<p>Elevation gradients significantly influence the effectiveness of plastic mulch in arid agriculture by regulating water and temperature stress, though the specific mechanisms remain unclear. In a field experiment conducted from 2008 to 2017 at four locations with different elevations, the effects of three mulching treatments (full plastic mulch, partial plastic mulch, and no mulch) on the growth of spring maize were assessed. The study revealed that elevation is the primary determinant of plastic mulch benefits. With increasing elevation, soil bulk density decreased by 4.7–6.2%, soil moisture content increased by 0.6–1.3%, microbial abundance significantly rose (bacteria + 10.2%, fungi + 22%), and maize yield increased by 38.6% overall. Elevation changes specifically influenced fungal community assembly processes, with negligible effects on bacteria. At higher elevations, full plastic mulching (PP) yielded the most pronounced benefits: it improved the soil micro-environment, enhanced fungal diversity, and consequently increased urease activity by 96–106%, effective nitrogen content by 15–20%, and microbial biomass carbon by 11.6%. This change promoted nitrogen allocation to grains, increasing grains per ear by 31.2%. Structural equation modeling confirmed fungal diversity as the key pathway driving nitrogen availability and yield formation. The study further identified soil moisture content thresholds (&gt; 41 mm) as essential conditions for these microbial-driven processes. Based on elevation differences, precise mulching strategies were proposed: PP is recommended for high-elevation arid areas, achieving up to 43.3% yield increase; partial plastic mulching (PB) is suitable for mid-to-low elevation areas, enhancing soil biological activity while keeping yield loss below 9%. This research provides theoretical foundations and practical pathways for sustainable intensive agriculture in arid regions.</p> Graphical Abstract <p></p>