Cover crop effects on nitrogen mineralization and availability in conservation tillage cotton
2004
Schomberg, H.H. | Endale, D.M.
Understanding cover crop influences on N availability is important for developing N management strategies in conservation tillage systems. Two cover crops, cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.), were evaluated for effects on N availability to cotton (Gossypium hirsutum L.) in a Typic Kanhapludult soil at Watkinsville, Ga. Seed cotton yields following clover and rye were 882 kg ha-1 and 1,205 kg ha -1, respectively, in 1997 and were 1,561 kg ha-1 and 2,352 kg ha-1, respectively, in 1998. In 1997, cotton biomass, leaf area index, and N were greater on some dates following crimson clover than following rye but not in 1998. During 1997, net soil N mineralized increased with time in both systems, but a similar response was not observed in 1998. Net soil N mineralization rates following crimson clover and rye averaged, respectively, 0.58 kg and 0.34 kg N ha-1 day in 1997 and 0.58 kg and 0.23 kg N ha-1 day-1 in 1998. Total soil N mineralized during the cotton growing season ranged from 60 kg ha-1 to 80 kg ha-1 following crimson clover and from 30 kg ha-1 to 50 kg ha -1 following rye. Soil N mineralization correlated positively with heat units and cumulative heat units. Net soil N mineralization rates were 0.023 kg ha-1 heat unit-1 once net mineralization began. Soil heat units appeared to be a useful tool for evaluating N mineralization potential. Nearly 40% of the rye and 60% of the clover biomass decomposed during the 6 weeks prior to cotton planting, with nearly 35 kg N ha-1 mineralized from clover.
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