EnglishThe use of biofertilizers combined with organic compost and natural sources of phosphorus may result in increased fertilizer efficiency. The aim was to evaluate the effect of the use of the filter cake with natural rock phosphate and biofertilizers on the population of microorganisms of the soil, the content of phosphorus in soil and plants and the production of dry matter of corn crop. The experiment was developed at greenhouse, using corn DKB 390 VTPRO II cultivar, sowed in pots of 5 dm3 containing Ultisol. Seven treatments were evaluated: only the soil; soil with phosphate rock (PR); filter cake; PR with filter cake; PR with filter cake and Biopack Sc®; PR with filter cake and Embrafos: FF organic Plus® and PR with filter cake and Azotofos. The experimental design was completely randomized, with three repetitions. The height, diameter of the stem, number of leaves and dry biomass of the plants, and the populations of microorganisms were determined, the content of phosphorus in soil and plants was also determined. The soils with filter cake, natural phosphate and biofertilizers presented higher population of total bacteria; however, they did not increase the mass dries, the phosphorus concentration in the soil and accumulation of phosphorus in the aerial part of the plants when compared only to the use of filter cake and natural phosphate. The filter cake in the fertilization promoted higher phosphorus content in the soil and accumulation for the plants, higher growth of the plants and microbial population in the soil, in relation to the treatments with filter cake absence. portuguesO uso de biofertilizante combinado com composto orgânico e fontes naturais de fosforo pode resultar em maior eficiencia da adubacao. Objetivou-se avaliar o efeito da torta de filtro associada com fosfato natural de rocha e biofertilizantes, sobre a populacao de microrganismos do solo, os teores de fosforo no solo, nas plantas e a producao de materia seca da cultura do milho. O experimento foi realizado em casa de vegetacao utilizando-se milho cultivar DKB 390 VTPRO II, cultivado em vasos de 5 dm3 contendo Ultisol (Argissolo Vermelho Amarelo Distrofico). Avaliaram-se sete tratamentos, sendo: controle (somente o solo); solo adicionado de fosfato de rocha (FR); torta de filtro; FR e torta de filtro; FR, torta de filtro e Biopack Sc®; FR, torta de filtro e Embrafos: FF organic Plus® e; FR, torta de filtro e Azotofos. O delineamento experimental foi o inteiramente casualizado, com tres repeticoes. Avaliaram-se a altura de plantas, diâmetro do colmo, numero de folhas por planta, massa seca das plantas, populacoes dos microrganismos no solo e o teor de fosforo do solo e nas plantas. Os solos com torta de filtro, fosfato natural e biofertilizantes apresentaram maior populacao de bacterias totais; porem, nao aumentaram a massa seca, o teor de fosforo no solo e o acumulo de fosforo na parte aerea das plantas quando comparado somente ao uso da torta de filtro e fosfato natural. A torta de filtro na adubacao promoveu maior teor de fosforo no solo e acumulo pelas plantas, maior crescimento das plantas e maior populacao microbiana do solo, em relacao aos tratamentos com ausencia de torta.