Cover Crops for Enriching Soil Carbon and Nitrogen Under Bioenergy Sorghum

Abstract

Soil carbon (C) and nitrogen (N) can be enriched with cover crops under agronomic crops, but little is known about their enrichment under bioenergy crops. Legume (hairy vetch [Vicia villosa Roth]), nonlegume (rye [Secale cereale L.]), a mixture of legume and nonlegume (hairy vetch and rye), and a control with no cover crop were grown in the winter to evaluate their effects on soil organic C (SOC), total N (STN), and nitrate-N (NO3-N) contents under bioenergy Sorghum from 2010 to 2013. Cover crop biomass and C and N contents were greater with vetch/rye mixture than rye and the control. The SOC at 5-15 and 15-30 cm was greater with vetch/rye than other treatments under forage Sorghum and at 0-5 cm and 5-15 cm was greater with vetch/rye and vetch than rye or the control under sweet Sorghum. The STN at 5-15 cm was greater with vetch/rye and the control than rye under forage Sorghum and at 0-5 and 5-15 cm was greater with vetch/rye and rye than the control under sweet Sorghum. Both SOC and STN at all depths increased linearly from 2010 to 2013, regardless of cover crops and Sorghum species. The NO3-N content at all depths varied with cover crops from 2011 to 2013. Bicultural cover crops, such as hairy vetch/rye mixture, have greater potential to sequester C and N than monocultures, such as hairy vetch and rye, or no cover crop due to greater crop residue returned to the soil under bioenergy Sorghum where aboveground biomass is harvested for bioenergy or feedstock.