Effects of Legume and Small Grain Cover Crops with Precision Planted Tillage Radish on Nutrient Cycling and Cotton Performance in Southeastern Virginia

Little research has been conducted on how cover crop mixes and conservation tillage affect nitrogen cycling and uptake in cotton (Gossypium hirsutum L.) grown on the coastal plain soils of Southeastern Virginia. The objective of this study was to examine the influence of two tillage practices {no-till with precision planted radish (Raphanus sativus) and strip till}, four cover crop mixes {fallow, legume mix [crimson clover (Trifolium incarnatum), hairy vetch: Vicia villosa, woolypod vetch: Vicia villosa R. ssp. dasycarpa)], cereal rye (Secaele cereale), and a legume mix/rye culture}, and four nitrogen (N) rates (0, 45, 90, and 135 kg N ha-1) on cover crop N uptake, soil N cycling, cotton response to N fertilization, and cotton lint yield. Cover crop mix and N rate responses were greater than tillage during 2017 & 2018. N uptake was greater in cover crop biomass that included legumes. Overall, the legume mix produced more soil nitrate-N within each month and sampling depth. Cover crop mix, N rate, and their interaction had a significant (p < 0.001) impact on lint yield, with the legume mix and legume/rye mix maximizing yields (1900-2017 kg ha-1) at 135 kg N ha-1. Cotton grown in unfertilized plots following a legume mix cover crop performed similarly to rye plots fertilized with 135 kg N ha-1 and fallow plots with 90 kg N ha-1. These results indicate that legume cover crops can independently provide adequate N nutrition in order achieve profitable cotton production and minimize fertilizer usage.