Phosphate-solubilizing bacteria as biofertilizers for upland rice

Rice is an important cereal in the basic diet of approximately one-third of the world’s population. The inoculation of seeds with solubilizing bacteria provides a source of P, thereby reducing the need for added inputs to the crop. Soil bacteria with the potential to solubilize phosphates were evaluated in greenhouse and field trials in a 4 × 3 factorial scheme for treatments, with 4 replications. The treatments consisted of a combination of four doses of P (0, 23.3, 46.6, and 70 kg ha?1), based on the use of 0, one-third, two-thirds, and full dose for upland rice, with the inoculation of three isolates of phosphate-solubilizing bacteria (AAC01 – Pantoea sp.; AAC02 – Enterobacter sp.; and AAC04 – Klebsiella sp.). In the greenhouse experiment, AAC02, together with a dose of 46.6 kg ha?1 of P, increased soil basal respiration (SBR) and shoot fresh mass. AAC01 increased soil basal respiration linearly up to 70 kg ha?1 of P and increased root fresh mass by 46.6 kg ha?1. In the field experiment, the P doses increased the P content of rice grains, roots, shoot dry mass, and plant height. AAC04 associated with 46.6 kg ha?1 provided equivalent levels of P in the soil and leaves, and P levels in the grains were higher than those in non-inoculated plants fertilized with 70 kg ha?1 of P. The AAC04 treatment yielded significant gains in both greenhouse and field experiments, with an approximately 33% reduction in phosphate fertilization, resulting in a greater number of panicles per square meter and full grains per panicle. Based on these findings, we recommend AAC04 as a biofertilizer to ensure environmentally healthier rice production in the future.