In addition to improving chemical attributes of the soil, such as pH, exchangeable Ca and available Si, calcium silicate fertilization in soils with low soluble silicon (Si) can also affect rice yield due to a greater resistance to lodging and increased photosynthetic area. The objective of this study was to evaluate Si availability in soils from the Brazilian savannas (Cerrado). The experiment was carried out in a greenhouse using upland rice. The treatments consisted of 5 Si rates (0, 120, 240, 480 and 960 kg ha-1) and four soil classes: LEa - Typic Acrustox (Latosol), LVa - Typic Acrustox (Latosol), LRd - Rhodic Acrustox (Latosol) and AQa - Ustoxic Quartzipsammentic (Quartz sand). A completely randomized design with 4 replications was used. Soil Si, Ca, pH, and rice grain yield were determined for all treatments. Calcium silicate application increased soil Ca and pH. The Si recuperation from the applied fertilizer varied with Si rate and soil type. The available Si in the soils increased in the following order: LRd > LEa = LVa > AQa. The critical Si level, based on relative yield, was 9.8 mg dm-3 to achieve 90% of maximum yield.
rice; silicon; base saturation; critical level; availability