Amelioration of salt‐affected soil using combined amendments for synergistic effects: Impacts and management implications

Saline acid sulphate soils are commonly ameliorated using traditional amendments like lime and cow manure. Biochar, derived from crop residues, is another potential remedy for this type of soil. Their combined use may create synergistic effects, necessitating further investigation. This study aims to assess the combined impacts of biochar with traditional amendments on soil quality, properties and rice yield. A field experiment was established with six treatments: no‐amendment (control), lime, cow manure, biochar, combined lime and biochar, and combined cow manure and biochar with rice (Oryza sativa) planted in four replicates. The study revealed that the effects of these amendments on soil properties were driven by their inherent characteristics and secondary processes, such as neutralization. Combining biochar with lime significantly increased soil pH (6.2), and exchangeable calcium (648.6 cmol(+) kg−1), while reducing exchangeable aluminium (11.83 cmol(+) kg−1) and iron (37.5 cmol(+) kg−1), compared to the control. Meanwhile, combining biochar with cow manure notably enhanced Mehlich‐1 phosphorous (3.4 mg kg−1), organic carbon (4.99%), ammonium (27.0 mg kg−1) and cation exchange capacity (17.2 cmol(+) kg−1). Biochar combined with cow manure exhibited greater synergetic effects on soil quality than when combined with lime. Consequently, these combinations improved the soil quality index, which exhibited a strong correlation with rice yield and biomass when its value was below 0.4. This finding indicates that these combinations exhibit insignificant synergistic effects on rice yield and growth. Further research is needed to elucidate these findings and explore the optimal application rates concerning soil properties for improved management practices.