Evaluating the effect of iron and zinc micronutrient on wheat quantitative and qualitative yield under salinity stress in Khuzestan climate

In Iran, salinity is a pervasive and limiting Factor of agricultural sustainable production. Plants in saline conditions are exposed to limited absorption of nutrients, water and toxicity of some elements and subsequently, their yield will be affected by salinity. Moreover, being calcareous, the salinity of soil and irrigation water, low organic matter in the country's arable soils, and excessive consumption of phosphate fertilizers cause a lack of available nutrients for the plant uptake. As regards more than three billion people in the world suffer from a lack of micro nutrients, the bio-enrichment in strategic products such as wheat is necessary.

 This study was carried out in Khuzestan province in a calcareous and saline soil with silty clay texture under wheat cultivation as a factorial experiment in a randomized complete blocks design with three replications. Factors included four levels of zinc (zero, 30, 60 and 120 kilograms per hectare of zinc sulfate) and the four levels of iron (zero, 2.5, 5, 7.5 kilograms per hectare of Fe- EDDHA). Zinc fertilizer treatments were used as application in soil and simultaneously with basic fertilizers (phosphorus and potassium fertilizers). While, iron fertilizer treatments were applied as irrigation fertilizer during wheat tillering stage. At the end of the growth season, wheat yield components (1000-seed weight, number of grains per spike, biomass weight, grain yield, number of tillers per square meter) and quality characteristics including hectoliters, seedling number, protein percentage, grain hardness and moisture content in different treatments were determined. MSTAT-C statistical software and Duncan's multiple range test were used to compare the means of the studied treatments.

The results showed that the interactions of zinc and iron on 1000-grain weight, number of grains per panicle and number of tillers and simple effects of zinc on total yield were significant (p< 0.01). The highest wheat grain yield was obtained in the treatment of 120 kilograms per hectare of Zn and 2.5 kilograms per hectare of iron and was equal to 6723 kilograms per hectare. The results showed that increasing one element alone had a negative effect on the number of plants per square meter. So that the lowest number of tillers per square meter (489 tillers per square meter) was observed when 60 kilograms per hectare of zinc fertilizer was consumed without iron fertilizer application. In other words, the imbalance in the amount of nutrients caused a significant reduction in the number of plants per square meter. Although the role of iron in yield and yield components of wheat in saline conditions was less than the element zinc, but the combined use of zinc and iron in a certain ratio had a positive effect on the yield components of wheat. Despite the less effect of iron application than zinc on wheat yield and yield components in saline conditions, the combined application of zinc and iron in a certain ratio had a positive effect on the wheat yield components. Combined and separate application of iron and zinc had no significant effect on wheat grain quality indicators including hectoliters, hardness and moisture. While the application of the most value of zinc caused a significant decrease in the wheat grain zeleny index. Higher levels of zinc fertilizer reduced the zeleny number of wheat grain, but the results showed that iron fertilizer levels followed the opposite trend rather than the element zinc. The least protein content (12.8%) was obtained in the treatment of 120 kg zinc fertilizer per hectare, which showed a statistically significant difference with the control treatment. Based on economic analysis, the application of 30 kg of zinc fertilizer per hectare, 2.5 kg of iron fertilizer per hectare and the combined application of both zinc and iron fertilizers resulted in a benefit-to-cost ratio of 2.3, 3.1 and 2, respectively.

 Based on the economic analysis of treatments, their effect on qualitative and quantitative yield of wheat and the role of these micronutrients in human health, application of 30 kg ha-1 Zn fertilizer (as application in soil) and 2.5 kg ha-1 Fe fertilizer (as Irrigation fertilizer) in the wheat tillering stage was suggested in saline soil and climate conditions of khuzestan province.
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