Crop tillage, soil depth, and their influence on extracellular enzyme activities

Abstract

Agricultural practices can alter both physicochemical properties and soil microbial parameters, modifying the dynamics of soil biochemical functioning and, consequently, nutrient cycling. This study evaluated the effect of land use on chemical and biochemical attributes, and relationships between environmental variables. We used a sampling design to collect soil samples at different depths in different agroecosystems. Soil samples from natural ecosystems (native Cerrado) and agroecosystems (cotton and sugarcane cultivation) were collected at 0–0.1 m, 0.1–0.2 m, 0.2–0.5 m, and 0.5–1.0 m from 12 areas in the State of Goiás, Brazil. Twelve chemical properties and two biochemical attributes (enzyme activity and microbial biomass carbon) were evaluated using a generalized linear model of variance and Tukey’s test with three factors: correlation between all soil attributes, multiple regression between soil attributes, and biochemical variables. Soil chemical and biochemical attributes were significantly affected by variable depth (p<0.05). Most of the metabolic activity in the soil occurred at 0 to 0.2 m, independent of land use class. Seasonality also affected enzyme activity in the soil, with higher activity during the rainy season. In contrast, microbial biomass carbon, an attribute generally related to organic matter and carbon mineralization, did not vary significantly with different soil depths and seasons. Thus, enzyme activity is an important indicator of soil fertility variations and is more sensitive than chemical and microbial parameters