Effect of legume green manuring on microbial populations and activity in a Brown loam

Abstract

In a seven-year plot experiment, conducted on a Brown Chemozemic loam at Swift Current, SK to evaluate four annual legumes for fallow (F) replacement green manuring (GM), the surface soil (0-10 cm) under wheat (W) stubble was sampled after 3 GM-W vs F-W cycles and 6-yr of continuous wheat (Cont W) cropping for soil biological analyses. Despite severe soil desiccation prior to sampling (in late fall 1990), the residual effects of all GM legumes on microbial populations and activities were very positive. Green manuring had improved the quantity and quality of soil organic matter as much as under N- and P-fertilized Cont W. The previous short-term legume growth and incorporation caused microbial populations to shift toward greater metabolic activity with increased respiration and enhanced enzyme levels.