EFFECTS OF UREA AND DEFOLIANT-CUEDTA IN A SINGLE OR A MIXED APPLICATION IN THE AUTUMN ON N RESERVES AND REGROWTH PERFORMANCE OF YOUNG ‘FUJI’/M26 APPLE TREES

One-year-old potted Fuji/M26 apple trees were grown outside during the growing season.
Uniform trees were selected and divided into four groups and sprayed with water (control), 0.5% CuEDTA, 3% urea or a mixture of 0.5% CuEDTA and 3% urea (CuEDTA + urea) on October 5. Leaf defoliation was recorded after the treatments.
All trees were harvested in late December, and half of the trees from each treatment were destructively sampled for N analysis and the other half, kept in 2°C cold storage, were repotted into nitrogen free medium (vermiculite: perlite = 1:1) in early April for evaluation of regrowth.
Both CuEDTA and CuEDTA + urea treatments promoted leaf defoliation, but CuEDTA slightly reduced, whereas CuEDTA + urea significantly increased, nitrogen reserve levels of the trees compared with control.
The regrowth performance in the following season was positively related to nitrogen levels, and the new growth biomass, leaf N and leaf colour (SPAD readings) were all increased with the increase of reserve N after two-month’s growth.

XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees

S. Dong, L. Cheng, L.H. Fuchigami

urea, CuEDTA, spray, defoliation, Malus domestica, apple

https://doi.org/10.17660/ActaHortic.2004.636.2