Variable Fertilization On Paulownia Seedlings Study On The Effect Of Growth

As an important fast-growing multi-purpose tree species,Paulownia has a wide range of adaptability,and has the advantages of deep root depth without competing with other crops for water and fertilizer.It is a potential afforestation tree species.The seedling stage of the tree species is also an important period of forest cultivation.High-quality seedlings are often used,and the growth status of adult plants will be better than that of ordinary plants.Cultivating high-quality seedlings is one of the key technologies for the development of forestry industrialization.Taking Liutang Village,Xiangyin County,Yueyang City,Hunan Province as the experimental sample,Paulownia 9501 seedlings were used as experimental materials,and the amount of fertilizer was used as a variable.The seedlings of the three periods of seedling(April-June),early growth(June-August),and fast-growing period(August-October)were selected.Four fertilization treatments were carried out and according to the different needs of Paulownia growth period for nutrients,as the growth period progresses,the demand for nutrients increases.The proportion of fertilization was dynamically increased to explore the effects of different fertilization rates on the biomass of Paulownia in different periods.By collecting the seedling height and ground diameter data of seedlings under different fertilization treatments,the optimal fertilization amount was obtained by preliminary analysis.Subsequently,soil samples were collected from the plots under four fertilization treatments in three periods,and 31 soil quality indicators were measured.The data were processed by grey correlation method,data envelopment model and factor analysis.The dynamic model was used to simulate the process of Paulownia fertilization to growth,and the response of Paulownia to fertilization was comprehensively measured to further accurately determine the optimal fertilization amount in each period.Finally,the effects of nutrients and soil fertility on the growth of Paulownia were explored by partial least squares method and structural equation model.The main research results are as follows.(1)The grey relational analysis method was used to screen the indexes of soil physical and chemical properties.Seven key soil quality indicators were screened out,including organic matter,total phosphorus,total nitrogen,available iron,non-capillary porosity,microbial nitrogen,and invertase.(2)Fertilization effectively promoted the growth of seedling height and ground diameter of Paulownia seedlings.From the fertilization treatment,the average seedling height growth values from treatment Ⅰ to treatment Ⅲ were 119.34%,94.59%and 107.27%of the control,respectively.The average ground diameter growth value was 177.04%,162.88%and 146.15%of the control group.In the seedling stage,the growth state of ground diameter and seedling height under treatment Ⅰ was the best.In the early stage of growth,the best fertilization amount of seedling height increment and ground diameter increment of Paulownia seedlings was treatment Ⅱ.In the fast-growing period,the best fertilization amount of ground diameter was treatment Ⅰ,and the best fertilization amount of seedling height was treatment Ⅱ.(3)According to the response model of Paulownia fertilization based on the dynamic model under Meta-frontier,in the meta-frontier model of soil fertility lag effect,treatment Ⅰ was the best fertilization amount at the seedling stage and early growth stage,but treatment Ⅱ was the most suitable fertilization amount at the fast-growing stage.Compared with ignoring the treatment heterogeneity and lag effect,the overall response coefficient of the dynamic model considering the soil lag effect under treatment heterogeneity was reduced,indicating that the Paulownia fertilization response coefficient under the dynamic model of soil lag effect under treatment heterogeneity was smaller and the result was more accurate.According to the dynamic SBM model under the group frontier,the average response coefficient of each fertilization treatment in the three periods was ranked as treatment Ⅱ>treatmentⅢ>treatment Ⅰ,and the response coefficient of fertilization changed greatly,indicating that the technical level of Ⅰ,Ⅱ and Ⅲ fertilization treatments was significantly different.From the perspective of technical gap rate,the average technical gap ratios of fertilization treatments Ⅰ-Ⅲ were 0.99,0.74 and 0.45,respectively,indicating that there was a gap between the actual technical level and the potential best technical level of each fertilization treatment,with 1%,26%and 55%improvement space,respectively.(4)From the results of PLS regression model,the relationship between nitrogen,phosphorus,potassium and Paulownia biomass growth,the increment of seedling height will increase with the increase of phosphorus content in seedling high school,and nitrogen and potassium are negatively correlated.With the increase of nitrogen and potassium content,the increment of seedling height gradually decreases.On the ground diameter,nitrogen and phosphorus were positively correlated with ground diameter,and potassium was negatively correlated.It can be seen that the response of Paulownia seedling height and ground diameter to nitrogen,phosphorus and potassium is different.In the analysis of the relationship between soil fertility and growth by structural equation model,it was found that total nitrogen had the greatest influence on the response of Paulownia seedlings to fertilization,followed by organic matter and sucrase,which indicated that different nutrient elements played different roles in the growth of Paulownia seedlings.It means that in the process of Paulownia fertilizer selection,we should pay attention to the content of total nitrogen and organic matter in fertilizer to ensure the normal growth of Paulownia.