عنوان مقاله [English]
An experiment was conducted in order to evaluate the effects of humic acid spraying on grain yield and yield components of wheat, in agricultural research and natural resources center of Tehran province, in 2010-11. a split-plot layout within randomized complete block design with three replications were used. main plots were three irrigation treatments contains of normal irrigation, non-irrigation at start of flowering stage (light stress) and non-irrigation at start of grain filling stage (severe stress), and sub plots were four levels of humic acid spraying (spraying with pure water, humic acid spraying with 200, 400 and 600 mg/l concentration). The result showed that, all of yield components except plant height and peduncle length affected significantly by drought stress on reproductive growth stage. The grain yield was significantly affected by Both light and severe stress treatments. The grain yield was decreased by 15.4% and 30.9% for light and sever stress respectively. humic acid spraying increased growth rate and leaf productionand also accelerated maximum LAI achievement. The grain yield increased with humic acid spraying for all three concentrations but, this was only significant in 600 mg/l.Protein and phosphorous percentage increased significantly with humic acid spraying.. Polynomial equation for LAI changes manner, showed that the maximum LAI was achieved in higher amount and erlier time for normal irrigation and higher concentration of humic acid.