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Cover Crop and Nitrogen Fertilization Influence Soil Carbon and Nitrogen Under Bioenergy Sweet Sorghum

Upendra M. Sainju, Hari P. Singh, Bharat P. Singh, Wayne F. Whitehead, Anuj Chiluwal, Rajesh Paudel
Agronomy journal 2018 v.110 no.2 pp. 463-471
Secale cereale, Sorghum bicolor, Vicia villosa, bioenergy, biomass production, cover crops, fertilizer rates, nitrate nitrogen, nitrogen, nitrogen fertilizers, rye, soil, soil organic carbon, sweet sorghum, winter, Southeastern United States
CORE IDEAS: Removal of aboveground biomass may affect soil C and N under sweet sorghum.The effect of cover crop and N fertilization on soil C and N under sweet sorghum was examined.SOC and STN were greater with vetch and vetch/rye mixture than other cover cropsNH₄‐N was greater with rye and NO₃‐N greater with vetch/rye than other cover crops.Vetch and vetch/rye can enhance soil C and N storage and optimize N availability. Sustainable production of sweet sorghum (Sorghum bicolor [L.] Moench) grown for bioenergy production depends on practices that maintain soil C and N levels. The objective of this study was to evaluate the effect of winter cover crops (hairy vetch [Vicia villosa Roth], rye [Secaele cereale L.], hairy vetch/rye mixture, and the control [no cover crop]) and N fertilization rates (0 and 90 kg N ha⁻) on soil organic C (SOC), total N (STN), NH₄–N, and NO₃–N contents at the 0‐ to 30‐cm depth from 2010 to 2014 in the southeastern USA. Cover crop biomass yield and C content were greater with vetch/rye than vetch and the control and N content greater with vetch and vetch/rye than the control in 2013 and 2014. The SOC and STN at 0 to 5 cm were greater with vetch/rye than the control and at 15 to 30 cm were greater with vetch than vetch/rye. At 0 to 5 cm, SOC increased at 0.55 Mg C ha⁻¹ yr⁻¹ and STN at 0.06 Mg N ha⁻¹ yr⁻¹, regardless of treatments. At most depths, NH₄–N content was greater with rye than the control and greater with 0 than 90 kg N ha⁻¹, but NO₃–N content was greater with vetch/rye than rye. Because of greater cover crop C and N inputs, soil C and N stocks can be enhanced and N availability can be optimized by growing vetch and vetch/rye mixture cover crops to replace the stocks reduced by the removal of aboveground sweet sorghum biomass.