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ARS Home » Southeast Area » Auburn, Alabama » Soil Dynamics Research » Research » Publications at this Location » Publication #252769
Title: Carbon and nitrogen mineralization and persistence of organic residues under conservation and conventional tillage

Author
item MULVANEY, MICHAEL - Virginia Polytechnic Institution & State University
item WOOD, WESLEY - Auburn University
item Balkcom, Kipling
item SHANNON, DENNIS - Auburn University
item KEMBLE, JOSEPH - Auburn University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2010
Publication Date: 7/19/2010
Citation: Mulvaney, M.J., Wood, W., Balkcom, K.S., Shannon, D.A., Kemble, J.M. 2010. Carbon and nitrogen mineralization and persistence of organic residues under conservation and conventional tillage. Agronomy Journal. 102(5):1425-1433.

Interpretive Summary: A combination of high biomass cover crops with organic mulches may be an option for no-till vegetable production, but mineralization rates from these residues is lacking. Scientists with USDA-ARS located at the National Soil Dynamics Laboratory in Auburn, AL in cooperation with Auburn Univ. initiated a study to assess nutrient release rates and persistence from mimosa, lespedeza, oat straw, and soybean residues under conventional and conservation tillage. Buried residues decomposed faster than surface residues. In spring, mimosa residue contained 78 kg N ha-1 when buried the previous fall, compared to 123 kg N ha-1 when surface placed; soybean residue showed similar results (39 kg N ha-1 when buried vs. 72 kg N ha-1 when surface placed). Results were similar for lespedeza (72 vs. 101 kg N ha-1, respectively), but not for oat straw (24 vs. 26 kg N ha-1, respectively). After one year, surface placed mimosa residue mineralized 33% of initial N compared to 71% when buried, while surface placed lespedeza mineralized 36% of initial N compared to 64% when buried. Soybean residue mineralized N quickly regardless of placement (73% when surface placed vs. 87% when buried). Straw did not mineralize appreciable amounts of N regardless of placement. Carbon sequestration was enhanced when residue was surface placed compared to incorporated. This study demonstrates that residues may be utilized under conservation tillage for the enhancement of soil organic matter (SOM), C sequestration, and soil N status.

Technical Abstract: A combination of high biomass cover crops with organic mulches may be an option for no-till vegetable production, but mineralization rates from these residues is lacking. The objective of this study was to assess nutrient release rates and persistence from mimosa, lespedeza, oat straw, and soybean residues under conventional and conservation tillage. The experiment was conducted in Tallassee, AL using litterbag methodology in a split-plot design (main plots: two tillage systems; subplots: four residue types). Buried residues decomposed faster than surface residues, particularly in the labile portion. In spring, mimosa residue contained 78 kg N ha-1 when buried the previous fall, compared to 123 kg N ha-1 when surface placed; soybean residue showed similar results (39 kg N ha-1 when buried vs. 72 kg N ha-1 when surface placed). Results were similar for lespedeza (72 vs. 101 kg N ha-1, respectively), but not for oat straw (24 vs. 26 kg N ha-1, respectively). After one year, surface placed mimosa residue mineralized 33% of initial N compared to 71% when buried, while surface placed lespedeza mineralized 36% of initial N compared to 64% when buried. Soybean residue mineralized N quickly regardless of placement (73% when surface placed vs. 87% when buried). Straw did not mineralize appreciable amounts of N regardless of placement. Carbon sequestration was enhanced when residue was surface placed compared to incorporated. This study demonstrates that residues may be utilized under conservation tillage for the enhancement of soil organic matter (SOM), C sequestration, and soil N status.