Effects of rational close planting on canopy structure and photosynthetic production characteristics of flue-cured tobacco with different plant types

Objectives The purpose of the research on the response of different density-tolerant flue-cured tobacco to close planting is to provide a theoretical reference on variety identification and rational close planting.

Methods A two-factor split zone design was used to study the response of agronomic characteristics, canopy structure, dry matter accumulation, yield and its composition of different plant types of flue-cured tobacco to close planting. Three flue-cured tobacco varieties (low density-tolerance Yunyan 97, medium density-tolerance NC71, high density-tolerance K326) were main plots; four levels of density (13890, 15150, 16660 and 18510 plant/hm²) were subplots.

Results Higher plant density significantly increased the plant height, and decreased the position of the maximum leaf, and the plant morphology gradually became tall and thin. Variety factor had significant effect on plant height and the position of the maximum leaf, and there was no significant difference in stem girth between different varieties. With the increase of planting density, leaf area index (LAI) showed a trend of increase, especially for NC71 and K326, which increased significantly. Close planting ensured structural production increase by improving population dry matter productivity to offset the decrease of dry matter accumulation per plant. The dry matter accumulation per plant of Yunyan 97 showed continued decline when the density was above 15150 plant/hm², declined by 8.41% to 21.08%. Under the plant density of 16660 plant/hm², the yield for Yunyan 97 was the highest, increased significantly by 15.51% compared with the control. The yield of NC71 showed no significant differences between the densities of 16660 plant/hm² and 18510 plant/hm², but resulted in 17.61% and 19.37% more yield over the control. Close planting effect for K326 was the largest, which showed the highest yield in 18510 plant/hm², and enhanced by 24.51% compared to the control.

Conclusions The structural productivity for flue-cured tobacco was fully developed in the rational close planting. The variation of density-resistance in different varieties was due to their different dull reaction of the dense planting. In order to balance the population structure and individual function, K326, NC71 and Yunyan 97 can be planted at the density of 18510 plant/hm², 16660 plant/hm², 15150 to 16660 plant/hm², respectively.