Subsurface Drip and Overhead Irrigation Effects on Conservation-tilled Cotton in the San Joaquin Valley

Conservation cropping systems are being developed for cotton (Gossypium spp.) traditionally grown on raised beds with several soil-disturbing tillage passes in the San Joaquin Valley (SJV) of California, USA. Overhead (OH) irrigation and subsurface drip irrigation (SSDI) systems are water-conserving techniques being tested with reduced tillage in the SJV. However, crop growth, yield, microclimate, and pest population dynamics in these systems have not been documented. A field study was conducted in 2011 and 2012 at Five Points, Calif., to evaluate the difference between the two irrigation systems. Cotton cv. Phytogen 725 RF was no-till planted into wheat residue. In both years, the soil surfaces in the OH plots were 1 degrees to 2 degrees C cooler and 5% to 15% wetter than the SSDI plots. These differences had no effect on crop growth, development, yield, or quality, but weed densities and biomass were lower in the SSDI than in the OH in both years. However, the SSDI plots had more spider mites (Tetranychus sp.) than the OH plots in 2011. The study showed that cotton could be successfully grown with conservation tillage, high residue systems, with either OH or SSDI systems in the SJV.