Eficiência agronômica e poder residual de biofertilizantes de rochas com acidithiobacilus em cultivos consecutivos com alface em solo do Cariri cearense

Abstract

Production of rock biofertilizers is a practical process with reduction of energy consumption and increasing nutrients availability in soils. A field experiment was carried out applying P and K biofertilizers from phosphate rock (Apatite-PR) and potash rock (biotite-KR) plus sulfur inoculated with Acidithiobacillus, on lettuce (cv. Crespa) in two consecutive crops with the aim do evaluate the agronomic efficiency and the residual effect of P biofertilizers in levels (BP0, BP1, BP2 e BP3) and SSP (simple super phosphate in recommended level) and K biofertilizers in levels (BK0, BK1, BK2 e BK3) and KCl (potassium chloride in recommended level), on lettuce and in some soil attributes. Level 1 is equivalent to 50% recommendation, 2 recommended level to lettuce and 3 is 150% of recommended level based in soil analyses. A control treatment was added without P and K (P0K0). Nitrogen was applied as basic fertilization in the conventional form used in the Cariri region (storm compound in level 600 mg/m2). The experiment was carried out in a representative soil of the Cariri region, with low available P and medium available K. The plant was cropped following the conventional system for lettuce. On plants were evaluated fresh biomass and dry biomass in shoots, plant height, number of leaves, commercial evaluation, total P and total K on shootdry biomass, and in soil were determined pH, available P and K in soil. In both crops the best results of lettuce yield were obtained when applied TSP, KCl, P and K biofertilizers in level BP2BK3. In reference to the effect of fertilization in pH values it was not observed significant response compared to pH in the natural soil, with greater reduction when applied SSP. Although in the second crop was evident the positive response of the biofertilizers, especially the residual effect when applied the P and K rock biofertilizers in treatment BP2BK3 showing that they may be alternative for substitution of soluble mineral fertilizers to lettuce in soil withlow available P and medium available K.