Effects of Combined Application of Nitrogen, Phosphorus and Potassium Fertilizers on the Growth of Middle-aged Eucommia ulmoides Plantation

Using Eucommia ulmoides as the study material, the “3414” complete fertilization experiment was carried out in the field to analyze the effects of different levels of nitrogen, phosphorus and potassium fertilizers application on the height and diameter of Eucommia ulmoides Oliv., and to explore the best fertilization combination for the growth of Eucommia ulmoides. The results showed that the combined application of N, P and K fertilizers could promote the growth of Eucommia ulmoides height and DBH. The growth of DBH increased significantly with the extension of fertilization years, and the increase after 2 years of fertilization could reach 1.7 times of that without fertilization. The growth of tree height was the highest in the first year of fertilization, which could reach 1.4 times of that without fertilization, and then the increase tended to be stable with the extension of fertilization years. Different levels of nitrogen, phosphorus and potassium treatments had different effects on the growth of Eucommia ulmoidest. Medium nitrogen, phosphorus fertilizer combined with potassium fertilizer had the most obvious promotion effect on DBH growth, while medium nitrogen fertilizer combined with phosphorus and potassium fertilizer (N₂P₁K₁) was more beneficial to the increase of tree height.