Abstract:

In order to study the effect of fertilization on root system distribution and biomass, an orthogonal experimental design was implemented on Eucalyptus urophylla ×E. grandis saplings with treatments of nitrogenous fertilizer (1 g, 3 g, 6 g), potassium fertilizer (1 g, 3 g, 6 g), phosphorus fertilizer (2 g, 6 g, 12 g), and eucalypt special fertilizer (1 g, 3 g, 6 g). The fresh weight was measured immediately after the entire root system was extracted. The results indicated that: (1) phosphorus fertilizer had significant effects on root vertical penetration, while other 3 fertilizers had similar effects, and much less than that phosphorus. The vertical distribution of the all seedling roots ranged from 32 cm to 57 cm; (2) Compared to the other 3 fertilizers, eucalypt special fertilizer had a significant effect on root horizontal extension. The horizontal distribution of the roots ranged from 57 cm to 86 cm; (3) Nitrogenous fertilizer had significant influence on number of root tips, while other three fertilizers did not. The number of root tips ranged from 47 to 71; (4) Eucalypt special fertilizer, as a key factor, had a significant effect on the length of the primary lateral roots. The length of the primary lateral roots ranged from 15.2 cm to 30.5 cm; (5) Phosphorus fertilizer had a significant effect on the total biomass of roots ranged from 14.739 g to 29.336 g; (6) When root diameters were in the range of 0 to 2 mm, 2 to 5 mm, 5 to 10 mm and larger than 10 mm, the root biomass would gradually increased. All the treatments had positive effects on the growth of root biomass when root diameter larger than 10 mm.