Yield and quality of milk thistle (Silybum marianum (L). Gaertn.) raw material grown in monoculture and in crop rotation. Part 2. Milk thistle reaction to potassium fertilization
Milk thistle grown on soil with average content of available potassium forms was treated with the doses of 0 (without potassium fertilization), 70 and 140 kg . ha-1 K2O prior to sowing. The content of potassium in dry vegetative mass, depending on fertilization dose, ranged from 2.3 to 3.5%. The potassium content was fixed in hulled achenes and amounted 0.6%. Crops in crop rotation took up high amounts of potassium and accumulated it mostly in vegetative mass. Yields of vegetative mass and potassium uptake by plants grown in monoculture were three-fold lower than in crop rotation. The potassium doses applied differentiated neither the milk thistle yields nor their silymarin content.