Thursday, November 8, 2007 - 8:45 AM
348-2

Comparison of the Field Decomposition of Cover Crops Biomass.

J. Hoorman, The Ohio State University Extension Center at Lima, 1219 W Main Cross, Findley, OH 45840, Y. Raut, The Ohio State University South Centers, 1864 Shyville Road, Piketon, OH 45661, and Khandakar Islam, Ohio State University - OARDC, OSU South Centers, 1864 Shyville Rd, Piketon, OH 45661-9749.

Field decomposition of incorporated cover crops residues is important to recycle and provide nutrients in the soil for growing agronomic crops. The objective of this study was to compare the field decomposition of various cover crops residues under no-till condition. Annual ryegrass, Austrian winter peas, Coriander, Cowpeas, Crimson Clover, Hairy Vetch, Jumbo Latino Clover, Mammoth Red Clover, Medium Red Clover, Sudan-Sorghum grass, Spelt, Red Clover, and White Clover were allowed to grow in 2002-2006. The experiment was laid-out in the field in randomized complete design with 3 replications. A 200 g composite fresh aboveground biomass sample from each replicated plot was taken in 4 nylon mesh bags and placed in close contact with the field soil. Mesh bags were collected from the field every 3 months, weighted, and oven-dried to calculate for temporal loss of residues. On average, a significantly greater decomposition of residues was found for winter pea (>89%) and lower decomposition rates for spelt (52%) and Sudan-sorghum grass (46%) residues. Within first 3 months, significantly greater decomposition was found for Clover, winter peas, Cowpeas, Hairy vetch than Ryegrass, coriander, spelt, and Sudan-sorghum grass residues, respectively. However, net difference in residue decomposition between 3 and 6 months was higher for coriander and clover than spelt and Sudan-sorghum grass. Cowpeas, Hairy vetch, and winter pea residues decomposition were significantly higher than Sudan-sorghum grass. The net difference in residue decomposition between 6 and 9 months was highest for ryegrass and lowest for clover. The net difference in residue decomposition between 9 and 12 months was highest for spelt and lowest for clover. On average, leguminous cover crops had a faster and higher decomposition rates than grasses used as cover crops. Results suggest that field decomposition of cover crop residues depends on C:N ratios, soil temperature and amount of rainfall. 

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