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K deficiency was identified for the first time in British Columbia orchard soils. Greenhouse-grown apple seedlings responded to K in soils low in available K. MacSpur McIntosh (Malus domestica Borkh.) had increased leaf K (above deficiency) and improved initial fruiting after surface applications of KCl in an orchard with low soil K.
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Neilsen et al. (1989) studied this question.
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