Foliar Spraying of Nano-Silicate and Nano-Zinc on Wheat (Triticum aestivum L.) Under Salt Stress Conditions Enhances Productivity and Reduces the Optimal Nitrogen Fertilizer Rate

Salinity stress poses a significant threat to agriculture, as it directly impacts crop growth and yield. The current study aimed at examining the role of foliar nano-silicate (nSiO(2)) and nano-zinc (nZnO) applications in increasing wheat productivity and nitrogen (N) use efficiency under salt stress conditions. A two-season field experiment was carried out on sandy soils irrigated with water from high-saline wells (4352 and 7040 mg L-1). The study was conducted in a split-plot design, with main plots assigned to three treatments of foliar application of nSiO(2), nZnO, and control (nZero), and sub-plots assigned to six N fertilizer rates (0-300 kg N ha(-1)). The use of nSiO(2) and nZnO increased wheat grain yield by 67 and 48% on average over nZero, respectively. When average wheat grain yields were plotted against increasing N fertilizer rates, a quadratic response curve was observed. Derivative solutions of the quadratic functions indicated that grain yield plateaued at 4641, 4560, and 3182 kg ha(-1) for nSiO(2), nZnO, and nZero treatments, respectively. The optimal N fertilizer rates for these yield levels were calculated to be 290, 353, and 386 kg N ha(-1). When the net returns to N fertilizer and nano-material use were considered, nSiO(2) had the highest net returns and the lowest optimal N fertilizer rate (229 kg N ha(-1)), followed by nZnO (272 kg N ha(-1)). The findings of the field experiment demonstrated that foliar spraying wheat with nSiO(2) and nZnO under salt stress conditions enhances productivity as well as responsiveness to N fertilizer.