Abstract
Milk Thistle (Silybum marianum) is one of the medicinal plants that has many drug properties. In order to evaluate effects of animal manures and chemical fertilizer on yield and yield components of Milk Thistle plant, an experiment was conducted in the Research Farm of Ferdowsi University of Mashhad in year 2008 based on completely randomized block design with three replications and four treatments. The treatments included: control (without any manure or fertilizer), chemical NPK fertilizer, cattle and sheep manures. The characteristics such as number of lateral stem per plant, height of plant, number of inflorescences per plant, inflorescence diameter, number of seeds per capitol, 1000 seed weight, seed yield, biological yield, harvest index, oil percentage, silymarin percentage (active ingredient), silybin percentage, oil yield and silymarin yield were recorded. The results showed that different treatments had no effect on yield components, but had significant effect on oil percentage, silymarin and silybin content of seeds. Cattle manure had more oil (21%) and silybin (21.7%) compared with other treatments. There was no significant difference in oil and silymarin percentage between control and chemical fertilizer treatments. Cattle manure and sheep manure had minimum percentage of silybin (16.4) and maximum percentage of silymarin (3.1) Compared with other treatments. There were positive correlation between height of plant with seed yield (r=0.86**) and inflorescence diameter (r=0.6*), which represents importance of these traits for final yield assessment. There were no positive correlation between seed yield and other yields components.

Keywords: Milk Thistle, Quantitative and qualitative characteristics, Animal manures, Medicinal plants