Nitrogen requirements and vegetative growth of pot-lysimeter-grown 'Fuji' apple trees fertilized by drip irrigation with three nitrogen rates

摘要

A pot-lysimeter experiment was designed to assess the N requirements of 'Fuji' M.9 apple (Malus domestica Borkh.) trees fertilized by drip irrigation with three N rates during 2.5 growing seasons (July 1996 to October 1998). Nitrogen rates of 17 (low), 34 (medium), and 67 mg l~(-1) (high) were chosen for comparison. Low, medium, and high N rates averaged 0.47, 0.89, and 2.18 g N tree~(-1) for 1996; 1.07, 2.35, and 4.90 g N tree~(-1) for 1997; 3.81, 6.93, and 13.69 g N tree~(-1) for 1998. Corresponding N accumulation was 0.37, 0.44, and 0.37 g N tree~(-1) for 1996; 0.74, 0.82, and 1.00 g N tree~(-1) for 1997; 2.93, 3.99, and 2.62 g N tree~(-1) for 1998. Dry mass increased by 360, 442, and 256 g tree~(-1), respectively. Soil inorganic N concentration increased with N rate, and considerable N was accumulated for soils receiving 67 mg N l~(-1). Average N uptake efficiency decreased with increasing N rates. However, uptake efficiencies of P and K were highest at 34 mg N l~(-1). Overall, trees receiving 67 mg N l~(-1) had significantly smaller trunk cross-sectional areas below and above the graft union, tree height, numbers of leaves and floral buds, and total leaf areas than the trees receiving the lower N rates. Trees receiving 34 mg N l~(-1) had greater dry mass, contents of N, P and K, and numbers of floral buds and shoots than trees receiving 17 mg N l~(-1). Based on tree vigour, budgets for N, P, and K and soil N status, N -50 kPa of soil water potential, without over-fertilizing and excessive growth.