Surface cover and biomass in no-tillage cropping systems as affected by crop rotation, winter cover crop, and winter weeds.
Forbes Walker, Nick P. Ryan, Don Tyler, Fred Allen, and Dan Yoder. University of Tennessee, Biosystems Engineering and Soil Science Department, 2506 E J Chapman Drive, Knoxville, TN 37996
The accumulation and maintenance of an adequate layer of surface residue is an essential characteristic of successful no-till systems. The quality and quantity of surface residue varies with cropping and management systems and the time of year. In 2002, a long-term, no-till rotational study was established at the University of Tennessee's Research and Education Center at Milan, Tennessee. The summer crops in this study (maize, Zea mays; cotton, Gossypium sp.; soybean, Glycine max) are rotated with wheat (Triticum aestivum)and hairy vetch (Vica villosa) and compared with a no cover-crop control. In April and May 2006, surface residue was assessed immediately prior to planting and several weeks post-planting for six common crop rotations: continuous corn, continuous cotton, continuous soybean, 2 year maize-cotton rotation, 2 year maize-soybean rotation, 3 year soybean-cotton-maize rotation. The percentage of residue coverage was assessed visually using a line-transect method and compared with the relative contributions to the residue biomass from previous crops, winter cover crops and winter weeds. Estimates of the organic carbon and organic nitrogen content of the biomass will be made and compared with soil carbon and nitrogen at 0 to 5 and 5 to 15 cm depths. Prior to planting, residue cover was greater than 90 percent for most rotations except for continuous cotton that was assessed at 75, 85 and 86 percent cover for the no winter cover-crop, wheat and hairy vetch (respectively). Differences in the quantity and quality of the biomass were observed between treatments. Further samples will be collected after the 2006 harvest and prior to the 2007 planting season.