alternative soil amendments

IS A PROJECT OF THE NATIONAL CENTER FOR APPROPRIATE TECHNOLOGY

Written by Bart Hall, July 1998Revised by Preston Sullivan, April 2001

800-346-9140

Appropriate Technology Transfer for Rural Areas

ALTERNATIVESOIL AMENDMENTS

ABSTRACT: This publication covers soil amendments that are not standard agricultural fertilizers. These include plant andanimal by-products, rock powders, seaweed, inoculants, conditioners and others. Much of the information is taken from researchreports by Iowa State University and the Rodale Institute Research Center, which cover the material in greater detail (2, 9). Thereader is referred to these works for additional information. Another ATTRA publication, Sources for Organic Fertilizers andAmendments, serves as a companion piece to this document. It provides sources for the materials discussed herein.

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

www.attra.ncat.org

Table of Contents

Amendments in Proper Context...........................................................2Plant & Animal By-Products ................................................................2Manure & Compost Based Products ....................................................3Rock and Mineral Powders ..................................................................4Seaweed Products ...............................................................................7Microbial Inoculants ............................................................................8Soil Conditioners ..................................................................................10Evaluate Products Carefully.................................................................10References ...........................................................................................11

HORTICULTURE TECHNICAL NOTE

// ALTERNATIVE SOIL AMENDMENTS

Amendments In Proper Context

The sustainability of a farm system is onlymarginally related to fertilizer and other inputs.Intrinsic soil factors such as slope, texture, andlocal rainfall, along with management-relatedfactors such as a forage-based rotation, soilorganic matter, aggregate stability, and tillagepractices, have a much greater influence on thesustainability of any given farm than does thetype or amount of soil amendments. Shiftingfrom conventional inputs to alternative ones doeslittle to increase overall sustainability.

For example, yields of most crops will be reducedin soils with poor or excessive drainage, andwhen soil pH is too acidic or alkaline for thecrop�s needs. Only if soil moisture, air, andacidity regimes are generally correct do the majornutrients�nitrogen, phosphate, and potash�begin to exert significant influence on yields. Inother words, if a soil is excessively acid andpoorly drained it doesn't really matter how muchfertilizer (conventional or alternative) is applied;yields will still be disappointing.

In most cases, alternative products areappropriate and effective as minor componentsof a highly developed system of whole-farmmanagement. They are most effective in fine-tuning a system that already functions relativelywell. This fact is well worth remembering whentalking with vendors at a trade show or planninga product purchase. It is wise to evaluate theirpotential usefulness in view of other use for thesame money.

Farmers for whom organic certification is animportant element of marketing should checkcarefully with their certification program beforebuying any product that they do not positivelyknow is approved on a brand-name basis.

Organic certification programs and their fieldinspectors have reported persistent problemswith alternative soil amendments other than thebetter-known alternative fertilizer materials. Some farmers have been refused certificationbecause they took the word of a productpromoter and applied an alternative soil

amendment without ensuring that it wasapproved by the program under which theysought certification. Some alternative soilamendments either contain ingredients thatdisqualify them from use in certified production,or contain "secret" ingredients that prevent acertification program from evaluating whether ornot that specific brand can be approved.

ATTRA has additional information on organiccertification, plus a list of certifiers, availableupon request. ATTRA has some goodintroductory material on sustainable soilmanagement; ask for ATTRA publicationsOverview of Cover Crops & Green Manures andSustainable Soil Management.

Plant & Animal By-Products

Assorted by-products of the food and fiberindustries are occasionally used as soilamendments, returning to the land nutrients thatmight otherwise be wasted.Many of these products are far too expensive tojustify their use in other than very specializedhorticultural applications.

Plant by-products

Alfalfa meal (or pellets) contains around 3%nitrogen and is commonly used as an animalfeed. It is an excellent fertilizer material inhorticulture, and is said to contain unknowngrowth factors which make its mineral contentmore effective as plant nutrients.

Cottonseed meal is a rich source of nitrogen (7%).Unfortunately, a substantial percentage of theinsecticides used in the U.S. are applied tocotton, and some of these tend to leave residuesin the seeds. Most organic certification programsrestrict or prohibit the use of cottonseed meal.

Fruit pomaces are what remain after the juice isextracted. They are heavy, wet productsnormally available only locally, and bestcomposted before use.

Leaf compost is increasingly available as moreand more municipalities compost urban and


suburban leaves. In principle, the product is agood one, but it is often contaminated with"impurities" ranging from transmission fluid totrash bags.

Soybean meal is, like alfalfa, most commonlyused as a protein supplement for animal feeds. With about 7% nitrogen it can be a useful, butexpensive, fertilizer material.

Wood ash contains about 2% phosphate and 6%potash, but may be contaminated with heavymetals or plastic and typically has a high saltcontent. Wood ash is rather alkaline, andexcessive use can be quite damaging to manysoils. Some organic programs restrict its use.

Animal by-products

Blood meal is dried slaughterhouse wastecontaining about 12% nitrogen. Unless usedcarefully, it can burn plants with ammonia, losemuch of its nitrogen through volatilization, orencourage fungal growth. In view of theextremely high cost of blood meal, farmersshould be sure that it really is the best source ofnitrogen in a given situation.

Bone meal is discussed under phosphate sources,in the section titled �Rock and Mineral Powders.�

Feather meal is a common by-product of thepoultry slaughter industry. Although totalnitrogen levels are fairly high (7 to 10%), thenature of feathers is such that they break downand release their nitrogen much more slowlythan many products of similar price.

Fish meal and fish emulsion are, like most animalby-products, rich in nitrogen. Fish meal containsabout 10% nitrogen, along with about 6%phosphate. It is most frequently used as a feedadditive, but can be used as a fertilizer. Thefertilizer analysis of fish emulsion varies withpreparation method. Whole fish and fish partsmust be digested to form a slurry, a processaccomplished with the aid of either phosphoricacid or special enzymes. Acid-digested fishemulsion usually has an analysis around 4-4-1,while enzyme-digested fish emulsion is usually

measured as 4-1-1. Fish emulsion may befortified with chemical fertilizer, so organicfarmers should be suspicious of any product witha nitrogen content in excess of 5%.

Leather meal is ground tannery waste with 10%nitrogen. Unfortunately, most leather meal alsocontains about 3% added chromium (a toxicheavy metal), and is thus prohibited in organicagriculture.

Manure and Compost BasedProducts

One of the most common types of prepackagedalternative soil amendments is the manure- orcompost-based blended fertilizer. Several ofthese products have national distribution, andmany more enjoy a loyal regional following. Suchproducts are typically analyzed at 2 to 5% foreach nutrient. Dried compost is used as abulking agent, source of nutrients, and organicmatter. It is blended with several of the materialsdiscussed in this publication, including rockminerals and plant and animal by-products.Nearly all products of this class sell for pricesabout three times greater than their conventionalfertilizer value, but may be quite effective in farmsituations. However, farmers with access to othersources of manure or compost can realizesubstantial savings by relying on local manureresources. Some manure-based, blendedfertilizers contain ingredients prohibited by oneor more organic certification programs and maynot be used in certified production; others may bedisqualified because the manufacturer refuses toreveal the "secret" ingredients.

Composted sewage sludge is marketed as afertilizer and soil amendment. This compostprovides organic matter and a number ofnutrients, and as marketed, is solid with littleodor. The greatest potential problems with usingcomposted sludge are heavy metals fromindustrial waste, along with assorted chemicalcontaminants (from household cleaners, latexpaint, and other things people flush down theirdrains). Pathogens are controlled fairly easilythrough proper composting, which raises thetemperature of the composting material


sufficiently to kill many microorganisms. TheU.S. Environmental Protection Agency hasestablished strict guidelines for pathogen control,which most sewage composting facilities follow.

Heavy metal contamination is a significant riskwherever industrial facilities contribute tosewage. Contamination by heavy metals andmany other chemicals is limited as much aspossible with current technology, but compostedsludge often contains levels that make itunsuitable for use on food crops. Before usingany composted sludge or other treated municipalwaste product in crop production, the growermust know the chemical composition of theproduct and whether it is safe to apply to foodcrops. Have the sludge tested. It is important tonote that at least 38 states regulate the productionof sewage compost. Its use is prohibited in allcertified organic production.

Rock And Mineral Powders

Phosphate sources

There are a number of alternative phosphatesources on the market, but it can be difficult forgrowers to determine which is the mostappropriate for their operation. Much of thedifficulty stems from confusion about thedifference between �total� and �available�phosphate. Chemical phosphate fertilizer is soldon the basis of available phosphate expressed asP2O5. In fact, �available phosphate� is the onlyallowable claim for fertilizer value.

Available phosphate designations are determinedby measuring the amount of phosphate thatdissolves in a weak citric acid solution believed toimitate conditions near plant roots. This testprovides a standard means of comparingdifferent phosphate sources. Unconventionalphosphates, because of their slow release, areoften promoted on the basis of total phosphatecontent. Neither available nor total phosphateanalyses give a particularly accurate picture ofhow different phosphate materials will performin natural systems, hence the importance ofdeveloping good powers of observation through

on-farm experimentation. A generalunderstanding of the principal phosphateproducts, however, will give some indication ofhow they are likely to act in differentcircumstances. Of particular importance is soilpH; phosphates will be released more quickly inmoderately acid soils than in neutral or alkalinesoils.

Colloidal phosphate consists of clay particlessurrounded by natural phosphate. Totalphosphate is around 20% and �available�phosphate about 2�3%. An efficient use ofcolloidal phosphate is to add it directly tolivestock manure in the barn or lot, where themanure acids dissolve much of the totalphosphate and the phosphate stabilizes thenitrogen in the manure. Many of the sameadvantages can be had by adding 20�50 poundsof colloidal phosphate to one ton (two cubicyards) of manure when composting. The ATTRApublication Farm-scale Composting Resource Listdirects the reader to many useful resources oncomposting. When direct land application ofrock phosphate is the only possibility, spreadingrates between 500 and 2,000 pounds per acre areappropriate, depending on phosphorus status,soil acidity, and finances.

Rock phosphates are usually derived fromancient marine deposits. They have a differentcomposition than collodial phosphate, generallymaking them less available. Total phosphate isaround 30% and available phosphate 1�2%. Theyare best used in the same manner as colloidalphosphate, and it is worth paying for several teststo determine how effectively this phosphatemoves into manure and soil. It may or may notbe a better buy than colloidal, depending greatlyon conditions and circumstances.

Hard-rock phosphates are usually derived fromigneous volcanic deposits and consist almosttotally of the mineral apatite. Although apatitecontains about 40% total phosphate, because ofthe mineral's composition, this phosphate islargely unavailable. In most circumstances it isnot a good buy, but in some situations is the idealproduct; again, trial and observation are the keysto a wise purchase.


Bone meal is so well known, especially inhorticulture, that it can hardly be considered analternative product. Typically it contains about27% total phosphate, and nearly all of that isavailable. There is a great deal of confusionabout the phosphate content of bone mealbecause much of it is sold as a feed additive. Inthe feed industry, phosphorus is expressed on thelabel as elemental phosphorus, while in thefertilizer industry it is expressed as phosphate. Phosphate gives a much bigger number (2.3 timesas big) for the same actual phosphorus content. Twelve percent phosphorus is the same as 27%phosphate, and bone meal is sold under either ofthose (or similar) numbers; it's the same good,but expensive, product in either case.

A by-product of the smelting industry, basic slagmay, if finely ground, be a source of phosphorusand minor elements. Use of basic slag in organicproduction is restricted.

Potassium from rock and mineral powders

Alternative potash (potassium) sources aresimilar to alternative phosphates in that there area variety of sources, with differing availabilityand fertility value. As with phosphate, there is adifference between available potash and totalpotash; similarly, there is a difference betweenpure potassium and potash, with the potashnumber being 1.2 times higher than potassiumfor the same amount of nutrient.

Two sources of potash, potassium sulfate andpotassium magnesium sulfate (langbeinite), arecommonly enough used in conventionalagriculture that they can hardly be consideredalternative, save for the fact that both areregularly used in certified organic agriculture. There are two forms of potassium sulfate on themarket. One is derived by reacting sulfuric acidwith potassium chloride. It is a good fertilizer,but not acceptable in certified organicproduction. Natural potassium sulfate, fromGreat Salt Lake, is extracted by a differentialevaporation process lasting three years. It can beused in organic farming. Langbeinite goes frommine to field with minimal processing.

Sulpomag® and K-Mag® are two brand names forlangbeinite.

The salt content and solubility of potassium-bearing sulfates dictate well-considered use, buttheir high potash content (22% for langbeiniteand 50% for potassium sulfate) does allow forgood plant response from relatively modestapplication rates. Although soluble salts, theseproducts are considerably less salty and lesssoluble than either kainite (a mixture ofpotassium sulfates and common salt) or muriateof potash, the most common conventionalpotassium fertilizer.

Granite dust is often sold as a "slowly available"potash source for organic production. Totalpotash contents in granite dust typically varyfrom 1 to 5%, depending on overall mineralcomposition of the rock, but granite is mostlyfeldspar, a mineral with low solubility. Therefore, little potash fertility is derived fromthis material.

Another source of slowly available potash,popular in alternative agriculture, is the clay-typemineral, glauconite, commonly sold asgreensand. Total potash content of greensand isaround 7%, all of which is deeply locked into themineral and only slowly available. Greensand isalso said to have desirable effects on soilstructure. Its high price, however, limits its usesolely to high-value horticultural applications.

Feldspar is one of the major potassium-bearingminerals of granite. Feldspar powder is fairlyeasily obtained through the ceramics trade. Unfortunately, most feldspar potash is as tightlybound within its mineral structure as is thepotash in greensand. Unless particularcircumstances provide a clear indication thatfeldspar is the most appropriate source of potash,it is proabably not cost-effective.

Certain micas, particularly biotite (black mica),contain several percent total potash, which,because of mica's physical structure (quitedifferent than feldspar or glauconite), is relativelyavailable in microbially active environments. Ifpure biotite can be obtained at a reasonable price,it may be cost-effective and useful.


A by-product of the cement industry, kiln dustcan be an affordable limestone substitute andpotash (about 6% soluble) source in areas whereit is available. Some cement kilns are fired usingassorted industrial wastes, sometimes includinghazardous wastes. Dust from these kilns mayitself be a hazardous product, and in severalstates is legally treated as such. Sources shouldbe verified carefully, and state regulationschecked. To date, the product is sold only inbulk. It is generally prohibited in certifiedorganic production.

Secondary and minor nutrients from rockpowders

A number of other rock dusts and powders areoccasionally available in various parts of thecountry; sometimes the results from local trialsare reported in national or internationalpublications, but it is important to remember thatwhat applies in one region may not be pertinentin another. Additionally, when dealing withnatural materials like rock, there is very littleproduct consistency from one batch to another;results from one trial may not be transferable toother situations.

Basalt dust, if available at a reasonable cost, canprovide a wide range of trace minerals toagricultural systems over a period of severalyears; as with most rock powders, transportationcosts are a major factor in determining cost-effectiveness. Most of the rich volcanic soils ofthe world are derived from basalt, which givessome indication of basalt's agronomic value, andeven when too expensive for land application,basalt dust can benefit farm systems when mixedwith manure in the composting process.

Any rock, of course, can be ground into powder,if the price is right. Various people haveproposed additions to the soil of assorted rockdusts, or even powdered gravel. One rationalefor this is the paramagnetic property that somerock minerals add to the soil�a factor believed tobe associated with high fertility. ATTRA hasadditional information on paramagnetism in soilsfor those interested.

Zeolites

Zeolites are mined alumino-silicate materials,containing only insignificant levels of plantnutrients. Their use in crop production stemsprimarily from high nutrient-exchange capacities,which allow them to absorb and release plantnutrients and moisture without any change in thenature of the zeolite. This action results from themineral�s porous-but-stable chemical structure.

Zeolites enhance the performance of fertilizers bymaking them resistant to leaching,immobilization, and gaseous losses. They are ofparticular use in reducing leaching in sandy soils.In one study, 4 to 8 tons of zeolite per acre wasapplied (1). Yield increases were reported forwheat (14%), eggplant (19�55%), carrots (63%),and apples (13�38%). Zeolites are widely used ineastern European and Japanese agriculture, buttheir use in the U.S. at this time is very limited.

Humates

Humates are commercial products usuallyprepared from leonardite, an oxidized form oflignite coal and clay. Leonardite may contain upto 60% humic and fulvic acids, which mimic the"active" part of soil humus. Soil scientists usevery broad definitions to describe soil organicmatter components; "fulvic acids" and "humicacids" are terms lumping complex families oforganic compounds together on the basis of howthey can be most easily extracted from soil. Forthe most part, however, the organic acidsextracted from leonardite bear little resemblanceto the humic or fulvic acids in soils. Althoughextremely useful and cost-efficient in certainsituations�as nutrient substrates in soillessgreenhouse production for example�humatesand similar products are less clearly helpful inmany field situations.

The sheer volume of organic matter in evenmoderately rich soils suggests that agronomicallyaffordable applications of humates may notproduce significant improvements. The top sixinches of soil weigh approximately 1,000 tons peracre; each percent of organic matter, therefore,weighs ten tons. Even assuming that the organicmatter in humate products actually is similar to


that in soil, it requires two tons of humates peracre to increase soil organic matter by 0.1%.

Research by the Rodale Institute determined that:

commercial humates...are not products thatcan substitute for adequate mineralnutrients.... Humates do contain highpercentages of humic acids and organicmatter, but at their recommended, oreconomically feasible rates it is likely theymay not significantly increase soil organicmatter. Likewise, the humic acids incommercial humates may have the abilityto...provide growth-stimulating effects, butin the soil they comprise only a minutefraction of the total soil humic acid content(2).

Additionally, the results indicated that humatescontaining unrefined leonardite can immobilizesoil phosphorus under some conditions, creatinga negative effect on plant performance.

The Rodale report also concluded that:

[while] humate products are based onsound principles and the potential fortheir beneficial action does exist...theeconomics and time involved to increaseorganic matter through commercialproducts, rather than through moretraditional organic-matter-buildingprograms, should be seriously considered(2).

Despite such determinations, many farmersreport significant benefits from the use ofhumates and related products. Where humateshave shown the most promise is as natural soilamendments in areas with alkaline, low-organic-matter soils. Such soils are common across awide range of agricultural production zones inthe southern and western U.S. Leonardite andsimilar products are generally consistent withorganic production practices, given that they arenatural products with proven benefit in certain

situations. Some extracts, however, are notacceptable in certified organic production,depending on the extraction process used.

Seaweed Products

Most seaweed fertilizers come from kelp that hasbeen harvested, dried, and ground. Kelp meal issuitable for application directly to the soil, or foraddition to the compost pile. It flows easily andis readily applied with most dry fertilizerapplicators. It is easily mixed with other dryfertilizers and amendments.

Soil application rates for kelp meal commonlyrange from 150 to 250 lbs/acre for pastures,forages and small grains. Two hundred to 400lbs/acre are advised for corn, horticultural crops,and gardens. Since it is expensive, kelp meal ismost commonly used only on high-value crops.

Dried raw seaweed tends to contain about 1%nitrogen, a trace of phosphorus, and 2% potash,along with magnesium, sulfur, and numeroustrace elements. Raw seaweeds are prepared byvarious methods and sold under a number ofbrand names.

More often, compounds from kelp and otherseaweeds are extracted by various methods inorder to concentrate both micronutrients andnaturally occurring plant hormones into asoluble, easily transported form. Such kelpextracts are sometimes applied as a foliar sprayby farmers seeking a natural source ofmicronutrients. For the most part, none of themicronutrient levels in kelp extracts is highenough to correct a deficiency, but as a "tonic"providing a broad array of micronutrients andother trace elements, seaweed extracts have wona measure of acceptance among organic farmers. Note that while most kelp products are allowedin certified production, a few have beensupplemented with commercial forms of potashand other nutrients and are prohibited.

Microbial Inoculants

Inoculants, which are dry or liquid preparationsof one or more species of microorganism, fall into

three broad groups: 1) those that inoculateindividual plants with symbiotic organisms(chiefly Rhizobia spp.), 2) those that inoculate the


soil with desirable organisms, and 3) those thatare used as �cover crops� (algae).

Rhizobia

The most clearly beneficial microbialpreparations for agricultural use are the differentstrains of Rhizobia used to inoculate legumes. Specific strains of these bacteria live in a mutuallybeneficial (symbiotic) relationship with specificspecies of legumes. The bacteria penetrate theplant roots, causing the formation of root nodulescontaining both plant tissue and bacteria. In verysimple terms, the plant supplies the physicalenvironment and certain nutrients to the bacteria;the bacteria "fix" nitrogen from the air intocompounds that then become available to theplant. Typical nitrogen fixation rates vary from50 lbs/acre to over 300 lbs/acre, depending onclimate, species, and soil conditions. On mostfarms these rates make it possible to harvest goodcrops without purchasing additional nitrogen.

Mycorrhizae

The mycorrhizae (my-cor-ry-�zee) group of fungilive either on or in plant roots and act to extendthe reach of root hairs into the soil. Mycorrhizaeincrease the plant's uptake of water andnutrients, especially in less fertile soils. Thesuperfine, root-like structures of these fungi aremore extensive and more effective than plant roothairs at absorbing phosphorus, and othernutrients as well. Phosphorus moves slowly insoils but the fungi can absorb it much faster thanthe plant alone can. This enhanced root feedingmakes it possible to reduce fertilizer rates forplants having a healthy colony of mychorrhizae. Some plants including citrus, grapes, avocados,and bananas, are dependent on mycorrhizafungi. Others that benefit from having them areartichokes, melons, tomatoes, peppers, andsquash.

Roots colonized by mycorrhizae are less likely tobe penetrated by root-feeding nematodes sincethe pest cannot pierce the thick fungal network.

Mycorrhizae also produce hormones andantibiotics, which enhance root growth andprovide disease suppression. The fungi benefit

from plant association by taking nutrients andcarbohydrates from the plant roots they live in.

In soils where mychorrhizae have been killed off,an inoculation may be beneficial. In healthy soilswhere they already exist there will be little or nobenefit to adding more. There are dozens ofmychorrizae species in nature. Additionally, thespecies found on plant roots may change as theplant matures. If those that are available are ofthe correct species, and are handled properly atall stages, they offer interesting potential benefitsto farmers in well-managed systems. Generally itis preferred to inoculate with several speciesrather than a single one. For information onrhizobial and mycorrhizal inoculation for diseasesuppression, request the ATTRA publicationSustainable Management of Soil-borne PlantDiseases.

Free-living soil organisms

A great many of the products in this category aredesigned to be sprayed on the soil surface or oncrop residues in order to inoculate the topsoilwith desirable microorganisms. Manufacturersof these products make numerous and varyingclaims about their beneficial effects, which fallinto three broad categories:

• The microbes will fix enough nitrogen fromthe air to allow the farmer to eliminate muchor all fertilizer.

• The product improves soil organic matter and"releases" soil nutrients to the crop.

• The product produces better yields, especiallyduring times of drought.

Many microbial products do indeed contain free-living (as opposed to symbiotic) microbes that areknown to fix nitrogen in certain circumstances. Those species, however, work best in wet,oxygen-poor conditions that most farmers andtheir crops would prefer to avoid. Rice paddiesare a notable exception. In the vast majority ofcropping situations other than rice production,the amount of nitrogen fixed by such free-living

microbes is not generally consideredeconomically significant (3). In other words, thevalue of any fixed nitrogen may be less than thecost of the product. Far greater nitrogen fixation,


for example, can be obtained via symbioticRhizobia on a legume sod or cover crop, for muchlower cost.

Soil microbes, like all living things, will thriveonly in the presence of their preferredenvironmental conditions�moisture, oxygen,temperature, pH, food, and shelter. Whenconditions are not within favorable ranges, themicrobes cease reproduction or die. Naturalmicrobial populations will be abundant if soilconditions are right. Adding a microbialamendment in such circumstances may not becost-efficient, because the naturally occurringindividuals will typically outnumber the samespecies supplied in a product by 10,000 to 1, ormore (4).

If soil conditions are not right, inoculantorganisms will reproduce just as slowly as theirnaturally occurring colleagues, which is to say,not at all. The consensus among agronomistsappears to be that these products perform bestwhen the soil is at or near optimum conditions tobegin with.

Algal mats

Another group of inoculants, sold as "covercrops," are commercial preparations ofsoil-inhabiting algae advertised as providingmany benefits, including reduced soil crusting,improved soil structure, increased soil organicmatter, improved drainage, and better moistureretention. A solution of the algae mixed withwater is sprayed on the soil surface. In theory itthen establishes itself to form a continuous matover the soil surface. If natural algae populationshave not been observed to populate a particularsoil already, management practices will have tobe adjusted to get successful growth of an algalcover crop.

Algae are susceptible to the vast majority ofherbicides in use today and would therefore beessentially incompatible in a conventional row

crop system. Mat establishment could only occurin the absence of soil disturbance. Therefore,application would need to be made only after afinal cultivation. Lastly, a continuously moist

surface is necessary. On most soils this wouldrequire irrigation.

Where weed management is a concern, atraditional cover crop will be more effective thanalgae. The algal mat is very thin and will notsuppress weeds adequately. The constant surfacemoisture required by the algae tends toencourage weed seeds to sprout. It can alsoencourage disease problems in the crop.

Enzyme-Based Amendments

Enzymes are involved in a number of soilreactions, particularly as catalysts in themicrobial breakdown of organic matter, but verylittle research has been done on the effects ofadding enzyme products to the soil. Nevertheless, commercial enzyme treatments forsoils are often advertised as having a largenumber of beneficial effects, including improvedsoil structure, nutrient "activation," greaternutrient availability, "detoxification" of the soil,better drainage, better water retention, andgreater microbial activity.

In nature, the microorganisms that process soilorganic matter produce the enzymes they need todo the job. Those enzymes, being proteins, arethemselves broken down by microbial action (5).Enzymes added to the soil would probably suffera similar fate in short order.

As with free-living soil organism products, thecircumstances where enzyme products are likelyto perform the best are in soils, that are alreadywell-balanced and in good condition.

Vitamin products are also sold as soil treatmentson occasion, but more often as sprays for theplants themselves. Plants might absorb some ofthe vitamin through leaves or roots, but much ofthe applied vitamin is broken down into simplecomponents before being absorbed by the plant(6, 7). Generally, plants in favorableenvironments synthesize all the vitamins they

need from the resources at hand. The most likelybenefit of applying a vitamin product would beas a �quick fix� measure for plants grown underpoor conditions, provided it is possible to


determine just which vitamins happen to bedeficient.

Soil Conditioners

Wetting agents and surfactants break the naturalsurface tension of water, overcoming its tendencyto form droplets, and allowing it to penetrate avariety of materials. Common clothes-washingsolutions, shampoos, and detergents rely onwetting agents or surfactants to functioneffectively. Similar compounds are also sold assoil conditioners and are heavily promoted asimproving water penetration, drainage, and soilstructure. They are also advertised as aids incontrolling erosion and reducing compaction orhardpans as a result of increased waterpenetration of the soil.

In general, wetting agents are effective where asoil's water-repellency is caused by turf orgrassland cover, by ash from the burning oforganic matter, or by single-grain soil structure(soil particles all of one size and not aggregated,as occurs in some sands). Conditionsin which wetting agents have little or no effectinclude poor drainage due to hardpans,compaction from tillage or traffic, and �tight� orfine-textured soils that have very small pores(such as some clays). In other words, wettingagents are likely to have some effect where waterinfiltrates a soil slowly because the soil surfacerepels water, but not where water penetratesslowly because there are no large pore spaces (8).Most soils with good structure have goodinfiltration rates. Soil structure can bemaintained and improved by a good rotation,regular additions of organic matter, and normalconservation practices. Beneficial effects shouldnot be expected on soils that are already wetable.

Commercial wetting agents can be quiteexpensive, especially when used to treat largeareas, and any results may not justify the cost ofthe product. Some farmers attempt to economizeby applying something like dishwashing soap or

shampoo instead of commercial wetting agents,but caution is advised since other ingredients inhousehold products may be detrimental to plantgrowth or may cause a breakdown of soil

structure. Note, too, that many wetting agentsare not acceptable in certified organic production.

Evaluate Products Carefully

Some non-traditional soil treatments are based onsound biological or scientific principles. Unfortunately, a number of studies cited in theCompendium (9, 10) and in the Rodale reportNovel Soil Amendments (2) show that using manyof the non-traditional products mentioned hereresults in negative net income for the farmer. Thesupposed beneficial effects of the products testedin these studies do not increase yields sufficientlyto offset the cost of applying the product. Inmany studies, the product tested had nomeasurable effect on either the crop or the soil.

Advertisements for these products often citestudies which the sellers claim prove theeffectiveness of their products. Those results,however, are usually taken out of context,obscuring the fact that the claimed yield increaseis due not to the tested product, but to normalrandom fluctuations in yield caused byenvironmental conditions within the study.In other words, the product doesn't really dowhat the vendors claim it does. Thoughgovernments do require companies to guaranteeanalyses and to back up sales claims forconventional fertilizers, alternative products are,for the most part, unregulated and uncontrolled.

At the same time, prejudice against alternativeproducts and practices has often resulted intesting that has been less than honest, and someoff-the-cuff rejections by researchers andExtension. As a result, farmers benefit the mostby evaluations done within the context of theirown farm operations. On-farm research trialstake some effort but are not difficult to perform. Contact ATTRA for a copy of the SustainableAgriculture Network's publication entitled Howto Conduct Research on Your Farm or Ranch.

References

1) Mumptom, Fredrick A. 1985. Using zeolitesin agriculture. p. 125�158 In: Innovative


Biological Technologies for Lesser DevelopedCountries. Congress of the United States,Office of Technology Assessment.Washington D.C. 246 p.

2) McAllister, J. 1987. A Practical Guide toNovel Soil Amendments. Rodale Press,Emmaus, Pennsylvania. 124 p.

3) Huang, P. M. and M. Schnitzer, (eds.) . 1986.Interactions of Soil Minerals with NaturalOrganics and Microbes, Special Publication17. Soil Science Society of America, Madison,Wisconsin. 606 p.

4) David PatriquinDepartment of Biology, Dalhousie Univ.Halifax, Nova Scotia

5) Stevenson, F. J., (ed.) . 1982. Nitrogen inAgricultural Soils. American Society ofAgronomy. Madison, Wisconsin. 940 p.

6) Vitosh, M. L. 1984. Biological Inoculantsand Activators: Their Value to Agriculture. North Central Regional ExtensionPublication. 168. 4 p.

7) Allison, F.E. 1973. Soil Organic Matter and itsRole in Crop Production. Elsevier ScientificPublishing Co., New York, 639 p.

8) Sunderman, H. D. 1983. Soil Wetting Agents:Their Use in Crop Production. North CentralRegional Extension Publication 190, 4 p.

9) NRC-103 Committee. 1986. Compendium ofResearch Reports on Use of Non-TraditionalMaterials for Crop Production, CooperativeExtension Service, Iowa State University,Ames. Varied pagination.

10) Ibid. Supplement 1.

By Bart Hall, July 1998Revised by Preston Sullivan, April, 2001NCAT Agriculture Specialists

The ATTRA Project is operated by the National Center for Appropriate Technology under a grant from theRural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do notrecommend or endorse products, companies, or individuals. ATTRA is located in the Ozark Mountainsat the University of Arkansas in Fayetteville at P.O. Box 3657, Fayetteville, AR 72702. ATTRA staffmembers prefer to receive requests for information about sustainable agriculture via the toll-freenumber 800-346-9140.

The electronic version of Alternative Soil Amendmentsis located at:http://www.attra.org/attra-pub/altsoil.html


Notes:Notes:

alternative soil amendments

Education

soil conditioners

soil ph

soil moisture

sustainable soil management

soil organic matter

alternative products

intrinsic soil factors

alternative ones