Leaf Tissue Standards For Blueberries Grown in Western Oregon Revised

By Bernadine Strik and Amanda Davis, Professor and
Senior Faculty Research Assistant, I Department of Horticulture and NWREC, Oregon State University

Growers and tissue (leaf) testing labs in the region have long used the Blueberry Nutrient Management Guide published by Oregon State University (https://catalog.extension.oregonstate.edu/em8918) to compare collected leaves to sufficiency standards for management of fertilizer programs.

The standards listed in this 2006 publication were developed from research experiments and estimates from large databases that related tissue nutrient levels to high-yielding blueberry fields. However, production systems for blueberry and the cultivars grown have changed considerably since the 1990s and early 2000s. Various production system research trials from 2006 to 2020, led by Bernadine Strik, have informed a needed revision to leaf nutrient sufficiency standards for optimal yield and quality for conventional and organic production in western Oregon.

Key points and changes are as follows:

What leaves to sample: Standards are based on nutrient concentrations in recent, fully expanded leaves on lateral shoots located below the fruiting zone. Do not sample whips on established plants.

Sample cultivars separately because they differ in the concentration of many nutrients. Sample blocks with very different soils or conventional versus organic management separately.

When to sample: Since leaf nutrient levels vary over the growing season, the recommended sampling time is when most or all nutrients are relatively stable to allow for comparison among years. Whether you are sampling an early-season cultivar like ‘Duke’ or a late-season cultivar like ‘Aurora’, sample all cultivars at the same time. The best time to collect leaves for tissue analysis is from late July to early August in western Oregon.

Sufficiency standards are ONLY relevant when leaves are sampled at the correct time of the season (late July to early August) because leaf nutrient levels change from spring to fall in a pattern unique to the nutrient. Key revisions to the leaf nutrient sufficiency standards are as follows (Table 1).

• Nitrogen: Adjusted the lower level of leaf N to account for levels commonly found in good-yielding organic fields. Adjusted the upper level of leaf N sufficiency to account for values that may be found in good performing younger fields and high-yielding, mature, conventional fields, considering the cultivars grown in this region.

• Phosphorus: Leaf P standards were lowered to better reflect levels found in young through mature cultivars grown in various production systems.

• Potassium: We found an optimal range in leaf K of 0.42% to 0.55% for maximum yield in organic production and 0.36% to 0.61% in conventionally managed blueberry cultivars. Sufficiency levels have been revised to discourage growers from applying fertilizer K when not needed as this may reduce yield. Added a footnote that leaf K may be higher in young establishing plants.

• Magnesium: Revised leaf Mg sufficiency to better reflect the lower levels found for some cultivars in organic and conventional production systems.

• Micronutrients: Sufficiency standard ranges for zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) were adjusted to better reflect levels in high-yielding fields in various production systems.

In Table 1 we have included leaf sufficiency levels published in the 2006 Blueberry Nutrient Management Guide and those for western and eastern Washington as a reference. We recommend all blueberry growers and tissue testing labs use the revised standards shown in Table 1, highlighted in green, for western Oregon.

 

Table 1. Leaf tissue nutrient sufficiency levels for blueberry in Oregon and Washington, including revised levels for western Oregon (in green).

z Currently published standards for western Oregon in Hart et al. (2006)
y Revised standards based on more current research findings
x From Davenport and DeVetter (2019)
w Range encompasses lower levels often found in organic production
v Leaf K may be higher in the first two growing seasons (young plants)

The research projects that led to these revisions can be accessed at the links below:

Davis, A.J. and B.C. Strik. 2021. Transitioning long-term mulch treatments and fertilizer source to alternative products improved yield and plant potassium status in long-term organic production of highbush blueberry. HortScience 56:363-367. ttps://doi.org/10.21273/HORTSCI15659-20

Strik, B.C. and A.J. Davis. 2021. Individual and combined use of sawdust and weed mat mulch in a new planting of northern highbush blueberry. III. Yield, fruit quality, and costs. HortScience 56:363–367. https://doi.org/10.21273/HORTSCI15659-20

Strik, B.C., A.J. Davis, D.R. Bryla, and S. Orr. 2020a. Individual and combined use of sawdust and weed mat mulch in a new planting of northern highbush blueberry I. Impacts on plant growth and soil and canopy temperature. HortScience 55:1280-1287. https://doi.org/10.21273/HORTSCI15122-20

Strik, B.C., A.J. Davis, and D.R. Bryla. 2020b. Individual and combined use of sawdust and weed mat mulch in a new planting of northern highbush blueberry II. Nutrient uptake and allocation. HortScience 55:1614-1621. https://doi.org/10.21273/HORTSCI15271-20

Strik, B.C. and A.J. Vance. 2015. Seasonal variation in leaf nutrient concentration of northern highbush blueberry cultivars grown in conventional and organic production systems. HortScience 50:1453–1466. https://doi.org/10.21273/HORTSCI.50.10.1453

Strik, B.C., A. Vance, D.R. Bryla, and D.M. Sullivan. 2017a. Organic production systems in northern highbush blueberry: I. Impact of planting method, cultivar, fertilizer, and mulch on yield and fruit quality from planting through maturity. HortScience 52:1201–1213. https://doi.org/10.21273/HORTSCI12179-17

Strik, B.C., A.J. Vance, and C.E. Finn. 2017b. Northern highbush blueberry cultivars differed in yield and fruit quality in two organic production systems from planting to maturity. HortScience 52:844–851. https://doi.org/10.21273/HORTSCI11972-17

Strik, B.C., A. Vance, D.R. Bryla, and D.M. Sullivan. 2019. Organic production systems in northern highbush blueberry: II. Impact of planting method, cultivar, fertilizer, and mulch on leaf and soil nutrient concentrations and relationships with yield from planting through maturity. HortScience 54:1777–1794. https://doi.org/10.21273/HORTSCI14197-19