- C M Menzel, G F Haydon and D R Simpson
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Maroochy Horticultural Research Station, Queensland Department of Primary Industries,
P.O. Box 5083, Queensland 4560, Australia - 1993
This paper reports on the study of the effects of time of nitrogen application on productivity of six-year-old Bengal lychee trees in subtropical Queensland, Australia. Treatments were: no nitrogen (control), or nitrogen application in winter or summer, or split between the two periods. Leaf nitrogen concentrations were lower in winter and higher in summer, with winter nitrogen applications. Application in summer gave the reverse pattern. However, these differences in leaf nitrogen were not large enough to affect yield. In contrast, yields of control trees after four years without nitrogen, were about half those of trees receiving nitrogen. These results demonstrate the difficulty in manipulating lychee yields in the field with fertilisers. Application of fertilisers should be supported by the results of tissue analyses, preferably just after panicle emergence.
Summary:
The study investigated the effect of timing of nitrogen (N) fertilizer application on productivity of six-year-old Bengal lychee trees in subtropical Southern Queensland, Australia.
Treatments included no nitrogen, winter nitrogen application, summer nitrogen application, and split application between winter and summer.
Leaf nitrogen concentrations were lower in winter and higher in summer with winter N application, and the reverse with summer N application, but these differences did not significantly affect yield.
Yields of trees without nitrogen for four years were about half those receiving nitrogen, showing the importance of nitrogen supply.
Leaf nitrogen concentration after panicle emergence (flower cluster emergence) was an important indicator for timing tissue analysis.
Nitrogen applied in summer resulted in quicker increases in leaf nitrogen compared to winter application.
There was no significant impact of nitrogen timing on leaf growth and flowering, but very high leaf nitrogen (>1.8%) in August led to poor flowering.
The yield response to nitrogen was difficult to manipulate in the field by timing alone.
The study recommended nitrogen application in winter as the best general approach for Southern Queensland lychee orchards, supported by tissue analysis for best timing.
Other findings highlighted the importance of soil type and rainfall in nitrogen leaching and retention, which influence leaf nitrogen and yield.
Overall, nitrogen is critical for good yields, but precise timing of application is less influential than previously thought.