MICROBIOLOGICAL PROPERTIES AND OXIDIZABLE ORGANIC CARBON FRACTIONS OF AN OXISOL UNDER COFFEE WITH SPLIT PHOSPHORUS APPLICATIONS ANDIRRIGATION REGIMES

摘要

Phosphorus fertilization and irrigation increase coffee production, but little is known about the effect of these practices on soil organic matter and soil microbiota in the Cerrado. The objective of this study was to evaluate the microbiological andoxidizable organic carbon fractions of a dystrophic Red Latossol under coffee and split phosphorus (P) applications and different irrigation regimes. The experiment was arranged in a randomized block design in a 3 x 2 factorial design with three split Papplications (PI: 300 kg ha~(-1) P_2O_5, recommended for the crop year, of which two thirds were applied in September and the third part in December; P2: 600 kg ha~(-1) P_2O_5 , applied at planting and then every two years, and P3:1,800 kg ha~(-1) P_2O_5, the requirement for six years, applied at once at planting), two irrigation regimes (rainfed and year-round irrigation), with three replications. The layers 0-5 and 5-10 cm were sampled to determine microbial biomass carbon (MBC), basal respiration (BR), enzyme activity of acid phosphatase, the oxidizable organic carbon fractions (Fl, F2, F3, and F4), and total organic carbon (TOC). The irrigation regimes increased the levels of MBC, microbial activity and acid phosphatase, TOC and oxidizable fractions of soil organic matter under coffee. In general, the form of dividing P had little influence on the soil microbial properties and OC. Only P3 under irrigation increased the levels of MBC and acid phosphatase activity.