Bioindicadores da qualidade da rizosfera da palma sob adubação potássica e nitrogenada no semiárido paraibano.

Abstract

Palm is a roughage widely used as animal forage, due to its nutritional and physiological characteristics of adaptation and high production in semi-arid regions. However, there are limitations regarding its productive potential, requiring fertilization management to increase crop biomass production and stabilize soil organic carbon, thus exerting influence on biological activities, which in turn is an attribute of soil quality. Therefore, determining the biological attributes of the soil is extremely important to evaluate the functioning of the microbiota and monitor the quality of the soil resulting from its use and management. In this context, the biological activities of the rhizospheric soil of palm cultivated under different doses of nitrogen and potassium fertilization in the semi-arid region of Paraíba were evaluated. The experiment was carried out under field conditions, at the Rolando Enrique Rivas Castellón Experimental Farm, São Domingos-PB, at the Federal University of Campina Grande (UFCG), at the Center for Agro-food Science and Technology (CCTA). A randomized block experimental design was used, with four blocks and thirteen treatments. The treatments were arranged according to the Plan Puebla III matrix and consisted of a combination of five doses of nitrogen (7.8; 46.8; 78; 109 and 148 kg ha-1) in the form of urea, five doses of potassium (30; 180; 300; 420 and 570 kg ha-1) in the form of potassium chloride, and a control (without fertilization). 183 days after transplanting, biological attributes were evaluated, consisting of basal soil respiration (RBS), microbial biomass carbon (CBM) and metabolic quotient (qCO2). There were significant differences between the treatments used on palm, doses of N and K mineral fertilizers, which influenced microbial activities and communities. Observed the occurrence of changes in the microbiological attributes of the soil resulting from use and management. The respirometry analysis indicated changes in the biological activity of the soil cultivated with palm. The assessment of biomass carbon demonstrates that the palm area has high and intermediate rates of microbial biomass. The values observed in the metabolic quotient indicate savings in energy use. The treatments, T11 (148.0 N and 30 K) and T8 (46.8 N and 30 K), stood out for presenting higher and lower qCO2 respectively.