Effect of foliar urea sprays on Granny Smith fruit colour
1989
Smith, R.G. (MAFTech, Palmerston North (New Zealand)) | Pinchin, A.J. | Taylor, M.P. (MAFTech, Hastings (New Zealand)) | Prasad, M. (Levin Horticultural Research Centre (New Zealand))
The application of nitrogen to Granny Smith apple trees as a means of increasing fruit greenness was studied in Hawkes Bay orchards between 1984 and 1987. Foliar application of 0.5% urea solution, applied fortnightly from mid-December, improved overall fruit colour both before and after cool storage, depending on the nitrogen status of the trees. Soil application of urea appeared to be less effective than foliar application. Despite variation in fruit colour between different positions within the tree, no consistent differences in colour response (as reflected in colorimeter readings) were found. The difference between sprayed and unsprayed fruit tended to increase with time after harvest. Increasing the urea concentration increased the colour response but also caused more leaf burn, a reduction in fruit size and an increase in fruit N content. A taste panel evaluation showed less preference for fruit sprayed with the higher concentration of urea. It is concluded that foliar application of urea can be used to improve fruit colour in Granny Smith orchards with a fruit colour problem, but the solution concentration should not exceed 0.5% urea to minimise adverse effects on fruit size, taste and storage ability
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