Trajectories of growth, nutrient uptake and interspecific competitive dynamics in wheat/maize and barley/maize intercropping
Intercropping plays an important role in tropical area as well as temperate area, due to its overyielding and effective resource utilization. Competition between the crop species is important for overyielding in intercropping systems, but little attention has been given to the dynamics of interspecific competition over time during the growing season. A field experiment with five cropping systems (wheat/maize, barley/maize intercropping, wheat, maze and barley sole cropping), two N levels (0 and 225 kg N ha-1) and two maize mulching treatments (with and without) was performed to investigate crop growth trajectories and interspecific competitive dynamics in responses to fertilization and mulching in the intercropping ecosystems fit with a logistic growth model.
Intercropping with maize significantly increased the maximum biomass, nutrient (N, P and K) uptake and growth rates of wheat and barley. The early growth rate and nutrient uptake of intercropped maize were suppressed by wheat and barley, whereas maize growth and nutrient uptake recovered after the wheat or barley was harvested. With film mulch and/or N fertilization, maximum biomass and maximum N and P uptake of intercropped maize were close to or significantly higher than those of maize grown alone. Intercropping significantly increased the maximum growth rate of wheat and barley, while decreased the maximum growth rate of maize. Intercropping increased maximum N and K uptake rate of barley, but decreased those of maize intercropped with barley. In contrast, intercropping did not significantly influence maximum N, P and K uptake of wheat or maize in wheat/maize systems. This suggests that temporal changes in resource capture and biomass production provide similar, but not identical, measurement of plant competition. Peak nutrient uptake rate occurred before peak growth rate for the three crop species, which indicates that more nutrient acquisition results in more biomass production. The time to attain maximum nutrient uptake and then growth rate was clearly separated between intercropped wheat or barley and maize. Fertilization and film mulch had little effect on the growth and nutrient uptake parameters of wheat and barley, but significantly increased those of maize in most treatments. Temporal niche differentiation was the major contributor to the yield advantage of the intercropping, and this has important implications for managing interspecific competition though agronomic practices to optimize yield advantages of intercropping.