effect of different levels of npk fertilizers on the productivity of milk thistle (silybum marianum) in peykan shahr area

milkthistle (silybum marianum l.) is a rangeland medicinal plant growing wild in different locations in iran. in the present research work, the effect of n, p and k in their different proportions of n0p0k0, n100p100k50, n150p150k100 and n200p200k150 kgha-1 as compared with control (no fertilizer application) on the plant's growth was put to test. suc variables as plant height, no. of capituls, no. of capituls per plant, diameter of capitul, no. of seeds per capitul, one thousand seed weight, and seed yield were assessed in a randomized complete block design of 4 treatments of each in 3 replications. results indicated that different proportions of npk exert different significant effects on plant height, no. of seeds per capitul and on seed yield. the highest plant height (107.81 cm) was resulted from n200p200k150 treatment, the greatest no. of seeds per capitul (223.08) from n150p150k100 and the greatest yield (3.6 tons ha-1) was the result of the treatment n100p100k50. there was a decrease in total silymarin and silybin observed with increase in npk application. increase in npk application caused increase in vegetative growth and decrease in silymarin and silybin. this is while non application of npk (control) resulted in an increase of 20.57% silymarin as compared with the n200p200k150 treatment. silybin content of silymarin was the highest in n150p150k100 treatment. this was while even though total silymarin in control was at the same level as in treatments n150p150k100 and n100p100k50, but silybin available in its silymarin was reduced to an even zero level. therefore it is concluded that the most suitable npk proportion as regards; seed yield, and silymarin and silybin contents in milkthistle, variety budakalazi, and in the area of peykan shahr, karaj, tehran would be n100p100k50.