The different physiognomies and soil conditions across the Cerrado gradient may influence soil microbial biomass. The present study evaluated the soil microbial biomass and enzyme activity across a preserved Cerrado gradient and correlated these with environmental conditions. The site, sampling period and their interaction influenced soil microbial biomass and activity. Soil conditions, i.e., chemical and microclimatic properties, varied across the Cerrado gradient and influenced soil microbial biomass and activity. The highest and lowest values for microbial biomass and enzyme activity were found in Cerradao and Campo graminoide, respectively, during both seasons. Multivariate analysis showed that the sites were clearly separated into different groups, indicating that distinct physiognomies and environmental conditions influenced soil microbial biomass and enzyme activities.

The use of different legume species, as green manure, may affect differently soil biological and chemical properties. The aim of this study was to evaluate the effect of four legumes species used as green manure on soil biological and chemical properties in short-term. We evaluated the following legume species: Crotalaria, Cajanus, Mucuna and Canavalia. The study was arranged in a completely randomised design with four replicates. The plants were incorporated into the soil (0-20 cm) by harrow and the chemical and biological properties were evaluated 30 and 60 days from the incorporation. Soil chemical and biological properties showed different trends according to legume species used. Soil P and K contents were highest in plot with Crotalaria, while soil Ca content was highest in plot with Mucuna. Soil microbial biomass was higher in plot with Mucuna as compared with others green manure species. Fluorescein diacetate hydrolysis was higher in plots with Mucuna and Canavalia than the others plots. Our results supported the hypothesis that different types of legume used as green manure affect differently the biological and chemical properties of soil. In this case, Mucuna was more effective to improve soil biological properties, while Crotalaria seems to be more efficient in the improvement of chemical properties.

The field study to evaluate the changes in soil chemical properties of TypicQuartzipsamment has been conducted from conventional to organic farming system in Piauí state, Northeastern Brazil. Three areas were were selected: organic (ORG) and conventional (CNV) farming system with "acerola" (Malpighia glabra L.) and native vegetation (NV). The soil samples were collected in the 0-10, 10-20 and 20-40 cm depths to evaluate soil pH, H + + Al 3+ , total organic carbon (TOC), exchangeable K + , Ca 2+ , Mg 2+ , available P, cation exchange capacity (CEC) and base saturation (BS). The soil in ORG showed higher pH values, TOC and available P contents than CNV system, in all depths. CEC and BS values in ORG were higher than CNV in the 0-10 and 10-20 cm depths. The agricultural practices in ORG provide high increase in soil pH, TOC and P content.