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ARS Home » Plains Area » Sidney, Montana » Northern Plains Agricultural Research Laboratory » Agricultural Systems Research » Research » Publications at this Location » Publication #170045
Title: Carbon accumulation in cotton, sorghum, and underlying soil as influenced by tillage, cover crops, and nitrogen fertilization

Author
item Sainju, Upendra
item WHITEHEAD, WAYNE - FORT VALLEY STATE UNIV.
item SINGH, BHARAT - FORT VALLEY STATE UNIV.

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2004
Publication Date: 6/1/2005
Citation: Sainju, U.M., Whitehead, W.F., Singh, B.P. 2005. Carbon accumulation in cotton, sorghum, and underlying soil as influenced by tillage, cover crops, and nitrogen fertilization. Plant and Soil. 273(1-2):219-234.

Interpretive Summary: Carbon accumulated in the above- and belowground biomass of crops as a result of photosynthesis from atmospheric CO2 can increase soil C sequestration in the terrestrial ecosystem and can help to mitigate some of the undesirable effects of global warming. Soil C sequestration can be dramatically increased if stalks of crop residues containing stems and leaves after grain or lint harvest are left in the soil instead of using them for other purposes, such as animal food (hay), litter, or fuel. Because C accumulation depends on biomass production which is influenced by soil and environmental conditions, soil and crop management practices, such as tillage, cover cropping, and N fertilization, can also affect crop yields, biomass production, and C accumulation. This study examined the effects 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), hairy vetch/rye mixture, and winter weeds or no cover crop], and three N fertilization rates (0, 60-65, and 120-130 kg N ha-1) on the amount of C sequestered in cotton lint (lint + seed), sorghum grain, and their stalks (stems + leaves), and roots from 2000 to 2002 in central Georgia, USA. In 2000, C accumulation in cotton lint was greater in NT with rye or vetch/rye mixture but in stalks, it was greater in ST with vetch or vetch/rye mixture than in CT with or without cover crops. Similarly, C accumulation in lint was greater in NT with 60 kg N ha-1 but in stalks, it was greater in ST with 60 and 120 kg N ha-1 than in CT with 0 kg N ha-1. In 2001, C accumulation in sorghum grains and stalks was greater in vetch and vetch/rye mixture with or without N rate than in rye without N rate. In 2002, C accumulation in cotton lint was greater in CT with or without N rate but in stalks, it was greater in ST with 60 and 120 kg N ha-1 than in NT with or without N rate. Averaged across treatments, C accumulation in lint was greater in NT than in ST and CT in 2000 but in grains, lint, and stalks, it was greater in CT and ST than in NT in 2001 and 2002. Similarly, C accumulation in lint was greater with rye but in grains and stalks, it was greater with vetch and vetch/rye mixture than with rye or weeds in 2000 and 2001. Carbon accumulation in lint was also greater with 60 than with 120 kg N ha-1 in 2000 but in grains and stalks it was greater with 60-65 and 120-130 kg N ha-1 than with 0 kg N ha-1 in 2000 and 2001. Total C accumulation in the above- and belowground biomass in cotton ranged from 1.7 to 5.6 Mg ha-1 and in sorghum ranged from 3.4 to 7.2 Mg ha-1. Carbon accumulation in cotton and sorghum roots ranged from 1 to 14% of the total C accumulation in above- and belowground biomass. Because of higher C accumulation, C sequestered in cotton and sorghum stalks can significantly increase C storage in the soil if these residues are left after lint or grain harvest, thereby helping to mitigate the effects of global warming. Carbon accumulated in roots is also significant and forms main source of soil organic C because roots are usually left in the soil after crop harvest. Conservation tillage, such as ST, with a mixture of legume and nonlegume cover crops and 60 to 65 kg N ha-1 can be used to increase C accumulation in cotton and sorghum biomass, sustain lint and grain yields, and improve environmental quality by reducing soil erosion and N leaching compared with CT with 120-130 kg N ha-1 and no cover crops. Regardless of the management practices used, C sequestration in crop production system remains an important part of global C sequestration in the terrestrial ecosystem. A C credit system should be encouraged to produce greater stalk production besides increasing crop yields using appropriate management practices that leaves the stalks in the soil so that atmospheric C sequestra

Technical Abstract: Soil and crop management practices may influence biomass growth and yields of cotton (Gossipium hirsutum L.) and sorghum (Sorghum bicolor L.) and sequester significant portion of atmospheric CO2, thereby helping to mitigate the undesirable effects of global warming. This study examined the effects 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), hairy vetch/rye mixture, and winter weeds or no cover crop], and three N fertilization rates (0, 60-65, and 120-130 kg N ha-1) on the amount of C sequestered in cotton lint (lint + seed), sorghum grain, and their stalks (stems + leaves), and roots from 2000 to 2002 in central Georgia, USA. A field experiment was conducted on a Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults). In 2000, C accumulation in cotton lint was greater in NT with rye or vetch/rye mixture but in stalks, it was greater in ST with vetch or vetch/rye mixture than in CT with or without cover crops. Similarly, C accumulation in lint was greater in NT with 60 kg N ha-1 but in stalks, it was greater in ST with 60 and 120 kg N ha-1 than in CT with 0 kg N ha-1. In 2001, C accumulation in sorghum grains and stalks was greater in vetch and vetch/rye mixture with or without N rate than in rye without N rate. In 2002, C accumulation in cotton lint was greater in CT with or without N rate but in stalks, it was greater in ST with 60 and 120 kg N ha-1 than in NT with or without N rate. Averaged across treatments, C accumulation in lint was greater in NT than in ST and CT in 2000 but in grains, lint, and stalks, it was greater in CT and ST than in NT in 2001 and 2002. Similarly, C accumulation in lint was greater with rye but in grains and stalks, it was greater with vetch and vetch/rye mixture than with rye or weeds in 2000 and 2001. Carbon accumulation in lint was also greater with 60 than with 120 kg N ha-1 in 2000 but in grains and stalks it was greater with 60-65 and 120-130 kg N ha-1 than with 0 kg N ha-1 in 2000 and 2001. Total C accumulation in the above- and belowground biomass in cotton ranged from 1.7 to 5.6 Mg ha-1 and in sorghum ranged from 3.4 to 7.2 Mg ha-1. Carbon accumulation in cotton and sorghum roots ranged from 1 to 14% of the total C accumulation in above- and belowground biomass. Carbon sequestered in cotton and sorghum stalks and roots can be significant in the terrestrial ecosystem and can significantly increase C storage in the soil if these residues are left after lint or grain harvest, thereby helping to mitigate the effects of global warming. Conservation tillage, such as ST, with legume or a mixture of legume and nonlegume cover crops and 60 kg N ha-1 can be used to increase C sequestration in cotton and sorghum biomass compared with conventional tillage, such as CT, without cover crops and N fertilization, thereby improving soil quality and reducing erosion.