Effect of Silicon Sources On Rice Biomass Silicon Uptake and Grain Yield.

Silicon (Si) is the second most abundant element in the Earth’s crust commonly found in the mineral components of the soil, the sand, silt and clay but extremely insoluble. In many areas where Si accumulator-crops such as rice are cultivated, Si fertilization may present several agronomic benefits.  Silicon supplements can be applied as wollastonite (natural source of calcium silicate – CaSiO₃), CaSiO₃ slag by-product or liquid silica formulations. A pot experiment was conducted to determine the effect of Si source on rice Si biomass uptake and grain yield. The treatments included two soil-applied (Wollastonite and CaSiO₃ slag) and two liquid silica formulations as Si sources. Wollastonite was applied at 8 MT ha^-1 while CaSiO₃ slag was applied at 4 and 8 MT ha^-1. The two liquid silica formulations (TAM 001 and 001h) were foliarly-applied and as soil drench at 2 L ha^-1 rate at early tillering, booting, and early flowering stages. Two checks were included, with and without lime (4 MT ha^-1).  All treatments were replicated five times and arranged in a randomized complete block design. Each pot was planted to four rice plants from which one plant was sampled one week after the scheduled application of liquid silica formulations. At harvest, both grain and straw weights were determined. Soil samples were collected and analyzed for pH, Mehlich-3 extractable nutrients, and 0.5 M acetic acid extractable Si. Silicon content and uptake of rice biomass among treatment means were significantly different at tillering and booting stages (P<0.10). Foliar application of TAM 001h silica formulation resulted in the highest grain yield followed by applications of TAM 001 as soil drench and 4 MT ha^-1 of CaSiO₃ slag (P<0.10). The results on biomass Si content across sampling times did not conform to the grain yield response. Further analysis on plant and soil samples should be conducted to elucidate the possible effect of Si on availability and absorption of plant-essential nutrients.