Objective The aims were to develop new technical models for soil improvement and quality promotion in newly reclaimed land, in order to understand the beneficial effects of different types of conditioners on acidic reclaimed soils in southern China.

Method Following the selection of five conditioners including quicklime, biochar, zeolite, mushroom residue, and potassium humate, field trials were conducted on sweet potatoes for three consecutive years to study the effects of different conditioners alone or in combinations on reducing soil acidity, improving soil organic matter and nutrients, and promoting soil structure.

Result All the tested conditioners in this experiment had increased soil pH (0.49 ~ 1.23) compared with the control without the conditioner, while the acid reducing effect was the most significant in quicklime applied treatments. The combination of quicklime and other conditioners (quicklime + biochar, quicklime + potassium humate, quicklime + mushroom residue), as well as biochar and potassium humate, not only improved soil pH and reduced soil bulk density, but also significantly enhanced soil organic matter, total nitrogen, available calcium, and cation exchange capacity. The single or combined application of conditioners, such as quicklime, potassium humate, and biochar, could effectively reduce exchangeable acids in soil and enhance the buffering ability of soil to acids. After the application of conditioners, there was a significant increase in both the biological yield of sweet potatoes and the commercial yield of commercial potatoes in the three seasons.

Conclusion The collaborative application mode of lime and organic materials such as "quicklime + biochar" and "quicklime + mushroom residue" can comprehensively improve soil quality and achieve the goal of accelerating soil maturation and quality improvement for newly reclaimed red soil with significant acidification and low nutrient content.