Influence of Silicon Application on Phosphorus Uptake in Rice and Phosphorus Availability in Acid and Neutral Soils, Central Thailand

Phosphorus (P) deficiency is a major problem in agricultural soils, and this problem can be addressed by various methods, one of which is the addition of silicon (Si) materials. The aim of this study was to examine the impact of Si on rice yield, P uptake, P use efficiency in rice, and P availability in two types of soil: very strongly acidic (Se) and neutral (Tr) soils, following rice harvesting. The experiment was conducted in a pot experiment using a completely randomized design (CRD) with five treatments and three replicates. The treatments were: control (no addition of Si) and addition of Si at 0.42, 0.84, 1.26 and 1.68 g SiO2/pot. The results showed that the application of Si at low doses (0.42 g SiO2/pot) increased the highest grain yield of rice (26.6 ± 1.07 g/plant) only in Se soil, while in Tr soils, increasing the amount of Si did not contribute to the increase in grain yield. The P concentration in grain and straw of rice grown on both Se and Tr soils tended to increase with increasing Si supply (1.26 - 9.46 and 0.16 - 34.7% for grain and 15.7 - 29.0 and -4.93-22.7% for straw in Se and Tr soils, respectively). In Se soil, P uptake was highest at low Si doses (0.42 g SiO2/pot), while in Tr soil, application of Si at high doses (1.68 g SiO2/pot) resulted in the highest P uptake. Only in Se soil did the phosphorus harvest index (PHI) decrease significantly with increasing Si application. For P availability in both Se and Tr soils after rice harvest, an increase in Si dose resulted in a significant increase in available P and phosphorus activation coefficient (PAC). The results indicate that increasing the amount of Si significantly increases P availability in the soil, but in acidic soils, applying Si at half the recommended dose is better for rice production and P uptake in rice.