STUDIES ON THE EFFECT OF RARE-EARTH ON NURSERY STOCK GROWTH IN PAULOWNIA SPP.

From 1987 to 1989, applied experiments with seedlings and rooted cuttings have been carried out both in greenhouse and nursery. It was shown that 5 ppm NL-1 or NL-32 treatment was optimum for P. elongata and P. tomentosa seedlings in solution culture experiments partly by steady state nutrition, average biomass increments of seedlings were up about 40% in comparison with control (no rare-earth). The growth of seedlings was inhibited at 50 ppm without ajusting pH value of culture solution (about 4), whereas biomass increased by 7%~30 % for P. elongata seedlings after ajusting pH near 6 with CaCO3. Spraying the leaves of nursery stocks in Paulownia spp. with NL-1 complex rare-earth solution at 50 ppm for the early two times and 75 ppm once later (pH5.0~5.5), the percentage of first class nursery stocks raised by a big margin in comparison with control, direct extra income per ha will be 3 000 yuan per year.