Qualidade do solo na cultura do arroz cultivado em várzea roraimense

Abstract

The search for sustainable agriculture has promoted the development of research in the soil field aimed at understanding the behavior that soil presents in response to different managements and crops. A large number of researchers has focused its efforts on identifying soil properties that are more efficient in inferring soil quality due to soil changing as result from use and management. The aim presented in this study was to evaluate the soil quality by chemical properties, soil microbiological and biochemical in an area with waterlogged rice cultivation under different years of cropping. The areas have the following rice cultivation times (1, 3, 8, 13 and 25 years) compared to a nature area (reference). Composite samples with four replications were collected at 0-10 cm depth. They were separated into two sub-samples, one for chemical analysis and one for microbiological and biochemical analysis, which were stored under cooling. In the laboratory the chemical attributes evaluated were: soil organic carbon (SOC), total nitrogen (TN), P available, K+, Ca2+, Mg2+ exchanges, Al3++H+ exchanges and pH, and calculated the CEC, and C/N ratio. The microbiological attributes were: microbial biomass carbon (MBC), microbial respiration (MR), calculated the CO2 coefficient (qCO2) and microbial coefficient (qMIC). The enzymes activities of acid phosphatase and urease were evaluated. The different years of rice cultivation were significantly different from the nature area in most of the soil indicators assessed, with higher expressivity, especially to SOC, NT, P, CBM and acid phosphatase variables. In the principal component analysis was observed the formation of two main groups of components (CP). SOC, C-BMS and NT were the main variables of the CP1, the acid phosphatase indicators, Mg2+ and P were the variables of greater expressiveness in CP2. The abrupt shift in soil quality from nature area converted to rice cultivation decreased the soil quality, but after 8 years of rice cropping the soil presented an improvement in soil quality.