Different Sources of Silicon by Foliar Spraying on the Growth and Gas Exchange in Sorghum

The efficiency of silicon (Si) foliar spraying in sorghum plants can be increased with new sources that may enhance the uptake of the beneficial element with reflexes in physiology. This study investigated the effect of foliar application of Si on different sources of absorption, gas exchange, and growth in sorghum plants, based on the hypothesis that there is a differential response to specific sources and concentrations of Si. An experiment was conducted in a completely randomized design with three replicates (in triplicate). The treatments consisted of five Si sources (nanosilica, silicic acid, stabilized sodium, potassium silicate, and potassium silicate) and four concentrations of Si (0, 0.5, 1.0, and 1.5 g L−1 of Si). Foliar spraying of Si on sorghum plants was effective at increasing the absorption of the beneficial element and the gas exchange of the plant. Nanosilica stood out as an alternative source of Si, and a promising option for foliar spraying in sorghum crops, as it promoted high uptake of the element by the plant. This source also promoted a high photosynthetic rate for both potassium silicate and alkaline silicate. In this study, spraying of 0.88 g L−1 (Si-alkali) and 0.84 g L−1 (Si-potassium) on sorghum at the phenological stages V4 and V8 (four and eight fully expanded leaves respectively) and R1 (beginning of flowering) was promising because it increased plant growth, reduced water loss through transpiration, and had a positive impact on gas exchange.