Organic Blueberry Production

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    IS A PROJECT OF THE NATIONAL CENTER FOR APPROPRIATE TECHNOLOGY

    By George L. Kuepper & Steve DiverNCAT Agriculture SpecialistsUpdated by K. Adam, February 2000

    Introduction

    The following is anintroduction to organicblueberry production,designed tosupplementinformation fromconventional sourceson basic cultivationpractices. Matters suchas pruning, training,variety choice, sourcesof propagation

    material, and plantingare essentially the samein both organic andconventional culture.Generic blueberryinformation can beobtained from theCooperative Extension Service and commonhorticultural texts and periodicals.

    The word organic has precise legal definitions inmost states, and there are certification groups that

    maintain standards for what can be certified andmarketed as organically grown, as well asprescribed record-keeping procedures. An

    organic certification agency or organic growersorganization should be contacted to determineexact requirements and a list of prohibitedpractices and substances.

    However, some smaller

    producers may wish tofollow organicpractices withoutbecoming formallycertified. Theinformation providedhere should be usefulto them, as well.

    This publication isgenerally applicable toorganic culture of all

    three cultivatedblueberry species.Information onimproved blueberrycultivars is continuallybeing released byresearch and extensionagencies.

    800-346-9140

    A ppropriate Technology Transfer for Rural Areas

    ORGANICBLUEBERRY

    PRODUCTION

    www.attra.ncat.org

    Abstract: This publication focuses on organic production practices for blueberry culture, with someinformation on marketing outlook. A list of resources includes websites.

    ATTRA is the national sustainable agriculture information center funded by the USDAs Rural Business -- Cooperative Service.

    Contents

    Introduction ................................................... 1Soils and Fertility............................................ 2

    Cultural Considerations.................................. 6Pests............................................................... 8(chart) ................................................... 10

    Diseases.......................................................... 9(chart) ................................................... 11

    Bird and Rodent Control................................. 9Marketing ....................................................... 9Summary ........................................................ 9References...................................................... 12

    Additional Resources...................................... 13

    Additional ATTRA publications onorganic certification include:Organic Certifiers Resource ListResources for Organic Marketing

    HORTICULTUREPRODUCTIONGUIDE

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    In the Far North, low-bush and dwarf highbushblueberry cultivars are more climaticallyadapted than are highbush types. The lowbushwild blueberry (V. angustifolium) iscommercially important in Maine. The WildBlueberry Association of North America(WBANA) website(http://www.wildblueberries.com) promotesmarketing and is an excellent source of

    information on production practices.

    Blueberries have fewer pest problems than mostother fruits, offering an advantage for organicproduction. Most insect and disease problemscan be controlled through cultural manipulation.Blueberries have a relatively low nitrogenrequirement and thrive on organic sources.Adjusting soil pH low enough and protectingfrom predatory birds and mammals are the majorproduction constraints. Weather fluctuations andgeographic seasonal advantage are the majoreconomic considerations.

    Generally, non-organic transplants can be usedfor establishing perennial crops. However, mostcertifiers require the plants to be grown at least 12months under organic conditions after trans-planting before any harvested product can bemarketed as organic.

    Soils and Fertility

    The Importance of Soil pH

    Blueberries are distinct among fruit crops in theirsoil and fertility requirements. As members ofthe Rhododendron family, blueberries require anacid soil, preferably in the 4.85.5 pH range. The

    reasons for this are several. First of all, when soilpH is appreciably higher than 5.5, iron chlorosisoften results; when soil pH drops below 4.8, thepossibility of manganese toxicity arises. In eithercase, plants do not perform well.

    Soils with a native pH above 5.5 pose specialproblems for organic producers. Recurrentapplications of acidifying agents are necessary inorder to keep pH from drifting back to its naturallevel. Non-organic methods may depend on

    acidifying agents such as ammonium sulfate ordi-ammonium phosphate which are not allowedunder organic certification criteria. Not allcertifiers allow the usual flowers of sulfur andferrous sulfate for pH correction in organicculture. Acceptable substitutes are cottonseedmeal (from organic cotton) and, if pH is not toohigh, sawdust or pine needle mulches, which canassist in lowering pH a few tenths of a unit.

    Soil pH also plays a significant role in crop

    nitrogen management. Research has shown thatblueberries are preferential to soil and fertilizernitrogen in the ammonium form, absorbing andutilizing it much more efficiently than nitratenitrogenthe form preferred by most othercommercial crop plants. Neutral and basic soilsfavor nitrificationthe rapid conversion ofammonium nitrogen to nitrate through theactivity of nitrifying microorganisms. When anacidic soil environment is maintained, theammonium form of nitrogen predominates and isreadily available to blueberries.

    This principle also applies to the addition ofsupplemental nitrogen fertilizers. Conventionalrecommendations routinely emphasize the use ofammonium fertilizers, particularly ammoniumsulfate, which also acts as a soil acidifier. When aslow-release organic fertilizer like fish meal isapplied, the nitrogen in the proteins is converted

    For more information about marketing

    options, see the ATTRA publications DirectMarketing and Farmers Markets. On-farmvalue-added blueberry products usually

    require setting up a second rural enterprisebesides farming, and may entail considerableadditional planning, management, and start-

    up expense.

    Rabbiteye (Vaccinium ashei)adapted type inthe South (roughly south of Interstate 40).

    Highbush (V. carymbosum)adapted tointermediate climates.

    Southern highbush (V. ashei x carymbosum)

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    first into ammonium. The ammoniumwhichwould rapidly convert to nitrate under neutralsoil conditionstends to remain in the desired,ammoniated form.

    One preferred method of lowering soil pH inorganic culture is application of sulfur. Pre-plantincorporation of sulfur to lower the pH to anoptimal blueberry range of 4.85.5 should bebased on a soil pH test. Because soil pH is subjectto considerable seasonal fluctuationespeciallyon cropped soilsit is advisable to do soilsampling and testing in winter or very earlyspring, when biological activity is at a low level.

    The table below provides guidelines for sulfurapplication on different soil types.

    Powdered sulfur takes about one year to oxidizeand reduce soil pH. Prilled sulfur takessomewhat longer. Limestone, too, requires timeto effect changes in pH and reactive time ishighly dependent on the fineness of grind.

    Single applications of sulfur should not exceed400 pounds. Best results are obtained byapplying 200 pounds in spring, followed by 200later in the fall for as many intervals as isrequired to deliver the total amount. It is

    advisable to re-test the soil one year after eachapplication to determine if additionalacidification is truly necessary (2).

    Organic growers are advised to be conservativein the application of soil sulfur. Sulfur has bothfungicidal and insecticidal action and can

    detrimentally affect soil biology if overused.Organic growers sometimes increase theirapplications of peat moss at planting time as it,too, is a soil acidifier (pH 4.8), reducing the needfor sulfur. The Ozark Organic GrowersAssociation suggests as much as 510 gallons ofpeat moss per blueberry plant. While costly, peatis resistant to decomposition and provides thebenefit of soil humus.

    Those seeking alternatives to spaghnum peatmoss might consider the use of pine bark orsimilar amendments incorporated in the plantingrows or holes. While viewed as less desirablethan spaghnum peat moss, pine bark can often beobtained locally at a much lower cost. A new

    commercial substitute for peat called coir, madefrom coconut fiber pith, appears promising, butonly if it becomes available at a reasonable price.

    It is advisable to monitor soil pH over time asproduction practices can cause gradual changesto occur. Irrigation water often contains calciumand magnesium, which may cause soil pH tocreep upwards, while repeated use of acidifyingfertilizers, such as ammonium sulfate orcottonseed meal, may lower pH. Fortunately, the

    presence of abundant organic materials such aspeat and the breakdown products of sawdust andwoodchip mulches tend to buffer soil pH.(Several organic growers have even observed thatblueberries grown in high organic matter soilswill perform well at a pH as high as 6.0 with fewapparent problems.) As a result, additional

    Approximate pounds per acre of sulfur or ground limestone to change soil pH one unit (1).

    Soil Texture Pounds per acre of sulfur tolower soil pH one unit (e.g. 6.0 to 5.0)

    Pounds per acre of lime to raisesoil pH one uni