Contrasting herbicide programs for grain sorghum

摘要

An experiment was conducted near Manhattan, KS, on a Reading silt loam soil with 2.5 percent organic matter and a pH of 5.8 to evaluate several herbicide treatments for annual weed control in grain sorghum. The experiment was a randomized complete block design with three replications. 'Pioneer 8505' sorghum was planted 1.5 inch deep on May 30, 2002, at 53,000 seed/A, in a tilled seedbed with less than 5 percent plant residue cover. The dominant weed was Palmer amaranth. Natural populations of ivyleaf morningglory and velvetleaf were present at low densities; additionally, they and domestic oilseed sunflower were seeded across the plots. Herbicide treatments were applied with a ractor-mounted boom to 10 ft by 25 ft plots. Rainfall was 0.24 inch onJune 4, apparently enough to stimulate amaranth and crabgrass germination and to at least partially activate preemergence herbicides. Thereafter, precipitation totaled 0.6 inch until July 27. Weeds were not stressed at the early postemerge treatments, but were becoming quite water stressed by the postemerge treatments.