The Interaction between Nano Silica and Phosphorus, Applied Using Various Techniques in Calcareous Soil, Affects the Productivity of Wheat and Maize Crops

Calcareous soils, abundant in calcium carbonate, are prevalent in most arid and semi-arid environments. When phosphorus fertilizer is applied to calcareous soils, a sequence of fixation processes occurs that progressively diminishes the fertilizer's solubility and, ultimately, its accessibility to plants. This study aims to determine the effects of nano silica (derived from rice husk) and phosphorus at different rates, which are applied by various techniques to wheat and maize crop productivity, as well as the status of silicon and phosphorus in both crops under calcareous soil conditions. Therefore, we performed a field study at the El-Nubaryia Agricultural Research Station, the Agricultural Research Center (ARC), Egypt, on studied crops. The split-split plot design was used; each treatment was replicated three times. The main plots had three nano silica rates: without nano-silica (NSi0), 2 mM SiO₂ (NSi1), and 4 mM SiO₂ (NSi2). The sub-main plots had four phosphorus rates for soil application: without P (P0), 8 (P1), 11 (P2), and 13 Kg P fed-1 (P3); for foliar application, the rates were 25 (P1), 50 (P2), and 100 mg P L-1 (P3). The sub-sub-main plots consisted of two application techniques: soil application (SA) and foliar application (FA) on the plant. The experimental treatments showed that, compared to the control, the yield components of wheat and maize crops (yield, straw or stover, and grain) increased significantly. This tendency was also observed in the overall silicon and phosphorus total content. The most effective treatment, found as NSi2P3 using the FA technique, yielded 3610 and 4449 Kg fed-1 for grain wheat and maize, respectively. Additionally, these treatments improved the chemical properties of calcareous soil by reducing the pH to 7.3 and the CaCO₃ content to 13.8% after wheat harvest, which enhanced the soil's accessibility to phosphorus (P) and silicon (Si). Finally, we can conclude that the use of nano silica made from agricultural waste may help reduce expenses by decreasing the amount of phosphate fertilizers required in calcareous soil. Therefore, using nano silica with phosphate fertilizers as a foliar application on wheat and maize plants in calcareous soil increased crop productivity and phosphorus efficiency. Additionally, this study helps the environment by managing waste and reducing the use of chemicals in agriculture.