California Agriculture

Although sudangrass hay is the second largest forage crop (next to alfalfa), grown south of Sacramento and its planted area has quadrupled in the past decade, little information is available about its water use or relative water value. We would expect the sudangrass yield-water use relationship to be similar to that of alfalfa. Limited data suggest that under moderate soil salinity conditions in the Imperial Valley, sudangrass water-use efficiency (WUE–-the ratio of hay yield to water used) approximates the low end of measured alfalfa WUE. However, when we account for an estimated salinity-induced yield loss of 15% in the Imperial Valley, sudangrass WUE approximates the high end of measured alfalfa WUE. In order to better characterize the relationship between water use and crop production, as well as develop information about the relative water value associated with sudangrass-hay production, we compared hay yields and prices with estimated crop water use from 1988 to 1999 in Merced and Stanislaus, Riverside and San Bernardino, and Imperial counties. Linear regression analysis between yield and crop water use from the five-county dataset resulted in different WUE values depending on whether or not the Imperial Valley data was included. Variability in the crop-yield-to-water-use ratio from year to year was greatest in Imperial County and least in Merced and Stanislaus counties, while irrigation-water values (not including production costs) for sudangrass hay were lowest with the greatest variability in the northern counties.