Accumulation and distribution of micronutrients in Willamette red raspberry plants

Abstract

Willamette red raspberry (Rubus idaeus L.) plants were sampled monthly to determine the accumulation and distribution of copper (Cu), boron (B), zinc (Zn), manganese (Mn) and iron (Fe) over the growing seasons of four different years. The soil (Marble Hill series) was typical of that commonly used for commercial raspberry production in the area. No micronutrients were applied. The micronutrients generally accumulated as the season progressed in a manner similar to the accumulation of dry matter. Maximum accumulation of micronutrients in the aboveground portion of the plants did not necessarily occur at the end of the growing season because of different growth patterns of the floricanes and primocanes. The ripe berries, which would be removed by harvesting, contained a significant proportion of the total accumulation of micronutrients: Cu (18–26%), Zn (15–25%), B (3–16%), Fe (5–8%) and Mn (4–7%). However, concentrations of the micronutrients in the various parts of the plant varied considerably from month to month and year to year. There was no obvious relationship between weather conditions and the variations in micronutrient concentrations. Extreme variations within and between growing seasons suggest concentrations of micronutrients in leaves cannot readily be used to develop tissue-analysis-based fertility recommendations. Floricane stem micronutrient concentrations were more stable but the relationship between these concentrations and the overall nutrient status of the plants needs to be determined before they can be used for diagnostic purposes. Before accumulation and distribution patterns of micronutrients in raspberry can be used as a basis for development of fertilizer management strategies, additional measurements from other locations are needed. The results from this study should serve as guidelines for developing sampling procedures and their practical applications. Key words: Copper, boron, zinc, manganese, iron, Rubus idaeus L.