Do Soil and Foliar Applied Minerals Improve Soil Health, Nutrient Density, and Flavor in organic Blueberries

Project Overview

Project Type: Farmer/Rancher
Funds awarded in 2015: $14,969.00
Projected End Date: 12/31/2017
Region: Western
State: Washington
Principal Investigator:
Larry Bailey
Clean Food Farm

Annual Reports


  • Fruits: berries (blueberries)


  • Production Systems: organic agriculture

    Proposal summary:

    Nutritional density for all fruit has fallen >15% since the USDA began publishing data in 1965. Skeptical small fruit famers cite evidence that certified organic fruits are not nutritionally superior to conventionally farmed fruit[i] and that “Certified Organic” is no assurance of superior nutrient density or better flavor. In a speech to sustainable producers, Jo Robinson, author of “Eating on the Wild Side” stated that nutritional density is primarily determined by fruit variety. [ii]  This trial will investigate if soil health and specific organic inputs measurably influence nutrient density and flavor over variety selection. There is anecdotal evidence that a few organic blueberry producers in Western Washington and Oregon grow fruit claimed to be nutritionally superior and better tasting. These producers also claim they receive a price premium over organic berries.[iii] We will trial similar inputs used by these growers to study the effects of soil and foliar applied minerals on soil health, nutrient density, and flavor. We will trial two organically-produced northern highbush blueberry (Vaccinium corymbosum) varieties: Elliot[iv], a variety known for greater nutrient density, and Aurora, which is not known to have greater nutrient density than other varieties. We will share project results with blueberry producers through an on-farm workshop, conference presentations, on-line video, a webinar, and social media.


    [i]  Smith-Spangler, C; Brandeau, ML; Hunter, GE; Bavinger, JC; Pearson, M; Eschbach, PJ; Sundaram, V; Liu, H; Schirmer, P; Stave, C; Olkin, I; Bravata, DM (September 4, 2012). "Are organic foods safer or healthier than conventional alternatives?: a systematic review."Annals of Internal Medicine 157(5): 348–366.


    [ii] Speech to Tilth Producers, 11-7-14 at annual conference in Vancouver WA


    [iii] accessed 11-12-14


    [iv] Elliot variety was among the highest in measured antioxidants in this peer-reviewed study (2011): Comparative Polyphenolic Content and Antioxidant Activities of Some Wild and Cultivated Blueberries from Romania, Andrea BUNEA, Dumitri?a O. RUGIN?, Adela M. PINTEA, Zori?a SCON?A, Claudiu I. BUNEA, Carmen SOCACIU*1 University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca, 3-5 M?n??tur Street, 400372,  Cluj-Napoca, România, Vol 39, No 2


    Project objectives from proposal:

    Anecdotal claims that particular organic input regimens produce better berries and improve soil health are not enough for most growers to spend money and labor implementing those practices. Organic growers need quantifiable data detailing the costs and benefits to support such changes in management regimens.

    Most blueberry producers test soil and plant tissue, but few test nutritional content of harvested blueberries. Additionally, buyers do not typically test blueberries for nutrition. Taste and nutritional content appear to be correlated; however, better taste is subjective and varies between individuals.[i]  Since organic blueberry producers get paid by the pound, there is little incentive to produce nutritionally superior, better-tasting blueberries. As long as their blueberries are average they are accepted by the buyer at organic market rate. The additional mineral and foliar inputs add cost to blueberry production over traditional organics. We will investigate if these additional organic input regimens measurably improve:

    1. Nutrient density
    2. flavor, and
    3. soil health.

    Blueberry producers have limited means to evaluate which input and management practices might produce superior flavor and nutrient density.  Additionally, producers typically “farm the input dollar cost,” not the output quality vs. price received. We will investigate if additional organically-certified inputs (such as those trialed in this study) actually produce a more nutritious better-tasting product which might be able to be marketed as such.

    Three management regimens will be evaluated in two blueberry varieties with a randomized complete block design with four replications. Management regimens include: 1) Control, 2) Control+Azomite, and 3) Control+Azomite+foliar. The control includes organic blueberry management practices recommended by Oregon State University Extension, including fertilizing with feather meal, rock phosphate, gypsum, manganese sulfate, and sodium borate as indicated by soil test results and mulching with compost topped by sawdust. Azomite™ is a complex silica ore high in trace minerals and the foliar application includes Pacific Gro fish hydrolysate with crab meal, Sea Crop, and coconut-based emulsifiers.

    Flavor profile will be analyzed with two blind taste tests conducted in 2016 and 2017. Consumers will be asked to rate on a 1-5 scale (one being the lowest/worst, five being the highest/best, three being average) attributes like flavor, texture, and sweetness. Consumers will be asked if they would pay more for a certain blueberry they are tasting.

    Soil will be tested annually for minerals, pH, and electrical conductivity. The Haney test will be used to track changes in soil health based on management regimens over the trial period. Tissue tests will be conducted to assess nutrient and mineral uptake in August 2016 and 2017. During the growing season, monthly field tests for pH and electrical conductivity will be made with instant reading electronic instrumentation to monitor changes in the soil.

    Nutritional content of blueberry fruit will be quantified in 2016 and 2017 by analyzing concentrations of vitamins A, C, E, and K and total phenolics, monomeric anthocyanins, pH, titratable acidity, and soluble sugars.  Brix will also be measured.

    Educational components include:

    1. Farm walk with small fruit growers
    2. Workshops at regional conferences for small fruit producers
    3. Social media – Facebook
    4. Fact sheets for producers and buyers
    5. PPTs and photographs for use in workshops and fact sheets
    6. You Tube video of research project for WSU website and for social media
    7. Potential publications
    8. Webinar


    List of Achievable Objectives


    Timeline Start

    1.     Perform soil tests


    Analyses include: pH, Buffer pH, Sum of Cations (CEC), Sulfur,

    Soluble Salts, Potassium, Zinc, Organic Matter, Calcium, Iron, Nitrate-Nitrogen, NH4, Magnesium, Manganese, Phosphorus, Sodium, Copper, Boron

    October 2015

    October 2016

    October 2017

    2.     Perform Haney Soil health tests

    Analyses include: total organic

    carbon and total organic nitrogen to determine a C:N ratio; Solvita CO2 Burst Test to assess microbial activity and potentially mineralizable nitrogen; and a weak acid (H3A) extraction to show some available plant nutrients.

    October 2015

    October 2016

    October 2017

    3.     Produce annual reports and provide participant evaluation summaries to SARE

    Per grant contract requirements

    December 2015, 2016, and 2017

    4.     Perform tissue tests on growing blueberry plants

    Plant analyses include: Nitrogen, Sulfur, Boron, Phosphorus, Zinc, Molybdenum,

    Potassium, Iron, Calcium, Manganese,

    Magnesium, Copper

    August 2016

    August 2017

    5.     Perform nutrient density tests on fruit from 24 test plots

    50 berry sample from each test plot. Each berry lot analyzed for: nutritional content, including vitamins C, A, K, and E plus total phenolics, monomeric anthocyanins, pH, titratable acidity, and soluble sugars. 

    August 2016

    August 2017

    6.     Conduct two blind fresh fruit taste test panels for both two blueberry varieties the 3 treatment-mgmt. methods

    Conduct berry taste tests at WSU Puyallup Research station


    Area farmers market

    August 2016



    August 2017

    7.     Conduct a producer farm walk with Tilth producers and WSU Small farm team


    September 2017

    8.     Produce two fact sheets

    One fact sheet for producers to include cost benefit analysis and one fact sheet for produce buyers

    September 2017

    9.     Produce a YouTube video documenting project

    Video and photographs will be taken throughout the project for use in annual reports and educational materials

    September 2017

    10.  Develop Facebook site for project


    August 2015 –updating through December 2017

    11.  Conduct two producer workshops with PPT, cost benefit analysis, and handouts

    a.     NW Small Fruit Annual Conference, Lynden WA

    Tilth Producers Annual  Conference

    December 2017



    November 2017

    12.  Submit popular and peer reviewed article for publication

    Producer: popular publication

    Technical Advisors: peer reviewed journal

    December 2017

    13.  Producer to develop and conduct a webinar based on materials presented during  a live workshop

    WSU Small Farms group will assist and be consulted – will submit to eOrganic webinars

    December 2017


    [i] accessed 11-12-14



    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.