Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/2/2005
Publication Date: 8/2/2005
Citation: Schomberg, H.H., Endale, D.M., Calegari, A., Peixoto, R., Miyazawa, M., Cabrera, M.L. 2005. Influence of cover crops on potential nitrogen availability to succeeding crops in a southern piedmont soil. Biology and Fertility of Soils. 42(4):299-307. Interpretive Summary: Conservation tillage is used on over 40 percent of the 24 million cropland acres in the southeastern USA. Black oat and oilseed radish, major cover crops grown in Southern Brazil and Paraguay, could be used as alternatives to the traditional cover crops, crimson clover, and winter rye to help increase cropping system diversity and reduce the potential for disease and pest buildup. Researchers from the Southern Piedmont Conservation Research Unit, the University of Georgia, Instituto Agronômico do Paraná, and EMBRAPA Agrobiologia investigated the influence of these cover crops on nitrogen availability over four years at the J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA. Black oat and oil seed radish produced similar amounts of biomass with similar amounts of nitrogen as crimson clover. Rye produced more biomass than the other cover crops but nitrogen availability following rye was reduced. Release of soil nitrogen following black oat and oil seed radish was similar to that following crimson clover. Greater availability of nitrogen following black oat and oilseed radish compared to rye indicates that no adjustments should be needed in N recommendations following these cover crops in conservation tillage systems and soils in the region. Producers can save on fertilizer costs and reduce the potential for negative environmental impacts by using black oat or oilseed radish as cover crops.
Technical Abstract: Black oat (Avena strigosa Schreb) and oilseed radish (Raphanus sativus L.) could be useful alternatives to crimson clover and winter rye cover crops in the southeastern USA. Successful adoption requires understanding of their influence on N availability in conservation tillage systems. Black oat and oilseed radish were compared to crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) for effects on N mineralization from fall 1998 to 2002 at the USDA Agricultural Research Service, J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, Georgia. Rye produced 40 to 60% more biomass while N contents were similar to the other cover crops. Oilseed radish and black oat N contents were similar to crimson cover. Black oat, oilseed radish and crimson clover C:N ratios were less than 30 while rye averaged 39. Amount of N mineralized in 90 days measured with in situ soil cores was 1.3 to 2.2 times greater following black oat, crimson clover, and oilseed radish than following rye. Variation in N mineralization was greater for two years when N fertilizer was applied to summer crops. Potentially mineralizable N (N0) was not influenced by cover crop but increased following N fertilizer application. The rate of N mineralization (k) was 20 to 50% slower following rye than the other three cover crops. The larger input of rye residue with a C:N ratio greater than 30 resulted in greater N demand by soil microorganisms. Soil N mineralization dynamics following black oat and oilseed radish were more similar to crimson clover than to rye which indicates that they could be used as cover crops in the southeast without changes in N recommendations for most crops.