Milk thistle (Silybum marianum L. Gaertn.) achene yield had a positive response to nitrogen fertilization, row spacing, sowing date, and weed control methods

Knowledge of the response of milk thistle to different levels of agronomic inputs and interactions is essential for the elaboration of the best production technologies. Field trials in a fractional factorial design are helpful in selecting the optimal production technology for plants whose agronomic requirements have not been sufficiently studied under given agroecological conditions. The experiment was set up in a 2n-1 design with a half-replication. It was located on fields of the Agricultural Experiment Station in Balcyny, Poland, and carried out in the years 2010-2012. The multifactorial experiments conducted under the same climatic and soil conditions helped to determine the optimal intensity of the main agronomic treatments. The experiment was designed to analyze the response of milk thistle to key yield-forming factors (nitrogen fertilization, potassium fertilization, sowing date, row spacing and weed control). The weather conditions during the experiment had a significant impact on most of the assessed parameters. Under the agroecological conditions of north-eastern Poland, a higher nitrogen fertilization dose (80 kg N ha(-1)) had a significant influence on the yield of milk thistle achenes (an increase of 7.1%), and the yield components improved significantly. An earlier sowing date also resulted in a higher yield of achenes (by 14.9%) and improved the yield structure elements. A positive influence on the yield was also produced by chemical weed control (a significant increase in the yield by 0.15 Mg ha(-1) - 12.2%). The spacing between rows and potassium fertilization (100 kg K2O ha(-1)) applied in milk thistle cultivation did not significantly affect the growth, development plant yield.