Impacts of Short-Term Fallowing on Soils and Crop Growth in the Palo Verde Irrigation District
Jeremy Cusimano1, Cassie Fausel1, Jeffrey Silvertooth1, Jean E. McLain1, Sharon B. Megdal1
1 Department of Soil, Water, and Environmental Science, University of Arizona
Many Southwestern states, including California and Arizona, are adjusting to the possibility of Colorado River water shortages as forecasts project less supply in coming decades. California has been forced to abide by its 4.4 plan, which was designed to reduce its Colorado River withdrawals down to its basic 4.4 MAF/year allocation. This, along with other factors, has led municipalities in parts Southern California to search for alternative water sources. One strategy being employed to meet municipal demand is the transfer of water from agricultural areas in parts of the California desert to urban areas in the Los Angeles basin. In 2004, the Metropolitan Water District of Southern California (MWD) completed an agreement with the Palo Verde Irrigation District (PVID) in Southeastern California for the transfer of up to 120,000 acre feet of Colorado River water annually. The program provides 35 years of supply to MWD through fallowing of up to 26,000 acres annually in the Palo Verde Valley. Many water transfers across the West require fallowing as a component of such agreements, which can have significant impacts on soils and agriculture productivity in these regions. Studies show that fallowing and land rotation are beneficial to soil health, crop production and overall long-term sustainability. This study aims to quantify impacts of short-term fallowing on soil health and agricultural productivity in the Palo Verde Valley. The study compared differences in soil fertility, crop growth, marketable yield and microbial activity between fallowed sites and continuously farmed sites at several locations in the PVID.