Effect of Phosphorus and Potassium on the Growth and Yield of Pot Marigold (Calendula officinalis L.)

Plant nutrition and reduction of element deficiency is one of the most important affecting factors on plant production. Our knowledge about the effect of nutritional elements on medicinal plants is rare. In order to determining these effects, a factorial experiment as randomized complete block design conducted on research farm of  university of Mohaghegh Ardabili. Treatments were four phosphorus fertilizer (P2O5) including 0, 40, 80 and 120 Kg ha-1 from the source of ammonium phosphate and four potassium fertilizer (K2O) as 0, 50, 100 and 150 Kg ha-1 from the source of potassium nitrate. Results showed that variation in growth indices trend was approximately similar in all potassium and phosphorus levels, but K2O had the major effects on the mean of growth indices. Solely P2O5 at 120 Kg ha-1 in different K2O levels had the various trend in relative growth rate in comparison to other treatments. The highest yield of grain and dry flowers was seen in the mixture of 80 and 150 Kg ha-1 P2O5 and K2O respectively, but had no significant difference with 80 and 100 Kg ha-1. In conclusion, using of K2O had more great effects on studied traits and effect of P2O5 was negligible.