Biochar Outperforms Biochar-Compost Mix in Stimulating Ecophysiological Responses and Enhancing Soil Fertility under Drought Conditions

Biochar (BC) can directly enhance soil fertility, thereby improving land productivity and crop health and restoring degraded lands. This study aims to investigate the potential of BC, alone or combined with compost (Co), to improve soil properties and plant drought tolerance, promoting sustainable agriculture amidst climatic and anthropogenic challenges.

Phragmites karka was cultivated in a controlled greenhouse with treatments: (i) 0% BC [control, well-watered, 65% water holding capacity (WHC)], (ii) 0% BC (drought), (iii) 1.5% BC (drought), and (iv) 1.5% BC + 1.5% Co (drought). Plant growth, water relations, mineral content, carbon and nitrogen content, proline, soluble sugars, gas exchange, chlorophyll, fluorescence, and soil respiration were measured using standard protocols and advanced instruments.

Applications of BC or BC + Co improved soil fertility, plant dry biomass, number of tillers, leaf development, and root-to-shoot ratio. Biochar-treated plants showed better leaf water and osmotic potential, essential for turgidity and growth. Biochar also increased leaf proline, soluble sugars, and Ca²⁺, Mg²⁺, and K⁺/Na⁺ ratios, enhancing osmotic adjustment and nutrient acquisition of plants. Net photosynthesis, carbon metabolism, photochemical efficiency, and electron transport rate were higher with BC under drought, outperforming the BC-Co mix. Both treatments significantly boosted soil respiration, enhancing soil fertility and drought resilience more effectively than unamended soils.

Our results show that amending soil with 1.5% BC was more effective in improving plant drought tolerance than a mixture of BC and compost for maximum water management, allowing P. karka to grow under water-limited environments.