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Title: TEMPORAL CHANGES OF FRUIT QUALITY AND ITS SIGNIFICANCE IN FERTILIZATION RECOMMENDATIONS FOR GRAPEFRUIT PRODUCTION

Author
item CALVERT, D - UNIVERSITY OF FLORIDA
item HE, Z - UNIVERSITY OF FLORIDA
item BANKS, D - UNIVERSITY OF FLORIDA
item DOU, H - UNIVERSITY OF FLORIDA
item Alva, Ashok

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2000
Publication Date: 11/1/2000
Citation: CALVERT, D.V., HE, Z.L., BANKS, D.J., DOU, H.T., ALVA, A.K. TEMPORAL CHANGES OF FRUIT QUALITY AND ITS SIGNIFICANCE IN FERTILIZATION RECOMMENDATIONS FOR GRAPEFRUIT PRODUCTION. AGRONOMY ABSTRACTS. P 274. 2000.

Interpretive Summary: Consumption of grapefruit has been demonstrated to result in significant health benefits. Acceptance of grapefruit in the fresh fruit industry depends on its external and internal qualities. For growers, the fresh fruit market brings high economic return. Therefore, cultural management that positively influences the fruit quality will have a major impact on the economic returns. In this study, the effects nutrient management of 30+ year old white Marsh grapefruit had on the fruit quality was evaluated. The treatments included 0 to 336 kg/ha N applied as water soluble granular fertilizer using a N:P:K blend. The changes in fruit quality were evaluated between October, 1999 and May, 2000. The fruit weight increased through the sampling duration. Juice content increased only from October to December. The changes in brix content were minimal during October to March, but decreased from March to May. The acid content decreased through the sampling period. The soluble solid content increased from October through March. The juice and soluble solid contents increased with the fertilizer rate.

Technical Abstract: Fruit quality is an important component of citrus production, which affects economic return. Information is needed on pre-harvesting changes of fruit quality for timing both fresh fruit marketing and processing. A field study was conducted to evaluate the temporal changes of some key external and internal fruit qualities of 30+ year old white Marsh grapefruit (C. Paradisi M.) Trees on sour orange rootstock (C. Aurantium L.) grown in a Riviera fine sand, as affected by fertilizer rates (0 to 336 kg N ha-1 yr-1 with N:K ratio = 1:00: 0.17: 1.02, applied as dry water soluble granular.) Fruit samples were collected for quality analysis from October, 1999, through late May, 2000. Individual fruit weight increased continuously from October to May and was up to 500 grams even at the highest fertilizer rate (336 kg N ha-1). The increase in juice contents was significant from October to December but was marginal from December to May. Change in fruit tBrix content was minimal from October to March but decreased from March to May. Fruit acid content decreased persistently from October to May. As a result, the Brix/acid ratio increased from October to May. Solids content significantly increased from October to March but the increase was marginal from December to May. Both juice and solids contents increased with fertilizer rates, especially at the early season.