ABSTRACT

Weed control input practices at "low" and "normal" levels were applied to cotton produced with conventional tillage and no tillage in 1992. "Low" input utilized 21-33% lower herbicide rates with no tillage and 21- 33% lower herbicide rates, no PPI or lay-by herbicide, and I to 2 fewer preplant and/or cultivation operations with conventional tillage, when compared with "normal" input practices. All herbicides were broadcast applied to no tillage and with PPI conventional tillage. All other conventional tillage herbicides were applied to a 20-inch wide band centered on the row. Cotton stand was poor with less than 30 thousand plants/acre with no-till, "low" and "normal" input and with conventional- till, "low" input in 1990. The conventional-till, "normal input stand was over 34 thousand plants/acre. An excellent stand was obtained with all treatments in 1991 (48.1-54.2 thousand plants/acre) and with the conventional-tW, "normal" input treatment (46.3 thousand plants/acre) in 1992. The other 1992 treatments had fair to good (30.5-33.2 thousand plants/acre) stands. The largest seed cotton yield in all years was the conventional, "normal" input treatment (2491, 3961, 3295 lb/acre). The yield from the conventional, low input treatment was reduced 15, 3, and 67%^1/ for 1990, 1991, and 1992, respectively. The severe yield reduction in 1992 resulted from the intense competition of a large horseweed population not controlled with the "low" input practices used. When compared with the largest seed cotton yield within years, the no-till, "normal" input treatment yield was reduced 37^1/, 26, and 23% and the no-till, "low" input treatment yield was reduced 67^1/, 33^1/, and 40^1/ for 1990, 1991, and 1992, respectively. The lower yield with both no-till treatments is attributed to greater weed populations of johnsongrass, pale smartweed, and smooth pigweed.