Influence of nitrogen fertilization on quality,respiration and storage life of Washington navel oranges |
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| Authors: | Mr R A de Fossard Dr F H Lenz |
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| Institution: | 1. Division of Food Preservation, C.S.I.R.O., N. Ryde, N.S.W.
3. Irrigation Research Laboratories, C.S.I.R.O., Griffith, N.S.W.
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| Abstract: | Summary The effects of N on quality and storage life of oranges were investigated in a factorial field experiment at Griffith N.S.W.,
Australia. The trees that did not receive any ammonium sulphate (N0) produced fruit with the best quality of juice. However, such trees had only one quarter of the total yield (by weight) of
trees receiving 2 kg ammonium sulphate (N1) per annum. Higher levels of ammonium sulphate (4 and 8 kg; N2 and N4 respectively) did not increase in yield or quality as judged by the total soluble solids (T.S.S.) to titratable acid ratio
of the juice. N1 — trees had produced more juice and total soluble solids than other treatments.
Organoleptic tests favoured juice with the highest T.S.S./acid ratio and the lowest percentage titratable acid.
Although fruit stored at 0°C had the least fungal wastage, that stored at 15°C had less rind breakdown and total wastage (fungal
+ rind breakdown). Low temperature rind breakdown was particularly evident at 7.5°C and most oranges were affected irrespective
of nitrogen treatment. At 20°C and 25°C, a high temperature rind breakdown was found with N4 — fruit on short storage, and
in other fruit after longer storage. Associated with the rind breakdown and preceding its appearance was a higher rate of
respiration. Some typicalSeptoria spot (with pycnidia) was found at 20°C and the high temperature rind breakdown is possibly related to this disease or its
due to another pathogen; it was not possible to decide definitely its origin, whether pathogenic or physiological. In general
N0 — and N1 —fruits stored better at most temperatures than N2 — and N4 — fruits.
Respiration rate at 20°C was similar irrespective of treatment; a climacteric rise in evolution of carbon dioxide was not
found.
Yield, internal quality and storage life of fruit, considered collectively, indicated that trees receiving 2 kg sulphate of
ammonia per tree per annum were, superior to all other treatments in this experiment. |
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