Nitrogen mineralization and microbial populations in cow dung, dung balls and underlying soil affected by paracoprid dung beetles

The effect of the dung beetle, Onthophagus lenzii Harold, on the decomposition of cow dung was studied with special reference to the relationship between microbial populations and N mineralization in residual cow dung, dung balls and soil beneath the dung. Two ammonification processes in the decomposition of cow dung were noted. Readily-decomposable organic N in the cow dung mineralized rapidly during the first 5 days, regardless of dung beetle activity. After 15 days, dung beetles accelerated or initiated another ammonification process in residual cow dung and dung balls. Dung beetles accelerated nitrification and fungal growth in residual dung and dung balls by producing aerobic conditions through a rapid decrease in moisture content. Organic N in cow dung fragments, particularly that buried in the upper part of the underlying soil by beetles, was mineralized and simultaneously nitrified. However, a small amount of inorganic N in cow dung diffused down to the underlying soil when dung beetles were absent. Microbial numbers in the soil were highly correlated to the organic matter concentration of the soil.