The effect of nitrogen-fixing bacteria, humic acid and foliar application of micronutrients on yield and morpho-phenological traits of soybean

Plant nutrition is one of the most important environmental factors affecting the yield and yield components of crops such as soybean. This study was conducted to investigate the effect of nitrogen-fixing bacteria, humic acid and foliar application of micronutrients on yield and morpho-phenological traits of soybean (cv. Saman) in a factorial randomized complete block design with three replications at Gorgan agricultural research station in two cropping seasons (2019-2020). Experimental factors include foliar application of humic acid at two levels including fulvic and humic acid; Bacterial seed at three levels including bacterial seed, bacterial seed+Azospirillium, and control; and nutrient spraying was applied at four levels including cobalt, cobalt+molybdenum, cobalt+molybdenum+boron, and control. Based on the results, the simple effects was significant on the studied traits. The bacterial Rhizobium+Azospirillum and cobalt+molybdenum+boron treatments significantly increased the traits than control. The highest grain yield was observed under the humic acid (2750 kg/ha), bacterial seed+Azospirillum (2238 kg/ha) and cobalt+molybdenum+boron (2388 kg/ha). In general, the results of this study indicate the efficiency of nitrogen-fixing bacteria as well as foliar application of micronutrients in increasing soybean yield.