Legume choice and planting configuration influence intercrop nutrient and yield gains through complementarity and selection effects in legume-based wheat intercropping systems

CONTEXT: By exploiting the complementarities between intercrops, cereal/legume intercropping provides an opportunity to increase legume production with sustained cereal yield. However, little is known about how legume choice and spatial configurations affect the performance and economic viability of legume-based wheat intercropping, especially in arid-irrigated conditions. OBJECTIVE: We conducted this study to investigate the complementarity of three different legumes (chickpea, soybean, and pea) with wheat and determine the appropriate strip width for intercrops. METHODS: A three-year study (2021−2023) was conducted to evaluate the effects of legume choice and spatial configuration (narrow strips of 0.6 m (NS) and partially wide strips of 1.2 m (pWS) for each intercrop) on wheat/soybean, wheat/pea, and wheat/chickpea intercropping, and results were compared with their sole systems for dry matter, nitrogen (N) and phosphorus (P) uptake, yield, and economic returns. We also quantified the intensity of the net biodiversity effect (NE), complementarity effect (CE), and selection effect (SE) for yield, N (NE_N, CE_N, and SE_N), and P (NE_P, CE_P, and SE_P) gains of legume-based wheat intercropping systems. RESULTS AND CONCLUSIONS: Our results show that intercrops achieved the highest dry matter, nutrient uptake, and grain yield with pWS compared to NS. The intercropped chickpea, soybean, and pea achieved 67–71%, 55–62%, and 62–70% of their sole system yield. The intercropped wheat with chickpea, soybean, and pea produced 66–69%, 57–62%, and 62–66% of sole wheat yield, respectively. Results also confirmed a positive NE with both NS and pWS, mainly due to the higher CE, which ranges from 37% to 104% of NE under all intercropping systems. The nutrient uptake gain with NS and pWS ranged from −3.4 kg ha⁻¹ to 101.5 kg ha⁻¹ (NE_N) and − 0.2 kg ha⁻¹ to 13.8 kg ha⁻¹ (NE_P). On average, maximum LER (1.36), NE (1012 kg ha⁻¹), NE_N (86 kg ha⁻¹), and NE_P (12 kg ha⁻¹) were obtained with pWS in wheat/chickpea, followed by wheat/pea and wheat/soybean intercropping. Overall, wheat/pea intercropping with pWS generated the highest net profit (2014, 1533, and 1394 USD ha⁻¹ in 2021, 2022, and 2023, respectively), which was primarily linked to the high market price of pea than chickpea and soybean. SIGNIFICANCE: These results imply that legume choice and spatial configurations influenced complementary and facilitation interactions between intercrops, and wheat/chickpea and wheat/pea intercropping with pWS could be adopted as a productive cropping strategy for obtaining higher and diverse crop yields with reduced land and nutrients than the sole wheat system.