Revised leaf tissue nutrient sufficiency standards for northern highbush blueberry in western Oregon

Leaf tissue sampling to determine nutrient concentration is a common practice. Lab results are compared to published sufficiency levels to help inform nutrient management programs. Published tissue nutrient standards were developed from research experiments and estimates from large databases that relate tissue nutrient levels to high yielding fields. Current leaf sufficiency levels are similar for nutrient management guides published in various regions for northern highbush blueberry. Standards are based on nutrient concentrations in recent, fully expanded leaves on lateral shoots located below the fruiting zone. Since leaf nutrient levels vary over the growing season, recommended sampling time is when most or all nutrients are relatively stable to allow for comparison among years. Commonly grown cultivars with fruiting seasons ranging from late-June to mid-September including ‘Duke’, ‘Bluecrop’, ‘Draper’, ‘Liberty’, ‘Legacy’, and ‘Aurora’ were evaluated in conventional and organic production systems. Cultivars differed in leaf nutrient levels, but all were best sampled from late July to early August despite differences in fruiting season. While yield was typical in research studies done from 2013 to 2020, levels of some tissue nutrients were outside of currently published sufficiency standards for the region, particularly for leaf P, K, Ca, and Cu. Leaf tissue sufficiency standards have thus been revised to 1) account for broader variation among cultivars that may result from differences in fruiting season and nutrient allocation, 2) narrow or lower sufficiency standards where research has shown a negative correlation with yield at the higher levels within current sufficiency standards, and 3) provide typical levels for Al; while Al is not an essential nutrient in northern highbush blueberry, leaf Al concentrations may be used along with leaf Mn to monitor changes in soil pH over time. Revised leaf sufficiency standards for macro- and micronutrients will be presented.