Abstract:

Agricultural green development aims to sustain high yields with fewer resources. While high planting densityboosts yield, it can suppress individual plant photosynthesis. However, it remains unclear whether high densitybenefits can offset the constraints of reduced water and nitrogen, or how chlorophyll fluorescence regulates lightcapture and carbon assimilation in densely planted maize. A two-year maize field experiment investigated theinteraction of reduced irrigation (W1, 20% less), reduced nitrogen (N1, 25% less), and increased plantingdensities by 30% D2 and 60% D3. The results showed that increasing density significantly raised ear number perunit area and improved pre-heading dry matter translocation to ear. Specifically, the combination of reducedirrigation with conventional nitrogen and a 30% higher density (W1N2D2) increased grain yield by 13.00% andbiomass by 8.64% compared to the conventional treatment (W2N2D1), with significant differences observed(P < 0.05). This is consistent with an increase in light-harvesting efficiency as indicated by SPAD and chlorophyllfluorescence indices. Key photosynthetic genes highly expressed from the V12 to R2 stages, were positivelycorrelated with grain yield and aligned with peak dry matter accumulation. In conclusion, synergisticallyincreasing planting density by 30% under conventional nitrogen application effectively compensates for reducedirrigation. This strategy optimizes canopy architecture and mitigates the suppression of individual plantphotosynthesis, thereby enhancing yield under water-saving conditions. This approach provides a practicalpathway for achieving the goals of agricultural green development.