Atributos químicos e biológicos de um neossolo regolítico cultivado com milho sob influência da aplicação de biofertlizantes fosfatados

Abstract

In tropical conditions, the availability of phosphorus (P) in the soil for plants is one of the main limiting factors. One of the alternatives to reduce the cost of fertilization is the use of natural phosphate rock. The activity of phosphate solubilizing microorganisms is critical to use of phosphate fertilizers of low solubility. This work aimed to evaluate the changes introduced in the chemical and biological attributes of a Entisol cultivated with corn, by the application of water-soluble phosphate fertilizer, Gafsa rock phosphate and phosphatic biofertilizers. The experiment was conducted in two stages. The first step was performed to produce biofertilizers and biofertilizers in the second stage that showed better solubilization of phosphorus were used in growing corn in pots in the greenhouse The biofertilizers: poultry manure + Gafsa Phosphate (CA + FG) and bovine manure + Gafsa Phosphate (EB + FG), were produced in plastic pots with a capacity of 1000 mL over a period of 60 days. The experimental design was completely randomized in a 6 x 2 factorial with four replications, six sources of phosphorus: Gafsa Phosphate (FG), simple superphosphate (SS), poultry manure + Gafsa Phosphate (CA + FG), bovine manure + Gafsa Phosphate (EB + FG), poultry manure + single superphosphate (CA + SS), bovine manure + simple superphosphate (EB + SS) and two application forms: Incorporated (I) and surface (S). The parameters evaluated were: dry mass of roots and shoots, chemical characterization of soil and plant, biological indicators of soil phosphatase enzyme activity and identification and quantification of organic acids in the soil and rhizosphere. The results were submitted to analysis of variance and the averages of the data separated by the Scott-Knott test, at 5% probability. The lower content of P in the soil was determined by the addition of FG (8.42 mg kg-1). Fertilization with EB + FG and CA + FG so embedded produced the highest dry matter (MSPA), 10.55 and 9.20 g plant-1. The EB + FG showed the highest values of microbial biomass carbon (C-MBC), total organic carbon (COT) and microbial quotient (qMIC) and lower values of basal respiration (C-O2), metabolic quotient (qCO2), water-soluble carbon (CSA), indicating high stability of the microbial activity. The highest activity of alkaline phosphatase was verified by treating EB + SS, while the highest acid phosphatase activity was verified by treatment with EB + FG. The samples analyzed in the gas chromatograph detected the presence of acetic acid, propionic acid and butyric, with acetic more significant. In samples from the rhizosphere of corn plants were identified three low molecular weight acids, acetic, propionic and butyric acids, but in much higher concentrations than in the soil.