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ARS Home » Plains Area » Sidney, Montana » Northern Plains Agricultural Research Laboratory » Agricultural Systems Research » Research » Publications at this Location » Publication #309702
Title: Cover crop effects on soil carbon and nitrogen under bioenergy sorghum crops

Author
item Sainju, Upendra
item SINGH, HARI - Fort Valley State University
item SINGH, BHARAT - Fort Valley State University

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2015
Publication Date: 11/5/2015
Publication URL: http://handle.nal.usda.gov/10113/61714
Citation: Sainju, U.M., Singh, H.P., Singh, B.P. 2015. Cover crop effects on soil carbon and nitrogen under bioenergy sorghum crops. Journal of Soil and Water Conservation. 70(6):410-417. doi:10.2489/jswc.70.6.410.

Interpretive Summary: Removal of aboveground biomass for bioenergy can have adverse effect on soil and environmental quality under bioenergy crops. Crop residue serves as carbon and nitrogen inputs to the soil and their removal can reduce soil carbon and nitrogen levels. Little is known about the effect of crop residue removal on soil carbon and nitrogen storage and nitrogen leaching under bioenergy crops. Improved management techniques, such as cover cropping, are needed to maintain soil carbon and nitrogen levels and mitigate greenhouse gas emissions from agriculture by sequestering carbon and nitrogen from the atmosphere to the soil. The objective of the study was to evaluate the effect of cover crops on soil organic carbon, soil total nitrogen, ammonium-nitrogen and nitrate-nitrogen contents at the 0- to 30-cm (0- to 12-in) depth under bioenergy sorghum crops from 2010 to 2013 in the southeastern United States. Treatments were two sorghum species (forage sorghum and sweet sorghum) as the main plot and four cover crops (legume [hairy vetch], nonlegume [rye], biculture of legume and nonlegume [hairy vetch/rye], and no cover crop [control]) as the split-plot treatment arranged in a randomized complete block with three replications. At 15 to 30 cm (6 to 12 in), soil organic carbon was greater with hairy vetch/rye than the control under forage sorghum. At 0 to 5 and 5 to 15 cm (0 to 2 and 2 to 6 in), soil total nitrogen was greater with hairy vetch and hairy vetch/rye than rye under forage sorghum and greater with hairy vetch/rye than the control under sweet sorghum. At 5 to 15 cm (2 to 6 in), nitrate-nitrogen was greater with hairy vetch/rye than rye in 2011, but was greater with rye and hairy vetch than hairy vetch/rye in 2012. At all depths, ammonium-nitrogen was greater under forage than sweet sorghum in 2012. Regardless of treatments, soil organic carbon and total nitrogen increased, but ammonium- and nitrate-nitrogen varied from 2010 to 2013. Although soil available nitrogen varied with cover crops, sorghum types, and climatic conditions from year to year, hairy vetch/rye can conserve and/or increase soil carbon and nitrogen storage compared with other cover crops under bioenergy sorghum in the southeastern United States. The results can be used to claim carbon credit, increase nitrogen cycling, and improve soil and environmental quality under bioenergy sorghum in the regions with similar soil and climatic conditions.

Technical Abstract: Cover crops can increase soil C and N storage and reduce the potential for N leaching under agronomic crops, but information on their benefits under bioenergy crops is scanty due to the removal of aboveground biomass. The objective of the study was to evaluate the effect of cover crops on soil organic C (SOC), total N (STN), NH4-N, and NO3-N contents at the 0- to 30-cm (0- to 12-in) depth under bioenergy sorghum (Sorghum bicolor [L.] Moench) crops from 2010 to 2013 in the southeastern United States. Treatments were two sorghum species {forage sorghum (Sorghum vulgare Pers.) and sweet sorghum (Sorghum bicolor (L.) Moench)} and four cover crops {legume (hairy vetch [Vicia villosa Roth]), nonlegume (rye [Secaele cereale L.]), biculture of legume and nonlegume (hairy vetch/rye), and no cover crop (control)} laid out in a split-plot arrangement in randomized complete block with three replications. At 15 to 30 cm (6 to 12 in), SOC was greater with hairy vetch/rye than the control under forage sorghum. At 0 to 5 and 5 to 15 cm (0 to 2 and 2 to 6 in), STN was greater with hairy vetch and hairy vetch/rye than rye under forage sorghum and greater with hairy vetch/rye than the control under sweet sorghum. At 5 to 15 cm (2 to 6 in), NO3-N was greater with hairy vetch/rye than rye in 2011, but was greater with rye and hairy vetch than hairy vetch/rye in 2012. At all depths, NH4-N was greater under forage than sweet sorghum in 2012. Regardless of treatments, SOC and STN increased, but NH4-N and NO3-N varied from 2010 to 2013. Although soil available N varied with cover crops, sorghum types, and climatic conditions from year to year, hairy vetch/rye can conserve and/or increase soil C and N levels compared with other cover crops under bioenergy sorghum in the southeastern United States. The results can be used to claim C credit, increase N cycling, and improve soil and environmental quality in the regions with similar soil and climatic conditions.