Tillage, Cover Crops, and Nitrogen Fertilization Effects on Cotton and Sorghum Root Biomass, Carbon, and Nitrogen

the main source of C in maintaining soil organic matter. The amount of C and N supplied by roots can be signifiManagement practices may influence cotton (Gossypium hirsutum L.) cant for maintaining or improving soil organic matter. and sorghum [Sorghum bicolor (L.) Moench)] root C and N inputs for As much as 7 to 43% of the total aboveground and belowimproving soil quality. We examined the influence of three tillage ground plant biomass can be contributed by roots (Kuo practices [no-till (NT), strip till (ST), and chisel till (CT)], four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye et al., 1997a, 1997b). Roots can supply from 400 to 1460 kg (Secale cereale L.)], biculture of legume and nonlegume (vetch and C ha 1 during a growing season (Qian and Doran, 1996; rye), and no cover crops (winter weeds)}, and three N fertilization Kuo et al., 1997a). Liang et al. (2002) found that roots rates (0, 60–65, and 120–130 kg N ha 1) on cotton and sorghum root contributed as much as 12% of soil organic C, 31% of C and N from the 0to 120-cm soil depth. A field experiment was water soluble C, and 52% of microbial biomass C within conducted in a Dothan sandy loam (fine-loamy, kaolinitic, thermic, a growing season. Roots may play a dominant role in Plinthic Kandiudults) from 2000 to 2002 in central Georgia. Root C soil C and N cycles (Wedin and Tilman, 1990; Gale et al., and N at 0 to 15 cm were greater in NT than in ST and CT in 200