Yield, nitrogen fixation and carbon allocation to root biomass and respiration in response to phosphorus fertilization in a wheat-chickpea intercropping system
摘要
Phosphorus (P) availability affects carbon (C) allocation to roots for nutrient acquisition and biological nitrogen fixation (BNF), which in turn impacts yield. It is unclear how P availability and inter-specific interactions affect these processes in intercropping systems. Methods: A pot experiment was conducted using a factorial randomized block design with four replicates, where wheat and chickpea were grown alone or together, with 44 mg P kg−1 (equivalent to 50 kg P ha⁻1) or without additional P fertilizer. We evaluated yield, BNF based on 15N natural abundance, plant P content, and C allocation to root biomass and respiration. Results: Phosphorus availability strongly modulated the coupling between C allocation and BNF that depended on interspecific interactions. Under intercropping, chickpea exhibited greater increases in yield and P uptake with P fertilization than in monocropping, reflecting enhanced competition for P when intercropped with wheat. Intercropping significantly increased BNF in chickpea that was further marginally increased by P fertilization, while both intercropping and P fertilization sharply increased specific root respiration, indicating higher metabolic investment to support BNF. However, chickpea allocated less C to root biomass under P fertilization and intercropping, suggesting a strategic shift in C partitioning from root growth to BNF. In contrast, wheat maintained C allocation to roots in both cropping systems under P fertilization, highlighting species-specific strategies for nutrient capture and symbiotic relationships. Conclusion: Our findings highlight the importance of optimizing nutrient management for BNF and P uptake in P-deficient soils and in intercropping systems.