All Issues

Forages dominate the low-desert agricultural landscape. Competition for water resources is intensifying in desert regions at the same time that demand for high-quality forage crops is increasing. California is a forage-deficit state and is likely to remain so in the future. To improve and sustain forage production in the desert, research and education efforts must address limited water supplies and pest problems. Forage research should focus on the critical issues of irrigation efficiency, pest control, use of alternative forages and improvements in forage quality.

Growth and development pressures and environmental regulations are forcing dairy enterprises in the Chino Valley to relocate. Alternative areas for producing raw milk for the Los Angeles–San Diego basin will be needed. Two areas of particular interest are the Imperial and Palo Verde valleys. For the scenario studied, milk can be produced in the Imperial Valley at least as efficiently and cheaply as in the southern San Joaquin Valley. Transportation costs will determine profitability. Establishing a viable dairy industry in the Imperial Valley will also depend on the size of herds, the establishment of milk processing plants and the regulatory environment that surrounds it.

Since 1991, the silverleaf whitefly has caused serious damage to alfalfa production in the southern desert region. Reports from the Imperial County Agricultural Commissioner suggest that direct and indirect effects of the whitefly have caused average forage yields to decrease by 17%. Recently developed plant-breeding procedures are proving successful in developing genetic resistance to this insect. We expect to have adapted cultivars with silverleaf whitefly resistance available to growers by 2000.

The amount of disease occurring in any given area depends on the presence of the pathogen in sufficient abundance, susceptible hosts and favorable climatic conditions. Each of these factors were severely limiting to the establishment of Karnal bunt (KB) in the Imperial Valley during the 1996 growing season, and none of the 1,476 fields (106,592 acres) tested was shown to be infected with KB. Karnal bunt does not appear to be a threat to wheat production in the Imperial Valley because desert conditions are unfavorable for its development. However, this does not rule out the possibility that low levels of disease may occur occasionally. Assuming that current growing conditions continue and that KB-free seed is planted, the Imperial Valley is at low risk for a KB outbreak.

Poor water penetration and high soil salinity can be particularly detrimental to crop production in arid regions. In the Imperial Valley, roughly half of the crop acreage is planted on clay soils with very low water infiltration rates. A 30-year study showed that traditional subsurface-drainage systems provide limited control of soil water content and salinity in the root zone in clay soils underlain by artesian aquifers. In a more recent 3-year study at the UC Desert Research & Extension Center, a shallow drainage-well system improved water movement through the soil profile and was useful in leaching salts from clay soils only after continuous surface ponding and groundwater pumping. Continuous ponding for 1 month was sufficient to leach some of the salt deeper in the heavy soil.

From 1972 to 1995, gravity irrigation (flood, furrow and so on) has decreased by about 20% on an acreage basis, while sprinkler irrigation has increased by about 8% and microirrigation, including drip and microsprinklers, has increased by about 12%. These statewide estimates exclude rice acreage and are based on surveys commissioned by the California Department of Water Resources and the U.S. Bureau of the Census. Irrigation districts, UCCE farm advisors and specialists, the Natural Resource Conservation Service (NRCS) and the U.S. Bureau of Reclamation (USBR) were other sources of information. Different irrigation methods have different implications for crop yield, water conservation and water-quality protection. With the advent of chemigation and fertigation, future surveys should collect information about both irrigation and associated agricultural chemical practices.