Abstract
Differences in soil moisture conditions and rhizosphere environments between cropping systems may alter wheat nitrogen(N) demand and yield formation, but how these environmental constraints reshape N-use strategies remains unclear. Field experiments in the Chengdu Plain, China, compared rice–wheat and upland wheat systems under contrasting N rates and basal-to-topdressing ratios to determine how cropping systems regulate canopy development, dry matter accumulation, and yield responses to N supply. The results showed that cropping systems markedly altered wheat growth strategies and N responsiveness. Rice–wheat exhibited weaker early canopy establishment, biomass accumulation, and grain yield, but greater yield responsiveness to optimized N supply. Increasing early-season N availability enhanced vegetative growth and pre-anthesis dry matter accumulation, thereby increasing assimilate remobilization to grains during filling. In contrast, upland wheat showed greater growth potential under more favorable soil conditions, with yield formation relying more strongly on sustained post-anthesis photosynthetic activity and assimilate accumulation promoted by appropriately delayed N supply. These contrasting responses revealed a rotation-dependent regulatory framework linking cropping system, soil ecological conditions, N supply dynamics, dry matter formation, and yield formation. The findings demonstrate that N management should be tailored to system-specific ecological constraints and biomass formation pathways, providing a mechanistic basis for precision N management across contrasting wheat rotation systems.
