Effect of foliar application of humic acid, Vitaspirin and zinc sulfate on yield and chlorophyll content of dryland wheat under climate condition of Kurdistan province

Kurdistan province has the country's highest area under cultivation and dryland wheat production. A study of factors that can increase the yield of dryland wheat will increase the stability of wheat production in the country. Proper nutrition of dryland wheat is one of the most critical forgotten managements in dryland farming. In the dryland area of Iran, deficiency of some elements, such as zinc, due to high acidity is observed to a large extent (Malakouti & Nafisi, 1997). The foliar application of nutrients is one of the most effective tools for resolving nutrient deficiencies in dryland crops (Liu et al., 2020). This method provides nutrients to the crop with relatively high efficiency and speed (Noulas et al., 2018). Therefore, the present study was conducted to investigate the effects of foliar application of various organic and inorganic compounds on physiological characteristics, yield, and yield components of dryland wheat (cultivar Azar 2).

Two field experiments were carried out during the 2018-2019 and 2019-2020 cropping seasons. The experiments were performed based on a randomized complete block design with eight treatments and four replications on dryland wheat (cultivar Azar 2) in Zarrineh city, 20 km from Divandere city, belonging to Kurdistan province. Foliar application treatments used in this study included: 1- Control (C, placebo) 2- Vitaspirin (V, 1 per thousand) 3- Humic acid (HA, 1 per thousand), 4- Zinc sulfate (ZS, 3 per thousand), 5- Vitaspirin + Humic acid, 6- Vitaspirin + Zinc sulfate, 7- Humic acid + Zinc sulfate, 8- Humic acid + zinc sulfate + Vitaspirin. Foliar application treatments were applied in Stages of stem elongation and heading.

In the 2018-2019 season, the foliar application of ZS, HA, HA+ZS, V+ZS, and V+HA caused to increase in the total chlorophyll content. While the biological yield was only affected by the foliar application of V+ZS in the 2018-2019 season, in the 2019-2020 season, the foliar application of V, V+HA, HA+ZS, V+ZS, and V+HA+ZS caused a significant change the amount of this trait. In the 2018-2019 season, the number of spikes increased due to the foliar application of HA, V, and V+ZS, and in the 2019-2020 season, this trait was influenced by the foliar application of V, V+HA, V+ZS, and, V+HA+ZS treatments. In the 2018-2019 season, thousand kernel weight was only affected by foliar application of V+ZS and V+HA+ZS, but in the 2019-2020 season, V, HA, V+HA, V+ZA, A+ZA, and V+HA+ZS treatments also affected the amount of this trait. As a result of these effects, yield in the 2018-2019 season was only affected by V+ZS treatment (14.04% increase), but in the 2019-2020 season, foliar application of V, HA+ZS, V+ZS, V+HA, and V+HA+ZS treatments increased grain yield by 22.13%, 29.63%, 27.07%, 26.57%, and 20.7%, respectively.

This experiment showed that among the compounds used, foliar application of V+ZS significantly increased grain yield in both cropping years (14.04% in 2018-2019 and 27.07% IN the 2019-2020 seasons). It seems that yield changes were due to the effect of different foliar application treatments on chlorophyll content, spike number, thousand kernel weight, and biological yield. Compared to the control (placebo treatment), the foliar application of V+ZS caused to increase in chlorophyll concentration, spike number, thousand kernel weight, and biological yield by 25%, 7.1%, 5.5%, and 14.04%, respectively, in 2018-2019 season. In the 2019-2020 season, the foliar application of V+ZS improved spike number (6.55%), thousand kernel weight (10.74%), and biological yield (16.92%) compared to the control. Overall, the results of this study showed that the combination of vitaspirin and zinc sulfate could improve the yield of dryland wheat fields. Due to easy access and relatively reasonable prices in the market will be recommended to farmers.