EFFECT OF CULTIVATION AND NITROGEN ON FRUIT QUALITY, YIELD AND COLOR OF McINTOSH APPLES GROWN IN IRRIGATED GRASS SOD COVER CROP

Nitrogen treatments from 0.15 to 0.90kg of nitrogen and cultivation treatments from zero to three shallow rotovations were applied in a split-plot design to 30-year-old McIntosh apple trees growing in irrigated grass sod.Fruit quality was very largely unaffected by the treatments. Pressure test after harvest was reduced from 6.61 to 6.44kg (P=0.10) as nitrogen increased. Number of rots increased from 2.7 to 3.9 per 60-fruit sample with increasing nitrogen. Titratable acidity and soluble solids after harvest and pressure test, titratable acidity, soluble solids, stem-cavity browning and core flush in tests after storage were all unchanged. In addition, none of these tests were affected by cultivation except pressure test, which decreased with more cultivation (P=0.10).Yield was not changed by either the nitrogen or the cultivation treatments, and terminal length increased only slightly with more cultivation. However, nitrogen concentration in the leaf was increased from 1.90 to 1.98% by the nitrogen treatments and from 1.83 to 1.98% by increasing cultivation. Extra Fancy grade was reduced and C grade increased by increasing nitrogen (P=0.10), but cultivation had no effect.The conclusion is drawn that grass sod can very largely eliminate the effect of widely different nitrogen fertilization levels on McIntosh apple, and that moderate cultivation changes this effect only slightly. In many mature orchards of high initial fertility, nitrogen fertilizer may be required in only small amounts or even not at all for optimum fruit color.

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