Effect of different levels of biochar, hydrochar and salicylic acid on the growth of ‎Calendula officinalis L.‎

Recently use of biochar and hydrochar have been considered as a suitable method for improving soil fertility, fixing soil pollutant and store carbon inside the soil. In this study the effect of different soil improvers at 5 levels including biochar at 1 and 2% w/w, hydrochar at 1 and 2% w/w and no soil improver and also salicylic acid at 3 levels (0, 200 and 400 mg-L) were applied on marigold plants. This experiment was a factorial based on complitly randomized design. Results showed that biochar and hydrochar at 2% w/w level increased flower life at 39 and 36%, respectively, but decreased ion leakage 22 and 21%, and also malondialdehyde at 36 and 29%, respectively compared to control treatment. Salicylic acid at 200 mg-L concentration increased flower life at 21% and decreased ion leakage and malondialdehyde by 19% compared to control treatment. Highest ratios of shoot dry weight, root dry weight, total chlorophyll content, peroxidase and ascorbate peroxidase enzyme activity were obtained by application of biochar or hydrochar at 2% w/w and salicylic acid at 200 mg-L. These results indicated the positive role of soil improvers.