1a. Objectives (from AD-416):
1: Evaluate a new technique using mid-infrared spectroscopy to characterize soil organic matter (SOM) properties and its effects on soil water holding capacity and to characterize erodibility of agricultural landscapes. 1A: Identify management-induced changes in SOM characteristics affecting soil water availability in sandy soils using a new technique for characterization of chemical composition of SOM, Fourier-transform Mid-infrared Spectroscopy. 1B: Quantify the combined effects of wind and water erosion on subsequent erodibility of agricultural landscapes. Objective 2: Compare and contrast water use efficiency among deficit irrigation strategies, and develop decision support tools to determine optimal irrigation and crop rotation strategies. 2A: Compare three types of deficit irrigation scheduling methods (Stress Time, Stress Degree Hours, and Crop Water Stress Index) in terms of final irrigation amounts, irrigation timing and cotton crop water use efficiency. 2B: Develop decision support tools to determine optimal irrigation and crop rotation strategies. 2C: Quantify the effects of wind speed, tillage type, and surface irradiance on the surface evaporation component of water use efficiency. 3: Conduct climate analysis and integrate large-scale hydrology models with process level-plant growth models in order to simulate optimum water and energy use for crop production on the Southern High Plains. 3A: Develop informational web sites to inform producers of the Ogallala region and other agricultural regions of recent climate trends. 3B: Develop and test a simulation model that will calculate landscape-scale mass and energy balance in pivot irrigated cotton systems at a detailed spatial and temporal resolution. 4: Monitor and model water depth in temporary playa wetlands for potential agronomic uses and also to determine the potential for aquifer recharge. 4A: Design, fabricate, deploy, evaluate, and maintain climatologic and hydrologic instrumentation in playa wetlands. 4B: Determine effects of proximate land use on playa basin hydrologic characteristics.
1b. Approach (from AD-416):
Our goal is to develop and evaluate models and methods that use limited water resources efficiently to maintain economically viable deficit irrigated and dryland agricultural production systems. New approaches will identify land management effects on soil organic matter properties and resulting effects on soil water holding capacity. The combined effects of both wind and water on subsequent erodibility of agricultural landscapes will be quantified. Effects of irrigation timing and total application rate on water use efficiency will be compared among different deficit irrigation scheduling methods. New research will explore the interactive effects of tillage and environmental variables on the surface evaporation component of water use efficiency. Decision support tools will be developed to determine optimal irrigation and crop rotation strategies while other studies will develop simulation models of landscape-scale mass and energy balances at detailed spatial and temporal resolutions. These modeling studies will be used to simulate optimum water and energy use for crop production on the Southern High Plains. Climate analyses will be conducted to develop informational web sites to inform agricultural producers of recent climate trends and potential impacts on future agricultural productivity. Finally, temporary playa wet lands will be evaluated to determine the potential for aquifer recharge as well as for future agronomic uses. 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:
Measurements of organic matter, bulk density, and wet aggregate stability were collected at depths of 0-5 cm and 5-10 cm in Feb. 2012. A double-ring infiltrometer was used to determine water infiltration rates after harvest but before any subsequent tillage in the fall of 2010 and then on only 7 plots in March 2012. The site was subsequently plowed to mitigate severe wind erosion caused by drought. Watersheds in New Mexico have been identified and surveyed to develop high resolution DEMs, and watershed boundaries have been identified. Pour points have been determined based on KINEROS modeling and 10-year return period storms. Instrumentation has been built. Installation of instrumentation on the first three watersheds is scheduled for Fall and Winter FY13. A paper developed the upper and lower baselines for calculating the Crop Water Stress Index (CWSI) for cotton at Big Spring, TX. Deficit irrigation using CWSI will be a central feature of experiments for the next four years. Objectives for this year changed to data acquisition of field instruments (Ta, Tc, PAR, and VPD) and data logger programing in order to schedule irrigations using CWSI in real time for these future experiments. A pre-beta version of a web application that helps Southern High Plains cotton producers determine optimally profitable irrigation levels for cotton under specified commodity price and production cost conditions is being developed. A paper describing the application's crop modeling and profit calculation component of the application was submitted to Agricultural Water Management but was withdrawn after initial review. Monolith shells have been constructed, and critical instrumentation has been procured. Modifications have been made to the original wind tunnel structure and the balances cleaned and serviced. Presently, the soils in the area are too dry to extract intact soil monoliths. PALMS and Cotton2K, have been integrated into a single model, PALMSCot. Both models use daily weather input data to calculate rate equations used in the energy, water, and carbon balances of cotton growth and development. Initial problems in the integration of the two models were related to defining end-points of the soil hydraulic parameters used to characterize soil hydraulic properties, which control water movement in the soil and affect root-water uptake and related processes. Minor debugging continues, and once finalized we will be able to test PALMSCot by comparing measured to calculated values of soil water content for several sites in the Texas High Plains. We developed a mesoscale double ring infiltrometer system that allows the direct measurement of macro- and micropore water infiltration through the basins of temporary playa lakes or simply "playas". These depressions in the landscape of the Southern High Plains temporarily fill with water following rainfall events. The water in these depressions either evaporates into the air or infiltrates into the ground where it becomes available for aquifer recharge. The device will allow researchers to check their assumptions about the amounts of water available for aquifer recharge.
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.
Brown, P., Cordero, E., Mauget, S.A. 2012. Reproduction of 20th century inter- to multi-decadel surface temperature variablilty in radiatively forced coupled climate models. Journal of Geophysical Research. 117:1-15.