Enhancing Vegetative Growth of Quinoa and Soil Properties Under Water Shortage through Targeted Organic Amendments

The scarcity of water resources is considered a major threat and challenge for agriculture. The water limitations could strongly affect the growth and development of many crops including quinoa, a nutrition-rich, climate-resilient crop that is gaining attention globally. The organic amendment application is reported as a suitable option to mitigate the detrimental impacts of water shortage on soil and plant growth. In this context, two experiments were conducted on Chenopodium quinoa 'Titicaca'; in the first one, we investigated the effect of different organic amendments i.e., woodchips biochar (BW), vineyard pruning biochar (BV), and vermicompost (V), applied (alone and mixed) at 2% soil dry weight, on soil properties and plant biomass of quinoa subjected to a water stress period during vegetative development. Among organic amendments tested, BW and BW+V increased plant biomass on average by 15%, while BV and BV+V reduced the plant biomass by 62% compared to non-amended soil. A significant reduction in soil pH was observed by BW (7.61) while BV increased pH (8.04) compared to non amended soil (7.76). The BW and BV reduced soil bulk density (BD) (1.19 g/m3) and (1.05 g/m3), respectively, compared to non-amended soil (1.28 g/m3). As BW performed better in the first experiment, the second one assess only BW at different doses i.e., 0%, 2% and 4% under water shortage by restoring 50% evapotranspiration losses when soil water content reached the 50% of available water content. The plants treated with BW2% showed 34% and 19% more biomass, while 36% and 66% more panicles than BW0% and BW4%, respectively. The BW2% decreases the soil pH (7.79 versus 7.85) and electrical conductivity (286 versus 307 mS/m) compared to BW0% that was not different from BW4%. No differences were observed in BD between BW0% and BW2% (on average: 1.28), while decreased in BW4% (1.06 g/m3). The findings of both experiments highlighted that the appropriate type and dose of biochar could improve soil properties and help the quinoa plants to grow better under water limited conditions.