WEED CONTROL IN CONVENTIONAL AND CONSERVATION TILLAGE COTTON SYSTEMS IN ARIZONA

摘要

The tillage operations required to grow an annual barley and cotton crop rotation were reduced by eliminating tillage prior to planting cotton, eliminating cultivations for weed control in cotton, and especially by eliminating tillage following cotton. Data collected in 2002, 2003 and 2004 in Marana showed that a weed sensing automatic spotspray system reduced the amount of spray volume and herbicide used by 40 to 60%, but data from Maricopa in 2003 indicated that the savings could be much greater when there was a thick layer of barley cover crop residue or much less when volunteer grain germinated after grain harvest in the cotton crop. At Maricopa in 2004, large volunteer cotton plants in the furrows in early planted no-till cotton also reduced the spray volume savings from using the weed sensing automatic spot-spray system. Weed control was similar with the weed sensing, automatic spot-spray system compared to the conventional continuous spray system for most weed species. In Marana (2002, 2003and 2004) and Maricopa (2003 and 2004), there were yield differences between treatments related to planting date, with late-planted cotton yielding less than early-planted cotton. At Marana, the no-till and conventionally tilled cotton yields in treatments with the same planting date were not statistically different in 2002 and 2003. However, in 2004, the early-planted conventionally tilled cotton out-yielded the barley cover crop/early-planted no-till cotton treatment. At Maricopa in 2003, the barley cover crop/early-planted no-till cotton treatment yielded less than the early-planted conventionally tilled cotton treatment (956 versus 1141 lb/A). In 2004, there were no yield differences between the two early planted cotton treatments; however, the late-planted conventionally tilled cotton yielded 28% more than the late-planted no-till cotton. Although the yield comparisons are not yet definitive, it appears that in some situations no-till cotton may yield less than conventionally tilled cotton.