Organic Vegetable Gardening

Agricultural Extension ServiceThe University of Tennessee

PB 1391

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Table of Contents

I. What is Organic Gardening?A. Organic Gardening and PesticidesB. Organic Gardening and Fertilization

II. Why Garden Organically?A. Quality

1. Nutrition2. Taste3. Pest Damage4. Residues

B. SoilsC. Psychological Effect

III. Limitations of Organic GardeningA. Lack of Organic AlternativesB. Climatic Effect (geographic and

annual)C. Population CyclesD. Inability to Tolerate DamageE. Cost of ProduceF. Sources of Nutrients and Organic

MatterIV. Alternative Means of Pest Control

A. Choose Vegetables and Varieties WiselyB. Grow Resistant VarietiesC. Grow Hybrid VarietiesD. Obtain Quality Seed and TransplantsE. Use Cultural ControlsF. Eliminate Plant DebrisG. Increase Soil Organic MatterH. Rotate Plant FamiliesI. Avoid StressJ. Try Companion PlantingK. Use IntercroppingL. Time Plantings CarefullyM. Time Irrigation ProperlyN. Provide Air CirculationO. Use MulchesP. Consider Using SolarizationQ. Avoid Introducing Pest ProblemsR. Use Plant Supports

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V. Other Alternative Means of Pest ControlA. BarriersB. RepellentsC. TrapsD. BaitsE. BirdsF. Beneficial InsectsG. Handpicking

VI. Protective Chemicals

VII. Natural Protective SubstancesA. WaterB. Bug JuiceC. Hot PepperD. SoapsE. OilsF. Microbial AgentsG. SulfurH. Copper I. Other Protective Chemicals J. Botanically-Derived Chemicals

VIII. Managing Soil OrganicallyA. IntroductionB. Maintaining or Increasing Soil Organic MatterC. Using Crop Residues

D. Crop RotationE. Green-Manure Cover CropsF. The Effect of Mulches on SoilsG. Making and Using Compost

IX. Using Lime and Organic FertilizersA. Increasing Soil pHB. Adding Nutrients — ManureC. Adding Nutrients — Non-manureD. Soil Amendments

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X. References 22

Organic Vegetable GardeningDavid W. Sams, Professor, Plant & Soil ScienceDarrell D. Hensley, Assistant Extension Specialist, Entomology & Plant Pathology

What is Organic Gardening?There is considerable discussion, even among

those claiming to be organic gardeners, as to exactlywhat constitutes organic gardening. Generally,however, organic gardening is a system of gardeningthat attempts to use only sustainable, ecologicallysound gardening procedures. Organic gardeninggenerally differs from traditional gardening in twoimportant ways: use of agricultural chemicals and useof artificial or processed fertilizers.

Commercially, organic growers in Tennessee arecertified by the Tennessee Land Stewardship Associa-tion. There are currently three levels of certification.More information may be obtained from T.L.S.A.,P.O. Box 328, Bell Buckle, TN 37020

Organic Gardening and PesticidesOrganic gardening rejects the use of all artificial

agricultural chemicals, including pesticides used tocontrol insects, diseases, weeds and nematodes, aswell as other agricultural chemicals used to affectphysiological processes and conditions such asflowering, fruit color and firmness. Organic gardenersdiffer concerning which, if any, naturally derivedpesticides are permissible and when and how theymay be used. Recent trends have been toward usingfewer pest control agents in organic gardening,regardless of their origin.

Organic Gardening and FertilizationMost organic gardeners consider soils to be a

living, biotic system and reject artificial chemicalfertilizers as too harsh to be applied to living soils.Organic gardeners emphasize building soil organicmatter and then rely on natural sources of supplemen-tal nutrients.

Why Garden Organically?Quality

Organic gardeners generally feel that organicallygrown food is superior to non-organically grown foodwith respect to one or more components of quality.Some would argue that organic food has higher

nutritional quality or better taste; however, there is noevidence to support this. Since plants take up nutri-ents dissolved in water as ions, and ions from allfertilizer sources are identical, there is no reason tosuspect taste or nutritional differences directlybecause of nutrient source. Organic fertilization can,however, affect soil organic matter content, structure,moisture retention and nutrient release. Some of thesemay affect plant vigor, cell size or content, therebyindirectly affecting nutritional quality or taste. Verypossibly, any effect on nutritional quality or taste isthe result of organically grown vegetables beinglocally grown and thus fresher. Both nutrient contentand taste are generally at a maximum at harvest anddecline thereafter.

Many people garden organically partially becauseof concern over pesticide residues on food, or in soilor groundwater. However, careful use of pesticidesaccording to their labeled instructions need not leaveresidues in soils or groundwater. Furthermore, theresidues found in food are generally believed to bemuch higher than they really are. One should alsoremember that residue tolerances for food are gener-ally set at only 1/100 of the amount thought to beharmful.

A discussion of the effect of organic gardening onfood quality should not end without mention of insectand disease damage. Organic gardeners are generallywilling to tolerate some damage that traditionalagriculture perceives as reduced quality. Organicgardeners generally feel occasional insect or diseaseinjury or reduced color and shelf stability are worththe environmental benefits of growing vegetablesorganically.

Effect on SoilsThere is little doubt that organic gardening

improves soils because of the emphasis on increasingsoil organic matter. Increased soil organic matterimproves soil tilth and structure, improves waterretention, evens out nutrient release and may reduceerosion and run off. It should be pointed out, how-ever, that the heavy applications of manure sometimesused by organic gardeners can create their own run-off problems.

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Psychological EffectA final reason for organic gardening, and perhaps

one of the best reasons, is that it helps some peoplefeel safer. When gardening organically, they no longerworry about damaging their environment or familywith chemicals. There seems to be little harm in this,as long as gardeners realize that even organic prod-ucts must be used as they are designed and labeled tobe used and can be harmful if misused.

Limitations of Organic GardeningLack of Organic Alternatives

Some pest problems are easily controlled byorganic alternatives. Others are controlled only withdifficulty or have no reliable organic controls. Somecrops either must be avoided by organic gardeners orthese gardeners must be willing to risk significantlosses from pests.

Climatic EffectClimate varies regionally and annually. A pest

may pose little or no problem in one climate but be asevere problem in another. Aphids, for example,require high humidity to shed their skins and are not asevere problem in regions of low humidity. They are,however, a severe problem in Tennessee and much ofthe humid Southeastern United States.

Even within a single state, climatic factors varywith altitude, nearness to bodies of water, slope of theland, etc. These differences also affect plant suscepti-bility to problems and limit the effectiveness oforganic controls as well as chemical controls.

There are also annual climatic differences whichaffect host and pest. An organic control measure thatworks well one year may not work well the followingyear because of this climatic variation.

Population CyclesNatural populations tend to expand until they are

limited by their food supply or by another organism.An insect species, for example, may have onlyscattered individuals in an area, but have ample food.Its numbers increase rapidly for a few years and itbecomes abundant. It then either consumes most ofthe available food or becomes infested by a diseaseorganism and most individuals die. The remainingscattered population then begins a new cycle. Thesignificance of this for organic gardeners is that a pestmay be much more severe in one year than in another.It is difficult to determine how well an organic controlis working because of these natural population cycles.

Inability to Tolerate DamageMany organic control methods rely on maintain-

ing an equilibrium between pest and host. This meansthe organic gardener frequently must be willing totolerate some damage. How much damage will betolerated depends on the individual and also onwhether or not any produce is to be sold. Consumersfrequently complain if even a single insect or fractionof an insect is found, and lawsuits are not unknown.

Cost of Organically-Grown VegetablesIt would seem, at first, that not using agricultural

chemicals or commercial fertilizers would reduce thecost of organically grown vegetables. This is seldomthe case. Organic vegetables are often more expensivethan traditionally grown vegetables for severalreasons.

First, organic sources of nutrients or organic pestcontrol measures are often more expensive thantraditional sources. Second, marketable yields arefrequently less with organic production. Lastly,organic produce may not store or ship as well astraditional produce.

Sources of Nutrients and Organic MatterOrganic production frequently relies, at least

partially, on manure, organic material and nutrientsbrought in from outside the growing area. Theseresources are limited and may restrict the expansionof organically-grown vegetables. Increased use ofcover crops, green manure crops, crop rotation, etc.can minimize the effect of the limitations of naturalresources.

Despite the limitations of organic gardening, thereare many proven techniques that will reduce the needfor artificial pesticides and improve soils withoutartificial fertilizers. We will now examine some ofthese.

Alternative Means of Pest ControlChoose Vegetables and Varieties Wisely

A few vegetables can frequently be grownwithout serious damage from insects and diseases.Examples include beets, carrots, garlic, okra, onions,radishes and many herbs. Many other vegetables aresusceptible to frequent attack by a number of insect ordisease organisms.

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Grow Resistant VarietiesThe University of Tennessee Agricultural Exten-

sion Service factsheet SP277-K, “Disease Resistancein Recommended Vegetable Varieties for HomeGardens,” lists more than 50 varieties of 21 veg-etables reported as resistant to one or more diseases.Many of these varieties have resistance to three ormore diseases. It is important to remember thatresistance is not immunity. A resistant variety willprobably not totally escape a pest, but may be at-tacked later or bear a fair crop despite being attackedby the pest. Selecting vegetable varieties resistant toseveral pests is well worthwhile if you desire toreduce the use of plant protective chemicals.

Grow Hybrid VarietiesHybrid varieties are often more pest resistant than

non-hybrid varieties. This is because hybrids arecrosses of true breeding lines. They are frequentlyselected to contain specific pest resistance from bothparent lines. Hybrids also tend to be high-yielding,earlier-bearing and longer-living than non-hybridvegetables, when grown under favorable conditions.Their increased vigor may permit them to tolerate oroutgrow a minor attack.

Unfortunately, many organic gardeners prefernon-hybrid varieties. Hybrid varieties do requirefavorable growing conditions to reach their fullpotential. They also must be grown from purchasedseed, which is expensive because of the labor in-volved in making the crosses necessary to produce theseed. Plants grown from seed saved from hybridvarieties will vary in numerous characteristics ratherthan being identical to the parent plants. Saving seedof hybrid varieties is not recommended.

Despite these disadvantages, hybrid vegetablesare generally a wise choice for gardeners. They haveincreased vigor, pest resistance and longevity, andseem to be equal in taste and nutrition to non-hybridvarieties. The fruit, in fact, frequently has improvedshelf life and improvements in both appearance andquality.

Obtain Quality Seed and TransplantsA last consideration in the choice of vegetables

and varieties is the source of the vegetable seed ortransplants. Seed collected locally may carry a widerange of diseases. It may not be true to type and willnot germinate well unless it is stored properly.

Commercially produced seed is much less likelyto carry diseases, because the seed are produced inareas having low humidity where diseases and insects

are much less common. Also, obviously diseased oroff-type plants are rogued out before they produceseed. These seed are also packed and stored properly,so they will germinate well.

Inspect transplants for the presence of insects,leaf spots or yellowing and dying leaves. Neverpurchase transplants showing signs of insect infesta-tion or diseases. Young, vigorously growing trans-plants in individual cells of a cell pack are likely togrow most vigorously; bare-root and older plants,least vigorously. Inspect the roots of bare-root plantsand do not buy them if the roots have dried and died.

Use Cultural ControlsA wide range of cultural techniques can be used

to reduce problems of home gardens. Methods ofcontrol vary considerably from one pest to another,depending on the kind of pest, the vegetable affectedand the interaction of the two. The damage or loss ofone or a few plants is usually considered insignificant.Control measures are generally aimed at saving themajority of the crop rather than individual plants.Most control measures aim at helping plants avoidcontact with pests, as well as eradicating or reducingthe numbers of pests in the area. These methodsinclude sanitation, proper row spacing, varyingplanting dates and seeding rate, crop rotation, plantingon raised beds, adding to soil organic matter, usingmulches, irrigating properly and many others. Mostcultural pest control methods are effective againstmore than one type of pest. Gardeners should befamiliar with them and use as many as possible.

Figure 1. Control weeds mechanically while they aresmall to reduce the need for herbicides.

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Eliminate Plant DebrisMany insects and diseases survive on plant

residues. Their numbers decrease markedly as thedecay process proceeds. Begin by maintaining thegarden area free from plant debris. Mow or mechani-cally remove weeds before they produce seed. Indi-vidual plants of some weeds can produce as many asa million seed. Remove dead, dying and spent veg-etable plants from the garden or chop them into piecesand turn them under as soon as harvest is complete.This will speed up decay and reduce potential fordisease and insect buildup by removing overwinteringsites of insects and diseases.

Multiple plowings or tillings will not only insurethat all plant residues are worked into the soil wherethey will rapidly decay, but will mechanically elimi-nate many soil insects such as grubworms, cutwormsand wireworms. Working the soil several times isespecially important in gardens that have previouslybeen in sod for several years, as soil insects are likelyto be present in the sod in large numbers. Weed seedswill germinate as they are brought to the surface andbe killed as the soil is worked. This can reduce futureweed problems.

Soil free from surface plant debris and organicmulches will also dry out earlier in the spring so it canbe worked and planted. This is important becausecool-season crops must be planted early if they are tomature before summer heat halts their growth andreduces yield and quality.

Increase Soil Organic MatterTurning plant debris under also increases soil

organic matter. This is discussed in considerabledetail in the “Managing Soils Organically” section ofthis publication (p 17). The primary concern here isthe effect of soil organic matter on nematode popula-tions. Increasing soil organic matter has been widelyreported to reduce nematode populations. Organicmatter apparently enhances the environment for otherorganisms that feed on nematodes or directly inhibitstheir growth. Plantings of wheat, oats, cereal rye orFrench marigolds seem especially effective in reduc-ing nematode populations when grown in massplantings and turned under several weeks before thegardening season. There is no evidence indicating thatscattered marigolds growing in a vegetable gardenwill significantly reduce insect or nematode popula-tions. For more information on nematodes, seeExtension factsheet SP341-L, “Nematode Control inthe Home Garden.”

Rotate Plant FamiliesRotation of plant families (closely related plants) is

yet another means of reducing insect and disease prob-lems. Families of plants tend to be susceptible to many ofthe same insect, disease and nematode problems. Bygrouping vegetable plants into families and moving eachfamily to a different location within the garden every year,many insect and disease problems can be reduced. Table 1lists several vegetable groups which can be rotated to helpreduce pest problems.

Table 1: Examples of Crop Groupings to Reduce Diseases1

Group Crop Disease(s) Reduced

Group A Cantaloupe MicrodochiumBlight

Cucumber Fusarium Wilt

Pumpkin Gummy stem blightSquash AnthracnoseWatermelon Scab

Belly rotAngular leaf spotNematodes

Group B Brussels sprouts Black legCabbage Club rootCauliflower Black rotCollardsLettuceMustardRadishRutabagaSpinachSwiss chardTurnip

Group C Eggplant Bacterial cankerIrish potato Early blightOkra NematodesPepper Potato scabTomato

Group D Beet ScurfCarrot Black rotGarlic WiltShallot NematodesSweet potato

Group E Sweet corn SmutGroup F Bean Fusarium root rot

Cowpea NematodesPeas Anthracnose

1 Rotate to a crop in a different group when plantingsuccessive crops in the same location in the garden

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Avoid StressHealthy plants withstand or outgrow problems

better than stressed plants. Maintain optimum grow-ing conditions to reduce plant stress wheneverpossible. Develop soils with proper pH, organicmatter content, particle size, particle arrangement(structure) and fertility as recommended in the“managing soils” section of this publication. Gardenonly in locations receiving six hours or more ofsunlight daily. Sidedress with nitrogen-containingfertilizers or compost (see Table 5). Choose a well-drained site or plant on ridges to improve drainage.Plant. recommended varieties at recommended dates,planting depths and spacings. Avoid purchasing plantsthat have been stressed. See Extension PB 901,“Growing Vegetables in Home Gardens,” and SP 291-A, “Growing Vegetable Transplants for Home Gar-dens,” for specific recommendations. Supplementrainfall with irrigation when necessary. Control weedswhile they are small, and insects and diseases beforethey become severe. The result will be vigorousplants better able to withstand occasional stress.

Try Companion PlantingCompanion planting is the concept of planting

plants together for their mutual benefit. A tremendousamount has been written about companion planting,but very little has actually been proven about itsbenefits. It is obvious that shade-loving plants in theforest benefit from taller plants that shade them. Itseems reasonable that deep-rooted plants absorbnutrients from deep soil layers and deposit them on ornear the surface as they decay. These nutrients canthen be used eventually by shallow-rooted plants.Some plants may benefit other plants by attracting orrepelling insects, diseases or nematodes by scent,color or various secretions. There is, however, littleconsensus as to what combinations are beneficial, andspecific companion planting recommendations willnot be made here.

It is known that black walnut trees produce asubstance that inhibits growth and causes wilting ofmany plants. Avoid planting vegetables, especiallytomatoes, near black walnut trees.

Use IntercroppingRaising two or more crops in the same area at the

same time is called intercropping. Intercropping canreduce a wide range of pest problems. Commonexamples of intercropping include either pole beansor pumpkins planted with corn, and a cool-season

vegetable such as lettuce or radishes planted betweentomatoes. The cool-season vegetable will mature andcan be harvested before the tomatoes need the space.

Insects seem to recognize large areas of a singlevegetable more easily than isolated plants or inter-planted combinations of several vegetables. Insectsand disease may also spread more slowly wheninfesting interspersed host and non-host plants thanwhen in large areas of only one vegetable.

Time Plantings CarefullyCareful timing of plantings is an excellent way to

reduce the severity of some problems. Cutworms,aphids and root maggots, for example, tend to bemore severe early in the spring and decline in severityas temperatures increase and rainfall decreases. Corn,however, usually suffers less damage from cornearworm, European cornborer and armyworms whenplanted early. The later corn is planted, the moresevere the damage from these insect pests becomes.Virus diseases and pickleworms also tend to increasewith later plantings of the vine crops. Know yourpotential problems and time plantings to avoid themwhen possible.

Time Irrigation ProperlyMany people believe that watering during the hot

part of the day causes plants to “burn” or die. There isvery little, if any, evidence that this is true. Wateringwhen it is hot or windy will increase evaporation andwaste water, but is unlikely to directly harm plants.Watering late in the evening may increase disease ifplants remain wet at night. Any kind of water applica-tion that wets foliage is likely to increase plant foliagediseases somewhat. Trickle, drip or furrow irrigationconserves water and avoids increasing foliage diseaseproblems, but can contribute to root rot problems.Sprinkler irrigation is probably best done during cool,non-windy morning hours.Another common error intiming irrigation is to apply small amounts of waterevery day or two. This works well when using drip ortrickle systems where a small amount of water willsoak deeply into the soil. When using sprinklerirrigation, however, apply 1 to 1 1/2 inches of waterat one time and then wait several days until the soilsurface dries before irrigating again. Less frequentirrigation will be less likely to increase plant foliageand root diseases and will not create a shallow layerof moist soil over drier, deeper layers. Plants will thenbe less dependent on frequent watering for growthand even survival.

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Provide Air CirculationThe longer a plant remains wet, the more likely it

is to develop a disease problem. Good air circulationis vital if plants are to dry off promptly and avoidundue disease problems. Planting on slight slopes orridges will help. Morning sun is also important indrying surfaces as soon as possible. Planting atrecommended spacings is very important, as areproperly pruning and supporting plants off theground. A pruned and supported tomato, for example,receives better sunlight because of reduced foliageand better air circulation. Fewer aphids colonize thedrier plant and it is easier to spray if sprays are used.The fruit are also held off the damp soil and are lesslikely to rot. If vegetable plants are spaced andsupported properly, many problems will be reduced.

Use MulchesMulches may reduce certain pest problems, but

can increase others. Mulches reduce plant stress,prevent weed growth and maintain soil moisture.They may reduce some insect and disease problems,as well as increase soil tilth and organic matter.Mulches are discussed more extensively in thispublication under “Barriers” (p.11). The soils sectionof this unit also contains a discussion of mulches asthey affect soils. Extension factsheet SP291-H,“Mulching Vegetable Gardens,” discusses the benefitsof mulches and how to mulch gardens with bothorganic and inorganic mulch.

Consider Using SolarizationSolarization offers one of the few non-chemical

possibilities for reducing some soil insects, nema-todes, diseases and weed seed simultaneously. Thisprocedure requires bare, moist soil and the hottestpossible temperatures. The best conditions for solar-ization are periods of bright, sunny weather, whichgenerally occur during the long, warm days ofsummer. Begin the procedure in June or early July.

To solarize soil, first remove all vegetation. Workthe soil as if it were to be planted, and water with asmuch water as it will comfortably hold. Cover thesaturated soil with a sheet of clear plastic stretchedtightly over the soil. Place 1 inch cubes of wood orplastic foam on the plastic about a foot apart. Coverthe grid with another clear sheet of plastic so youhave two sheets of plastic with a 1-inch air spacebetween them. Seal the edges with soil. Leave theplastic in place one to two months. During sunny, hotdays, the soil temperature should reach 120 degrees F,or more, at a 2-inch depth, which will reduce thepopulation of many soil pests. If only a single sheet ofplastic is used, temperatures will not be as high or stayhigh as long, and the treatment will be less effective.After solarization, it is very important that soil not beworked deeply. The deeper soil is worked, the morelikely it is that disease organisms and weed seed will bebrought to the surface where they will grow.

Figure 2. Soil solarization procedure.

ample soil to anchor plasticduring strong storms

squares of styrofoam insulation, bricks,or wood separating plastic sheets

two layers of plasticsheeting

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Avoid Introducing Pest ProblemsPlant diseases, nematodes, weed seed and even

insects can be carried from place to place on equip-ment, introduced into the garden with transplants ormoved by insects and human hands. Keep equipmentclean. Remove soil from tillers and garden equipmentafter using them. This is especially important if theyare to be moved between farms, fields or even parts ofthe yard.

Transplants grown in pasteurized soil or artificialmedia will be less likely to harbor pests. Purchasetransplants certified free of insects and disease ifpossible. Always inspect transplants for the presenceof insects and diseases before purchasing them.

Avoid the use of tobacco if you grow tomatoes,peppers or Irish potatoes. Tobacco contains tobaccomosaic virus (TMV) which will get on your handsand be spread to plants which you touch. Equipment,insects or anything touching an infested plant andthen another plant is also likely to transfer the diseasefrom plant to plant. TMV is very hard to control andreduces both fruit set and fruit size. Total yield ofTMV-infested plants may be reduced slightly ornearly wiped out. Leaves of infested plants may bedistorted and will probably have a mottled appearancerather than a solid green color. Remove isolated plantsshowing these symptoms as soon as they appear.

Use Plant SupportsPlant supports can be an important part of the

organic garden. They make plants easier to tend andharvest and extend the harvest season. More impor-tantly, supported vegetable plants have fewer diseaseand insect problems because of improved air circula-tion and less contact with wet, disease-infested soil.

Tomatoes, English peas, sugar snap peas, cucum-bers and pole beans are some of the vegetables thatare commonly grown on supports. These vegetablesmay be trained on a fence, in a wire cage or on atrellis. Pole beans may be grouped around individualstakes or several stakes may be pulled together at thetop and tied for additional strength. Trellises may beconstructed from cane supported by a wire on top,string woven between top and bottom wires or fromnylon netting.

Tomatoes respond especially well to verticalculture, since many of the fruit may rot if they touchthe ground. Tomatoes are usually supported by 5-or 6-foot stakes or a trellis. Use stakes at least 1 1/2 inchessquare and drive them a foot or more into the ground.Plants are pruned to one or two stems and tied looselyto the support at 8- to-12-inch intervals.

A second method of supporting tomatoes is withwire cages constructed from concrete reinforcingwire. Cages should be 20 to 22 inches in diameter,which requires a 6-foot length of wire bent into acircle. Firmly anchor each cage so it will not blowover. Cages may be anchored by tying them to stakesor by tying them to a wire that is attached to posts ateach end of a row of cages.

Set a single tomato plant in each cage. Allow theplants to grow without pruning. Push the ends backinto the cages as they grow out. Harvest fruit byreaching through the mesh.

Grow caged cucumbers like caged tomatoes butuse a 10-foot length of concrete reinforcing wire. Thiswill make a 3-foot diameter cage that will probablynot need anchoring. Plant cucumbers 6 to 10 inchesapart around the outside of the cage. Push the grow-ing vine tips into the cage until they begin to climb. Asmall hollow in the center of the cage makes aconvenient place to fertilize and water the cucumbers.Benefits of this system include more fruit, an ex-tended harvest season, increased ease of harvestingand reduced disease pressure.

Other AlternativesSeveral things can be done to prevent some

insects and diseases from reaching plants. Methods ofcontrolling certain insects without using insecticidesare also available. Most of these are compatible withthe organic gardening philosophy and can be of helpto gardeners.

BarriersSeveral types of barriers can be used to prevent

certain insects from reaching a plant or plants. Smallpaper or plastic cups with the bottoms removed, forexample, can be pushed into the ground around youngtransplants to protect them from cutworms. Alumi-num foil wrapped around young plants will servemuch the same purpose. Six-inch lengths of sewerpipe may also be placed over young plants as acombination cutworm barrier and windbreak. Nylonbird mesh or mesh berry baskets placed over theplastic cups or sewer pipe will protect young seed-lings from birds.

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Figure 3. Mechanical barriers can reduce cutwormdamage to young plants.

Figure 4. Netting will prevent birds from feeding onbush fruits and small fruit-bearing trees.

Diatomaceous earth, a chalk-like substanceconsisting of microscopic, sharp, shell particles,sprinkled around young plants may protect them fromslugs, snails and some soft-bodied insects. Woodashes are reported to have the same effect.

Individual collars placed around cabbage orbroccoli will frequently protect them from rootmaggots. Cut 6-inch squares or disks of foam rubber,carpet padding or tarpaper. Punch a small hole in themiddle and make a slit from the edge to the hole. Fitthe barriers tightly around vulnerable plants and covereach barrier with enough earth to hold it down.

Hot caps, small domes made of translucent paper,may also prevent insects or disease spores fromreaching individual plants. Other barriers can protectentire rows of plants. Spun-bonded row covers, forexample, can be placed over young plants of thecabbage family to exclude various cabbage feedinginsects, or over cantaloupe and cucumbers to keep

cucumber beetles off. Spun-bonded row coversshould be applied loosely so they can be lifted by theplants as they grow. Heavy rain may cause the coversto become stuck to mineral soils, requiring re-loosen-ing of the covers. Apply them immediately afterplanting before insects attack the plants. Removecovers from cucumbers and other plants requiringpollination when the plants begin to flower. Waterwill pass through spun-bonded row covers, but asmall amount of heat will be retained as an additionalbenefit of this material. Controlling weeds growingbeneath the covers may be a severe problem. Removethe row covers when it is cloudy and water the plantsto reduce shock.

Mulches, both plastic and organic, can serve as abarrier against diseases that are spread partially bysoil splashing onto plants. Early blight and buckeyerot of tomatoes are examples. Mulches will noteliminate these diseases, but may delay their onsetand eventual severity. Organic mulch applied aroundtomatoes while the soil is still cool may delay ripen-ing a few days, but black plastic mulch will warm thesoil and speed ripening.

Figure 5. Apply organic mulches 2 to 3 inches deeparound established plants after the soil warms up.

Mulches also reduce numbers of some insects,such as Colorado potato beetles, by preventing theiremergence from the soil where they overwintered andby slowing their migration from weedy overwinteringsites to plants in the garden.

Gardeners should be aware that mulches canserve as hiding places for some insects and increasethe incidence of some diseases by retaining too muchwater around plant roots. Black plastic, for example,may increase damping off and root rot of peas and

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beans, or bacterial diseases of tomatoes. This isespecially true when it is used around seedlingsgrowing in poorly-drained soil.

RepellentsIt would be great to be able to use a repellent to

keep insects from bothering plants but, unfortunately,there are no effective, broad-based repellents. Somegardeners have used solutions made from hot peppers,garlic or strong-smelling herbs to discourage insects.It is unclear whether these solutions are toxic to someinsects, repel them or work at all. The ExtensionService has no data regarding their usefulness butcautions that these solutions are seldom legal to useon vegetables grown to be sold.

Reflective plastic mulch in various colors andaluminum foil mulch can be used to repel thrips andaphids on some vegetables. Reducing aphid and thripsinfestations may also reduce the spread of virusescarried by these insects. These mulches apparentlyconfuse thrips and aphids, making it more difficult forthem to locate vegetable plants.

Mulch the area under very young plants com-pletely for best results. However, mulching too earlymay prevent the soil from warming up and delaymaturity. It may also be necessary to provide holes inthe mulch to allow moisture to reach the plant roots.

Numerous repellents have been used to keepmoles from gardens. These include caster beans,gopher spurge, windmills, etc. Their common trait isthat none of them produce consistent results. The bestway to eliminate moles is to trap them. Mole traps aredifficult to use properly, but can be very effective.More detailed information can be found in Extensionfactsheet SP293-A, “Mole Control in Tennessee.”

TrapsShingles, boards and even inverted cabbage

leaves placed in the garden will collect slugs, cut-worms, squash bugs and other pests that hide inmoist, dark places. They can be collected from thesehiding places and destroyed by dropping them into acontainer of water covered with a thin layer of oil.

Pheromone traps are mechanical devices contain-ing scents that attract a specific insect species.Pheromone traps are available for Japanese beetlesand a wide range of other insects. The insects areenticed into the trap by the scent and are unable to getout. These traps attract pests from a considerabledistance, but do not immediately catch all the insectsthey attract. They are best used some distance fromthe garden to attract the insects away from, not into,

the garden. Pheromone traps may provide adequatecontrol of several pest species.

Light traps have been used outdoors for control ofvarious flying insects. There is little or no evidencethat light traps adequately control many gardeninsects.

Sticky red spheres or sticky yellow traps willattract and trap a variety of insects. They are betterused to monitor insect populations than to controlspecific insect species.

BaitsSometimes pests can be attracted away from

growing vegetables and killed. Some slug baits, forexample, can be placed in small piles on boards or incontainers. Slugs are attracted to these baits, eat themand die.

Another way to trap slugs is to place shallowcontainers filled with beer in the soil with the top ofthe container level with the soil surface. Slugs will beattracted to the beer and drown. A solution of 1 poundof sugar and 1 teaspoon of yeast in a gallon of waterfermented two or more days works well. This makesuse of both the trap and the bait concept.

All of these baits must be replenished frequently.Traps need to be cleaned and refilled. Baits will lastlonger if some sort of a cover is provided to keep rainfrom diluting or destroying them.

BirdsMany birds eat large amounts of insects or weed

seed. Encouraging these birds can greatly reduceinsect and disease problems in home gardens. Encour-age birds by planting berry-forming shrubs and smalltrees, by providing a source of water (a bird bath) andby providing nesting sites and birdfeeders. Extensionfactsheet SP239-D, “Building Bird Houses,” dis-cusses construction of a wide range of bird housesand how to locate them.

Some birds also consume vegetables. Do notpermit any seed to remain visible on the surface of theground when planting vegetables. It may also benecessary occasionally to make use of netting orspun-bonded row covers to protect vegetables frombirds. Imitation snakes, owls and hawks repel birdsonly if they are moved frequently from place to placeand then only for a short time. Plastic foam cupsinverted over corn ears after pollination may protectripe corn ears from blackbirds.

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Beneficial InsectsMost insects are neither particularly harmful nor

beneficial to home gardens. It is important to identifythe insects present in a garden to determine whetheror not controls are needed. It is also important to

study the insect’s life cycle to determine how best toassist or control it. Table 2 lists some commonbeneficial insects and the pests they feed on.

Table 2. Some Common Beneficial Insects

Insects Description Pest(s) Controlled

Ground Beetles Large, shiny, dark brown Feed on caterpillars, armyworms and cutwormsbeetles

Ladybugs Small, round, colorful beetles; Feed on aphids, mites, scale and many insect eggsblue-yellow striped larva

Predaceous Stink bugs Medical shield shape Feed on many insects

Ambush Bugs Large, dark bug with long, Feed on whatever they can catchnarrow head

Tachnid flies Drab small fly Parasitize many insect larvae

Lacewings Stalked egg 1 inch long insect Feed on aphids, mites, scale insects and many insectlacy wings eggs

Praying Mantids 3-inch long insect with Many insectstriangular head

Predatory Mites Very small, 8 legs, Spider mitesnot true insects

Some gardeners purchase and release variousbeneficial insects into their garden to control harmfulinsects. A variety of companies sell beneficial insects.Extension factsheet SP290-Z, “Commercial Sources forPredators and Parasites,” lists several such companies.

Lady bugs and many other beneficial insects areextremely mobile and may not stay where you putthem. Others such as preying mantids will consumeeach other. Introducing large numbers of insects into asmall garden may be of limited value. Encouragingnatural populations, however, can be very helpful.Begin by growing a variety of vegetables in thegarden. Allowing natural vegetation to survive nearthe garden may increase beneficial insects, but mayalso increase harmful insects. To successfully use

beneficial insects, you should learn not only whichinsects are beneficial, but also which host plantsencourage which insects. Unnecessary chemicalapplications should also be avoided if beneficialinsects are to be encouraged.

HandpickingGardeners may control some insects by handpick-

ing. This method of control is most successful insmall gardens and with large insects that are presentin small numbers. Tomato hornworms, squash bugs,cabbage worms, Colorado potato beetles and otherlarge insects may be controlled this way. After insectsare removed from the plants, they may be killed bycrushing or being dropped into a container of soapy

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water or water covered with a thin layer of oil orkerosene. While handpicking squash bugs, also crushor remove the reddish or bronze egg masses found onor under the leaves.

Insects such as blister beetles and some caterpil-lars can sting or burn when they are touched. Weargloves or learn to identify common garden insects.

Protective ChemicalsSometimes the severity of a pest problem in-

creases until the gardener must either actively controlthe problem or lose yield and quality. Following thebasic principles of pest control will make controleasier, more effective and less damaging to non-targetorganisms.

Begin by inspecting the garden frequently. Walkthough it several times a week looking for weeds,insects, diseases, plants that need pruning or staking,rows that need thinning, etc. The first step in control-ling a pest problem is to recognize its presence.

Next identify the problem. Many agriculturalchemicals work on only one, two or a few pests.When the problem is identified, select a pesticide thatwill control the problem but damage few otherorganisms. A properly selected treatment is morelikely to be effective and less likely to damagebeneficial insects and other non-target organisms.

Line drawings of common garden insects andtheir description are shown in Extension PB 595,“You Can Control Garden Insects.” This publicationand other Tennessee publications mentioned areavailable to Tennessee residents at no charge at UTcounty Agricultural Extension Service offices. CountyExtension personnel can also assist in identification ofinsects, diseases and weeds.

Begin control practices early. Plant diseases cansometimes be halted, but they can seldom be re-versed. If damage is too severe when control mea-sures are begun, losses in production and quality willoccur. Control insects while they are immature andfew in numbers. The more mature the insects and thelarger their populations, the more difficult they are tocontrol.

Sprays are generally more effective in controllinginsects and disease than dusts.

Sprays cover the complete surface of the plant.Sprays are also easier to apply to the bottom surfaceof leaves than dusts. Many insect problems begin onthe bottom surface of the leaf rather than the top. Usethe least toxic spray that will be effective. Sometimesa stream of water, horticultural oil or an insecticidal

soap solution will be effective. Use the more toxicchemicals only when less toxic sprays will not do the job.

Lastly, always follow the label. Any material soldas a crop protection chemical in the United Statesmust be registered with the Environment ProtectionAgency (EPA) and labeled. The label must be fol-lowed. Failure to do so is illegal and can be danger-ous. Labels list time and rate of application and thevegetables and pests on which the product can beused. They also contain other information, such assafety precautions. Always read the label and use thechemical only where and how it is permitted. It ispossible to cause severe environmental or bodilyinjury if agricultural chemicals are misused. In nocase does the Agricultural Extension Service recom-mend the use of any plant protection substance in amanner inconsistent with its label.

Natural Protective SubstancesWater

The simplest natural substance for removinginsects from plants is water. A forceful stream ofwater may be applied to the underside of plant leaveswith any type of sprayer or even with a hose andnozzle. Aphids, spider mites, thrips, whiteflies andother small pests can be dislodged and washed to theground. Many will be unable to find their way backonto the plants and may die. Repeated treatments maybe required to destroy all pests. More pests may hatchfrom eggs or mature from crawling stages that cannotbe washed from plants. Be aware, however, that themore frequently water sprays are used, the moredisruption of natural enemies may occur. Frequently,water sprays may also increase plant disease prob-lems, especially if plants remain wet at night.

Bug JuiceMany organic gardeners have had success in

controlling some insects using diluted solutionscontaining ground up caterpillars or mature insects.Anywhere from a few individuals to a half a cup ofinsects are collected and blended with two cups ofwater. The liquid is strained through cheesecloth,diluted and used to spray vegetable crops. Success isnot consistent. Success is more likely if dead or dyinginsects are used, since they are more likely to bediseased and spread the disease to other insects. Thistechnique may be more successful when used incombination with other biological sprays. Do not useyour household blender.

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Hot PepperHot pepper sprays are also widely used by

organic gardeners. One half cup, or more, of hotpeppers are chopped or ground, then mixed with apint of water. The mixture is allowed to stand a day ortwo, then strained and sprayed on the infested plant.Be careful not to get this spray in your eyes and besure to wash your hands. Sometimes crushed garlic,onions or strong-smelling herbs are added to thesesprays. There are many, many recipes that have beentried. A garlic repellent is also commercially avail-able. Unfortunately, home remedies are neitherlabeled for use as pesticides, nor does The Universityof Tennessee have information concerning theireffectiveness. Their use is not recommended.

SoapsMany types of soaps have been used to kill,

dislodge or repel certain garden pests. They varygreatly in effectiveness and in toxicity to plants. Theyare frequently effective against thrips and other small,soft-bodied insects such as aphids, mealybugs andwhiteflies. Their disadvantages are that they areexpensive and they need to be reapplied frequently,possibly every three or four days.

Several commercial brands of soap are especiallyformulated and labeled for use on garden vegetables.Some of these may be mixed with other pesticides toincrease the effectiveness of both. Commerciallylabeled soaps are the only soaps recommended for usein the home garden. Be sure to use them only asrecommended on the label.

OilsMore than one grade of oil can be used as a spray

on horticultural plants. Most are heavy-grade oilssuitable for use only on dormant plants. The newer,lighter-weight horticultural spray oils are thinner andcan be tolerated by many growing plants. They workby suffocating mites, scales and soft-bodied insects,and may be the preferred method of controlling somescale insects. Use them precisely according to thelabel to avoid crop damage.

Mineral oils are also used to reduce corn earworminfestation. Two or three drops applied to corn silkwith an eyedropper may protect the ear from infesta-tion by corn earworms for a few days. Do not applyuntil the silk has wilted and begun to turn brown onthe ends or pollination may be affected.

Microbial Agents“Bacillus thuringiensis” (Bt) is a type of bacte-

rium that kills certain harmful insects and is harmlessto beneficial insects. The most common forms of Btare sold under the tradenames DipelTM, ThuricideTM

and MVPTM. They are effective against the larva ofbutterflies and moths and may be used on a widerange of plants. They can be reapplied as plants growwithin the limits listed on the labels.

A new form of Bt, sold as M-oneTM, is effectiveagainst Colorado potato beetles. Other forms of thebacterium are being investigated and may soon beavailable to control additional insects.

Another bacterium, “Bacillus papillae”, causesmilky spore disease in grubs of Japanese beetles. Thisproduct is commercially available as DoomTM orJapademicTM but may be very hard to locate. Thepowder is applied to the ground and, in time, infectsthe grubs over large areas. Once established, thebacteria may survive in the soil for several years.

SulfurSulfur may be used to control certain fungal

diseases of a variety of vegetables, fruits and grains aswell as several kinds of mites. It is one of the fewsubstances used by organic gardeners to controldiseases. Some organic gardeners do not use sulfurbecause of the possibility that it might disrupt soilmicroorganisms. It can also have a negative effect onbeneficial insects and burn plants when used duringhot, humid weather. Products that contain sulfurinclude Wettable Sulfur (recommended for commer-cial use only), ThioluxTM, Lime-Sulfur and severalcombinations of sulphur and other materials generallyacceptable to organic gardeners.

CopperBasic copper sulfate, copper oxychloride sulfate

and derivations of these products are used to controlmildews, rots, blight and leafspots on many crops.These can be effective but may also damage plants.Be sure to follow the label precisely and to observeall precautionary statements.

Other Protective Chemicals Used byOrganic Gardeners

Sodium hypochlorite, also called commonhousehold bleach, has been used as a seed treatment.Seeds are soaked for one minute in a solution contain-ing one part bleach and 10 parts water. This solutionmay also be used to sterilize pruning shears, grafting

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tools and seeding containers to reduce the spread ofdisease-causing agents.

Avermectin (AvidTM) is a product used in com-mercial crop production. The chemical is produced bybacteria and is used to control leafminers and spidermites. Sodium aluminofluoride or cryolite(KryocideTM) has been used for many years in organiccrop production. This product is used to control severaltypes of insects on a wide variety of crops.

ClandoSanTM is a chitin protein found in crusta-cean shells and is labeled for nematode control.ClandoSanTM is a new product still being evaluated.The product acts to stimulate the growth of certainsoil microorganisms that produce chitanase and otherenzymes that destroy plant-pathogenic nematodes.

Botanically-Derived ChemicalsSeveral insecticides are extracted from plants.

These are frequently referred to “botanical insecti-cides.” Five of the most common include pyrethrin,rotenone, ryania, sabadilla and neem. These aresometimes used by organic gardeners because theyare effective against many insect pests and becausethey quickly break down into substances thought tobe harmless. Gardeners should follow the sameprecautions when using these insecticides as whenusing any other insecticide. Always follow the label.Use the insecticide only on the vegetables, at thetimes and in the concentrations for which it is labeled.Even botanicals are toxic and care must be followedin applying them. Special restrictions should be notedif environmental damage is to be avoided. Rotenone,for example, is 10 times more toxic to people thanMalathion and is very dangerous to fish. Sabadilla istoxic to bees. Lastly, remember that botanical insecti-cides will not differentiate between beneficial andharmful insects and may severely damage populationsof beneficial insects.

Managing Soil OrganicallyIntroduction

Soils consist of a combination of gases, water,minerals and organic compounds. They vary greatlyin how much of each of these they contain, the size ofthe particles, particle arrangement and in the compo-sition of each of the four individual components.There are also differences in the amount and types ofliving organisms found in soils, in the ability of soilsto hold or release water and in nutrients.

Soils are important to plants because they providesupport and supply plants with water and nutrients.Growing plants remove large amounts of water andsmaller amounts of nutrients and gases from soils.The nutrients removed are especially significant whenplants or plant parts are harvested, as is the case withgardening. Therefore, gardeners must return nutrientsto the soil and maintain the soil’s ability to retainthem until they are required by growing plants. Thereare two approaches to this problem, that of traditionalagriculture and that of organic farming and gardening.

Traditional agriculture views soil as a relativelyinert holder of moisture and nutrients. Effort is madeto conserve the soil, maintain its structure and resup-ply nutrients and water as they are removed. Theeasiest and cheapest way to supply water is throughirrigation. The easiest way to supply nutrients is in themost concentrated form, high-analysis chemicalfertilizers.

Organic gardeners consider soil to be a complexsystem which includes lifeforms, gases, water,minerals and organic materials. Chemical fertilizersare viewed by most organic gardeners as too harsh tobe applied to living soils. They are believed tocontribute to the loss of proper soil function and torestrict the life processes of beneficial organisms thatrecycle nutrients and contribute to the health of livingsoils. This section will attempt to assist the organicgardener in maintaining or improving the ability ofgarden soils to support and provide nutrients tovegetable plants.

Maintaining or Increasing SoilOrganic Matter

High soil organic matter is the basis of managingsoils organically. Organic matter improves soilstructure so it will hold water and oxygen and beeasier to work. It greatly increases the microbialcontent of soils, which is sometimes thought to reducea plant’s chances of becoming diseased. Most impor-tantly, soil organic matter plays a large role in storingand releasing nutrients for plant use.

Soil organic matter is a product of the decay ofplants and animals. It usually includes a large numberof things in various stages of decomposition. Mostplant and animal materials break down rapidly at first,then more slowly as the easily decomposed partsdisappear. All of these plant and animal residues arecollectively referred to as organic matter. The fractionof organic matter in a relatively advanced state ofdecay, now decaying only slowly, may be referred toas humus.

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The amount of organic matter in a soil is abalance between the amount produced and the amountlost, mostly through decomposition. More is producedwith long growing seasons and soils that supportvigorous plant growth. More is lost in warm-moistclimates, and in soils rich in oxygen and soil microor-ganisms. Coarse soils usually contain less organicmatter than fine soils. The more soil mixing thatoccurs, the greater the potential for decomposition.Because Tennessee has a warm, moist climate,relatively large amounts of organic matter are decom-posed annually. Because of this, organic matter willquickly decrease to less than 1 percent in Tennesseesoils unless it is replaced.

Organic gardeners utilize a wide range of proce-dures to increase soil organic matter. Some of thesefollow.

.Using Crop Residues

Crop residue is the portion of plants remainingafter harvest. This residue is a significant source oforganic material. It can be left on the surface where itgrew, used as a mulch, composted or turned under.Leaving crop residue on the soil surface where it grewor around plants as a mulch allows it to help controlsoil erosion. Breakdown of the organic material isslowed so total soil organic material increases. It may,however, increase insect, disease and weed problemsdue to these pests overwintering in this debris.Turning crop residue under breaks it down faster,which may release nutrients. Some insects anddiseases are also less likely to survive if their hostplant material is eliminated.

Crop RotationCrop rotation is a regular scheme of planting

requiring that a different crop be grown in a givenlocation each year for two, three, four or more years.The section concerned with pest control (p 8) dis-cusses rotation for that purpose and makes specificrecommendations concerning groups of plants torotate. Crop rotation can also play a part in maintain-ing soil high in organic matter and fertility. Somevegetables, such as Irish potatoes, tomatoes, canta-loupe, corn and the cabbage family, are heavy feedersand remove large amounts of nitrogen, phosphorusand potassium from the soil. Others, such as rootcrops and herbs, are light feeders. Legumes have theability to absorb and hold nitrogen from the air andcan actually add nitrogen to the soil. One might plantheavy-feeding vegetables in a given area the firstyear, a legume green-manure cover crop the second

year and light feeders the third year. This is anexample of a three-year rotation.

Green-Manure Cover CropsGreen-manure cover crops are usually planted in

late summer or early fall and plowed under either latein the fall or several weeks before spring planting.They provide large amounts of organic matter, somenutrients and protection from erosion over the winter.They are useful to gardeners trying to improve theirsoils, especially those who are unable to compostenough material for their large gardens. They may alsobe used over the growing season in a rotation systemdesigned to control plant pests or improve soils.

There are two types of green-manure cover crops,legumes and non-legumes. Legumes can add nutrientsto the soil because they have root nodules that containnitrogen-fixing bacteria. They fix more nitrogen whenmixed with a non-legume crop in the garden thanwhen grown by themselves. It is not unusual for amixed legume planting to fix 100 pounds of nitrogenper acre. Legumes may also have very deep roots,which improve soil drainage and bring up nutrientsfrom the subsoil to levels where shallow-rooted plantscan use them. Peas, beans, clover, vetch and alfalfaare examples of legumes.

The non-legumes used as green-manure covercrops are mostly grasses. They are grown becausethey are economical, easily established and canquickly produce large amounts of organic material.Examples include annual rye, oats, wheat and millet.

A list of suitable green-manure cover crops andsome of their characteristics is contained in Table 3.

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Table 3. Green-Manure Cover Crops for Tennessee Growers

Crop Legume/ Annual/ Planting Seed per CommentsNonlegume Perennial Time 1,000 ft.

Alfalfa Legume Perennial Spring or fall 1/2 lb. Deep-rooted. Apply lime if pHis below 6. High in protein andnitrogen.

Buckwheat Nonlegume Annual Late spring to 2 lbs. Deep-rooted. Attracts bees.early fall Multiple crop possible.

Field Peas Legume Annual Late spring to 2 1/2 lbs.early fall

Crimson Legume Annual Aug. 15Clover Sept. 15 1/2 lb. Does well in mixture of

ryegrass. Hard seed maygerminate over several years.

AnnualLespedeza Legume Annual Spring or fall 1 lb.

Millet Nonlegume Annual May to July 1 lb. Attracts doves.

Oats Nonlegume Annual To Oct. 1 1 1/2 lb. Will overwinter.

Annual Rye Nonlegume Annual Sept. 15Oct. 15 1/2 lb.

Soybeans Legume Annual Spring to 2 lbs.mid-summer

Sudangrass Nonlegume Annual April to July 1/2 lb.

Many are available. They may be chopped or mowedwith a rotary lawn mower if they are too tall to easily turnunder. Do this before their seed matures.

Cover crops may also be chopped and left to decayon the soil surface. Allowing a cover crop to remain on thesoil surface will provide about the same amount ofnitrogen as turning it under, and may help to reduceerosion. It could, however, also provide a place for insectsand disease pathogens to overwinter. A cover crop left onthe soil surface will help retain soil moisture. This may bea disadvantage when planting an early, cool-season crop,but is an advantage later in the growing season. If covercrops are turned under, be sure to allow at least six weeksfor them to decay before planting. This will reducenitrogen tie-up problems.

The Effect of Mulches on SoilsThere are two kinds of mulches, organic and

inorganic. Black plastic is the most common inor-ganic mulch. It absorbs sunlight and increases soiltemperature compared to un-mulched soils. In addi-tion to controlling weeds and retaining soil moisture,mulch reduces erosion and the need to cultivate.

Plastic mulch is applied over moist, worked,fertilized soil a week or so before planting. Becausesoil beneath plastic remains moist, plant roots growmore profusely near the surface. Crusting is reduced.Earthworms and soil microbes are also encouraged byplastic mulches. The result is that soils beneath blackplastic mulch generally are looser, easier to work andhave better tilth than un-mulched soil.

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Organic mulches have many of the same effectson soil as inorganic mulches. One major difference isthat they are lighter in color than un-mulched soil andreduce the rate at which soil warms up. A seconddifference is that organic mulches will decay and canbe worked into the soil at the end of the growingseason, where they will add to soil organic matter.Plastic mulches will not decay and their removal anddisposal should be considered when using them.

Almost any organic material may be used as amulch. Some common organic mulches include grassclippings, hay, sawdust, pine needles, leaves, compostand newspapers. Fresh material, such as grass clip-pings, should be composted or allowed to dry a fewdays before use so it will not injure plants as it heatsup. It should also be placed a few inches away fromplants. A few sheets of newspaper may suffice as amulch, but several inches of leaves or pine needleswill be required as these materials settle. Whenmaterials high in carbon, such as sawdust, are used asa mulch, their decay will tie up significant amounts ofnitrogen. Extra nitrogen should be supplied to avoidproblems with nitrogen deficiencies. More informa-tion on using mulches in home gardens can be foundin Extension factsheet SP291, “Mulching VegetableGardens.”

Making and Using CompostCompost is partially decayed organic matter.

Composting greatly decreases the volume of organicmaterial, making it easier to handle. Nutrient concen-tration and microorganism numbers are increased.Insects, disease and viable weed seed decrease andmay even be eliminated. Materials such as manure orkitchen waste become more pleasant to work with.Sometimes the large mass of material produced in thegarden or around the home is difficult to incorporatedirectly into the soil. This might be the case, forexample, with cornstalks, grass clippings or leaves. Acompost pile can be a convenient place to store thesematerials, as well as bulky materials brought in fromelsewhere to amend soils.

Composting, however, is more than a way ofrecycling plant wastes. Compost builds soil structure,increases the ability of soil to retain water, reduceserosion, improves aeration and supplies nutrients.Nutrients from compost are supplied slowly early inthe season when plants are small, then more rapidlyas soils warm and plants grow faster. Certain nutrientscontinue to be supplied for several years as compostbreaks down; thus, compost enriches soils in propor-tion to the amount used.

Almost any organic material can be composted,but avoid meat scraps, grease, bone and other animalremains. It is also best not to compost weeds withmature seed or diseased plants, since weed seed anddisease organisms may not be destroyed duringcomposting.

Begin by chopping or shredding the organicmaterials. This increases their surface area so micro-organisms can break them down faster. The compostpile can be also be turned and kept moist more easilyif it consists of small particles.

Build a 6-inch layer of plant residue, then cover itwith a 2-inch layer of manure. Dried or dense plantmaterials tend to contain too much carbon and notenough nitrogen to compost rapidly. Unless nitrogen-rich materials are added, they will compost veryslowly. Fresh manure, bone meal, cotton seed mealand other high-nitrogen, organic fertilizers can supplythe needed nitrogen, as can large amounts of succu-lent plant material such as grass clippings. If manureis not used, a one-eighth inch covering of soil willprovide needed microorganisms. A sprinkling of lime,phosphate rock, granite dust or wood ashes willincrease the pH and mineral content of the pile.

Additional layers may be added to the heightdesired. Keep the pile moist but not soggy. It mayheat up to almost 150❍ F in only a few days and beginto shrink in size. Turn it with a pitchfork after two orthree weeks and again after five or six weeks. Be sureto place the outer parts of the pile toward the centerwhen it is turned. The heat generated will kill manyweed seed, insects and disease organisms. Compostmade this way should be ready to use in three to sixmonths. A pile of plant materials not chopped,amended or turned may require a year or two tocompost properly. Compost is ready to use when theplant residues are fragmented, dark brown and havean earthy odor.

Use compost by working a 1- to 3-inch layer intothe top 4 inches of soil a month or so before planting.Some gardeners use compost as a mulch aroundgrowing plants or as a sidedressing.

Organic materials may also be placed in a layerover garden soil and allowed to compost where theyare to be used. This is called sheet composting. Amore detailed discussion of composting is available inExtension PB 1479,”Composting Yard, Garden andFood Wastes at Home.”

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Figure 6. Raised beds are highly suited to organicgardening techniques.

Using Lime and Organic FertilizersSometimes it may be desirable to add nutrients in

a form more quickly available or more concentratedthan those derived from the above soil-buildingtechniques. It may also be desirable to adjust the soilacidity so the nutrients present are more available tovegetable plants. There are a number of ways to addnutrients and adjust soil pH that are acceptable toorganic gardeners.

Increase Soil pHGround limestone (lime) is usually used to

increase the pH of acid soils, thus making them lessacid. The amount of lime needed depends on anumber of factors, such as the current acidity level ofthe soil, the quality of the limestone and the soil it isapplied to. The only really accurate way to know howmuch lime is required is to have a soil test done.Local county Extension offices can explain how totake a soil sample, where to send it for analysis andthe nominal fee involved. Testing soil before applyinglime is important because too much lime createsplant-growth problems very similar in appearance totoo little lime.

Various liming materials are used to raise soil pHin addition to ground limestone. Organic gardeners,however, generally use only calcitic or dolomiticlimestone. Calcitic limestone is essentially calciumcarbonate. As it reacts in the soil, it frees calcium, anessential nutrient for plants. Dolomitic limestonecontains both calcium and magnesium and can supplyboth of these to growing plants. Both kinds of limeare equally effective in raising soil pH, but someorganic gardeners prefer not to use them.

Basic slag, a by-product of iron ore smelting, issometimes used in place of ground limestone. It isabout 70 percent as effective as ground limestone.Wood ashes are yet another substance having theability to raise pH. Its efficiency varies depending onthe type of wood, completeness of combustion, purityof the ashes and whether or not water has leached anyof the materials out of them. Fresh hardwood ashesare about 30 percent or more as effective in alteringsoil pH as ground limestone. It is important thathousehold ashes be spread over a considerable areaand not thrown in the same place over long periods oftime, as they may raise soil pH too high. Wood ashesalso contain phosphorus and potash as listed in theorganic fertilizer table of this publication.

Adding Nutrients — ManureManure is probably the most common organic

fertilizer. It contains nitrogen, potassium and phos-phorus ,as well as other essential plant nutrients andlarge amounts of organic material. These nutrients canbe concentrated enough in fresh manure to burntender plant materials or dilute enough in leachedmanure to make no appreciable differences in soilfertility levels. It is thus important to store manure outof the rain until it is used. The type of animal, itsbedding, diet, age, and the amount of decompositionof the manure are some of the factors that influencenutrient content of manure. These variables make itdifficult to accurately estimate the amount of nutrientscontained in a given kind of manure. Table 4 containssome general estimates of the three primary nutrientsfound in various animal manures.

Table 4. Chemical Composition of VariousAnimal Manures1

Animal Percent Pounds Per Ton Water Nitrogen Phosphate Potash

Broiler 25 34 37 30Hen 35 47 60 24Beef 80 14 9 11Dairy 84 12 5 12Horse 60 12 5 9Sheep 65 21 7 19Pig 75 10 7 13

1 Varies greatly according to bedding material,moisture, length of storage, application method, etc.

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Applying manure to vegetable gardens can bedone in a variety of ways. We have already mentionedits usefulness in producing compost. A second way isto make a manure tea of 100 pounds of manure in a60-gallon barrel of water. Let the solution steep fortwo or three weeks, then stir and use the solution towater plants. Manure may also be used to mulchplants, so long as it is kept several inches away fromplants so it won’t burn them.

The most common way to use manure is to spreadit uniformly over the garden area several weeksbefore planting and to turn it under. Two hundred andfifty to 500 pounds of large animal manure per 1000square feet will improve soil fertility significantlywhile adding considerable organic material to the soil.One hundred to 200 pounds of poultry manure willsuffice.

Some vegetable crops respond better to manurethan others. Squash, pumpkins, cucumbers, canta-

Table 5. Percentage Composition of Common Organic Fertilizers

Fertilizer Nitrogen(N) Phosphate(P2O5) Potash(K2O)

Blood meal 8-15 0-3 ———

Bone meal 2-4 12-28 ———

Cornstalks 0.75 0.5 0.9

Cottonseed meal 6-7 1-2 1 -1.5

Granite dust ——— ——— 3.5

Greensand ——— 1 - 1 1/2 5-6

Guano 1/2 - 12 4-8 1-3

Oak leaves 0.8 0.35 0.15

Phosphate rock ——— 25-32 ———

Wood ashes ——— 1-2 3-7

loupe and watermelon respond especially well and aresometimes planted in hills or rows over concentra-tions of manure.

Corn, leafy greens and root crops also do well inmanured soil. Irish potatoes and sweet potatoes areexceptions. Irish potatoes tend to develop scab and sweetpotatoes to crack when fertilized with manure. Peas andbeans require little if any supplemental nitrogen and donot respond well to manure applications.

Adding Nutrients — Non-manureOrganic gardeners use several substances besides

manure to add nutrients to garden soils. Some arewidely available, while others are available only viamail order or in small localized areas. The composi-tion of these substance also varies widely. Some ofthe more commonly found organic fertilizers and theappropriate ranges of nutrient concentrations aregiven in Table 5.

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Also, remember that nutrients obtained from organicfertilizers will generally be much more expensive than thesame nutrients obtained from commercial fertilizers.Rather than broadcasting these expensive materials overthe entire garden, they can also be banded near the row orapplied only to the area to be planted.

Gardeners must check their particular source oforganic fertilizers to be sure how much nutrient theycontain. Sometimes it is possible to use a single substancesuch as guano or cottonseed meal as a fertilizer. It may benecessary to mix a substance high in one nutrient withothers to make up a complete fertilizer high in all threeprimary nutrients. You should also consider how quicklythe nutrients will be released for plants to use. Fertilizersthat dissolve, such as blood meal, release nutrients morerapidly than more stable substances, such as granite dust.The best organic fertilizers contain significant amounts ofthe three primary nutrients, some of which dissolvequickly and some very slowly.

Traditional agriculture considers only those sub-stances containing one or more of the three primarynutrients as fertilizers. Many companies sell mixtures ofthe above substance designed to contain all three of theprimary nutrients, i.e., designed to be complete

fertilizers. Numerous other acceptable, completeorganic fertilizers are derived from fish, fish products,seaweed and combinations of many organic substances.These will have three numbers on their container toexpress their nutrient content. The first number alwaysrepresents the percent of nitrogen in the fertilizer. Thesecond number represents the percent of phosphate andthe third, potash.

Soil AmendmentsMany organic gardeners broaden the definition of

fertilizer to include anything added to the soil to improvefertility. Traditional agriculture considers substances suchas lime added to the soil primarily to alter soil propertiesto be soil amendments. Organic gardeners sometimes usea wide range of products designed to add trace elements,vitamins or microorganisms to the soil or to assist varioussoil reactions. These substances are soil amendments.They are generally quite expensive and have little proveneffect on soil fertility. There are a great many of them andthey come and go very rapidly. The use of most of them isnot recommended by The University of TennesseeAgricultural Extension Service.

ReferencesSeveral fact sheets and publications referred to in this publication may be useful to organic gardeners. They may be

obtained from your county Agricultural Extension Service. These include:

No. TitlePB595 You Can Control Vegetable Garden InsectsPB901 Growing Vegetables in Home GardensPB1215 Disease Control in the Home Vegetable GardenPB1228 Gardening for NutritionPB1479 Composting Yard, Garden and Food Waste at HomePB1622 Disease and Insect Control in Home Fruit PlantingsSP277-K Disease Resistance in Recommended Vegetable

Varieties for Home GardensSP290-Z Commercial Sources of Predators and ParasitesSP291-H Mulching Vegetable GardensSP291-I Weed Control in Home GardensSP293-A Mole Control in TennesseeSP293-D Building Bird HousesSP341-L Nematode Control in the Home Garden

Precautionary StatementTo protect people and the environment, crop protection chemicals must be used safely. This is everyone’s responsibil-

ity, especially the user. Read and follow label directions, carefully before you buy, mix, apply, store or dispose of thesechemicals. According to laws regulating them, they must be used only as directed by the label.

This information is directed at home gardeners rather than production for sale. State and federal regulations mayregulate commercial production and should be consulted before considering commercial production of organic vegetables.

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PB1391-7.5M-8/99(Rev) E12-2015-00-062-00The Agricultural Extension Service offers its programs to all eligible persons

regardless of race, color, age, national origin, sex, disability, religion or veteran statusand is an Equal Opportunity Employer.

COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS The University of Tennessee Institute of Agriculture, U.S. Department of Agriculture,

and county governments cooperating in furtherance of Acts of May 8 and June 30, 1914. Agricultural Extension Service

Billy G. Hicks, Dean

Visit the Agricultural Extension Service Websiteat: http://www.utextension.edu/