Supplementary file 1_Beyond symmetry: asymmetric input shocks, the mechanization paradox, and dynamic pathways to grain yield stability in China (1983–2023).docx

This study employs a Dynamic ARDL simulation framework on national data from 1983 to 2023 to dissect the short- and long-run effects of irrigated area, cultivated land, fertilizer use, and agricultural mechanization on grain yield. Long-run elasticities reveal that irrigated area, cultivated land, and fertilizer exert positive and significant effects on grain yield, whereas mechanization exhibits a negative coefficient.

Short-run dynamics indicate that only irrigation and cultivated land confer immediate benefits; mechanization and fertilizer effects materialize over multiple years, with a stable and rapid error-correction mechanism confirming swift adjustment toward equilibrium. Dynamic simulations further reveal three robust patterns: positive irrigation and land shocks generate sustained yield gains; mechanization shocks initially suppress yield before a delayed recovery; and fertilizer shocks are fundamentally asymmetric—positive shocks stabilize yields at higher levels, whereas negative shocks paradoxically produce short-run spikes followed by substantial long-run losses.