Straw and Tillage Management Practices in Soybean-Wheat Double-Cropping

Managing straw residue in wheat (Triticum aestivum L.)-soybean [Glycine max (L.) Merr.J double-cropping systems can be a problem, and many management systems are currently being used. Type of tillage used is, to some extent, determined by the straw management practice. In this study, five tillage-straw management practices were studied on Brooksville silty clay (fine, montmorillonitic, thermic Aquic Chromudert) for 4 years. Only 3 years' data are reported, however, since all treatments failed 1 year because of extreme drought. Objectives were to determine effects of tillage-straw management practices on (a) stand establishment, growth and yield of double-cropped soybeans, (b) surface soil organic matter content, and to (c) compare costs and net returns of the wheat-soybean systems and the monoculture soybeans. In 1 of 3 years when rain did not soon follow planting, preparing the soil by disking, whether the straw was burned or not, resulted in reduced germination and growth. During 1 year, germination was adversely affected when the straw was shredded and left on the soil surface. Yields were highest and most consistent when soybeans were no-till seeded into the burned stubble, but these yields did not differ from systems where straw was burned followed by conventional tillage or where straw was shredded followed by no-till planting. The average soybean yield was 29% less for the best double-crop practice than for monoculture soybeans (1,370 kg/ha vs. 1,927 kg/ha). Wheat yields averaged 3,384 kg/ha and were not affected by the tillage-straw management practices. Excluding a year in which all double-crop systems failed, all double-crop systems except where the wheat straw was incorporated in land preparation gave greater economic returns than monocrop soybeans. The double-crop system in which straw was burned followed by no-till seeding and cultivation, gave the greatest average net return.