Agronomic effectiveness of a granular poultry litter-derived organomineral phosphate fertilizer in tropical soils: Soil phosphorus fractionation and plant responses

Abstract

Production of organomineral phosphate fertilizers (OMF) from poultry litter (PL) has been suggested to reduce the dependence on phosphorus (P) reserves. Here, we compared a granular PL-derived OMF to triple superphosphate (TSP) in two contrasting tropical soils (Oxisol and Entisol) by using isotope dilution with 32P. Our study aimed to gain insight into soil P fractionation, and P availability to maize plants achieved by P fertilization (0, 25, 50, 75 and 100 mg kg−1 of soil), in order to investigate the agronomic effectiveness of OMF. Despite μ-XRF maps revealing that the mixture of PL and TSP as OMF resulted in P hot spots disseminated in a low-concentration background, whereas for the TSP treatment higher P concentration was uniformly distributed in the granules, there was no difference in maize yield and fertilizer P recovery (%R) between P sources in both soils. In the Oxisol, there was no difference between fertilizers in any of the soil P pools, but larger readily phytoavailable P and smaller moderately labile P fractions were obtained with OMF. In the Entisol, the labile P pool was larger with TSP. Nevertheless, acid and alkaline phosphatase activity and microbial biomass were affected by P rate and P source. The results show that OMF is an effective substitute for conventional phosphate fertilizers, since OMF promotes P recovery, plant P uptake and biomass yields compared to those obtained with TSP.