Changes in microbiological attributes of a red latosol under different cropping systems

Abstract

The objective of this study was to evaluate changes in microbiological attributes of soils under different growing systems. Three cropping systems were evaluated (1) no-tillage system (NTS); (2) conventional tillage system (CTS); and (3) newly scarified no-tillage system (SNTS). The three systems were maintained for 20 years. In addition, a primary forest (PF) fragment was used as a reference. Soil samples were collected at depths of 0.0-0.1 m, 0.1-0.2 m, and 0.2-0.3 m. The following variables were measured: microbial biomass carbon (MBC); soil respirometry (RESP) using the fumigation and incubation method; microbial biomass nitrogen (MBN) using fumigation and extraction; metabolic quotient (qCO2) using the RESP-MBC ratio; and number of spores (NS) of mycorrhizal fungi by plate counting of spores extracted from the soil by wet sieving. Treatments were arranged in a completely randomized block design with five replicates. The different management systems affected the soil microbiota, especially in the superficial layer of 0.0-0.1 m. At a depth of 0.0-0.2 m, the PF presented significantly higher values for all analyzed attributes, except for NS. There were no significant differences in the studied characteristics between the NTS and SNTS at the three depths, indicating that scarification performed only once in the NTS was not sufficient to produce changes in soil microbiological attributes. However, the adoption of the CTS for 20 years promoted a decrease in MBC and MBN. RESP and NS were not significantly different between the cropping systems. Principal component analysis indicated a significant difference in microbiological characteristics between the PF and the areas under management. Therefore, different growing systems change the soil microbiota, and the lower the degree of tilling (NTS and SNTS), the smaller the changes in soil microbiological attributes. Soil preparation practices used in conventional tilling negatively affect soil microbial biomass, decreasing the levels of MBC and MBN.