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United States Department of Agriculture

Agricultural Research Service

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

Authors
item Sainju, Upendra
item Singh, Bharat - FORT VALLEY STATE UNIV.
item Whitehead, Wayne - FORT VALLEY STATE UNIV.

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 12, 2005
Publication Date: August 17, 2005
Citation: Sainju, U.M., Singh, B.P., Whitehead, W.F. 2005. Tillage, cover crops, and nitrogen fertilization effects on cotton and sorghum root biomass, carbon, and nitrogen. Agronomy Journal. 97:1279-1290.

Interpretive Summary: Root biomass is an important part of crop biomass which grows inside the soil profile, absorbs nutrients and water for translocation into the aboveground biomass, and provides physical support for the plant. After harvest of grains or lint, straws containing stems and leaves are either harvested for making hay, animal litter, or fuel, or left in the soil as residue while roots are always left in the soil and form an important source of soil organic matter. Because of the significant amount of carbon (C) and nitrogen (N) inputs supplied by root biomass, roots can improve soil quality and productivity by cycling nutrients and increasing organic matter. Soil and crop management practices, such as tillage, cover cropping, and N fertilization, may influence soil properties, thereby affecting crop root growth, biomass, and C and N accumulations. This study examined the influence of three tillage practices (no-till, strip till, and chisel till), four cover crops [legume (hairy vetch), nonlegume (rye), mixture of legume and nonlegume (hairy vetch/rye mixture), and no cover crop (winter weeds)], and three N fertilization rates (0, 60 to 65, and 120 to 130 kg N ha-1) on root biomass yield and C and N accumulations of cotton and sorghum from 2000 to 2002 in central Georgia. Root biomass yield and C and N accumulation at 0- to 15-cm depth accounted for 29 to 50% of total biomass and C and N accumulation from 0- to 120-cm depth. Root biomass and C and N accumulations at 0- to 15- and 30- to 60-cm were greater in no-till or strip till than in chisel till and greater with vetch/rye mixture than with vetch or weeds. Total root biomass and C and N accumulations from 0- to 120-cm were greater in no-till or strip-till with vetch and rye than in chisel-till with weeds and greater with 60 and 120 than with 0 kg N ha-1. The results suggest that conservation tillage, such as no-till or strip till, with hairy vetch and rye cover crop and 60 kg N ha-1 can increase root biomass yield and C and N accumulations of cotton and sorghum compared with conventional tillage, such as chisel till with no cover crop and N fertilization. Increasing root biomass and C and N accumulations in cotton and sorghum using management practices will improve soil quality and productivity by increasing soil organic matter and C and N cycling.

Technical Abstract: Management practices may influence cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench)] root growth and C and N accumulations for soil sequestration. 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 to 65, and 120 to 130 kg N ha-1) on biomass yield and C and N accumulations of cotton and sorghum roots from 0- to 120-cm depth. Field experiment was conducted in a split-split plot design on a Dothan sandy loam (fine-loamy siliceous, thermic, Plinthic Paleudults) from 2000 to 2002 in central GA. Root biomass and C and N accumulations 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 were greater in ST than in NT and CT in 2000 cotton. Root biomass and C and N at 0- to 15-cm were also greater with vetch and rye biculture than with vetch and winter weeds in 2001 sorghum. Total root biomass and C and N accumulations at 0- to 120-cm were greater in ST with vetch than in ST with rye or in CT with winter weeds in 2000 cotton. In contrast, total biomass and N were greater in NT with rye than in ST with rye or CT with vetch in 2001 sorghum and 2002 cotton. Total root biomass and N were 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 were greater in ST with 60 kg N ha-1 than in NT with 0 kg N ha-1 or in CT with 120 kg N ha-1 in 2002 cotton. Conservation tillage, such as NT or ST, with vetch and rye cover crops and 60 kg N ha-1 increased cotton and sorghum root biomass yield and C and N accumulations compared with conventional tillage, such as CT, with no cover crops and N fertilization, thereby increasing C and N inputs from cotton and sorghum roots for improving soil quality and productivity.

Last Modified: 12/18/2014
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