Managing Vegetation on the Orchard Floor in Flood Irrigated Arizona Citrus Groves

Abstract

Several orchard floor management strategies were evaluated beginning in the fall of 1993 in experiments on the Yuma Mesa in a 'Limoneira 8A Lisbon' lemon grove and in a 'Valencia' orange grove at the University of Arizona Citrus Agricultural Center (CAC) in Waddell, Arizona. On the Yuma Mesa, disking provided satisfactory weed control except underneath the tree canopies where bermudagrass, purple nutsedge, and other weed species survived. Mowing the orchard floor suppressed broadleaf weed species allowing the spread of grasses, primarily bermudagrass. Pre-emergence (Solicam and Surffan) and post-emergence (Roundup and Torpedo) herbicides were used to control weeds in the clean culture treatment in Yuma. After three harvest seasons (1994-95 through 1996-97), the clean culture treatment resulted in greater yield than the other treatments. At the CAC, clean culture (in this location no pre -emergence herbicides were used,) mowed resident weeds, and Salina strawberry clover orchard floor management schemes were compared. Again the clean culture treatment yielded more than the mowed resident weeds. The yield of the strawberry clover treatment was somewhat less than the clean culture yield but not significantly less. The presence of cover crops or weeds on the orchard floor were found to have beneficial effects on soil nitrogen and soil organic matter content, but no effect on citrus leaf nutrient content. The decrease in yield in the mowed resident weed treatments compared to the clean culture treatment in both locations was attributed to competition for water.