Woody Biochar Differently Influences Plant Water Status and Growth of Five Quinoa (Chenopodium Quinoa Willd.) Varieties Under Water Stress

Only few studies have evaluated the responses of quinoa varieties to biochar amendment under water-limited conditions during the early growth stages. We examined the interaction between soil treated with and without biochar and water stress applied during the vegetative development on water relation and growth of quinoa varieties. Five varieties (Titicaca, Quipu, Regalona, UAFQ7, and Q126) were grown in soil without and with 2% (w/w) woodchip biochar and subjected to two successive water stress cycles, by withholding water until soil reached the permanent wilting point, started from 12-leaf stage. The morpho-physiological attributes, leaf nutrients and total bacterial count were assessed during the experiment. Biochar significantly improved plant growth, water use efficiency (WUE), and yield-related traits across all varieties under water-stressed conditions. Biochar under water-limited conditions enhanced plant water status, indicated by lower pre-dawn water potential and increased relative water content compared to non-treated soil. The UAFQ7 showed superior growth with biochar, producing more leaves and larger leaf areas (1517 vs. 1378 cm(2)/plant). Titicaca was more sensitive to drought, with a considerable reduction in leaf area (1268 vs. 1386 cm(2)/plant), fresh and dry biomass (6.4 vs. 7.4 g) compared to well-watered conditions. Quipu produced longer panicles, further enhanced by biochar (17 vs. 12 cm). A significant increase of 17% in WUE was observed in biochar-treated plants compared to non-amended ones. Woodchip biochar seems to mitigate the adverse effects of water stress in quinoa, but the responses vary among varieties.