基于偏最小二乘回归的假植期烤烟幼苗生长的水氮耦合效应研究

The Study on the Coupling Effect of Water and Nitrogen on the Flu-cured Tobacco Seedlings at Provisional Planting Stage Based on Partial Least Squares Regression

合理的水氮管理是影响假植期烤烟幼苗壮苗指数的重要因子,为研究烤烟幼苗假植期的水氮配比,通过模拟不同土壤相对含水率和施氮量2个因素耦合对烤烟幼苗生长的影响,并利用偏最小二乘回归方法拟合出了烤烟幼苗假植期的水氮耦合比例。结果表明,土壤相对含水率和施氮量均对烤烟幼苗的生长有明显的影响,整体表现为随着土壤相对含水率的增加烤烟幼苗的生长参数除地下部生物量外均呈先增加后降低趋势,而其生长参数随着施氮量的增加各参数的变化规律并不一致。土壤相对含水率和施氮量2个单因素除对烤烟幼苗地下部生长量影响不显著外,对其他生长参数均具达显著或极显著的影响,但水氮耦合效应对各参数的影响仅对地下部鲜质量和地下部生物量影响显著,对其他生长参数的影响较小。利用偏最小二乘回归方法拟合烤烟幼苗各生长参数对土壤相对含水率和施氮量的二次多项式方程可以发现,仅地下部生物量拟合系数R2较低,其他各生长参数拟合系数均较高,方程中施氮量(X2)的系数明显高于土壤相对含水率(X1),即施氮量对烤烟幼苗生长的正效应大于土壤相对含水率。对拟合方程综合分析得出本试验条件下假植期烤烟幼苗生长状况最佳土壤相对含水率为58.46%,在培养基质碱解氮为0.34g/kg时的最佳施氮量为1.53 g/kg。

Reasonable water and nitrogen management is a pivotal factor affecting the sound seedling index of the flu-cured tobacco seedlings at provisional planting stage.In order to study the ratio of water and nitrogen for the flu-cured tobacco seedlings at provisional planting stage,this article studied the coupling effect of relative moisture content and nitrogen application amount on the growth of flu-cured tobacco seedlings and got the coupling ratio of water and nitrogen of the flu-cured tobacco seedlings at provisional planting stage using partial least squares regres-sion method.Results showed that both of the relative moisture content and nitrogen application amount significantly affected the growth of flu-cured tobacco seedlings.Specifically,all of the growth factors except of ground biomass showed a tendency of first increased and then decreased along with the rising relative water content of soil.Where-as,the changing patterns of growth factors were not consistent with the rising nitrogen application amount.The two single factors relative water content of soil and nitrogen application amount had dramatic influence on all of growth factors excepted for ground biomass.Whereas,the coupling effect of water and nitrogen had significantly influenced rather on underground fresh weight and ground biomass than other growth factors.The quadratic polynomial equation obtained by matching growth factors of flu-cured tobacco seedlings with relative water content of soil and nitrogen application amount using partial least squares regression method indicated that only the fitting coefficient R 2 of ground biomass was poor,but other growth factors were high.The coefficient of nitrogen application amount(X2 ) in the equation was distinctly higher than that of relative water content of soil(X1 ),namely the positive effect of nitro-gen application amount on the growth of flu-cured tobacco seedlings was greater than that of relative water content of soil.The optic relative water content of soil was 58.46% and which corresponded to the best growth status of flu-cured tobacco seedlings at provisional planting stage was determined by using the obtained quadratic polynomial e-quation at the conditions of this study.Well,the optic nitrogen application amount was 1.53 g/kg with an alkali-hy-drolyzable nitrogen of culture medium at 0.34 g/kg.