8 AGRONOMY NEWS
Soil and Water Management Projects
Improving Prediction of Forage Water Use
Danny Smith
Accurate water use inventories are essential for administration of interstate compact agreements among states and individual water rights within all western states. In many remote areas, crop water use estimates are subject to significant errors because they are based on maximum and minimum daily temperature alone. Improved expressions of temperature and other easily monitored weather variables are needed to adjust existing models to account for local weather conditions. Use of these adjusted models to compute water use estimates, combined with installation of low-cost weather-monitoring devices, would result in more accurate accounting of crop water use throughout the western US. A locally adapted version of the Hargreaves radiation method should be more accurate in assessing consumptive water use in irrigated mountain meadows than Blaney-Criddle methods, even with crop coefficients adjusted to local conditions. Previous results have demonstrated that water use is poorly correlated with average daily temperature regardless of the temperature expression used. Thus, the conventional approach of adjusting Blaney-Criddle crop coefficients to local conditions was inadequate because it failed to account for climatic variability associated with years and sites. Previous analyses indicate that radiation accounts for a much greater proportion of crop coefficient variability than any expression of average daily temperature. During the current reporting year, more detailed analysis of the data demonstrates that variability in solar irradiance on a daily basis can be estimated using the difference between maximum and minimum daily temperature. Data from 2001 and two additional growing seasons will be used to refine existing models using the Hargreaves approach.
Improving Traditional Soil Salinity Measurements
Grant Cardon
The main objective of this project is characterizing salinity's extent and severity in current soil, surface, and ground water in order to determine strategies for salinity control in irrigated fields along 40 miles of the lower Arkansas River basin. This region of the basin is currently estimated to be losing an average of 10 to 20% in yield due to soil salinity, or about 900,000 bushels of corn, and 24,000 tons of alfalfa. The correlation of laboratory, labor-intensive measures of soil salinity with more rapid indirect methods will provide a critical salinity control tool for growers and resource managers. Rapid indirect measures provide a means of mapping soil salinity, as well as temporally and spatially monitoring changes, enabling fast, accurate, and cost effective evaluation of salinity control strategies. Cardon used the indirect soil salinity assessment tools Electromagnetic Induction meter (EM meter) and Hach Company's in-field, quick salinity test kit. With about a third of the samples processed, preliminary analysis showed correlation between soil saturated paste extract EC and commercial quick test EC.
