Effect of cattle dung on soil microbial biomass C and N in a permanent pasture soil

The effects of cattle dung on soil microbial biomass (SMB) C and N were examined in grazed grassland. In a field study using artificially placed pats no effects on the SMB could be demonstrated even though concentrations of mineral N increased (P < 0.001) in the underlying soil. When dung was mixed with grassland soil under controlled conditions the size of the SMB increased (P < 0.001). Respiration rate also increased (P < 0.001) and specific respiration (q) was higher (P < 0.05) in soil treated with beef cattle dung than in that treated with dairy cow dung. The presence of added inorganic N (NH4NO3) had no further effect. The potential effects of dung on the SMB which were demonstrated under controlled conditions may therefore be diluted in field conditions.