Optimisation of canopy architecture of field-grown tobacco based on three-dimensional modeling
Optimisation of canopy structure of field-grown tobacco is of importance for improving tobacco yield and quality. The architecture of individual K326 tobacco plants grown in an experimental field in Yuxi, Yunnan Province was measured by using 3D digitising and laser-scanning methods, and a three-dimensional (3D) architectural model of tobacco was built that can accurately represent the structure characteristics of tobacco plants grown in the field. A number of canopy architectural models were then derived by adjusting the distances between plants and rows, row direction and leaf number of individual tobacco plants. Different virtual experiments were conducted and spatial distribution of Photosynthesis Active Radiation (PAR) and potential photosynthesis rate of each virtual canopy under contrasting sky conditions were computed using a 3D canopy light interception and photosynthesis model. The simulation results showed that the net daily potential photosynthesis rate of the canopies only marginally increased after the row distance up to 110 cm and plant distance up to 60 cm. The largest PAR interception was reached when the row direction was around north-south (±20°). Removing two leaves at the top and two leaves at the foot of each tobacco plant did not decrease the daily potential photosynthesis rate of the canopy, and this can benefit the growth and quality of the remaining leaves by improving their light condition. The yield of flue-cured tobacco was only reduced by 1.57%, the proportion of fine tobacco was improved by 6.36%, the value was increased by 4.45%, sugar-nicotine ratio was more appropriate, as opposed to the control. This study provides the basis for optimising plant spacing, row direction and leaf number of individual tobacco plants.