Tillage and manure effect on soil microbial biomass and respiration, and on enzyme activities

Application of liquid pig manure on soil for agricultural use increases the organic matter content and constitutes an important input of nutrients into the soil, increasing microbial activity through the direct addition of nutrients and microorganisms. The objective of this study was to determine the influence of both tillage and liquid pig manure application on soil microbial biomass, enzyme activities and microbial respiration in a meadow soil. The results obtained did not show any significant effect of tillage and manure on microbial biomass carbon (C) and nitrogen (N) nor on soil acid phosphatase activity. However, these treatments significantly increased microbial biomass P, urease, alkaline phosphatase and ammonification rates. The maximum microbial activity was observed in surface soil layer both under conventional tillage and zero-tillage. In fact, microbial respirations (CO 2) of bacteria and actinomycetes were higher in the surface soil and increased with the level of manure. Tillage and manure application had no significant effect on fungal respiration but interaction between tillage and manure application significantly influenced soil urease and ammonification rates. Hence, we suggested that soil microbial biomass and enzyme activities were closely correlated to the N mineralization potential, N and C mineralization rates, total amounts of C or N, soil pH, ammonification rates and soil structural stability.