EFFECT OF THE ADDITION OF COMPOST ON THE BEHAVIOR OF THE PHOSPHATASE AND CELLULASE ACTIVITY IN AGRICULTURAL SOIL

Quality of soil is determined by microbiological, biochemical, physical and chemical characteristics and it is very important for agricultural systems, due to it defining the use capacity of the soil, sustainable management and agricultural productivity. The goal of this assay was to evaluate, the behavior of cellulase and phosphatase activity in relation with % organic oxidizable carbon (%OOC) as quality indicators in a soil destined for intensive cultivation of oil palm. The assay was divided into 5 treatments (compost, compost + chemical fertilizers, compost + inoculant, inoculant + chemical fertilizers and compost + inoculants + chemical fertilizers) using the chemical fertilization as control. The soil enzyme activities were evaluated over 8 months. It was shown that the effect of compost, a phosphate solubilizing-phosphatase-producing bacterial inoculant (PSB) and chemical fertilizers were factors that affect those enzymatic activities. It was found that the cellulolytic activity did not have statistically significant differences among treatments (p=0.73), behavior which was attributed to the low %OOC of the compost (10.9%) and the high organic carbon level of the soil controls, showing no differences in %OOC between treatments (p=0.93). Regarding phosphatase activity, it was significantly higher in soils treated with compost and inoculant (p=0,0001), showing that this activity was enhanced by the increasing populations of phosphatase-producing microorganisms and by the organic P content in the compost. Finally, it was possible to determine a positive correlation between organic carbon content with cellulolytic (R²=0.48) and phosphatase (R²=0.62) activity in soil, which confirms that quantification of these enzymes serves as quality indicator for fertility in agricultural soils. Similarly, it was possible to demonstrate that the addition of microbial inoculants with phosphatase activity increases the activity of this enzyme and the addition of traditional fertilizers favors the soil enzyme activity.