Uptake and Partitioning of Nutrients in Blackberry and Raspberry and Evaluating Plant Nutrient Status for Accurate Assessment of Fertilizer Requirements

Knowledge of annual accumulation of nutrients and periods of rapid uptake allows for better management of fertilization programs. Raspberry and blackberry (Rubus sp.) plantings have relatively low nutrient requirements compared to many other perennial fruit crops. Annual total N accumulation in the aboveground plant ranged from 69−122 kg·ha^-1 and 37−44 kg·ha^-1 in field-grown red raspberry and blackberry, respectively. Research on the fate of applied ¹⁵N has shown that primocanes rely primarily on fertilizer N for growth, whereas floricane growth is highly dependent upon stored N in the over-wintering primocanes, crown, and roots; 30% to 40% of stored N was allocated to new growth. Plants receiving higher rates of N fertilizer took up more N, often leading to higher N concentrations in the tissues, including the fruit. Reallocation of N from senescing floricanes and primocane leaves to canes, crown, and roots has been documented. Accumulation of other macro- and micronutrients in plant parts usually preceded growth. Primocanes generally contained the highest concentration of most nutrients during the growing season, except Ca, Cu, and Zn, which often were more concentrated below ground in roots. Roots typically contained the highest concentration of all nutrients during winter dormancy. Nutrient partitioning varied considerably among elements due to different nutrient concentrations and requirements in each raspberry and blackberry plant part. This difference not only affected the proportion of each nutrient allocated to plant parts, but also the relative amount of each nutrient lost or removed during harvest, leaf senescence, and pruning. Macro- and micronutrient concentrations are similar for raspberry and blackberry fruit, resulting in a similar quantity of nutrient removed per ton of fruit harvested; however, yield may differ among cultivars and production systems. Nutrient removal in harvested red raspberry and blackberry fruit ranged from 12−20 kg·ha^-1 N, 2−4 kg·ha^-1 P, 11−21 kg·ha^-1 K, 1−2 kg·ha^-1 Ca, and 1−4 kg·ha^-1 Mg. Pruning senescing floricanes in August led to greater plant nutrient losses than pruning in autumn. Primocane leaf nutrient concentrations are used in nutrient management programs, but concentrations often differ among cultivars and with leaf sampling time. Development of tissue standards that are specific to the type of caneberry grown (e.g., primocane- and floricane-fruiting raspberry or blackberry, and erect vs. trailing blackberry) would be an important tool for nutrient management programs.