Tillage, cover crops, and nitrogen fertilization effects on cotton and sorghum root biomass, carbon, and nitrogen

Management practices may influence cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench)] root C and N inputs for improving soil quality. We examined the influence of three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)], four cover crops [legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secale cereale L.)], biculture of legume and nonlegume (vetch and rye), and no cover crops (winter weeds)), and three N fertilization rates (0, 60-65, and 120-130 kg N ha(-1)) on cotton and sorghum root C and N from the 0- to 120-cm soil depth. A field experiment was conducted in a Dothan sandy loam (fine-loamy, kaolinitic, thermic, Plinthic Kandiudults) from 2000 to 2002 in central Georgia. Root C and N at 0 to 15 cm were greater in NT than in ST and CT in 2000 cotton and 2001 sorghum, but at 30 to 60 cm they were greater in ST than in NT and CT in 2000 cotton. Root C and N at 0 to 15 cm were also greater with vetch and rye biculture than with vetch and weeds in 2001 sorghum. Total root C and N at 0 to 120 cm were greater in ST with vetch than in ST with rye or in CT with weeds in 2000 cotton. In contrast, total root N was greater in NT with rye than in ST with rye or CT with vetch in 2001 sorghum and 2002 cotton. Total root N was also greater in CT with 60 kg N ha(-1) than in NT or CT with 120 kg N ha(-1) in 2000 cotton, but was greater in ST with 60 kg N ha(-1) than in NT with 0 kg N ha(-1) or CT with 120 kg N ha(-1) in 2002 cotton. The NT or ST with vetch and rye cover crops and 60 kg N ha(-1) may increase cotton and sorghum root C and N compared with CT with no cover crops and N fertilization, thereby helping to improve soil quality and productivity.