Effect of organic fertilizer on some biochemical, quantitative and qualitative characteristics of white radish (Rhaphanus sativus var. longipinnatus) under drought stress conditions

Enhanced soil fertility results in plant tolerance against environmental stresses, including drought stress. In order to investigate the effect of different fertilizers on biochemical, quantitative and qualitative characteristics of white radish under drought stress conditions, a split plot experiment was conducted as a randomized complete block design in 2020-21 at University of Hormozgan. Experimental factors were included drought stress levels as the main factor in three levels of control, medium and severe, based on providing 100, 75 and 50% of readily available water and five fertilizer levels included control (without fertilizer application) and 100 kg of pure nitrogen from urea, animal manure, biochar and vermicompost sources as a sub-factor. Our findings revealed that drought stress results in a significant decrease in leaf chlorophyll a and b content, leaf number and root diameter. Comparing with the control level, this decrease was estimated to be 29.4%, 24.2%, 27.4% and 36.2% for chlorophyll a and b content, leaf number and root diameter respectively. On the other hand, severe drought stress caused a significant increased (41.8%) in root nitrate content compared to the control. These results highlight that fertilizer application could improve the biochemical and quantitative properties of white radish. The highest amount of plant pigments, catalase and peroxidase activity and Fv/Fm index and the lowest content of malondialdehyde were obtained with the use of vermicompost. These results showed that although in severe drought stress conditions, the highest root yield was obtained with the use of urea fertilizer, but there was no significant difference with other fertilizers. On the other hand, under these conditions, the use of organic fertilizers maintained the quality characteristics of white radish root.