ISHS Acta Horticulturae 448: III International Symposium on Mineral Nutrition of Deciduous Fruit Trees
COMPENSATORY RECOVERY OF SURVIVING APPLE ROOTSTOCK LAYERS FROM INJURY CAUSED BY MONOAMMONIUM PHOSPHATE STARTER FERTILIZER |
| Author: | F.J. Peryea |
| Keywords: | Malus domestica, replant, phosphorus, nitrogen, mineral nutrition, apple, rootstock |
| Abstract:
Excessively high rates of monoammonium phosphate (MAP) starter fertilizer may injure and possibly kill newly planted apple trees (Malus domestica Borkh.) because of transitory soil salinization; however, by the end of the first growing season, it is often difficult to visually differentiate within a single planting between the trees that initially showed injury symptoms and did not die and the trees that never displayed symptoms. This qualitative field observation was evaluated by growing M.7a apple rootstock layers in a glasshouse in Burch sandy loam soil amended with MAP at five rates (0, 1, 2, 3, 5 kg/m3). Layer survival and the mass of new shoot (all newly grown shoots and leaves), old shoot (original whip), and root tissues were determined at 69, 100, 131, and 156 days after planting. New shoot mass of the surviving layers was greater at all sampling times in the 1 and 2 kg/m3 treatments than in the 0 kg/m3 treatment. New shoot growth of the surviving layers in the 3 and 5 kg/m3 treatments was the same or less than the 0 kg/m3 treatment until after 100 days, when it increased to levels comparable to the 1 and 2 kg/m3 treatments. Old shoot mass and root mass were only weakly related to MAP rate but exhibited responses qualitatively similar to those of new shoot mass. The highest MAP rate associated with maximum survival (1 kg/m3) was lower than those associated with maximum new shoot growth at 156 days (≥2 kg/m3). The results quantitatively substantiate the field observation that apple trees that survive excessive rates of in-hole MAP starter fertilizer appear to compensate for poor early growth with increased growth rates later during the growing season. | |
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