EFFECTS OF THE NITROGEN SOURCES ON THE GROWTH OF RABBITEYE BLUEBERRY UNDER SOIL CULTURE

Three experiments were conducted to obtain the data for the recommended method of fertilizer application in rabbiteye blueberry.

One-year-rooted cuttings of ‘Homebell’ was grown over two years (experiment I) or three years (experiment II and III) under soil culture (used ten plants per treatment. pot culture. the mixed soil with peat-moss and orchard soil). N, P, K, Ca and Mg fertilizers were applied as for basal fertilizer at April, and applied at May, June and August as for side dressing in each year.
Tap water adjusted to the pH between 4.5–5.5 were irrigated on demand.
Repotting carried out making use of the larger size pot at the beginning of April in each year.

The growth of whole plant, top and root were the most superior in the treatments of NH₄-N and Urea (in each N application rate per 1/2000 are Wagner pot), however, fruit yield were the superior in the low N application rate of NH₄-N and NH₄-N+NO₃-N treatments in experiment I. The best growth of top and root was gained from the treatment of NH₄-N:NO₃-N = 5:1 (N application rate was 1.2 g per pot at third year), although the much more fruit yield was NH₄-N:NO₃-N = 6:0 in experiment II. In experiment III, the many kind of NH₄-N fertilizers [(NH₄)₂SO₄Cl, (NH₄Cl) ₂HPO₄. N application rate was 1.0 g per pot] produced the best growth and the most fruit yield.

The least growth were gained from the treatments of NO₃-N in experiment I, from the NH₄-N:NO₃-N = 0:6 (NO₃-N only applied) in experiment II, and the NO₃-N fertilizer [KNO₃, Ca(NO₃)₂4H₂0, NaNO₃] in experiment III.

The treatments of NH₄-N+NO₃-N [mixed (NH₄)₂SO₄ with NaNO₃], NH₄NO₃ and NH₄-N: NO₃-N = 3:3 produced better growth than the NO₃-N, though, was worse growth than the NH₄-N in all three experiments.

N concentration of leaves were the most in the plants applied NH₄-N, however, the plants applied NO₃-N were the least, and the plants of NH₄-N+NO₃-N and Urea treatments were the medium.
The relation between P, K, Ca and Mg contents of leaves and N forms were different from in each experiment.
The difference of accessory elements of N sources had the little effects on the growth.

It is concluded that the NH₄-N form fertilizers is essential for the growth of ‘Homebell’ in rabbiteye blueberry.

V International Symposium on Vaccinium Culture

T. Tamada

https://doi.org/10.17660/ActaHortic.1993.346.27