Effectiveness of phosphate and potash rocks with Acidithiobacillus on sugarcane yield and their effects on soil chemical attributes

Experiments were conducted to evaluate the effectiveness of biofertilizers produced from phosphate and potash rocks mixed with sulfur inoculated with Acidithiobacillus oxidizing bacteria on sugarcane yield and their effects on some chemical attributes of a Brazilian tableland soil. The experiment was arranged in a completely randomized factorial design 2 x 4 x 3 + 1, with four replicates. Two varieties of sugarcane, four rates of three sources of P and K (apatite + biotite, P + K biofertilizers with Acidithiobacillus, and soluble fertilizers--triple superphosphate and potassium chloride) were tested. A control without P and K fertilization was applied. A significant reduction in soil pH was observed with biofertilizers, especially when applied at higher rates, although no harmful effect on sugarcane yield was observed. Available P and K and exchangeable Ca and Mg increased with biofertilizer application compared to mineral fertilizers and P and K rocks. Biofertilizers may be used as an alternative source of P and K for sugarcane grown in soils with low available P and K.