Increased Strip Width Balancing Interspecific Competition and Enhanced Yield in Maize–Flax Intercropping Systems

Interspecies interaction is key to achieving intercropping advantages. However, in semi-arid rainfed agricultural areas, research on how strip width influences interspecific relationships and system productivity in maize–flax intercropping remains insufficient. A three-year field experiment was conducted to assess the impacts of varying strip widths (80, 120, and 160 cm) on system productivity and interspecies interactions in a maize–flax intercropping system. The results demonstrated that the 160 cm strip-width treatment achieved the highest land equivalent ratio (LER) and total system yield, with average increases of 11.3% and 37.5%, 7.3% and 38.8% compared to the 120 cm and 80 cm strip-width treatments, respectively. The improvement in grain yield was primarily attributed to synergistic increases in maize kernel number per ear and 1000-kernel weight, as well as enhanced capsule number per plant, seeds per capsule, and 1000-seed weight of flax. Analysis of interspecific competition dynamics revealed that flax exhibited stronger competitive ability during its later growth stages (kernel-filling and maturity stage) under the 160 cm strip width, with an average increase of 97.2% compared to other treatments. Furthermore, the wider strip width optimized the relative crowding coefficient (RCC) and promoted the recovery effect of maize (RE) after flax harvest. Correlation analysis indicated a significant negative relationship between the intensity of interspecific competition during the maize V3 and V12 stages and flax yield. In conclusion, adopting a 160 cm strip width in the maize–flax intercropping system maximizes overall productivity by optimizing yield components, promoting dry matter accumulation, and balancing interspecific interactions.