The effect of foliar application of nutrients and humic acid on grain yield and quality of bread wheat cultivars under drought stress

Absorption of nutrients from the soil depends on soil moisture, fertilizer application, soil nutrients and other factors. Foliar application of nutrients under water stress is one of the ways to reduce the effect of stress on the quantity and quality of agricultural products. Today, in many countries, a variety of organic acids such as humus fertilizers are used to improve the quantity and quality of crops and orchards. These fertilizers can be used with irrigation, foliar application, hydroponic cultivation, soil application and seed inoculation. One of the objectives of this project was to identify new wheat cultivars tolerant to water stress condition and use micro elements to introduce suitable cultivars and the effect of these elements in increasing grain yield.

In order to study the effect of foliar application of nutrients on grain yield and grain quality of bread wheat cultivars in conditions of water stress, the field studies were carried out during 2017-2018 and 2018-2019 at the Agricultural Research Station of Miandoab, in West Azerbaijan province, Iran (46º 3´ E, 36º 58´ N, altitude 1142 m). The experiment was performed as a factorial split plot in a randomized complete block design with three replications. Irrigation treatments in the main plots were included stopping irrigation at flowering stage until maturity and full irrigation until seed maturity. Sub-plots were foliar application treatments with zinc, potassium, phosphorus, magnesium and humic acid with four cultivars of wheat included Orum, Zare, Mihan and Heidari Each plot was planted in six rows with a length of four meters and a width of 1.2 meters at row intervals of 20 cm. Foliar application of micro elements was at the time of spike emergence and before flowering. Grain yield in the final harvest stage and removal of half a meter from the beginning and end of each plot was performed by a combine of grain experiments. After final sampling, 30 g of seeds per plot after digestion was used to measure micro elements in the grain using an atomic absorption. Combined analysis of variance of data from two years of study and drawing graphs was performed using MSTATC, SPSS and Excel software.

In this study, foliar application of zinc, increased 1000-grain weight, grain yield, harvest index, iron, manganese, zinc, and copper content in grin under normal irrigation by 9.30, 15.99, 18.30, 35.35, 102.10, 18.34, and 20.45 percent respectively under normal conditions and by 9.73, 4.36, 9.00, 41.81, 65.51, 43.24 and 29.78 percent respectively under drought conditions, Under normal irrigation conditions, foliar application of zinc in Mihan cultivar had the highest 1000-grain weight, grain yield, harvest index, manganese, zinc, and copper content in grain. Under drought stress conditions, the highest 1000-grain weight, grain yield, harvest index, manganese, and zinc content were allocated to foliar application of zinc in the Mihan cultivar. In this study, foliar application with zinc, potassium, phosphorus, and humic acid treatments in Mihan cultivar had equal grin yield and more than the control foliar application under normal irrigation conditions and was able to replace some of the water requirement of plant, Therefore, foliar application of these treatments along with selecting the appropriate cultivar can be a solution to improve the quantitative and qualitative yield of wheat in areas where the plant experiences periods of water deficit stress with different intensities.

Considering the favorable effect of foliar application of nutrients, especially zinc and humic acid on the quality and quantity of wheat grains, it is suggested that extension projects be carried out to transfer these results to farmers. Also, due to higher grain yield and high grain quality of Mihan cultivar, it is suggested that this cultivar gradually replace the previous cultivars.