Efeito residual da cinza de casca de arroz na acidez e na disponibilidade de fósforo, silício e potássio no solo

Abstract

The rice husk ash has as one of the main uses their incorporation in agriculture, nowadays. This waste, obtained from burned rice husk and that contains high values of silica, works like corrective of soil acidity and increases values of exchangeable base cations as well as the availability of phosphorus (P), silicon (Si) and potassium (K). Researches about rice husk ash potential as soil acidity corrective and fertilizer have focused, basically, on their immediate effects, in the other words, its residual effect is still unknown. Therefore, this investigation aimed to evaluate the residual effect of rice husk ash in acidity and release of P, Si and K on soil. To this end, a field experiment was conducted with five treatments: four rice husk ash dosages 0, 30, 60 and 120 t.ha-1 and one treatment with recommended soil lime and fertilizer where five soil samples were collected in the layers 0,00 – 0,10 m and 0,10 – 0,20 m to the 15, 211, 400, 517 and 804 days after ash incorporation. Chemical attributes were determined: soil pH (pH), soil base, exchangeable cation values (Ca, Mg, K and Na), values of C, N, P and Si and cation exchange capacity (CEC) at pH 7. Results showed that as greater was rice husk ash dosage applied in soil higher is the residual effect of exchangeable values Ca, Mg and K, in soil base, in pH and in availability values of P and Si. As a source of phosphorus and potassium, the residual effect of rice husk ash is lower than soluble fertilizers. The residual effect of rice husk ash in silicon availability is greater than in phosphorus availability. And, as corrective of soil acidity, the residual effect of rice husk ash is just the required time to occur the natural process of reacidification and leaching of base cations.