Effect of organic fertilizer on kinetics of potassium release and rice uptake in inceptisols Kalitirto, Sleman

This study aims to determine the effect of organic fertilizer on kinetics of potassium release and uptake and to find the best kinetic models describing K release from soils. The treatments included control, inorganic fertilizer, 10 ton/ha cow manure, 5 ton·ha−1 green manure, and 7.5 ton·ha−1 cow + green manure (2:1). The experiment was analyzed using RCBD with three replications. The kinetics of non-exchangeable K release was extracted with 0.01 M CaCl2for 2hto 168 h and data of K release were fitted to five mathematical models: zero-order reaction, first-order reaction, power function equation, parabolic diffusion and Elovich equation. The results showed that plant and root-K uptake from control, inorganic fertilizer, cow manure, green manure and cow + green manure were respectively 45.16; 62.33; 61.46; 55.66; 68.89 mg/clump and 15.63; 23.09; 44.91; 17.53; 23.41 mg/clump. The treatments were not significant on plant uptake, root uptake and K release so organic fertilizer can be used to replace inorganic fertilizer application. Among the five equations, power function best described the K release pattern with R-square was 0.50. The constant b, an index of K release rate, ranged from 0.003 to 0.018 ppm·h−1 in the power function model.