Soil amendments mitigate the adverse impacts of salt stress on quinoa under greenhouse conditions

Abstract

Abstract BACKGROUND Salinity stress is a detrimental abiotic constraint that threatens agricultural productivity worldwide. Quinoa ( Chenopodium quinoa Willd.), although moderately salt‐tolerant, still suffers significant physiological and yield losses under high salinity. This study aimed to evaluate the effectiveness of five soil amendments (biochar ‘Bc’, compost ‘Cp’, black soldier fly frass ‘If’, cattle manure ‘Cm’ and phosphogypsum ‘Pg’) on enhancing the salinity tolerance of three quinoa varieties (Puno, ICBA‐Q5 and Titicaca) grown under 16 dS m −1 NaCl stress in greenhouse trials, alongside salinized (C−) and non‐salinized (C+) controls. RESULTS Salinity stress significantly reduced quinoa performance across all agrophysiological traits in the three varieties. However, soil amendments effectively alleviated these effects. ‘Cm’ notably improved leaf water potential by 48%, 18.66% and 18.19% in Pn, Q5 and Tc, respectively. Biochar increased leaf water potential by 56.61% for Puno. Amendments also reduced membrane damage, with a reduced relative leakage ratio by 30% in Pn by ‘Cm’ and 36% in Tc by ‘Pg’ application. Nitrate reductase activity was highest with ‘If’ compared to ‘C−’ in Q5 variety (1.479 vs. 0.889 mmol NO₂ − g −1 h −1 ). Phosphogypsum significantly enhanced 1000‐grain weight by over 187% in all varieties. CONCLUSION Soil amendments substantially improved quinoa's physiological resilience and productivity under severe salinity, with phosphogypsum effectiveness for grain weight, cattle manure and biochar for water relations, and insect frass for nitrogen metabolism. These findings highlight the value of integrating these amendments to sustain quinoa cultivation in saline soils and warrant further field validation to optimize amendment combinations for broader agro‐ecological contexts. © 2025 Society of Chemical Industry.