Bioensaios com fósforo e indicadores químicos, microbianos e bioquímicos do solo, em áreas sob cerrado, pinus e plantio direto

Abstract

The microbial activity in soil has great importance in regulating the processes of transformation of carbon and nutrients, like phosphorus. However, the microbial activity is strongly linked to agricultural practices in land use. In Chapter I, the study aimed to compare three systems of land use in relation to the response of microbial metabolic activity, while the addition of phosphorus and glucose in dystrophic savannah stage. The systems of land use were: area of Cerrado (CE), pine forest with trees of 32 years (PF) and no-tillage (NT) at 11 years. The soil samples were collected at a depth of 0-10 cm, in January, June and December 2008, and were assessed for released carbon (C-CO2) by microbial activity and organic carbon (TOC), carbon microbial biomass (MBC), total glucose (TG) and metabolic performance. The addition of increasing doses of P increased soil respiration of the three systems use. P addition increased microbial activity (respiration rate, an increase in microbial biomass) and metabolic performance (efficiency of utilization of glucose), especially when added together with a carbon source (glucose). The use of tests of soil incubation with added nutrients may be used to characterize the potential for metabolic response of soils with different usage characteristics and are useful in working knowledge of soils from the cerrado. In Chapter II, the objective was to evaluate the impacts of use phase savanna Oxisol on the biochemical properties and soil microbes in the three areas reported in Chapter I, collected at the same depth (0-10 cm) and at the same times of the year 2008 (January, June and December). The soil samples were evaluated for: total organic carbon (TOC), microbial biomass carbon (MBC) and enzyme activity (β-glucosidase, dehydrogenase and acid phosphatase, neutral and alkaline). The systems use and the times of sampling of soil affected the biological indicators and forms of soil organic carbon. Among the systems of land use, the NT is highlighted when comparing the respiratory activity, TOC, MBC and activity of dehydrogenase, β-glucosidase and phosphatase. The use of microbial and biochemical indicators shown to be sensitive to changes in land use and is therefore indicated in studies of this nature. The results of principal component analysis (PCA), through the joint assessment of microbiological and chemical indicators of soil showed that the NT was superior to CE systems and especially PF.