Decomposition and Nutrient Cycling of Three Cover Crops In Strip-Tillage Cotton.

The adoption of conservation tillage and cover cropping techniques in cotton (Gossypium hirsutum L.) has aided significantly in reducing soil losses to erosion in the southeastern U.S.  Cover crops also aid in cycling organic matter and nutrients back to soil, an important consideration in cotton systems that typically provide only minor soil organic matter additions.  Thus, the objective of this study was to measure the decomposition of cover crop residues and cycling of nutrients from residues to soil and a subsequent cotton crop.  Cotton was grown in strip-tillage with a crimson clover (Trifolium incarnatum L.), wheat (Triticum aestivum L.), or rye (Secale cereale L.) cover in 2007 and 2008 in Tifton, GA.  Soil samples and plant tissue samples from cover crop residues and cotton plants were collected throughout the growing season and analyzed for nutrient concentration and biomass.  Total percent biomass degradation did not differ among crimson clover, rye, or wheat residues (67%, 63%, and 65%, respectively) both years (p < 0.05).  Similarly, reduction in total content of N, P, and K did not differ among cover crops (p < 0.05).  Cotton biomass accumulation was greatest in 2007, but did not differ among cover crop treatments in either year (p < 0.05).  Total content of N and K in vegetative cotton tissue was greatest (p < 0.05) with crimson clover (295 kg ha^-1 and 254 kg ha^-1, respectively) in 2007.  However, differences among cover crop treatments in N, P, and K content in cotton vegetation were not significant in 2008.  Seed cotton yields among treatments ranged from 3532 kg ha^-1 to 3567 kg ha^-1, with no significant differences (p < 0.05).  Based on these results, under standard management of cotton in strip-tillage, there are few differences among these three cover crops in nutrient uptake and final seed cotton yield.