Evaluation of Extract Percentage and Vegetative Growth of Marigold (Calendula officinalis) in Nitrogen, Phosphorus and Potassium Treatments

Today, the cultivation of medicinal plants is more attractive among farmers. marigold is an annual herbaceous plant that belongs to the chicory family and is known as a medicinal plant along with its ornamental nature. The use of marigold extract in the treatment of some diseases has made its crop management important in order to increase the growth and percentage of the extract. Thus, the optimal supply of nitrogen, phosphorus, and potassium should be considered as a part of crop management in this research.

Since the ratio of nutrients absorbed by the plant is important in predicting the amount of nutrients supplied from the soil, two sample groups from two different climates (Fars and Kohgiluyeh and Boyer-Ahmad provinces) were prepared and the concentration and ratio of nitrogen, phosphorus, and potassium were measured. Due to the high concentration of potassium after nitrogen and subsequent phosphorus, the treatments used were based on the evaluation of the potential supply of these elements from the soil in a completely randomized experimental design with three replications including nitrogen (18.4, 20.7 and 23 mg/kg) phosphorous (23 and 34.5 mg (P2O5) /kg) and potassium sulfate (0 and 12.5 mg (K2O) /kg) from Urea, superphosphate and potassium sulfate respectively were applied in greenhouse conditions. After completing the plant growth (opening of 90% of flower buds(, some morphological characteristics, the concentration of nitrogen, phosphorus, and potassium as well as the percentage of plant extract were measured.

The samples from Fars, Kohgiluyeh and Boyer-Ahmad provinces showed that after nitrogen, potassium has the highest concentration. Soil test results showed that except for potassium, the soil suffers from nitrogen and phosphorus deficiency. The highest growth characteristics of the plant were obtained in the application of 20.7 and 23 mg/ kg of nitrogen and phosphorus, respectively, and the application of potassium had no significant effect on these characteristics. The highest percentage of the extract was in the same treatment, but on the other hand, the use of the same treatment with potassium increased the number of flowers.

In this study, it was observed that the highest percentage of the extract was obtained in the treatment of 20.7 and 23 mg/ kg of nitrogen and phosphorus respectively. The addition of potassium could not significantly change this characteristic and, according to the results of the soil test which showed the amount of potassium in the optimal range, was unexpected. On the other hand, compared to the application of 23mg (P2O5) /kg, consumption of 34.5mg(P2O5)/kg caused a sharp decrease in the plant extract. Despite the lack of phosphorus in soil, it indicates sensitivity in consuming this element. It is possible that the increase in phosphorus has caused a decrease in the uptake of micronutrients, especially iron and zinc, and as a result, a decrease in the percentage of the extract in the plant, which requires further study.