Biomassa e atividade microbiana de solo sob diferentes sistemas de plantio e sucessões de culturas.

Abstract

Whereas the importance of soil microorganisms, the present study aims to evaluate the biomass and microbial activity in a Red-Yellow Ultisol, submitted to no-tillage and conventional systems and successions of corn-beans and soybean-wheat, for ten years. A Split-plot scheme in balanced completely randomized design was used, with three replications. In the plots were arranged the planting systems and, in the subplots, the crops successions. Soil samples were collected at depth 0-5, 5-10 and 10-15 cm, and the analysis were soil microbial biomass carbon, soil microorganism respiration rate and total organic carbon, and calculated the indices metabolic quotient and microbial quotient. There was no difference in the microbial biomass carbon between planting systems and crop successions in any of the depths sampled. The respiratory rate differed between crops successions at depth of 0-5 cm, with a higher value for the soybean-wheat succession. The organic carbon at depths of 5-10 and 10-15 cm was 27.1 and 37.5% higher in conventional tillage than in no-tillage, respectively. The microbial quotient at depth of 10-15 cm was better for no-tillage. It is concluded that the culture succession influences the respiration rate, mainly in a lower depth. The soybean-wheat succession provides greater microorganisms activity in the studied soil. There was no difference in biomass and microbial activity between the conventional and no-tillage system in the superficial layers of the soil, after ten consecutive years of cultivation. This may have occurred because there were no marked chemical and/or physical restrictions, such as compaction, in both tillage systems.