Uso da cinza de casca de arroz como corretivo e condicionador do solo

Abstract

Deriving from rice processing, rice husk is a high calorific and low cost waste that has been replacing the wood used as energy source in rice industries. Rice husk ash is the product resulting from the burning of rice husk. Although high amounts of rice husk ash have been produced by rice processing in the south region of Rio Grande do Sul, few studies have been done on the use of these residues as a soil corrective and conditioner. Therefore, this investigation aimed to evaluate the potential of rice husk ash as a soil acidity corrective, fertilizer and conditioner. Thus, a field experiment was conducted with twelve treatments: ten rice husk ash dosages (0, 10, 20, 30, 40, 60, 80, 100, 120 and 140 t ha-1) and two references (an absolute control and a recommended soil lime plus fertilizer). For chemical analysis, soil samples were collected at two times: 15 and 180 days after rice husk ash incorporation in the 0.00-0.10 m and 0.10-0.20 m soil layers. The following chemical properties were determined: soil pH (pH), base saturation (V %), relative power of total neutralization (PRNT), neutralization power (PN), exchangeable cation values (Ca, Mg, K, Na), H + Al, C, N, Si and P and cation exchange capacity (CEC) at pH 7.0. The soil samples for physical analysis were collected 180 days after rice husk ash incorporation in the 0.00-0.10 m and 0.10-0.20 m soil layers. The treatments 0, 40, 80 and 120 t ha-1 of rice husk ash and absolute control were considered for the following physical atributes were determined: soil bulk density, total porosity, macroporosity, microporosity, water stable aggregate size distribution, mean weight diameter of aggregates, available soil water, S parameter and soil compressibility. Results showed that rice husk ash acts as a soil acidity corrective, reacting faster than conventional limestone, even with its low PRNT (around 3 %). The use of rice husk ash increased the levels of Mg, K, Na, Si and P in the soil. As a soil conditioner, the rice husk ash caused a reduction of soil bulk density and increased total porosity and 10 macroporosity in the 0.00 to 0.10 m soil layer. The S parameter, the pre-consolidation pressure and the compression index values converges with the improvements of soil porous space.