The effect of density and foliar application of humic acid on quantitative yield and nutrient uptake of maize (Zea mays L.) under drought stress conditions

Environmental stresses such as drought stress are one of the main obstacles in the production of crops in many parts of the world, especially in arid and semi-arid regions such as Iran. Therefore, in order to evaluate the effect of acidic solution in drought stress conditions on grain yield and absorption of corn grain in different plant densities, an experiment a split plot experiment was carried out in a randomized complete block design in three replications during 2015-2016 and 2016-2017 cropping years. The main factor was drought stress with three levels (optimal irrigation, irrigation cut off stage 6 to 8 leaf and irrigation cut off at crown stage). Subplots with three levels of foliar application of humic acid (control treatment (no humic acid), 2 and 4 liters per hectare humic acid) and sub-subplots including three plant densities (60, 75 and 90 thousand plants per hectare). The results of combined analysis of variance showed that the effect of drought stress and humic acid on grain yield, 1000 seed weight, number of seeds per ear, zinc concentration, iron concentration and protein content were significant. In drought stress conditions, grain yield and nutrient uptake, such as iron, zinc and phosphorus, decreased but the protein content increased. The highest grain yield (9580 kg.ha-1) was related to irrigation. Humic acid spraying increased seed yield, zinc concentration and grain iron content. With increasing water deficit in soil, the effect of humic acid application on seed yield significantly decreased. Grain yield and protein percentage had a positive correlation with increasing plant density. In general, the results of the experiment indicate that application of 4 liters per hectare of humic acid at a density of 75 thousand plants under suitable moisture conditions can increase the absorption of the elements, grain yield and yield components of maize and, in general, improve the production of corn.