Optimizing maize canopy structure to enhance resource use efficiency in maize-soybean intercropping systems

In water-limited regions, optimizing irrigation is fundamental to the sustainability of maize-soybean intercropping. However, the synergistic mechanisms through which irrigation modulates canopy structure to alleviate interspecific light competition and enhance water productivity remain poorly understood. This study investigated the ecophysiological responses of the intercropping system to the interplay between maize canopy architectures and deficit irrigation strategies. A two-year field experiment was conducted in northwest China, a representative arid region. The sole cropping treatments included compact maize (M1), spreading maize (M2), and shade-tolerant soybean (S), while the intercropping treatments comprised M1S and M2S. Based on the traditional irrigation (full irrigation for both maize and soybean), single-crop deficit irrigation and dual-crop deficit irrigation strategies were implemented. Results showed that the compact maize architecture inherently improved light transmittance (Tau, +30.3 %), boosting photosynthetically active radiation (PAR, +20.8 %) and net photosynthetic rate (Pn, +13.9 %) for intercropped soybean. More significantly, the "maize-full, soybean-deficit" irrigation strategy synergistically modulated maize morphology, further increasing its canopy Tau by 19.0 %. This architectural modification amplified PAR for soybean by 40.9 % and its Pn by 46.4 %, effectively mitigating light competition and balancing interspecific aggressivity (Ams ≈ 0). Critically, this integrated strategy achieved substantial water savings (9.4–16.6 % less irrigation) without compromising system yield, while significantly increasing irrigation water productivity (IWP, +10.2 %) and water equivalent ratio (WER, +13.7 %). Our findings demonstrate that synergistic regulation of canopy architecture via precision irrigation is a potent strategy for achieving water-saving and high-yield goals in intercropping systems, offering a valuable paradigm for sustainable agriculture in arid zones globally. • Improving compact maize canopy light transmittance promotes photosynthetic efficiency of intercropped soybean. • Deficit irrigation for intercropped soybean further increases water productivity without yield loss. • Canopy optimization combined with moderate water-saving achieves synergistic improvement of water and light use.