Effects of increased planting density and reduced nitrogen on physical properties of flue-cured tobacco rotated in rice paddy field

To study the feasibility of increased planting density and nitrogen-saving on flue-cured tobacco rotated with rice paddy in Shaoyang tobacco planting areas, physical properties of flue-cured tobacco were analyzed by constructing physical property index and adopting partial Eta² value via a bi-factorial experiment. The results showed that: 1) The effects of planting density and nitrogen level on the physical properties of flue-cured tobacco were different, planting density mainly affected leaf openness and single leaf weight, and nitrogen level mainly influenced leaf openness, single leaf weight, leaf thickness and weight per unit leaf area. 2) In Shaoyang rice paddy-tobacco rotation areas, the physical property index of tobacco was the best at the planting density of 18 182 plants/ha and the nitrogen level of 120 kg/ha. 3) The effect of nitrogen level on physical properties of flue-cured tobacco was maximum (accounted for 48% ), followed by that of planting density (accounted for 40% ), and that of their interaction accounted for 12%. Therefore, in order to achieve better physical properties of flue-cured tobacco, properly increasing planting density and reducing nitrogen fertilizer are recommended for tobacco planting in Shaoyang rice paddy-tobacco rotation areas.