WATER-N COUPLING ENHANCEMENT OF YIELD WATER EFFICIENCY AND OUTPUT VALUE COMBINING PRELIMINARY FITTING WATER-N COUPLING YIELD MODELING OF FLUE -CURED TOBACCO

A reasonable water and nitrogen (N) coupling management should be use to get good quality and high yield of flue -cured tobacco. In this paper, ten water-N coupling treatments were designed to treat tobacco 'Yunyan85' (Nicotiana tabacum L.85) as W1N1, W2N1, W3N1, W1N2, W2N2, W3N2, W1N3, W2N3, W3N3, W2NO (conducted as check). WI, W2 and W3 showed water systems as 50%70%-60% (lower limited water control at ratio of field capacity at rooting stage -vigorous stage -mature stage -nitrogen application), 60%-80%-70% and 70%-90%-80%, respectively. The N applications wereN0 at 0, Ni at 4.0 g/plant, N2 at 6.0 g/plant and N3 at 8.0 g/plant. Irrigation amount at the whole or three growing stages were displayed as I or II, 12 and 13, respectively. The evapo-transpiration quantities were showed as ET, ETI, ET2 and ET3. Yield (Y), water use efficiency (WUE), irrigation water use efficiency (IWUE) and unit output value (UOV) were analyzed. Water-N coupling yield models as Jensen model and four polynomial models (Linear, Interaction Function, Pure Quadratic Function, Total Quadratic Function) from MATLAB 2018 were fitted. Results showed that water-N coupling treatment remarkably enhanced productivity efficiency. W1N2 significantly reduced irrigation and evapo-transpiration (p<0.05). W3N3 got the obvious largest tobacco yield at 2.92 t/hm2 (p<0.05), while W1N3 received the evident largest WUE (0.58 kg/m3), IWUE (0.44 kg/m3) and UOV (735.8 USD/mm/hm2) (p<0.05), respectively. Projection Pursuit Classification Model (PPC) confirmed 50%-70%-60%-8.0 as the bestmanagement model on production efficiency for 'Yunyan85' (Nicotiana tabacum L. 85). The Linear equations of Y(ET I, ET2, ET3, N), Y(ET, N), Y(I, N), and total quadratic functioned Y(II, 12, 13, N)were successfully functioned (p<0.001) at first, which could be used to manage growth of Tunyan85'(Nicotiana tabacum L. 85). These results would be referred to guiding the flue -cured tobacco growth in the future.