Wheat Growth Is Stimulated by Interspecific Competition after Faba Bean Attains Its Maximum Growth Rate

Competition and facilitation adequately explain high yield and high resource use efficiency in intercropping; however, little research has focused on dynamic trajectories and interaction in a wheat (Triticum aestivum L.) and faba bean (Vicia faba L.) intercropping system under different P application rates. Field experiments were conducted with three planting patterns (monocropped wheat [MW], monocropped faba bean [MB], and wheat and faba bean intercropping) and three rates of P fertilization (0 [P0], 45 [P45], and 90 kg P2O5 ha(-1) [P90]). The biomass of faba bean and wheat was sequentially sampled 10 and 11 times, respectively, during each growing season, and growth parameters and species interaction were simulated and calculated. Wheat and faba bean suffered different competition pressures in intercropping, but intercropping still showed yield advantages, and the interaction between wheat and faba bean was not regulated by P rate under moderate soil P fertility. Wheat was not dominant in intercropping until faba bean reached its maximum growth rate (R-max). The R-max, maximum biomass production, and grain yield of wheat increased by 12 to 18, 4 to 16, and 16 to 17%, respectively, when wheat was intercropped with faba bean relative to MW, and all of these variables for intercropped wheat at P45 were equal to those for MW at P90 due to the interactions between planting pattern and P rate. The findings suggest the time to reach the R-max of faba bean is a turning point for the intercropping effects on wheat, and intercropping shows potential to maintain higher system productivity than monocropping under reduced P application.