Sewage sludge-based organomineral fertilizer improves phosphorus efficiency in Urochloa brizantha

ABSTRACT Sewage sludge (SS) from wastewater treatment has reasonable phosphorus (P) levels, which could be used as fertilizer in agriculture. However, SS-P content is lower than mineral fertilizers, which limits its operational application. The blend of organic and mineral material can increase the P content, formulating organomineral fertilizers (OMF) with higher P levels, enabling agricultural use. This study aimed to assess the agronomic efficiency and residual effect of organomineral fertilizers derived from SS as phosphorus sources for Urochloa brizantha. A greenhouse pot experiment was conducted to evaluate the successive cultivation of U. brizantha over eight cycles, with the following treatments: SS organic compost (SSC) powder; SSC pelletized (SSP), SSC+MAP pelletized (S+MAP) and SSC+AshDec ® pelletized (S+ASD); AshDec ® powder (ASD), monoammonium phosphate (MAP) and a control (no P). In each Urochloa cycle, height, tillering, shoot dry mass (SDM), and leaf P were evaluated. After eight cycles, the soil was subjected to P fractional analysis. Our results showed that tillering was higher in all treatments with P compared to control (No P). Shoot dry mass production in the first cycle was higher with S+MAP (21.8 g pot -1 ) than MAP (17.5 g pot -1 ), and after eight cycles, the accumulated SDM of all treatments (>140 g pot -1 ) was superior to MAP (132 g pot -1 ), except for S+ASD (118 g pot -1 ). No significant difference in plant height was observed. Total P uptake was higher in the treatments with recycled sources, however, plants fertilized with S+MAP accumulated more P during establishment, while SSC, SSP, and ASD promoted higher accumulation during 4 to 6 cycles. After eight cycles, soil labile P content was higher in treatments with OMFs compared to mineral sources, indicating a residual effect of organomineral fertilization. These results showed that SSC-derived OMFs are more efficient than conventional fertilizers if mixed with soluble mineral sources (MAP), but the same is not true with insoluble sources (ASD). Organomineral S+MAP can replace MAP, providing greater efficiency in forage establishment and a greater residual effect.