Physiological responses of coffee (Coffea arabica L.) plants to biochar application under water deficit conditions

Water deficit is one of the main abiotic stressors in crop production. The development of strategies to improve plant tolerance to water deficits has gained importance. Biochar application can be considered an alternative to mitigate abiotic stress. The use of coffee pulp to produce biochar could be a novel strategy for improving drought tolerance in coffee crops. Coffer plants cv. ‘Castillo’ were grown in pots or PVC pipes filled with silt loam soil in two separate experiments to evaluate the effect of coffee pulp biochar application on physiological responses under water deficit conditions. Four different biochar doses (0, 4, 8, and 16 t · ha-1) were used. A water deficit was imposed through progressive reduction irrigation (25%, 50%, 75%, and 90% of water lost via evapotranspiration). The leaf gas exchange, maximum quantum yield of PSII (Fv/Fm), biomass, and water status were measured. Reduced irrigation negatively affected the Fv/Fm, leaf gas exchange, biomass, and water status. Biochar (8 t ha-1) increased photosynthesis in both well-irrigated plants (6 µmol m-2 s-1) and with reduced irrigation (3.5 µmol m-2 s-1) compared to 0 t ha-1 biochar (reduced irrigation: 1.8 µmol m-2 s-1 and well irrigated: 3.9 µmol m-2 s-1). In conclusion, 8 t ha-1 biochar can be a recommended practice for coffee production, not only to capture carbon and reintroduce it to the soil, but also to alleviate the effects of moderate water deficit. In future investigations, biochar application can be evaluated as an alternative to soil management or coffee plant nutrition, and its interaction with drought stress scenarios.