Residual effects of biochar on improving growth, physiology and yield of wheat under salt stress

• Residual effects of biochar on wheat were studied under different salinity levels.
• Biochar mitigated negative effect of salinity by reducing Na+ uptake in plant.
• Biochar had positive residual effects on plant growth in salt affected soils.
• Biochar may be used to enhance crop production in salt affected soils.

Salinity is one of the major threats to global food security. Biochar amendment could alleviate the negative impacts of salt stress in crop in the season. However, its long-term residual effect on reducing Na+ uptake in latter crops remains unknown. A pot experiment with wheat was conducted in a greenhouse. The soil used was from an earlier experiment on potato where the plants were irrigated with tap water (S0), 25 mM (S1) and 50 mM (S2) NaCl solutions and with 0 and 5% (w/w) biochar amendment. At onset of the experiment, three different EC levels at S0, S1 and S2 were established in the non-biochar control (2.3, 7.2 and 10.9 dS m−1) and the biochar amended (2.8, 8.1 and 11.8 dS m−1) soils, respectively. A column leaching experiment was also conducted in the greenhouse to study the adsorption capacity of biochar to Na+. The results indicated that biochar addition reduced plant sodium uptake by transient Na+ binding due to its high adsorption capacity, decreasing osmotic stress by enhancing soil moisture content, and by releasing mineral nutrients (particularly K+, Ca++, Mg++) into the soil solution. Growth, physiology and yield of wheat were affected positively with biochar amendment, particularly under high salinity level. It was concluded that addition of biochar had significant residual effect on reducing Na+ uptake in wheat under salinity stress. However, more detailed field studies should be carried out to evaluate the long-term residual effects of biochar for sustaining crop production in saline soils.