Reaction rate and residual effect of rice husk ash in soil acidity parameters
ABSTRACT The rice husk ash has been applied in agricultural land, with potential of replace limestone and, supply phosphorus and potassium. However, its residual effect in soil is still unknown. This investigation aimed to evaluate the reaction rate and residual effect of rice husk ash in soils acidity parameters. 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 (dolomitic limestone to reach pH 6, 150 kg ha-1 P2O5 as single superphosphate and 80 kg ha-1 K2O as potassium chloride) where five soil samples. Soil samples were collected in the layers 0.00 - 0.10 m and 0.10 - 0.20 m at 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) and cation exchange capacity (CEC) at pH 7. Results showed that reaction rate of rice husk ash is faster when compared to liming. As greater was rice husk ash dosage applied in soil, higher is the residual effect in pH. 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 basic cations, about 33 months for soils and weather conditions similar to this work.