ISHS Acta Horticulturae 512: XXV International Horticultural Congress, Part 2: Mineral Nutrition and Grape and Wine Quality
PRODUCTIVITY, POSTHARVEST PHYSIOLOGY, AND SOIL NITRATE MOVEMENT AS INFLUENCED BY NITROGEN APPLICATIONS TO 'DELICIOUS' APPLE |
| Author: | E. Fallahi |
| Keywords: | Malus domestica, apple postharvest, fruit nutrition |
| Abstract:
'Redspur Delicious' apple trees on M.7 rootstock used in this experiment were planted in 1980. Urea, at five rates, was applied to the soil within the drip line of trees 1) all at full-bloom; 2) half at full-bloom and half in late spring; and 3) all in fall. Samples were taken for leaf analysis and fruit quality was measured at harvest and after storage in 1992 to 1994. Fruit red color decreased with every incremental increase in the rate of applied N. Fruit from trees with 45 and 181 g N/tree had greater red color than did those to which higher quantities of N had been applied. Firmness of fruit from trees with 45 g N/tree was higher than that from all other treatments. Trees receiving 590 g N/tree had lower yield and smaller fruit size in 1994. High N increased fruit ethylene and respiration. Monitoring nitrate movement through the soil profile showed that application of N at 454 g/tree or greater resulted in excess levels of NO3-N in the soil, increasing the possibility of underground water contamination. Application of up to 318 g N/tree did not show excess soil nitrate at a depth of 106 to 152 cm. Considering all factors studied in this experiment, optimum yield, high fruit quality at harvest and after storage, and low soil nitrate were produced when leaf N concentration was about 2.03 % to 2.16% dry weight. Under conditions of this experiment, these levels were achieved by application of up to 181 g N/tree. Application of N at 45 g/tree or less (leaf N less than 2.03% dry weight) may not be sufficient for yield and fruit soluble solid concentration at harvest. | |
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