Microrganismos como indicadores de alteração do uso do solo em sistema integração lavoura-pecuária

Abstract

The present work aimed the quantitative and structural characterization of microorganism activity by the quantification of phospholipids using the PLFA (Phospholipid - Derived Fatty Acids) technique in a soil from Cerrado biome under crop-farming system determining the relation between the changes in the tillage and the activity and diversity of microorganisms in the soil. These factors were related with physical and chemical soil variables. In this study, a typical acric Red Latosol with clayey texture under crop-farming integration was targeted, being samples collected from one year formation pasture, three years formation pasture and forest as reference. The sampling was performed on March and August 2013. Multivariate analysis using permutation test (based on 1000 permutations) and the Principal Component analysis regarding Instrumental Variables (PCAV) were used. The tillage and the management applied on the soil under crop-farming system affected the distribution, the structure and the physiological conditions of the microbial population in the soil. The distribution of these organisms was higher in pasture areas comparing to forest area, where organisms presenting opportunistic habit were predominant in contrast to forest area where the dominant presence was of strategist organisms. The difference in the time of pasture introduction has not influenced the structure of the microbial community, once that the distribution was the same in both studied areas. The stress index were higher in forest site than in pasture sites in both periods, probably due to the naturally low fertility level of this soil as much as its high acidity. The soil fertility data could explain the microbial variation under rainy and dry seasons. The organic matter in pasture sites was similar independent of the formation time. In the forest area, there is a higher contrast regarding the organic matter availability, which can explain the high heterogeneity on this area comparing to pasture areas.