Abstract
The aim of this study was to evaluate P availability, P and C contained in the microbial biomass, and enzymatic activity (acid phosphatases and β-glucosidases) in a Nitisol with the application of mineral and organo-mineral fertilizers. The experiment was performed in a protected environment with control over air temperature and soil moisture. The experimental design was organized in a "5 x 4" factorial arrangement with five sources of P and four times of soil incubation. The sources were: control (without P), triple superphosphate, diammonium phosphate, natural Arad reactive rock phosphate, and organo-mineral fertilizer. The experimental units consisted of PVC columns filled with agricultural soil. The columns were incubated and broken down for analysis at 1, 20, 40, and 60 days after application of the fertilizers. In each column, samples were taken at the layers of 0-2.5, 2.5-5.0, and 5.0-15.0 cm below the zone of the fertilizers. The application of soluble phosphates and organo-mineral fertilizer temporarily increased P availability in the zone near the fertilizers (0-2.5 cm), with maximum availability occurring at approximately 32 days. Microbial immobilization showed behavior similar to P availability, and the greatest immobilizations occurred at approximately 30 days. The organo-mineral fertilizer was not different from soluble phosphates.
Highlights
Most Brazilian soils are highly weathered and exhibit great capacity for the adsorption of phosphorus (P), such as the Nitisols
Temporal variation was quadratic in the cases of triple superphosphate, diammonium phosphate, and organo-mineral fertilizer (Fig. 2a)
At 20 days, the P availability increased, and the sources of P were divided into two groups: triple superphosphate = diammonium phosphate = organo-mineral
Summary
Most Brazilian soils are highly weathered and exhibit great capacity for the adsorption of phosphorus (P), such as the Nitisols. Conte et al (2002) and Rheinheimer et al (2008) affirm that stimulating the microbial biomass of the soil by adding carbon (C) and P could increase the immobilized P content in the biomass, preventing its adsorption to the soil, and increasing the efficiency of phosphate fertilization. After the death of the microorganisms, the microbial P would be mineralized and gradually released in the soil solution This behavior would delay adsorption and would increase the probability of the nutrient use by plants, as long as there was synchronism between the mineralization of microbial P and the uptake by plants (Conte et al 2002, Martinazzo et al 2007)
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