they break, resulting in a phenomena called xylem cavitations. We attempted to relate xylem cavitations to drought stress. We were able to demonstrate that drought leads to a characteristic pattern of xylem cavitation events that release ultrasonic acoustic emissions (AEs) that can be detected with current technology. Field experiments revealed that the primary obstacles to quantitation of AEs were wind noise and availability of rugged instrumentation. While irrigation scheduling using AEs as a basis for stress detection is possible, it is not currently agronomically feasible, at least in field settings. A portable, open, transparent chamber system for measuring canopy gas exchanges in the field was developed and successfully tested. This prototype chamber was then copied to develop a total of six chambers for field deployment. Finally, these chambers have been further modified to control internal atmospheric CO2 concentration. Because atmospheric CO2 is rising and because atmospheric CO2 directly impacts both plant photosynthesis and transpiration, methods for measuring whole canopy gas exchange responses under CO2 enrichment are needed for breeding programs aiming to develop crop cultivars resistant to stresses like drought in a future higher CO2 world. Playa wetlands, the predominate geomorphic feature of the Southern High Plains are marginal croplands that occupy about 5% of the regions land area. They are typically not agronomically exploited, and many have been targeted for the Conservation Reserve Program. We investigated whether these lands could be managed, or even exploited, for forage production. We identified one species that seemed capable of forage production in the ecotomes, eastern gamagrass. We also found that not all playas exhibit similar flooding patterns. Some that remain flooded for extended periods decimated gamagrass, while others flood for only 4-6 weeks at a time allowing the crop to thrive. Our research is now investigating the flooding frequency and duration of the hydroperiod and relating this to the types of species that live in the playas, with the ultimate goal of managing these systems as biomass and forage production systems. The results of the 2007-2011 climate forecasting research was generally consistent with previous work using statistical methods to predict seasonal climate over the central U.S. Although potential for winter forecasts and winter crop management based on ENSO state was found, similar forecast skill was not apparent for summer forecasts. Although the initial goal was to develop a Visual Basic agro-climate application for the entire U.S., the decision was made to narrow the application's focus to the Ogallala region. However, the Ogallala Agro-Climate Tool's data management algorithms may be adapted for use in a future web-based application that will focus on the entire continental U.S.
1. Ogallala Agro-Climate Tool PC application. Over the latter half of the 20th century and the first years of the 21st, pumping from irrigated agriculture has led to water level declines in the Ogallala Aquifer that have not been compensated for by natural recharge. The drawdown of this important water resource has led to questions about the long-term viability of the area's agricultural economy. The Ogallala Agro-Climate Tool, a Visual Basic application that can be run on Windows 2000, XP, and Vista operating systems, has been developed by ARS scientists in Lubbock, Texas, to provide accurate information about the required irrigation levels for a range of crops, in addition to climate and crop evapotranspiration statistics for the Ogallala region. By providing estimates of the water requirements of the area's major crops, this easy-to-use PC tool may help producers to identify wasteful irrigation practices and conserve the water resource of the aquifer.
Goebel, T.S., Mckinnes, K., Lascano, R.J., Marchand, L., Davis, T. 2011. Modifying polymer flocculants for the removal of inorganic phophate from water. Tetrahedron Letters. 52(41): 5241-5244.