Uso de indicadores biológicos para avaliação da qualidade do solo sob cultivo de culturas agroenergéticas em Pedro Afonso, Tocantins

Abstract

Soil is an essential natural resource for life maintenance, but intensive and incorrect uses have accelerated the degradation process of this resource, which compromises the agricultural systems and environmental sustainability. However, management practices including low soil disturbance and cropping systems with high C addition to the soil appear to be among the most important to restore soil quality. Thus, the attributes, which have an intimate relationship with the soil organic matter, such as soil microorganisms, have the greatest potential to be used as indicators of soil quality. After that, in this study we aimed to evaluate the soil microbial communities dynamic under differents agro-energy cropping systems, such as sugarcane, soybeans and corn, and we used the soils under native Cerrado as reference. The soil samples were collected on commercial fields from Brejinho Farm (in Pedro Afonso municipality, Tocantins State), considering two depths, 0-5 cm and 5-10cm. We determined the microbial biomass carbon, total organic carbon, microbial respiration, and we calculated the metabolic quotient (qCO2) and the microbial quotient (qM). The microbial biomass carbon and microbial respiration were changed by the different cropping systems. The sugarcane cropping system, which involved conventional tillage, without crop rotation, suffered greater reduction of microbial activity compared with the cropping systems under no-till. Thus, to maintain and increase soil quality, it is necessary to expand the conservation management techniques adoption that provide less soil disturbances and increase soil aggregation, allowing water retention and maintenance of soil moisture, and with crop rotation as a source of C addition to soil and microbial diversity.