Granulated Organomineral Fertilizer Based on Poultry Litter As Alternative of Phosphorus Fertilization in Maize.

Phosphorus (P) is one of the most important nutrients for plants. In tropical regions, in general, most of soils have low P-availability, as well as high P adsorption capacity due these soil are rich in iron and aluminum oxyhydroxides. In addition, mineral P reserves in the world are finite. In this sense, the search for technologies in order to improve the efficiency of P fertilization by increaseing crop productivity and extend the lifespan of mineral reserves is necessary. In this context, the use of phosphate organomineral fertilizers may be a interesting aternative. This study was aimed to evaluate the response of maize plants subjected to P rates of mineral and organomineral fertilizers. The experiment was carried out in greenhouse condition with pots filled with 5 kg of  a Typic Hapludox at CENA/USP, in Piracicaba, Brazil. The experimental design was completely randomised, accounting four replicates, set up in a 2×4+1 factorial scheme. The P sources used were: Triple superphosphate (TSP) and, Granulated organomineral fertilizer (OMF). The P rates used were: 0, 25, 50, 75 and 100 mg kg^-1 soil. The OMF is based in poultry litter plus TSP. At 50 days after sowing, maize plants were harvested and dried at 65°C to determine shoot dry weight (SDW). The data were submitted to ANOVA and the means were compared by Tukey test and regression (α=0.05). Moreover, means were contrasted with the control by Dunnett test. The production of SDW was significantly influenced by P rates in both P sources. Treatments with both fertilizers resulted in higher yields than control (p≤0.01). Therefore, P fertilization limits plant growth. Until the rate of 50 mg kg^-1, no differences were found in the production of SDW comparing TSP and OMF. However, from this rate, dry matter yield achieved by OMF source was 7,25% higher than TSP.