The effect of application of vermicompost and salicylic acid on activity of antioxidant enzymes and yield of milk thistle (Silybum Marianum L.) in different irrigation conditions

In order to investigate the effects of different irrigation methods on yield and some physiological characteristics and activity of antioxidant enzymes of milk thistle (Silybum marianum L.) under using of vermicompost and salicylic acid, a field experiment was conducted as split-factorial based on randomized complete block design (RCBD) with three replicates on Shahr-e-Rey station during 2014-15 growing seasons. Irrigation methods as the main factor were conducted on four levels (including drip irrigation, basin irrigation, furrow irrigation, and alternate middle irrigation) and using of vermicompost on two levels (0 and 15 ton/ha) and application of salicylic acid on two levels (0 and 1 mM) were performed as minor factors. The results showed the highest activity of antioxidant enzymes including catalase, superoxide dismutase, peroxidase, ascorbate peroxidase, and glutathione peroxidase were observed in alternate middle irrigation with the combined consumption of vermicompost and salicylic acid and the lowest them activity in drip irrigation. The amount of malondialdehyde was higher in alternate middle irrigation than drop irrigation and application of vermicompost and salicylic acid simultaneously was decreased amount of malondialdehyde. Also, the highest seed yield and chlorophyll content were observed in drip irrigation with the combined consumption of vermicompost and salicylic acid. The results of this study showed that consumption of vermicompost and salicylic acid has a role in eliminating the negative effects of stress, and can improve the activity of antioxidant enzymes and increase the yield of milk thistle plant.