Research On Dense Planting Effect For Different Density-Tolerant Flue-cured Tobacco And Regular Pattern Of Matter Accumulation

The 6%～10%of China’s financial revenue is contributed by the tobacco industry,and stabilizing the production of tobacco is essential to the development of the national economy.However,in order to ensure the stable consumption of stored tobacco,the tobacco companies strictly controlled the transplanting area and greatly reduced the output of tobacco.Rational close planting is an important measure to improve the photothermal resource utilization rate and potential yield increasing.Two factor split plot design was used to study the influence of varieties(low density-tolerance Yunyan 97,medium density-tolerance NC71,high density-tolerance K326),and density(13890,15150,16660 and 18510 plant hm-2).Variety factor was assigned to the main plot and density factor to the subplot.Research on dense planting effect for different density-tolerant flue-cured tobacco(agronomic characters,canopy structure,material accumulation,yield and its composition)and investigate a model to simulate,effectively predict the variation characteristics of dynamic dry matter accumulation and NPK accumulation and distribution law for variety identification and effectively predict the material production conditions,and provide a theoretical basis for rational close planting and higher productivity.The following is a summary of the primary results:(1)Higher plant density significantly increased the plant height,and decreased the position of the maximum leaf,which plant morphological was changed to taller and thinner gradually.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 an increasing trend,especially NC71 and K326,which increased significantly.The increase of population dry matter accumulation under dense planting offset the decrease of dry matter accumulation per plant,which ensured the higher grain yield.The dry matter accumulation per plant of Yunyan 97 showed continued declines when the density was above 15150 plant hm-2,which declined 8.41%-21.08%.Under the plant density of 16660 plant hm-2,the yield for Yunyan 97 was the highest,which was increased significantly 15.51%compared with the control.The yield of NC71 showed no significant differences between 16660 plant hm-2 and 18510 plant hm-2,but all of which was increased significantly by 17.61%and 19.37%than that of the control.Dense planting effect for K326 was the largest,which showed the highest yield in 18510 plant hm-2,and enhanced 24.51%compared to the control.The structural productivity for flue-cured tobacco was fully developed in the rational dense planting.The variation of density-resistance in different varieties was due to their different dull reaction of the dense planting.(2)A MMF curve equation,y =(ab+cxd)/(b+xd),was developed for relative DMA and relative accumulated time by the normalization method.The dynamic model could make a good estimation for DMA dynamics with the accuracies(k)of 0.9032-1.0482,and the precision(R2)above 0.94.It was also found that the equation had the characteristics of the origin,the boundedness and the monotone increasing,and it was in accordance with the biological significance.The DMA of flue-cured tobacco was divided into the slow growing stage,rapid growing stage and decelerated growing stage with further analysis of its characteristic parameters.The time to maximum rate(Tm),the initiation time and ending time of rapid growing stage showed different degrees of advance with increasing plant density.The duration(Td)and accumulation radio(Ra)of rapid growing stage increased significantly under the condition of high density(D3,D4).Path analysis indicated that Td or Ra significantly correlated with DMA(0.6500*,0.7758**),the direct path coefficient of Ra was 1.7097 and its regression contribution also reached 1.3264.(3)The nitrogen(N)and potassium(P)content of flue-cured tobacco showed a decreasing trend with the growth process,which could be fitted by exponential function(y=ae-bx、y=aeb/x)and Weibull model(y=a-bexp(-cx^-d)),respectively,and the P content of flue-cured tobacco showed a single peak curve,which could be fitted by the vapor pressure model(y=exp(a+b/x+cln(x)));Accuracy(equation fitting coefficient of determination R2)were more than 0.97,standard error 0.0136-0.1114,the fitting value and the measured value was significantly correlated;The effects of planting density on N content in different degrees:the initial concentration parameter,the peak concentration parameter and the change rate parameter,especially after fast-growing stage(63 d),with the increase of planting density,the nutrient content decreased;In addition,with close planting the peak value of P content increased,and the dynamic curve tended to be high and thin.Regression analysis showed that the dynamic Logistic model can be used N,P and K accumulation in flue-cured tobacco(y=a/(1+b*exp(-cx)))fitting equation,the fitting accuracy was above 0.98,and the fitting value and the measured value was significantly correlated;After the close planting,the time of N,P and K rapid accumulation,the time of termination and the maximum nutrient accumulation rate of flue-cured tobacco had different degrees of advance,and the maximum nutrient accumulation rate increased significantly;In different growth stages,the nutrient accumulation in each growth period increased significantly with the increase of planting density before the fast-growing stage(63 d before transplanting),and the close planting effect was significant;The nutrient accumulation in Medium(D3),high(D4)dense planting of Yunyan 97 and D4 of NC71 decreased significantly after the fast-growing stage.During the flowering stage,the nutrient accumulation in roots and lower leaves of flue-cured tobacco increased significantly,and the nutrient accumulation of middle and upper leaves was limited;Different cultivars showed that the nutrient accumulation of Yunyan 97 was the most affected by dense planting,and the second was NC71,which had less effect on nutrient accumulation of K326.(4)On the one hand,reasonable close planting is to obtain structural yield increasing,leaf area index,the duration(Td)and accumulation radio(Ra)of rapid growing stage of DMA,nutrient accumulation increased under dense planting;The second aspect was the slow response to the negative effects of individual growth,and then achieved functional yield increasing,by which there was a smaller decline on DMA per plant and nutrient content.The density-tolerance in different plant types was manifested as Piping(K326)>Drum(NC71)>Tower(Yunyan 97).In order to balance the population structure and individual function,the suitable planting density of K326,NC71 and Yunyan 97 was 18 510(D4)plant ha-1,16 660(D3)plant ha-1 and 15 150(D2)-16 660(D3)plant ha-1,respectively.