Published online by Cambridge University Press: 12 June 2017
Under the erractic rainfall distribution of the Southern Great Plains, average pigweed (Amaranthus sp.) control in five studies with seven herbicides was enhanced by incorporation in 1 or 3 inches of soil with a power rototiller. Compared to no incorporation, 9-inch incorporation improved pigweed control with two herbicides, had no effect on weed control with two others, and decreased weed control with another three. Soil incorporation at 1 or 3 inches did not increase weed control with three compounds if 0.4 inch of rainfall occurred within 2 weeks after application. Incorporation into 1 or 3 inches of soil improved weed control with four herbicides even when rainfall occurred within 2 days after application. In four of the trials, neither herbicides nor incorporation depth affected cotton stand or vigor. Under the soil moisture conditions prevailing in the one trial where yield data were obtained, cotton (Gossypium hirsutum L.) stand and lint yield decreased lineally with depth of soil incorporation. Herbicides did not affect cotton stand or yield.