BURNING, TILLAGE AND HERBICIDE EFFECTS ON THE SOIL MICROFLORA IN A WHEAT SOYBEAN DOUBLE-CROP SYSTEM

As sustainable crop management systems are developed, an assessment of the effects of these practices on the soil microflora is essential to ensure maximum productivity. A 3-year field study was established to determine the effects of crop residue burning, no-till management and four preemergence herbicides on soil microorganisms. Numbers of actino mycetes, algae, bacteria, fungi and nitrifiers were evaluated during t he soybean [Glycine max (L.) Merrill] growing season in a wheat (Triti cum aestivum L.)-soybean double-cropping system. Residue burning and t illage had no effect on numbers of bacteria and nitrifiers. Non-distur bed (non-burned or no-till) plots had greater numbers of actinomycetes , algae and fungi 7 days after herbicide application each year, but th e increases generally did not persist through the season. Herbicide ap plication had no effect on microbial numbers. This is particularly imp ortant with recent increased emphasis on protection of soil and water resources from pesticide contamination. As new management systems are developed, their effects on biological properties must be carefully as sessed, since the soil microflora play such a vital role.