In an attempt to reduce the incidence of late-season leaf spot complex in cotton (mainly caused by Alternaria spp.), muriate of potash (KC1) was broadcast before planting at 0, 30, 60, 120 lbs./acre. In sub-plots, foliar applications of 10 lbs./acre of potassium nitrate (KNO₃) were made four times on a two-week interval starting at blooming stage. Both methods of application were tested on no-till as well as conventional tillage systems at the Ames Plantation Experiment Station in 1993 on low K testing soil. The cultivar Deltapine 50 was planted in 30 foot plots, four rows wide in a split-plot design with the main plot as soil applied K₂O rates.

Significantly less fungal leaf spots and higher yield were noted as K₂O rates were increased in both conventional as well as no-till plots. No-till plots had significantly more leaf spot and higher yield at each K₂O rate compared to the conventional tillage system.

Foliar KNO₃ applications also reduced the leaf spot complex and increased yield. Again, no-till plots had significantly more leaf spots and higher yield than conventional plots.

The data from 1993 agrees favorably with the previous year's data except the conventionally tilled plots out-yielded the no-till plots in 1992. This is mainly because the 1993 growing season was very dry and the 1992 season was much wetter. In many situations no-till cotton may out-yield conventional cotton under dry conditions, however the leaf-spot complex may still be more severe.