Effects of NPK fertilization on the response of root growth and nutrient absorption of seedlings of Cypress funebris to calcium addition in low fertility soil

Objectives To explore the response of root development and nutrient absorption of Cupressus funebris families to calcium addition under different nutrients, to provide theoretical basis for improving cypress seedling quality, forest productivity and forestland selection.

Methods 1-year-old seedlings of 5 cypress families were used as materials to set up CaSO₄ 0, 3 and 6 g/kg treatments (Ca₀, Ca₃ and Ca₆) in 3 g/kg NPK and no NPK fertilizer plot. The responses of cypress family growth, root morphology and N, P and Ca absorption to CaSO₄ fertilizer were analyzed.

Results In 3 g/kg NPK fertilizer plot, the addition of calcium had no significant effect on the seedling height, dry matter weight, N and P absorption of cypress, but inhibited the development of D2 and D3 roots, the Ca absorption of cypress was the highest under Ca₆ treatment, which was higher than Ca₀ treatment by 73.86%. There was significant difference in seedling height, dry matter weight and N, P and Ca absorption among 5 cypress families, and T2 families performed best. In no NPK fertilizer plot, Ca₃ treatment significantly increased the seedling height and root and stem dry matter weight, P and Ca absorption, which were respectively higher than Ca₀ treatment by 9.15%, 19.85%, 16.67%, 27.46% and 44.02%. Ca₆ treatment increased Ca absorption, which was higher than Ca₀ treatment by 39.95%, but inhibited the seedling height and the development of D1–D4 root system. With or without NPK fertilizer application, families and CaSO₄ treatments had significant interaction effects on cypress height and root dry matter weight.

Conclusions When NPK fertilizer is applied in low fertility soil, Ca fertilizer will not affect the growth of aboveground and root parts of cypress seedlings, but cypress families will. Without application of NPK fertilizer, applying a certain rate of Ca fertilizer could improve the Ca and P absorption, and the development of fine roots of the cypress seedlings. Therefore, good families should be considered firstly for seedling cultivation and afforestation, the supply of CaSO₄ is not so necessary under application of NPK fertilizer and can add a certain rate of Ca fertilizer under no NPK fertilization.