Atividade enzimática do solo em sistemas de manejo da Carnaúba (Copernicia prunifera) no bioma Caatinga

Abstract

The Northeast of Brazil is inserted under the domain of the Caatinga biome, whose intrinsic vegetation contributes to the development of the region. Among the diversity of plant species, the Carnaúba (Copernicia prunifera) stands out, the k-strategist character allows the palm tree adaptability to saline soils, making it a useful plant in management plans for revegetation of these areas. For this reason, the rational management of the palm tree is related to the conservation of the species. For this, the biological processes comprise the basis for soil health and quality. Soil enzymes are sensitive and efficient indicators for assessing environmental variations, effectiveness of the types of management employed in agricultural systems and environmental monitoring. Considering the economic, cultural and scarce scientific literature on the Caatinga ecosystem, the present work sought to investigate the influence of different types of management on soil enzyme activity in carnauba areas in the municipality of Caucaia CE. Enzymes related to the cycles of the nutrients Carbon (C), Sulfur (S), Phosphorus (P) and Nitrogen (N) were analyzed, being: β-glucosidase, arylsulfatase, acid phosphatase and urease, respectively. Soils from 4 distinct areas were studied: 1. Unmanaged and flooded carnauba area (A1), 2. Unmanaged and unflooded area (A2), 3. Managed and flooded carnauba areas (A3), and 4. Managed and unflooded area (A4). In each of the areas, soil samples (bulk soil) were collected, about 15 cm from the base of the stem, from 6 carnaubas of similar size, being evaluated 24 samples (4 treatments x 6 repetitions). The enzymatic determinations followed the methods based on colorimetric measurement after the release of NH4+ (for Urease) and ρ nitrophenol for the other enzymes, when they were previously incubated in specific buffers and corresponding temperatures. The activity of β-glucosidase was significantly lower in A1, when compared to the other treatments. For arylsulfatase, treatment A2 was significantly higher than treatments A1 and A4, which did not differ significantly from each other, but mainly from A3. The activity of acid phosphatase was significantly higher in A2 compared to the other treatments. As a conclusion, it was demonstrated that: the palm trees in the A2 area due to the ecological preservation and, mainly, the non-flooding of the soil, are able to potentiate enzyme activity, overcoming the plants of Treatment 1; the adequate management of carnauba, regardless of soil conditions, for A3 and A4 did not cause major differences related to the enzyme of the C cycle. This study reinforces the importance of adequate soil management and native species of the Caatinga to sustain their ecological functions, such as the cycling of C, S, P and N, given the participation of these enzymes in the mineralization of organic material of each associated with these cycles.