Impacts of Different Amounts of N, P, and K Fertilizer Applications on Growth of Cirsium japonicum var. ussuriense Related to Soil Properties

Cirsium japonicum var. ussuriense is a perennial herb grown widely in Korea and also known as Korean thistle which is used in oriental medicine with various pharmacologic effects. This study was conducted to investigate the growth of Korean thistle and the changes of soil chemical properties in the thistle fields as influenced by different application levels of nitrogen (N), phosphorus (P), and potassium (K) fertilizers as N, P2O5, and K2O, and to determine the optimal application levels of N, P, and K fertilizers for cultivating the Korean thistle. The N, P, and K fertilizers were applied as 0 (0%), 0.5 (50%), 1.0 (100%), 1.5 (150%), and 2.0 (200%) times based on the level of N, P, and K treatments (N-P2O5-K2O = 61-70-72 kg ha-1) for conventional thistle cultivation. Selected chemical properties of soils at harvesting stage of the plant as compared to those before transplanting the plant were as follows: soil pH value and available P concentration decreased. Electrical conductivity (EC) value and N concentration increased with increasing the amounts of P application , but soil organic matter (SOM) content was not changed. In particular, the concentrations of exchangeable Mg were proportionally increased with increasing N applications. The plant uptake of N increased up to 100% of the N application level, but it decreased with over 150% of the N treatment level. On the other hand, P and K uptake increased up to 100% of the P and K application levels, but the K uptake was not changed with over 150% of the K level. Based on productivity of the plant aerial part, we suggest that the optimal rates of N, P, and K fertilizer applications would be as N-P2O5-K2O = 87-52-81 kg ha-1. In addition, the concentrations of selected phytochemicals in the plant were also changed with the different fertilizations. Total flavonoid concentration in the plant was highest at 50% of the N application level and control K level. Total polyphenol concentration was highest at 50% of the N level and lowest at 200% of the K treatment level.