Determination of Kaolin Optimum Dose to Inhibit Iron Toxic Effect on Rice Plant in Lowland Rice Cultivation

In tropical areas, lowland rice cultivation with or without water control is often faced with iron toxicity constraint. This problem causes a drop of the rice grain yield when the iron concentration in soil solution is more than 300 ppm. To resolve iron toxicity problem, drainage and fertilizers as industrial silicon applying have been recommended. However, the used of industrial silicon is not adopted by the farmers because of his high cost and his accessibility. Kaolin contains 54.7% of SiO2 the aim of this research is to explore the potential of kaolin as a natural substitute of industrial silicon. A pot test was carried in 900 ppm iron toxicity condition. of Fe2+ the condition out for two successive rice cultivation cycles by applying 900ppm of Fe2+. Five kaolin treatments were analyzed (T0 = 0, T1 = 366, T2 = 735, T3 = 1097 and T4 = 1465 kg kaolin ha-1) in a complete randomized block design with 5 repetitions. The dose of 366 kg ha-1 reduced the symptoms of iron toxicity on rice plant. kaolin applying improved the grain yield of rice (0 tha-1 to 1.8 tha-1). The dose of 1465 kg kaolin ha-1 gave the best grain yield (1.08 t ha-1). The response of rice to kaolin doses was an equation RDG = 0.98 ×Dose more linear than quadratic and the dose of 1465 kg kaolin ha-1 was recommended as the optimal dose in the conditions of 900 ppm Fe2+.