Production of rock biofertilizers is a practical process which reduces energy consumption and increases nutrients availability in soils. A field experiment was carried out applying phosphate biofertilizer (PB) and potash biofertilizer (KB) from rocks plus sulfur with Acidithiobacillus, applied in different rates, comparing with the mineral fertilizers simple superphosphate (SFS) and potassium chloride (KCl), on yield of lettuce (cv. Crespa-Grand Rapids), in two consecutive crops and in soil chemical attributes (pH, and available P and K). A control treatment was added without P and K (P0K0). In the two consecutive crops the biofertilizers BP, BK, and chemical fertilizers SFS and KCl were effective on lettuce yield. In the first crop the best results were obtained with the treatments SFS700 BK90, SFS700 BK60, and in the consecutive crop applying the treatments BP700 BK90, SFS700 BK60 and SFS700 BK90. In the two crops the positive response of the PK biofertilizers and PK mineral fertilizers was evident. Residual effect was observed when the treatment BP1050 BK90 was applied. Soil pH was not affected by application of PK biofertilizers plus worm-compound, increasing available P and K, especially for available P in the consecutive crop. The PK rock biofertilizers, plus worm-compound, may be applied as an alternative to PK mineral soluble fertilizers.
Lactuca sativa L.; apatite; available P and K; biotite; sulfur oxidation
