Absolute and specific enzymatic activities of sandy entisol from tropical dry forest, monoculture and intercropping areas

Abstract

The transformation of tropical dry forests in intensive agricultural areas affects soil organic carbon with consequence in microbial and enzymatic activities, regardless of the type of use. The activities of soil enzymes (fluorescein diacetate hydrolysis dehydrogenase, β-glucosidase, arylsulfatase, urease, acid phosphatase and alkaline phosphatase), total organic carbon (TOC) and soil microbial biomass carbon (MBC) were measured in sandy entisol covered with forest, monocultures (grass, prickly-pear cactus, pepper and cucumber) and intercropping (corn and cowpea; cassava, pigeon pea and cowpea). The data showed that the TOC content decreased with land use. The quantity of MCB was increased in soil covered with monoculture and intercropping related to forest. There was a change in the different sandy entisols uses in relation to enzymatic activities. The soils with prickly-pear cactus monoculture were highest in enzyme activity, except to alkaline phosphatase. The tropical dry forest conversions in monoculture do not follow the same model of intercropping to enzyme activity. In sandy entisol, the specific enzymes activities per unit of TOC and MBC were more important in explaining differences between soils than absolute enzyme activities. We recommend the use of specific enzymes activities per unit of TOC and MBC to be used as a tool for detecting changes in sandy entisol. By multivariate analysis intercropping and forest create a similarity group related to enzymes activities, TOC and MBC, demonstrating that less intensive practices like intercropping causes less impacts on balance of biogeochemical cycles and organic matter dynamics than monoculture in sandy entisols of tropical dry forest. This is the first record of these parameters in the region and can serve as indicators to promote its use as a tool in the decision-making of the farmers to avoid soil degradation.