Studies have been conducted since 1980 to determine the feasibility of producing dryland cotton in a wheat fallow-cotton cropping sequence using no or limited tillage. The soil was Pullman clay loam containing one-third each of sand, silt, and clay with organic matter, and a pH of 7.0. The most successful herbicides in the fallow from wheat harvest to cotton planting were atrazine, propazine, and fluometuion. Over a three year period, average yields of cotton lint were 215, 255, and 194 lb/A, respectively where 1.5, 2.0, and 3.0 lb/A atrazine was used to control weeds during the fallow. Propazine at 1.5, 2.0, and 3.0 lb/A used to control weeds in the fallow from wheat harvest to cotton planting resulted in lint yields of 207, 225, and 199 lb/A respectively. Applying fluometurorl at 1.6 or 2.4 lb/A under the same conditions produced yields of 237 and 221 lb/A of lint. Yields from an adjoining area that was sweep tilled averaged 222 lb/A lint. In 1984, it was very dry at cotton planting time in May and June. Because of this, cotton seed was planted in dry soil and irrigated for emergency. Stands were very erratic; boll counts were made but yields were not obtained. Atrazine applied to wheat stubble at 1.5 lb/A eliminated the cotton. Propazine at 1.5 lb/A caused some injury by itself, but when mixed with fluometuron at 1 lb/A, plant vigor and boll counts were equal to untreated check areas where weeds were controlled with glyphosate during the fallow period. Weeds growing in the wheat stubble at harvest were controlled with glyphosate or paraquat mixed with the soil acting herbicides. When wheat stubble was about 1 ton per acre in 1980, soil water storage was increased by the mulch with no-tillage and resulted in increased cotton yield.

In the fallow from cotton planting to wheat harvest, chlorsulfuron was the best herbicide to use. Herbicides were applied to cotton stubble in the spring of 1982. It was very dry during the summer and only one sweep tillage operation on untreated plots was needed to control weeds prior to planting wheat in the fall of 1982. The winter of 1982-83 was very wet and wheat yields were about 40 bushels per acre. In Addition to chlorsulfuron, other herbicide treatments resulting in equally high yields were atrazine mixed with chlorsulfuron at 0.5 + O.31 lb/A, 2,4-D + terbutryn, 2,4-D + cyanazine, and 2,4-D and metribuzin.