Biculture legume-cereal cover crops for enhanced biomass yield and carbon and nitrogen

Authors: Sainju, Upendra; WHITEHEAD, WAYNE - FORT VALLEY STATE UNIV GA; SINGH, BHARAT - FORT VALLEY STATE UNIV GA

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2005
Publication Date: 9/18/2005
Citation: Sainju, U.M., Whitehead, W.F., Singh, B.P. 2005. Biculture legume-cereal cover crops for enhanced biomass yield and carbon and nitrogen. Agronomy Journal. 97(5):1403-1412.

Interpretive Summary: Cover crops can influence soil physical, chemical, and biological properties by supplying additional plant residues which increase soil organic matter. Because soil organic matter is a key indicator of soil quality and productivity that influence crop yield and environmental quality, it is necessary to examine the type and amount of plant residues, especially carbon (C) and nitrogen (N) inputs supplied from above- and belowground biomass of cover crop species. Legume cover crops can supply N needs of the succeeding crops and therefore can reduce the rate of N fertilization. In contrast, nonlegume cover crops are more effective in increasing soil organic matter and reduce N leaching. As a result, a mixture of legume and nonlegume cover crops may supply N, increase soil organic matter, and N leaching. Little information is available about the mixture of legume and nonlegume cover crops in supplying C and N inputs and their effects on crop yields and soil and water properties. We examined C and N inputs from above- and belowground (0- to 120-cm depth) biomass of a legume (hairy vetch), nonlegume (rye), and biculture of legume and nonlegume (vetch and rye) cover crops planted without tillage in the fall of 1999 to 2001. After cover crop kill in the following spring, cotton and sorghum were planted using three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)] with three N fertilization rates (0, 60 to 65, and 120 to 130 kg N ha-1). Field experiment was conducted in a split-split plot design with three replications on a Dothan sandy loam (fine-loamy siliceous, thermic, Plinthic Paleudults) in central Georgia. Our objectives were to: (1) examine biomass yield, C and N concentrations, and C and N accumulations in the above- and belowground biomass of fall planted hairy vetch, rye, biculture of hairy vetch and rye, and winter weeds (no cover crops) in the plots planted to cotton and sorghum in the spring from 2000 to 2002, (2) evaluate the amount of C and N inputs supplied by biculture of hairy vetch and rye compared with monoculture of each species, and (3) determine the effects of tillage and N fertilization applied to previous summer crops (cotton and sorghum) on cover crop C and N inputs. Although C and N inputs from aboveground biomass of rye decreased from 2000 to 2002, inputs from above- and belowground biomass of vetch, biculture, and winter weeds (no cover crops) and from belowground biomass of rye varied by year. Except in 2002, C input from rye was greater due to higher biomass yield but N input from vetch was greater due to higher N concentration. Carbon and N inputs from biculture were similar to or greater than those from monocultures of each species in all years. Belowground C and N inputs were also greater in ST than in CT in 2000. Belowground biomass contributed 9 to 32% of the total (above- and belowground) C and N inputs and biomass at 0- to 15-cm contributed 42 to 55% of the total (0- to 120-cm) belowground C and N inputs. Biomass of biculture had similar to or higher C and N levels than predicted by biomass of monoculture based on the seed rate. Belowground biomass of cover crops can be a significant source of C and N inputs for improving soil quality and productivity besides aboveground biomass. Biculture of hairy vetch and rye can be used to supply greater C and N levels in the soil than monoculture without any species interference.

Technical Abstract: Carbon and N inputs from above- and belowground biomass of cover crops can influence soil organic matter level and therefore soil quality and productivity. We examined C and N inputs from above- and belowground (0- to 120-cm depth) biomass of a legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secale cereale L.)], and biculture of legume and nonlegume (vetch and rye) cover crops planted without tillage in the fall of 1999 to 2001. After cover crop kill in the following spring, cotton (Gossypium hitsutum L.) and sorghum [Sorghum bicolor (L.) Moench)] were planted using three tillage practices [no-till (NT), strip till (ST), and chisel till (CT)] with three N fertilization rates {0, 60 to 65, and 120 to 130 kg N ha-1). Field experiment was conducted in a split-split plot design with three replications on a Dothan sandy loam (fine-loamy siliceous, thermic, Plinthic Paleudults) in central GA. Although C and N inputs from aboveground biomass of rye decreased from 2000 to 2002, inputs from above- and belowground biomass of vetch, biculture, and winter weeds (no cover crops) and from belowground biomass of rye varied by year. Except in 2002, C input from rye was greater due to higher biomass yield but N input from vetch was greater due to higher N concentration. Carbon and N inputs from biculture were similar to or greater than those from monocultures in all years. Belowground C and N inputs were also greater in ST than in CT in 2000. Belowground biomass contributed 9 to 32% of the total (above- and belowground) C and N inputs and biomass at 0- to 15-cm contributed 42 to 55% of the total (0- to 120-cm) belowground C and N inputs. Biomass of biculture had similar to or higher C and N levels than predicted by biomass of monoculture based on the seed rate. Belowground biomass of cover crops can be a significant source of C and N inputs for improving soil quality and productivity besides aboveground biomass. Biculture of hairy vetch and rye can be used to supply greater C and N levels in the soil than monoculture without any species interference.