Impact of biochar soil amendment on alleviation of single and combined effect of drought and salt stresses on vicia faba seedlings planted in alkaline soil

Abstract

The aim of this study was to evaluate the effect of the addition of biochar (0, 2, 5, and 8% designed by C, B2, B5, and B8, respectively) on the single and interactive effects of salinity and drought treatments on the growth of vicia faba plants in alkaline soil. 21 morphological, physiological, and photosynthetic parameters were evaluated. The amendment of biochar, carbon-rich material developed from combustion of biomass under no or limited oxygen supply, in alkaline soil under salinity stress performed positive effects on internal concentration of CO2 (+ 96.16% at B8), transpiration rate (+ 83.79% at B5), stomatal conductance (+ 30% at B2), and net CO2 assimilation (+ 37.84% at B2). Under drought stress, the addition of biochar had no effect on internal concentration of CO2 and the water use efficiency. Under combined conditions, the maximum increase (+ 40%) of internal concentration of CO2 was registered at B5. Also, addition of 2% of biochar (B2) can increase the transpiration rate to + 116%. Biochar was alleviating the effect of combined stress on vicia faba leaves by ameliorating the stomatal conductance to + 58.73% at B2. We, also, noticed that net CO2 assimilation rate increase with the increase of biochar concentration. On the other hand, biochar addition did not have effect on lengths of shoot, roots, and total plants and fresh biomass, spad value, and leaf number. However, the amendment of biochar has slightly ameliorated the electrolyte leakage, protein content, and foliar surface. The pH and the EC of initial and final treatment were also evaluated. The statistical analysis demonstrates that addition of 2% (B2) of biochar can significantly mitigate the negative effect of single effect of salinity and combined salinity drought in alkaline soil. On the other hand, the addition of 5% (B5) of biochar can alleviate the individual effect of drought compared to their respective controls. This result confirms the positive effect of biochar addition in alkaline soils. Thus, a better understanding of biochar addition on physiological basis for faba bean growth under drought and salinity stress in alkaline soil will be beneficial for sustainable agriculture.