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Drought and low amounts of organic matter are two main constraints in arid and semiarid regions and their adverse effects on soils and plants can be alleviated by biochar (B). Therefore, the influence of 0 (0B), 1.25 (1.25B), 2.5 (2.5B) and 5% (5B) cattle-manure biochar on the growth and physiological traits of spinach and physical characteristics of postharvest soil under field capacity (FC), 0.7FC and 0.55FC conditions was evaluated. Drought decreased stomatal conductance (SC), water use efficiency (WUE), shoot dry matter yield (SDMY), soil water repellency (WR) and saturated hydraulic conductivity (Ks) by 13–45%, 3–17%, 27–51%, 48–60% and 26–36%, respectively. Whereas, all B treatments increased SC, Ks and total porosity by 11–63%, 82–221% and 2–12%, respectively. Application of 1.25B increased SDMY and WUE, whereas higher B levels were ineffective, i.e. 2.5B did not significantly affect the measured parameters and 5B reduced them. At all B levels, drought reduced SDMY. However, the lowest decrease in SDMY was observed by 1.25B. Despite their positive influence on soil’s physical quality, high B levels induced excessive salinity. Therefore, a low B level (1.25B) may be recommended since it provides positive impacts on the plant’s growth and yield while mitigating the adverse effects of drought.
Gavili et al. (Fri,) studied this question.