Five-year nutritional study of apples in commercial high density orchards

The purpose of the study was to examine nutrient levels in high density commercial apple orchards. Leaf samples were collected from 12 commercial apple orchards located in the mid-Atlantic region of the US over 5 years. The plantings were part of a uniform trial of ‘Honeycrisp’/M.26EMLA (HC) and ‘Cameo’/M.9NAKBT337 (CA) established in 2008 at a spacing of 1.4×4.25 m (1709 trees ha^-1). Leaf calcium (Ca) and potassium (K) levels were lower in HC than in CA 5 out of 5 and 4 out of 5 years, respectively. Calcium levels in HC were below the minimum desired level for apples, 1.3% dry weight, in 3 out of 5 years. The ratio of the percent leaf dry weight of N/Ca was always higher in HC than in CA and significantly higher 4 out of 5 years. Leaf levels of the Ca/Mg ratio were always lower in HC and significantly lower 4 out of the 5 years. Micronutrient levels of manganese were the only consistent differences between the cultivars. Manganese (Mn) was always higher in HC and significantly higher 4 out of 5 years. There were no consistent differences between the cultivars for leaf nitrogen (N), phosphorus (P), magnesium (Mg), (Mg+K)/Ca ratio or the other micronutrients. Soil nutrient analysis was measured just prior to planting and again in 2014 at 11 of the sites. Levels of Ca, K, P, Mg and the cation exchange capacity (CEC) tended to decline, however; the extent of the decline varied by site.