Impact of Biochar in Mitigating the Negative Effect of Drought Stress on Cabbage Seedlings

Drought stress is a serious threat for sustainable crop production throughout the world especially in arid and semi-arid regions. Biochar has been proposed as a new approach to improve long-term productivity and water use efficiency. The study was purposed to evaluate the potential of biochar in enhancing the physiological and biochemical attributes of drought tolerance in cabbage seedlings. The study was conducted as a pot experiment under greenhouse conditions in Department of Horticulture of Atatürk University in Turkey. Three biochar doses (as %0 control (B0), 5% (B1), and %10 (B2) biochar addition rate) as drought-mitigating treatments were applied by weight. The irrigation levels were the control treatment (full-irrigated; I0) and the I1 treatment which was adjusted to 50% (I1) of the I0 treatment. Drought stress negatively affected the plant growth characteristics of cabbage seedlings while biochar applications alleviated the negative impacts of drought stress on plant growth characteristics of cabbage seedlings. Irrigation quantity noticeably affected the leaf water relative content (LWRC), stomatal conductance (gs), net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), and transpiration rate (Tr). The gs, Pn, Ci, and Tr of cabbage seedlings significantly reduced by 19%, 55%, 24%, 11%, and 41% respectively under lower irrigation levels. However, biochar applications caused the increase in LWRC and photosynthetic activities of cabbage seedlings under I1 compared to the control treatment. Lower irrigation level increased malondialdehyde (MDA), hydrogen peroxide (H2O2), proline, and sucrose content by 14%, 21%, 37%, and 11% respectively compared to the I0 treatment. Biochar applications reduced MDA, H2O2, proline, and sucrose content of the cabbage seedlings grown under lower irrigation levels. Drought stress conditions elevated significantly the antioxidant activity of cabbage seedlings. Biochar applications lowered the antioxidant activity of cabbage seedlings under water deficit conditions. Drought-stressed plants had less plant nutrient element content of leaf and root than non-stressed plants. However, biochar applications caused the nutrient element content of cabbage seedlings to increase under drought stress. In conclusion, biochar amendment improved the plant growth, photosynthetic activity, nutrient uptake, and modified physiological and biochemical characteristics in cabbage seedlings under water deficit conditions.