Simulation of crop growth curve and analysis of interspecific interaction in wheat and faba bean intercropping system.

Interspecific interactions are closely related to the intercropping yield advantage. Little attention was paid to the dynamic changes of interspecific interactions. In this study, the growth curves of wheat and faba bean under different planting patterns (wheat monocropped, faba bean monocropped, and wheat and faba bean intercropping) and phosphorus (P) fertilization levels [P0, 0 kg P2O5·hm-2(the control); P1, 45 kg P2O5·hm-2; P2, 90 kg P2O5·hm-2, repetitively] were simulated by Logistic analysis in a two-year field experiment. The dynamics of interspecific interaction were analyzed. The results showed that wheat yield was increased by 10.5%-18.6% when wheat was intercropped with faba bean as compared to monocropped wheat (MW). The yield of intercropping faba bean (IF) was decreased by 4.8%-12.3% relative to monocropped faba bean (MF). However, wheat and faba bean intercropping still showed yield advantage, with the values of land equivalent ratio (LER) and relative crowding coefficient (K) being 1.01-1.15 and 1.12-3.20, respectively. Both the yields and key growth parameters for wheat and faba bean were regulated by P level, but LER and K were not affected by P level. The maximum growth rate (Rmax) and the initial growth rate (r) of wheat were increased by 21.8%-38.7% and 20.8%-38.9% when wheat was intercropped with faba bean as compared to corresponding MW, respectively. The planting pattern had no effect on the key growth parameters of faba bean. No difference in growth curve between monocropping and intercropping crop was found under different P fertilization levels during the early growth stages. The interspecific competition was dominant in wheat and faba bean intercropping system during the early growth stages, without any intercroping biomass advantage (LER<1, K<1). Increased growth rate and decreased intraspecific competitive pressure for wheat were observed when faba bean attaining its maximum growth rate (Tmax) in intercropping system, with both intercropping biomass and yield advantage (LER>1, K>1). In conclusion, the interaction between wheat and faba bean varied with growth stages. Wheat and faba bean intercropping stimulated the growth rate of wheat during the middle and late growth stages, which was a foundation for intercropping advantage.