Fertilizer application may promote significant changes in soil reaction and on the availability of important nutrients for plants. The utilization of rock biofertilizers is a practical process that reduces energy consumption and increases nutrient availability in soils. In a field experiment, the effect of biofertilizers produced with phosphate and potash rocks plus Acidithiobacillus inoculation were evaluated on the chemical attributes of an Argisoil from the São Francisco Valley, Pernambuco State, Brazil, after melon cultivation. The experiment was arranged in a factorial 3²+2 scheme in randomized block design, with four replicates. Two sources of P biofertilizer (PB) and K biofertilizer (KB) were applied in the same doses recommended for simple superphosphate (SS) and potassium chloride (KCl), and in doses which corresponded to two and three times the recommended ones. Additional treatments were carried out (soluble fertilizers (SS) and potassium chloride KCl), applied in the recommended dose, and control treatment with no addition of P and K (P0+K0)). Biofertilizers reduced soil pH and higher available P and K values were obtained when higher doses of biofertilizers (PB and KB) were applied. Mg content increased when KB biofertilizers were applied in higher rates, probably due to the solubilization of Mg present in the biotite. The rock biofertilizers with Acidithiobacillus may be recommended as an alternative to soluble fertilizers by the residual effect in nutrient availability, especially in sodic soils or in limed acid soils.
Cucumis melo; Acidithiobacillus; apatite; biotite; available P and K; sulfur oxidation
