【Objective】Newly reclaimed red soils are generally characterized by high acidity and low organic matter content, which severely constrain soil fertility improvement and crop productivity. This study aimed to evaluate the effects of combined application of organic materials and calcium-based amendments (lime and calcium salts) on soil fertility enhancement and acidification control in newly reclaimed red soil.【Method】A field experiment was conducted in Ji’an, Jiangxi Province (since 2023) with six treatments: chemical fertilizer alone (CK); CK plus natural humic material (9 000 kg·hm?2), biostimulant (1 500 kg·hm?2), organic fertilizer (7 500 kg·hm?2), and 1 500 kg·hm?2 calcium salt (T1); CK plus the same organic materials combined with 3 000 kg·hm?2 calcium salt (T2); CK plus the same organic materials combined with 1 500 kg·hm?2 lime (T3); CK plus the same organic materials combined with 3 000 kg·hm?2 lime (T4); and CK plus the same organic materials combined with 7 500 kg·hm?2 fermented residue (T5). Soil physicochemical properties, carbon fractions, and crop growth were analyzed using physical fractionation, scanning electron microscopy, and multivariate statistical methods.【Result】The addition of lime and calcium salts significantly regulated soil acidity, with soil pH increasing by up to 16.2%, and markedly enhanced phosphorus availability, as available phosphorus increased by more than six fold. Application of natural humic materials rapidly increased soil carbon pools, with soil organic carbon and particulate organic carbon increasing by up to 84.0% and 263.9%, respectively. However, the sole application of fermented residue aggravated soil acidification and reduced carbon stability. Microscopic observations and multivariate analyses further demonstrated that the combined application of natural humic materials with low rates of lime or calcium salts synergistically improved soil pore structure, increased microbial biomass carbon and dissolved organic carbon (by up to 94.6% and 122.7%, respectively), and substantially promoted both aboveground and belowground biomass of rapeseed (increases exceeding 7-fold).【Conclusion】The combined application of organic materials and calcium-based amendments effectively regulates soil acidification, enhances carbon stability, and promotes coordinated improvement of soil fertility and crop growth in newly reclaimed red soil. This strategy provides a scientific basis and technical reference for the rapid improvement of soil quality in newly reclaimed farmland.