Calcium amendments promote yield on reclaimed land via synergistic microbial life-history shifts and soil quality enhancement

Calcium-based ameliorants are widely applied in saline-alkaline farmland to restore soil quality and enhance crop productivity. While it is understood that microbes regulate soil function, precisely how microbial functional traits mediate the improvements in soil quality and crop yield induced by calcium-based amendments remains to be empirically validated. Herein, a controlled experiment comprising two treatments: control (CK) and calcium lactate addition (CL), was conducted in field plots across five geographical regions. The results demonstrated that CL improves soil quality (An index of 29 soil properties) by 28.21%. At the time of harvest, CL plots had 42% greater crop yield than control CK plots. Calcium addition drove changes in soil structure and nutrient availability, increased the proportion of small macroaggregates and improve soil porosity, while also drawing down available soil phosphorus (P). Calcium lactate addition significantly alleviated microbial carbon limitation, as quantified via enzymatic stoichiometry. Furthermore, CL shifted bacterial communities from r- to k-strategists and promoted a transition in fungal communities from symbiotic to saprotrophic types, reflecting complex responses in microbial functional traits. Structural equation modeling revealed that calcium lactate amendment influenced soil quality by altering microbial metabolic characteristics and life-history strategies, which ultimately enhanced crop yield. This study provides critical insights into the functional responses of microorganisms under amelioration practices and the mechanisms supporting sustainable yield increase in the context of global change.