Effect of Silicon Sources on Grain Yield and Silicon Accumulation of Rice Grown Under Different Phosphorus Rate.

Silicon (Si) fertilization is becoming a standard practice in rice (Oryza sativa) production and accomplished through soil-based application of silicate slag and recently, by foliar Si solution sprays.  Phosphorus (P) is one of the major plant essential nutrients applied to rice and has a known interactive effect with Si. A greenhouse experiment was carried out to elucidate the effects of different Si sources on grain yield and Si accumulation of rice supplied with varying P rates. The treatments included three P rates (0, 112, and 224 kg P₂O₅ ha^-1) and three Si sources:  two soil-applied (wollastonite and silicate slag at 4.5 Mt ha^-1) and a liquid silicon formulation (6000 Si mg L^-1) applied as foliar spray at rates of 2, 4, and 8 L of concentrated solution (diluted in 600 L water) ha^-1. All treatments were replicated four times and arranged in a randomized complete block design. Soil-based Si sources were applied before seeding while foliar applications of Si solution were done at early tillering, booting, and early flowering stages. A week after each foliar application biomass samples were collected and analyzed for Si and plant essential nutrient content. In general, there was no significant interaction between Si and P observed on measured variable across all growth stages and at harvest. Main effect of P was not observed as well. Tiller number and biomass at booting stage was significantly increased with application of foliar Si formulation at 4 L ha^-1 rate and 4.5 Mt ha^-1 of silicate slag (P<0.10). However, at harvest, higher panicle yield was attained with 8 L ha^-1 foliar application rate of Si. Apart from enhanced Si content, foliar Si application showed positive effect on potassium, phosphorus, and manganese content.