Effects of Nitrogen, Dicyandiamide, and Tillage on Cotton Nitrogen Concentration and Yield
Conservation tillage has the potential to increase N leaching from sandy soils by increasing water infiltration. The nitrification inhibitor dicyandiamide (DCD) can reduce this risk, but cotton (Gossypium hirsutum L.) may be sensitive to DCD. Field studies were conducted at the E.V. Smith Research Center in Macon County, AL on a Norfolk soil (fine, loamy, siliceous, thermic Typic Paleudult) to determine the effects of DCD on cotton N concentration and yield of conventional and striptill cotton. Nitrogen treatments included four preplant N rates (0,67,100, and 134 kg ha−) with and without DCD (10% of N rate). Leaf N concentration was generally greater in treatments receiving N fertilizer than no N; however, regressions between N concentration and N fertilizer were not always significant. Whole plot effects on yield due to tillage were significant. Optimum N rate for seed cotton production was 67 kg ha− N in 1984 and ranged between 100 and 134 kg ha− N in 1985 and 1986. The application of DCD decreased yields by 30% in 1984. At the 134 kg N ha− rate in 1985, DCD increased yields by 24%. In 1986 seed cotton yields in the strip-till treatment receiving 134 kg ha− N were 20% less with DCD than without. It is concluded that application of DCD is beneficial, with typical rainfall patterns, if high rates (13 kg ha−) are used. However, if rainfall is less than the historical average during first square to first bloom stage, DCD application has little effect or is detrimental to seed cotton yield.
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