Cranberry nutrients, phenology, and nitrogen-phosphorus-potassium

The objective of this study was to compile and interpret nutritional and developmental data for cranberry (Vaccinium macrocarpon Ait.) as the basis for standardizing experimental techniques (particularly data collection) and tissue analysis, including tissue to sample, time of sampling, and normal element concentrations for \u27Early Black\u27. Seasonal nutrient levels were determined in tissues of \u27Early Black\u27 cranberry under 10N-8.7P-8.3K fertilization (O, 170, 335, and 505 kg/ha). After three years, N, P, and K concentrations in new shoot tissues were positively affected by N-P-K supply. The N-P-K supply had no effect on Ca and Mg concentrations in new shoot tissue but B concentrations were lowest in unfertilized plants. N, P, K, and Cu concentrations in new shoots declined during the season, whereas those of Ca, Mg, B, and Mn rose. Element concentrations in the tissues indicated that mobilization of elements into new shoots from old leaf and woody stem tissues occurred. In an average crop (17 Mg/ha), 8.5 kg N/ha and 14.7 kg K/ha were removed from the cranberry bog. Vegetative growth (dry weight, upright length) was positively correlated with N-P-K supply, but the highest yields were associated with 335 kg N-P-K/ha. Upright density, percent of uprights flowering, and fruit set were the important determinants of yield. These variables were proposed as standards for data collection. Growing degree day (GDD) accumulations were recorded during this study using a base temperature of 6.5C (lower than previously recommended). Based on GDD accumulations at the canopy level, the correct base temperature for cranberries is most likely 4.5C or lower. However, for a single location over several years, day number was superior to GDD as a predictor of developmental and nutritional status. A period of stable element concentration in new shoot tissue (10 August to 15 September) was identified and recommended as the time to collect cranberry tissue samples for analysis. Mixed vegetative and flowering new upright tips were recommended as the tissue to sample, and standards for \u27Early Black\u27 were proposed. Element concentrations in \u27Howes\u27, \u27Stevens\u27, \u27Pilgrim\u27, \u27Bergman\u27, and \u27Franklin\u27 were determined and compared to the \u27Early Black\u27 standard values