Dung Decomposition and Microbial Dynamics Within Dung and the Underlying Soil in a Pasture: Effects of Corn Silage Supplementation

ABSTRACT

Cow dung serves as a nutrient source in pastures mainly through decomposition by microorganisms, whose abundance and composition can influence nutrient concentrations and microbial biomass in the underlying soil during this process. The primary objective of this study was to clarify the microbial dynamics within both dung and the underlying soil during dung decomposition and to examine the effects of corn silage (CS) supplementation on these processes. Two types of dung, one from dairy cows fed pasture forage only (PO) and the other from cows fed pasture supplemented with CS, were deposited on the pasture. Changes in the disappearance of chemical components, microbial biomass, and community composition were monitored over 70 days in the dung and underlying soil (0–5‐cm depth). Microbial properties were assessed using phospholipid fatty acids (PLFAs). By Day 70, the remaining masses of dung organic matter ( p  < 0.1) and neutral detergent fiber ( p  < 0.05) were lower in the CS than in the PO treatment. Microbial biomass within the dung increased over time in both treatments ( p  < 0.01). By Day 70, the CS dung was higher in the biomass of gram‐negative bacteria ( p  < 0.05), fungi ( p  < 0.01), and arbuscular mycorrhizal fungi ( p  < 0.05) than the PO dung. Differences in dung chemical properties also influenced the soil nutrient dynamics beneath the dung patches. The soil nitrate‐nitrogen content was higher in the PO treatment ( p  < 0.05), whereas the available phosphate content was higher in the CS treatment ( p  < 0.01). Overall, differences in the chemical properties of cow dung affected the microbial biomass within the dung, thereby altering the decomposition rate of dung in grazed pastures. Differences in the chemical properties of cow dung affected the soil nutrient content beneath the dung but had no influence on soil microbial biomass.