Yield and quality of raw material of milk thistle (Silybum marianum (L.) Gaertn.) grown in monoculture and in crop rotation. Part I. Reaction of milk thistle to the sowing date
Yields of milk thistle grown in a monoculture were about 40% lower than yields obtained in crop rotation. The yield decrease was mainly due to a damage of roots caused by Cleonus piger larvae. Two sowing dates were applied: April 1 and 22. In crop rotation higher fruit yields were obtained applying the early-sowing date and in monoculture the reaction changed across years. The delay in the sowing date resulted in an increase in the content of silymarin in fruits from 0.3% to 0.5%. The content of silymarin was mostly correlated with the sum of mean daily air temperatures from the beginning of inflorescence stalk formation to plant harvest.