Ricardo Franci Gonçalves, Regiane Pereira Roque
Abstract Phosphorus recovery from human waste is a cornerstone of circular nutrient management, yet the behavior of recovered phosphorus minerals in highly weathered tropical soils remains poorly understood. This study evaluated the agronomic performance and phosphorus dynamics of human urine-derived struvite (HU-Struvite) in a tropical Oxisol cultivated with maize (Zea mays). HU-Struvite achieved substantial shoot biomass production under tropical soil conditions, although monoammonium phosphate (NH₄H₂PO₄) generally produced higher shoot dry mass at the highest phosphorus application rates. More importantly, HU-Struvite maintained substantially higher residual Mehlich-1 extractable phosphorus after cultivation, indicating sustained labile phosphorus availability and reduced phosphorus immobilization in the highly weathered soil. By integrating plant response, phosphorus uptake, residual soil phosphorus, and phosphorus fractionation behavior within a single soil–plant system, the study demonstrates how the controlled-release characteristics of urine-derived struvite influence phosphorus retention under tropical conditions. These findings suggest that controlled phosphorus release may mitigate rapid fixation associated with iron and aluminum oxides while sustaining plant-available phosphorus over time. Our results demonstrate that, during the early vegetative growth of maize, urine-derived struvite is a promising strategy for improving phosphorus-use efficiency and advancing circular nutrient management in tropical agricultural systems.