Carbon, microbial biomass carbon and enzyme activity of a soil under natural forest, grassland and cotton culture

摘要

This work was carried out to evaluate the alterations in organic-C, microbial-C and in the activities of the enzymes cellulase and amylase in soil samples of a Rhodustalf collected in the summer at 0-10, 10-20 and 20-30 cm depths, under natural forest (NF), 20 (P20) and 25 (P25) year old pastures and 10 year old cotton cultivation. Organic-C and microbial-C contents and the amylase and cellulase activities were very similar in NF, P20 and P25. Reduction of 18% in organic-C was observed in P25, when compared to NF at the depth of 0-10 cm. The conventional cultivation of cotton for 10 years caused reductions from 54 to 81% in microbial-C and in the activity of amylase in relation to NF, in the three sampling depths, presenting a microbial-C/organic-C ratio smaller than 1.0%, which suggests reduced organic matter dynamics. Microbial-C was positively correlated to amylase and cellulase activities at the three depths, but the organic-C was only correlated to the analyzed parameters at the 0-10 cm depth.