Effect of Fe and Zn Spraying on Yield and Nutrients Bioavailability of Bread Wheat Cultivars

Wheat is one of the most important foods for the people in the world. For many Central Asia and Middle Eastern nations, wheat provides ≈50% of the daily energy consumption and the proportion can exceed 70% in rural areas. The production of high-yielding modern cultivars may provide the amount of energy needed by humans, but these cultivars, due to the low concentration of micronutrients such as iron (Fe) and zinc (Zn), are usually deficient and cause health problems. This shortage is intensified in dryland areas due to dryness, alkalinity, and so on. Two-thirds of the total area under wheat cultivation in Iran belongs to rainfed wheat. Declines in the concentration of micronutrients such as Fe and Zn in cereal grain which are often important sources of micronutrients for humans cause several diseases. Agronomic fortification (e.g., fertilizer application) is imperative and necessary for improving micronutrient concentrations in grains in a short period. Phytic acid has a high potential for binding Zn and Fe, making them less bioavailable for humans. If the amount of phytic acid in the wheat grain is high, the absorption of small elements in the intestine decreases. The use of micronutrient fertilizers, such as zinc reduces the amount of phytic acid and enhance grain zinc concentration. Therefore, the purpose of this research was to investigate the role of zinc and iron fertilizers on the performance and quality of modern and local cultivars of bread wheat. To investigate the role of iron and zinc Nano-chelate fertilizers on the improvement of grain yield and elemental composition of bread wheat cultivars, a factorial experiment based on randomized complete block design with three replications arranged in Moghan Agricultural and Natural Resources Research Center, 2015-2016. The first factor was control and spraying with iron, zinc, and iron + zinc. The cultivars included Aftab (G1), Karim (G2) and two new genotypes (G3 and G4). Foliar application of Khazra iron and zinc Nano-chelate fertilizers was carried out at tillering, early of heading and milky stages with a ratio of 2 and 1.5 per thousand, respectively. Iron, zinc, and iron + zinc Nano fertilizers at the rate of 2 kg ha-1, 1.5 kg ha-1 and 2 + 1.5 kg ha-1 were sprayed at every stage. Ammonium phosphate and urea fertilizers at a rate of 50 kg ha-1 from each one of them were applied before planting. Measurement of Fe and Zn elements was carried out at wavelengths of 233.28 and 2333 nm, respectively with the use of the atomic absorption device Shimadzu, AA-6300. Measured traits included a number of spikelets per spike, number of grains per spike, number of seeds per spike, and 1000 grain weight per the main spike, grain yield m2, zinc concentration, iron concentration, phytic acid, and phytic acid molar ratio to zinc and iron. The results showed that cultivar G1, G2, and G3 produced significantly higher seed yield than G1. This was mainly due to an increase in spikelet number, the number of seeds per spikelet, and/or both. The G1 and G2 cultivars had a higher concentration of zinc in comparison with the new genotypes. Cultivar G1 had the highest Phytic acid and phytic acid to zinc and iron molar ratio, and genotype G4 had the lowest values. Maximum grain yield, Zn and Fe concentrations were obtained at the foliar application of Fe + Zn, Zn, and Fe, respectively. Zinc application had the lowest amounts of phytic acid and phytic acid to Zn molar ratio in comparison with the other spraying levels. As a result, the foliar application of iron and especially zinc in dryland farms, by improving the bioavailability of iron and zinc and increasing wheat yield, can play a significant role in providing daily energy intake and reducing health risks.