Effects of Mixed Planting of Horizontal- and Erect-Leafed Varieties on Canopy Light Use and Growth in Sugarcane

Improving sugarcane canopy structure using varietal mixtures, by exploiting the diversity of plant types available, is effective for improving biomass production and cane yield. A single variety cannot meet the demands for optimal canopy structure at each growth stage and for adaptability to changing within- and above-canopy light environments. The present study performed mixed planting of two varieties with different plant types to demonstrate the effects of such a mixture on canopy growth and its light use in simulated canopy conditions at the early growth stage. The varietal mixture induced plasticity of plant size, leaf allocation, and nitrogen accumulation, and altered the growth habit of each variety compared with that when each was grown as a monocrop. Mixed-variety planting increased the plant size of the erect-leafed variety while decreasing that of the horizontal-leafed variety; however, the total canopy biomass of the mixture was greater than the one predicted on the basis of the two-component monocropped ones. Leaves of the erect-leafed variety were distributed at a higher canopy layer, whereas those of the horizontal-leafed variety were distributed at a lower canopy layer under mixed planting than under the monocrops. Through such habitat segregation, lower light extinction coefficients were obtained with the moderate leaf area index of the mixture.