Introduction The Hexi Oasis irrigation area is endowed with abundant light and heat resources, making it suitable for intercropped maize systems. However, increasing water scarcity and the need for irrigation reduction have made the conventional full-irrigation, high-yield pathway difficult to sustain. Under reduced irrigation, yield penalties may occur because water limitation directly constrains stomatal opening and carbon assimilation during the critical silking–grain filling period. Whether intercropped maize can stabilize yield under limited water supply through coordinated maintenance of photosynthetic performance and regulation of key C 4 enzymes remains unclear. Methods To address this gap, a field experiment was conducted in 2022–2024 to systematically evaluate the coupled effects of tillage (no-tillage, NT; conventional tillage, CT), cropping pattern (intercropping, IM; monocropping, SM), and three irrigation regimes (low, I1; medium, I2; high, I3) on maize grain yield, photosynthetic physiology, and key enzyme regulation. Results The results showed that compared with the NT×IM×I2 group, the grain yields of the CT×IM×I2 and NT×SM×I2 groups increased significantly by 10.5% and 27.2% respectively. During the silking–grain filling stage, this treatment maintained the highest relative chlorophyll content, net photosynthetic rate, stomatal conductance and effective quantum yield of PSII photochemistry, along with the lowest intercellular CO 2 concentration and quantum yield of non-regulated energy dissipation. Enzyme activities of phosphoenolpyruvate carboxylase, ribulose-1,5-bisphosphate carboxylase/oxygenase, and pyruvate phosphate dikinase increased by 6–11%, 8–10%, and 9–14%, respectively, with corresponding gene expression upregulated by 30–80%. Conclusion In summary, NT combined with moderate irrigation enhanced intercropped maize yield stability under limited water supply through a dual mechanism of “photosynthetic performance maintenance + C 4 enzyme activity/transcription enhancement.”
Guo et al. (Fri,) studied this question.