Application of organic fertilizers is one of the most important plant nutritional alternatives in comparison with chemical fertilizers especially in organic management of herbal plants. In order to study the effects of humic acid and plant density on yield, yield components and quality characteristics of the medicinal herb called Balangu (Lallemantia royleana B.), a factorial experiment on the basis of randomized complete block design with nine treatments and three replications was conducted in the farms of agricultural faculty of Ferdowsi University of Mashhad in 1390-91 crop years. The first factor was considered as plant density at three levels (20, 30 and 40 plants per square meter) and the second factor was three different concentrations of humic acid (0, 5 and 10 liters per hectare). The results showed that planting density has significant effects on the plant height, number of branches, flowering shoot, seed yield, biological yield and harvest index of Balangu. So that by increasing plant density from 20 to 40 plants per square meter, all of the mentioned traits showed significant increase except the number of branches and flowers that decreased. For example, the maximum height of 32.48 centimeter and the maximum yield and biological yield also observed at a rate of 38 and 357 grams per square meter respectively all in 40 planting density of the Balangu. A positive impact was observed on the plant height,flowering shoot, seed and biological yields of the plant when different concentrations of humic acid had been supplied. Using of 5 and 10 liter per hectare of Humic acid (32 and 37 grams per square meter respectively) caused 27 and 45 percent increasing in the seed yield compared to the control treatment. The most biological yield obtained at a rate of 349 grams per square meter when 10 liter per hectare of humic acid had been used in comparison with 275 grams per square meter performance in the control treatment which showed the least yield. References [1] Al-Ramamneh, E. A. D. M. Industrial Crops and Products. 2009, 30, 389-394. [2] Berimavandi, A. R.; Hashemabadi, D.; Ghaziani, M. V. F.; Kaviani, B. Journal of Medicinal Plant Research, 2011. 5, 5110-5115. [3] Razavi, S.; Karazhiyan, H. Food Hydrocolloids. 2009, 23, 3, 908-912.

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