Microbial Changes Associated with Residue Management with Reduced Tillage
1980
Doran, J. W.
The effects of corn residue on soil microbiological populations for dryland corn (Zea mays L.) production in Nebraska were closely related to placement of residue and soil water and pH regimes. Populations of bacteria, actinomycetes, and fungi increased two- to sixfold as a result of mulching. The response of fungi populations to residue application was limited by competition from bacteria and actinomycetes as related to changes in soil water content and pH regimes. Counts of nitrifying and denitrifying organisms in the surface soil increased 2- to 20-fold and 3- to 43-fold, respectively, in plots receiving surface applications of corn stover. The physical, chemical, and biological characteristics of the between-row area differed dramatically from those of the within-row area with the tillplant system. The soil-water content, microbial populations, soil pH, and soil nitrate content of the between-row area were significantly higher than those within-row. Many of these differences were associated with the distribution of residue, soil, and surface applications of lime. Under more uniform moisture and soil conditions in the greenhouse, surface application of corn stover resulted in two- to fivefold increases in microbial populations. The additional responses of microbial populations to residue in the field were related to increased soil water contents. In addition, residues influenced the microbial response to application of both lime and herbicides. The application of residue reduced the inhibitory effect of herbicides on nitrifier populations. The changes in microbial ecology associated with residue management should influence decisions for alternate residue-management and fertilizer practices with reduced tillage.
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