Intercropping of Cowpea and Buckwheat: A Sustainable Strategy for Higher Yield and Weed Suppression Under Water Deficit

Enhancing water productivity and weed control through intercropping is critical for sustainable production in semi-arid regions. A two-year field study (2022–2023) evaluated the combined effects of irrigation level, planting pattern, and weed-control duration on buckwheat (Fagopyrum esculentum) and cowpea (Vigna unguiculata). Treatments included three irrigation regimes (100%, 85%, and 70% of crop water requirement), five planting patterns (100B, 100 C, 75B–25 C, 50B–50 C, and 25B–75 C), and five weed-control durations (0–8 weeks after sowing). Significant triple interactions (p < 0.05) were found for grain yield, biomass, irrigation water productivity (IWP), weed biomass, and land equivalent ratio (LER). Buckwheat and cowpea monocultures yielded up to 2397 and 1316 kg ha⁻¹ under full irrigation with eight weeks of weed control, while the 50B–50 C intercrop maintained higher yield stability and weed suppression under deficit irrigation. IWP peaked at 0.57 kg ha⁻¹ mm⁻¹ for buckwheat and 0.46 kg ha⁻¹ mm⁻¹ for the 50B–50 C intercrop. Weed biomass declined sharply within four weeks of control, and species such as Amaranthus retroflexus density was reduced by more than 50% in intercrops. The 50B–50 C pattern consistently achieved land equivalent ratio (LER) > 1.0 across irrigation levels. Artificial neural network modeling (R² = 0.87–0.92) accurately predicted vertical biomass distribution, emphasizing the strong influence of irrigation and weed control on canopy structure. Overall, balanced intercropping (50B–50 C) combined with moderate deficit irrigation (85%) and at least six weeks of weed control optimized yield, water productivity, and weed suppression in semi-arid conditions.