抄録
Long-term straw returning is known to improve soil quality and winter wheat productivity, yet its effects on the spatial regulation of grain formation within the spike and the underlying mechanisms remain poorly understood, particularly in structurally constrained sandy ginger black soils. Based on a long-term field experiment in the Huaibei Plain of China, this study compared four straw management practices to elucidate how long-term straw returning regulates yield formation across two hierarchical spatial scales: main-stem versus tiller spikes and spikelet versus grain positions. Long-term straw returning significantly reshaped the spatial pattern of spike fertility, although the magnitude and pathway of regulation differed among straw management strategies. Wheat straw mulching after shredding most effectively enhanced the fertility of main-stem spikes, increased grain set in upper spikelets, and promoted grain filling at key grain positions, whereas maize straw incorporation preferentially improved grain filling in tiller spikes and inferior grain positions. In contrast, continuous wheat–maize straw returning produced comparatively smaller improvements in yield formation. Rather than simply increasing grain number, long-term straw returning enhanced yield primarily by optimising within-spike assimilate allocation through improved soil hydrothermal conditions, more synchronised nutrient supply, and stronger source–sink coordination, thereby simultaneously increasing grain number per spike and grain weight. These findings establish a multiscale spatial regulatory framework linking soil management to within-spike grain formation, providing new mechanistic insight into how long-term straw returning enhances wheat productivity and offering a theoretical basis for precision residue management in structurally constrained soils.
