Effect of biochar and hydrogel on morphophysiological and biochemical characteristics of Salvia officinalis L. under drought stress

Drought and low organic carbon content are two main problems for agriculture in arid and semiarid regions. Drought stress is responsible for at least 40% of crop losses in the world.The use of biochar (BC) and hydrogels can decrease adverse effects of drought on the plant. The objective of this study was to evaluate the effect of BC and hydrogel application on morphophysiologic and biochemical parameters of Salvia officinalis L. under drought stress (DS).

A factorial experiment with a randomized complete block design with three replicates was conducted to investigate the BC and hydrogel effects on the growth, physiological and biochemical characteristics of Salvia officinalis L. under drought stress condition. The BC and hydrogel was applied by mixing dry soil at rates of 0, 10, and 20 ton BC.ha-1, 100, and 200 kg hydrogel.ha-1 with three DS levels of D1 (irrigation in 80% field capacity (FC) as no-stress conditions), D2 (irrigation in 60% FC as mild-stress conditions) and D3 (irrigation in 40% FC as severe-stress conditions). The growth responses were examined included morpho-physiological (i.e., chlorophyll content, leaf area, relative water content (RWC), ion leakage (IL), and phytochemical (i.e., antioxidant activity (AA) and total phenolic content (TPC)) parameters.ResultsResults showed that drought stress significantly decreased growth parameters and RWC while increased IL, AA and TPC. Application of 200 kg hydrogel.ha-1 and 20 ton BC.ha-1 significantly increased chlorophyll index, root and shoot dry weight compared to the control under severe stress condition. At mild stress, all treatments significantly reduced the root:shoot ratio compared to the control. However, in severe stress, only application of 10 and 20 ton BC.ha-1 significantly reduced this parameter compared to the control.In no stress and sever stress, use of 200 kg hydrogel.ha-1 increased RWC in plant in comparison with control (15.9 and 5.1% respectively).

indicated that 200 kg hydrogel.ha-1 and 20 ton BC.ha-1 treatments significantly decreased IL and TPC in mild and sever stress conditions in comparison with control. All treatments significantly decreased AA in severe stress and control has the highest amount of AA in this level of drought.

It seems that use of BC and hydrogel in soil increased soil water holding capacity and improve soil structure. In addition, BC contains various elements that can improve plant nutrition under drought stress. The amount of BC and hydrogel application is very important on the effectiveness of these amendments on the plant characteristics under stress conditions.