Alternative Soil Amendments


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Alternative Soil Amendments

  1. 1. 800-346-9140 ALTERNATIVE SOIL AMENDMENTS A ppropri e Technol at ogy Transf f R ural A reas er or HORTICULTURE TECHNICAL NOTE ATTRA is the national sustainable agriculture information center funded by the USDA’s Rural Business -- Cooperative Service. ABSTRACT: This publication covers soil amendments that are not standard agricultural fertilizers. These include plant and animal by-products, rock powders, seaweed, inoculants, conditioners and others. Much of the information is taken from research reports by Iowa State University and the Rodale Institute Research Center, which cover the material in greater detail (2, 9). The reader is referred to these works for additional information. Another ATTRA publication, Sources for Organic Fertilizers and Amendments, serves as a companion piece to this document. It provides sources for the materials discussed herein.Written by Bart Hall, July 1998Revised by Preston Sullivan, April 2001 Table of Contents Amendments in Proper Context...........................................................2 Plant & Animal By-Products ................................................................2 Manure & Compost Based Products ....................................................3 Rock and Mineral Powders ..................................................................4 Seaweed Products ...............................................................................7 Microbial Inoculants ............................................................................8 Soil Conditioners ..................................................................................10 Evaluate Products Carefully.................................................................10 References ...........................................................................................11 IS A PROJECT OF THE NATIONAL CENTER FOR APPROPRIATE TECHNOLOGY
  2. 2. Amendments In Proper Context amendment without ensuring that it was approved by the program under which theyThe sustainability of a farm system is only sought certification. Some alternative soilmarginally related to fertilizer and other inputs. amendments either contain ingredients thatIntrinsic soil factors such as slope, texture, and disqualify them from use in certified production,local rainfall, along with management-related or contain "secret" ingredients that prevent afactors such as a forage-based rotation, soil certification program from evaluating whether ororganic matter, aggregate stability, and tillage not that specific brand can be approved.practices, have a much greater influence on thesustainability of any given farm than does the ATTRA has additional information on organictype or amount of soil amendments. Shifting certification, plus a list of certifiers, availablefrom conventional inputs to alternative ones does upon request. ATTRA has some goodlittle to increase overall sustainability. introductory material on sustainable soil management; ask for ATTRA publicationsFor example, yields of most crops will be reduced Overview of Cover Crops & Green Manures andin soils with poor or excessive drainage, and Sustainable Soil Management.when soil pH is too acidic or alkaline for thecrop’s needs. Only if soil moisture, air, and Plant & Animal By-Productsacidity regimes are generally correct do the majornutrients—nitrogen, phosphate, and potash— Assorted by-products of the food and fiberbegin to exert significant influence on yields. In industries are occasionally used as soilother words, if a soil is excessively acid and amendments, returning to the land nutrients thatpoorly drained it doesnt really matter how much might otherwise be wasted.fertilizer (conventional or alternative) is applied; Many of these products are far too expensive toyields will still be disappointing. justify their use in other than very specialized horticultural applications.In most cases, alternative products areappropriate and effective as minor components Plant by-productsof a highly developed system of whole-farmmanagement. They are most effective in fine- Alfalfa meal (or pellets) contains around 3%tuning a system that already functions relatively nitrogen and is commonly used as an animalwell. This fact is well worth remembering when feed. It is an excellent fertilizer material intalking with vendors at a trade show or planning horticulture, and is said to contain unknowna product purchase. It is wise to evaluate their growth factors which make its mineral contentpotential usefulness in view of other use for the more effective as plant nutrients.same money. Cottonseed meal is a rich source of nitrogen (7%).Farmers for whom organic certification is an Unfortunately, a substantial percentage of theimportant element of marketing should check insecticides used in the U.S. are applied tocarefully with their certification program before cotton, and some of these tend to leave residuesbuying any product that they do not positively in the seeds. Most organic certification programsknow is approved on a brand-name basis. restrict or prohibit the use of cottonseed meal.Organic certification programs and their field Fruit pomaces are what remain after the juice isinspectors have reported persistent problems extracted. They are heavy, wet productswith alternative soil amendments other than the normally available only locally, and bestbetter-known alternative fertilizer materials. composted before use.Some farmers have been refused certificationbecause they took the word of a product Leaf compost is increasingly available as morepromoter and applied an alternative soil and more municipalities compost urban and // ALTERNATIVE SOIL AMENDMENTS Page 2
  3. 3. suburban leaves. In principle, the product is a measured as 4-1-1. Fish emulsion may begood one, but it is often contaminated with fortified with chemical fertilizer, so organic"impurities" ranging from transmission fluid to farmers should be suspicious of any product withtrash bags. a nitrogen content in excess of 5%.Soybean meal is, like alfalfa, most commonly Leather meal is ground tannery waste with 10%used as a protein supplement for animal feeds. nitrogen. Unfortunately, most leather meal alsoWith about 7% nitrogen it can be a useful, but contains about 3% added chromium (a toxicexpensive, fertilizer material. heavy metal), and is thus prohibited in organic agriculture.Wood ash contains about 2% phosphate and 6%potash, but may be contaminated with heavy Manure and Compost Basedmetals or plastic and typically has a high salt Productscontent. Wood ash is rather alkaline, andexcessive use can be quite damaging to many One of the most common types of prepackagedsoils. Some organic programs restrict its use. alternative soil amendments is the manure- or compost-based blended fertilizer. Several ofAnimal by-products these products have national distribution, and many more enjoy a loyal regional following. SuchBlood meal is dried slaughterhouse waste products are typically analyzed at 2 to 5% forcontaining about 12% nitrogen. Unless used each nutrient. Dried compost is used as acarefully, it can burn plants with ammonia, lose bulking agent, source of nutrients, and organicmuch of its nitrogen through volatilization, or matter. It is blended with several of the materialsencourage fungal growth. In view of the discussed in this publication, including rockextremely high cost of blood meal, farmers minerals and plant and animal by-products.should be sure that it really is the best source of Nearly all products of this class sell for pricesnitrogen in a given situation. about three times greater than their conventional fertilizer value, but may be quite effective in farmBone meal is discussed under phosphate sources, situations. However, farmers with access to otherin the section titled “Rock and Mineral Powders.” sources of manure or compost can realize substantial savings by relying on local manureFeather meal is a common by-product of the resources. Some manure-based, blendedpoultry slaughter industry. Although total fertilizers contain ingredients prohibited by onenitrogen levels are fairly high (7 to 10%), the or more organic certification programs and maynature of feathers is such that they break down not be used in certified production; others may beand release their nitrogen much more slowly disqualified because the manufacturer refuses tothan many products of similar price. reveal the "secret" ingredients.Fish meal and fish emulsion are, like most animal Composted sewage sludge is marketed as aby-products, rich in nitrogen. Fish meal contains fertilizer and soil amendment. This compostabout 10% nitrogen, along with about 6% provides organic matter and a number ofphosphate. It is most frequently used as a feed nutrients, and as marketed, is solid with littleadditive, but can be used as a fertilizer. The odor. The greatest potential problems with usingfertilizer analysis of fish emulsion varies with composted sludge are heavy metals frompreparation method. Whole fish and fish parts industrial waste, along with assorted chemicalmust be digested to form a slurry, a process contaminants (from household cleaners, latexaccomplished with the aid of either phosphoric paint, and other things people flush down theiracid or special enzymes. Acid-digested fish drains). Pathogens are controlled fairly easilyemulsion usually has an analysis around 4-4-1, through proper composting, which raises thewhile enzyme-digested fish emulsion is usually temperature of the composting material // ALTERNATIVE SOIL AMENDMENTS Page 3
  4. 4. sufficiently to kill many microorganisms. The on-farm experimentation. A generalU.S. Environmental Protection Agency has understanding of the principal phosphateestablished strict guidelines for pathogen control, products, however, will give some indication ofwhich most sewage composting facilities follow. how they are likely to act in different circumstances. Of particular importance is soilHeavy metal contamination is a significant risk pH; phosphates will be released more quickly inwherever industrial facilities contribute to moderately acid soils than in neutral or alkalinesewage. Contamination by heavy metals and soils.many other chemicals is limited as much aspossible with current technology, but composted Colloidal phosphate consists of clay particlessludge often contains levels that make it surrounded by natural phosphate. Totalunsuitable for use on food crops. Before using phosphate is around 20% and “available”any composted sludge or other treated municipal phosphate about 2–3%. An efficient use ofwaste product in crop production, the grower colloidal phosphate is to add it directly tomust know the chemical composition of the livestock manure in the barn or lot, where theproduct and whether it is safe to apply to food manure acids dissolve much of the totalcrops. Have the sludge tested. It is important to phosphate and the phosphate stabilizes thenote that at least 38 states regulate the production nitrogen in the manure. Many of the sameof sewage compost. Its use is prohibited in all advantages can be had by adding 20–50 poundscertified organic production. of colloidal phosphate to one ton (two cubic yards) of manure when composting. The ATTRARock And Mineral Powders publication Farm-scale Composting Resource List directs the reader to many useful resources onPhosphate sources composting. When direct land application of rock phosphate is the only possibility, spreadingThere are a number of alternative phosphate rates between 500 and 2,000 pounds per acre aresources on the market, but it can be difficult for appropriate, depending on phosphorus status,growers to determine which is the most soil acidity, and finances.appropriate for their operation. Much of thedifficulty stems from confusion about the Rock phosphates are usually derived fromdifference between “total” and “available” ancient marine deposits. They have a differentphosphate. Chemical phosphate fertilizer is sold composition than collodial phosphate, generallyon the basis of available phosphate expressed as making them less available. Total phosphate isP2O5. In fact, “available phosphate” is the only around 30% and available phosphate 1–2%. Theyallowable claim for fertilizer value. are best used in the same manner as colloidal phosphate, and it is worth paying for several testsAvailable phosphate designations are determined to determine how effectively this phosphate moves into manure and soil. It may or may notby measuring the amount of phosphate that be a better buy than colloidal, depending greatlydissolves in a weak citric acid solution believed to on conditions and circumstances.imitate conditions near plant roots. This testprovides a standard means of comparing Hard-rock phosphates are usually derived fromdifferent phosphate sources. Unconventional igneous volcanic deposits and consist almostphosphates, because of their slow release, are totally of the mineral apatite. Although apatiteoften promoted on the basis of total phosphate contains about 40% total phosphate, because ofcontent. Neither available nor total phosphate the minerals composition, this phosphate isanalyses give a particularly accurate picture of largely unavailable. In most circumstances it ishow different phosphate materials will perform not a good buy, but in some situations is the idealin natural systems, hence the importance of product; again, trial and observation are the keysdeveloping good powers of observation through to a wise purchase. // ALTERNATIVE SOIL AMENDMENTS Page 4
  5. 5. Bone meal is so well known, especially in Sulpomag® and K-Mag® are two brand names forhorticulture, that it can hardly be considered an langbeinite.alternative product. Typically it contains about27% total phosphate, and nearly all of that is The salt content and solubility of potassium-available. There is a great deal of confusion bearing sulfates dictate well-considered use, butabout the phosphate content of bone meal their high potash content (22% for langbeinitebecause much of it is sold as a feed additive. In and 50% for potassium sulfate) does allow forthe feed industry, phosphorus is expressed on the good plant response from relatively modestlabel as elemental phosphorus, while in the application rates. Although soluble salts, thesefertilizer industry it is expressed as phosphate. products are considerably less salty and lessPhosphate gives a much bigger number (2.3 times soluble than either kainite (a mixture ofas big) for the same actual phosphorus content. potassium sulfates and common salt) or muriateTwelve percent phosphorus is the same as 27% of potash, the most common conventionalphosphate, and bone meal is sold under either of potassium fertilizer.those (or similar) numbers; its the same good,but expensive, product in either case. Granite dust is often sold as a "slowly available" potash source for organic production. TotalA by-product of the smelting industry, basic slag potash contents in granite dust typically varymay, if finely ground, be a source of phosphorus from 1 to 5%, depending on overall mineraland minor elements. Use of basic slag in organic composition of the rock, but granite is mostlyproduction is restricted. feldspar, a mineral with low solubility. Therefore, little potash fertility is derived fromPotassium from rock and mineral powders this material.Alternative potash (potassium) sources are Another source of slowly available potash,similar to alternative phosphates in that there are popular in alternative agriculture, is the clay-typea variety of sources, with differing availability mineral, glauconite, commonly sold asand fertility value. As with phosphate, there is a greensand. Total potash content of greensand isdifference between available potash and total around 7%, all of which is deeply locked into thepotash; similarly, there is a difference between mineral and only slowly available. Greensand ispure potassium and potash, with the potash also said to have desirable effects on soilnumber being 1.2 times higher than potassium structure. Its high price, however, limits its usefor the same amount of nutrient. solely to high-value horticultural applications.Two sources of potash, potassium sulfate and Feldspar is one of the major potassium-bearingpotassium magnesium sulfate (langbeinite), are minerals of granite. Feldspar powder is fairlycommonly enough used in conventional easily obtained through the ceramics trade.agriculture that they can hardly be considered Unfortunately, most feldspar potash is as tightlyalternative, save for the fact that both are bound within its mineral structure as is theregularly used in certified organic agriculture. potash in greensand. Unless particularThere are two forms of potassium sulfate on the circumstances provide a clear indication thatmarket. One is derived by reacting sulfuric acid feldspar is the most appropriate source of potash,with potassium chloride. It is a good fertilizer, it is proabably not cost-effective.but not acceptable in certified organicproduction. Natural potassium sulfate, from Certain micas, particularly biotite (black mica),Great Salt Lake, is extracted by a differential contain several percent total potash, which,evaporation process lasting three years. It can be because of micas physical structure (quiteused in organic farming. Langbeinite goes from different than feldspar or glauconite), is relativelymine to field with minimal processing. available in microbially active environments. If pure biotite can be obtained at a reasonable price, it may be cost-effective and useful. // ALTERNATIVE SOIL AMENDMENTS Page 5
  6. 6. A by-product of the cement industry, kiln dust Zeolitescan be an affordable limestone substitute andpotash (about 6% soluble) source in areas where Zeolites are mined alumino-silicate materials,it is available. Some cement kilns are fired using containing only insignificant levels of plantassorted industrial wastes, sometimes including nutrients. Their use in crop production stemshazardous wastes. Dust from these kilns may primarily from high nutrient-exchange capacities,itself be a hazardous product, and in several which allow them to absorb and release plantstates is legally treated as such. Sources should nutrients and moisture without any change in thebe verified carefully, and state regulations nature of the zeolite. This action results from thechecked. To date, the product is sold only in mineral’s porous-but-stable chemical structure.bulk. It is generally prohibited in certifiedorganic production. Zeolites enhance the performance of fertilizers by making them resistant to leaching,Secondary and minor nutrients from rock immobilization, and gaseous losses. They are ofpowders particular use in reducing leaching in sandy soils. In one study, 4 to 8 tons of zeolite per acre wasA number of other rock dusts and powders are applied (1). Yield increases were reported foroccasionally available in various parts of the wheat (14%), eggplant (19–55%), carrots (63%),country; sometimes the results from local trials and apples (13–38%). Zeolites are widely used inare reported in national or international eastern European and Japanese agriculture, butpublications, but it is important to remember that their use in the U.S. at this time is very limited.what applies in one region may not be pertinentin another. Additionally, when dealing with Humatesnatural materials like rock, there is very littleproduct consistency from one batch to another; Humates are commercial products usuallyresults from one trial may not be transferable to prepared from leonardite, an oxidized form ofother situations. lignite coal and clay. Leonardite may contain up to 60% humic and fulvic acids, which mimic theBasalt dust, if available at a reasonable cost, can "active" part of soil humus. Soil scientists useprovide a wide range of trace minerals to very broad definitions to describe soil organicagricultural systems over a period of several matter components; "fulvic acids" and "humicyears; as with most rock powders, transportation acids" are terms lumping complex families ofcosts are a major factor in determining cost- organic compounds together on the basis of howeffectiveness. Most of the rich volcanic soils of they can be most easily extracted from soil. Forthe world are derived from basalt, which gives the most part, however, the organic acidssome indication of basalts agronomic value, and extracted from leonardite bear little resemblanceeven when too expensive for land application, to the humic or fulvic acids in soils. Althoughbasalt dust can benefit farm systems when mixed extremely useful and cost-efficient in certainwith manure in the composting process. situations—as nutrient substrates in soilless greenhouse production for example—humatesAny rock, of course, can be ground into powder, and similar products are less clearly helpful inif the price is right. Various people have many field situations.proposed additions to the soil of assorted rockdusts, or even powdered gravel. One rationale The sheer volume of organic matter in evenfor this is the paramagnetic property that some moderately rich soils suggests that agronomicallyrock minerals add to the soil—a factor believed to affordable applications of humates may notbe associated with high fertility. ATTRA has produce significant improvements. The top sixadditional information on paramagnetism in soils inches of soil weigh approximately 1,000 tons perfor those interested. acre; each percent of organic matter, therefore, weighs ten tons. Even assuming that the organic matter in humate products actually is similar to // ALTERNATIVE SOIL AMENDMENTS Page 6
  7. 7. that in soil, it requires two tons of humates per Seaweed Productsacre to increase soil organic matter by 0.1%. Most seaweed fertilizers come from kelp that hasResearch by the Rodale Institute determined that: been harvested, dried, and ground. Kelp meal is suitable for application directly to the soil, or for commercial humates...are not products that addition to the compost pile. It flows easily and can substitute for adequate mineral is readily applied with most dry fertilizer nutrients.... Humates do contain high applicators. It is easily mixed with other dry percentages of humic acids and organic fertilizers and amendments. matter, but at their recommended, or economically feasible rates it is likely they Soil application rates for kelp meal commonly may not significantly increase soil organic range from 150 to 250 lbs/acre for pastures, matter. Likewise, the humic acids in forages and small grains. Two hundred to 400 commercial humates may have the ability lbs/acre are advised for corn, horticultural crops, to...provide growth-stimulating effects, but and gardens. Since it is expensive, kelp meal is in the soil they comprise only a minute most commonly used only on high-value crops. fraction of the total soil humic acid content (2). Dried raw seaweed tends to contain about 1%Additionally, the results indicated that humates nitrogen, a trace of phosphorus, and 2% potash,containing unrefined leonardite can immobilize along with magnesium, sulfur, and numeroussoil phosphorus under some conditions, creating trace elements. Raw seaweeds are prepared bya negative effect on plant performance. various methods and sold under a number of brand names.The Rodale report also concluded that: More often, compounds from kelp and other [while] humate products are based on seaweeds are extracted by various methods in sound principles and the potential for order to concentrate both micronutrients and their beneficial action does exist...the naturally occurring plant hormones into a economics and time involved to increase soluble, easily transported form. Such kelp organic matter through commercial extracts are sometimes applied as a foliar spray products, rather than through more by farmers seeking a natural source of traditional organic-matter-building micronutrients. For the most part, none of the programs, should be seriously considered micronutrient levels in kelp extracts is high (2). enough to correct a deficiency, but as a "tonic" providing a broad array of micronutrients andDespite such determinations, many farmers other trace elements, seaweed extracts have wonreport significant benefits from the use of a measure of acceptance among organic farmers.humates and related products. Where humates Note that while most kelp products are allowedhave shown the most promise is as natural soil in certified production, a few have beenamendments in areas with alkaline, low-organic- supplemented with commercial forms of potashmatter soils. Such soils are common across a and other nutrients and are prohibited.wide range of agricultural production zones inthe southern and western U.S. Leonardite and Microbial Inoculantssimilar products are generally consistent withorganic production practices, given that they are Inoculants, which are dry or liquid preparationsnatural products with proven benefit in certain of one or more species of microorganism, fall intosituations. Some extracts, however, are not three broad groups: 1) those that inoculateacceptable in certified organic production, individual plants with symbiotic organismsdepending on the extraction process used. (chiefly Rhizobia spp.), 2) those that inoculate the // ALTERNATIVE SOIL AMENDMENTS Page 7
  8. 8. soil with desirable organisms, and 3) those that from plant association by taking nutrients andare used as “cover crops” (algae). carbohydrates from the plant roots they live in.Rhizobia In soils where mychorrhizae have been killed off, an inoculation may be beneficial. In healthy soilsThe most clearly beneficial microbial where they already exist there will be little or nopreparations for agricultural use are the different benefit to adding more. There are dozens ofstrains of Rhizobia used to inoculate legumes. mychorrizae species in nature. Additionally, theSpecific strains of these bacteria live in a mutually species found on plant roots may change as thebeneficial (symbiotic) relationship with specific plant matures. If those that are available are ofspecies of legumes. The bacteria penetrate the the correct species, and are handled properly atplant roots, causing the formation of root nodules all stages, they offer interesting potential benefitscontaining both plant tissue and bacteria. In very to farmers in well-managed systems. Generally itsimple terms, the plant supplies the physical is preferred to inoculate with several speciesenvironment and certain nutrients to the bacteria; rather than a single one. For information onthe bacteria "fix" nitrogen from the air into rhizobial and mycorrhizal inoculation for diseasecompounds that then become available to the suppression, request the ATTRA publicationplant. Typical nitrogen fixation rates vary from Sustainable Management of Soil-borne Plant50 lbs/acre to over 300 lbs/acre, depending on Diseases.climate, species, and soil conditions. On mostfarms these rates make it possible to harvest good Free-living soil organismscrops without purchasing additional nitrogen. A great many of the products in this category areMycorrhizae designed to be sprayed on the soil surface or on crop residues in order to inoculate the topsoilThe mycorrhizae (my-cor-ry-‘zee) group of fungi with desirable microorganisms. Manufacturerslive either on or in plant roots and act to extend of these products make numerous and varyingthe reach of root hairs into the soil. Mycorrhizae claims about their beneficial effects, which fallincrease the plants uptake of water and into three broad categories:nutrients, especially in less fertile soils. Thesuperfine, root-like structures of these fungi are • The microbes will fix enough nitrogen frommore extensive and more effective than plant root the air to allow the farmer to eliminate muchhairs at absorbing phosphorus, and other or all fertilizer.nutrients as well. Phosphorus moves slowly in • The product improves soil organic matter andsoils but the fungi can absorb it much faster than "releases" soil nutrients to the crop.the plant alone can. This enhanced root feeding • The product produces better yields, especiallymakes it possible to reduce fertilizer rates for during times of drought.plants having a healthy colony of mychorrhizae.Some plants including citrus, grapes, avocados, Many microbial products do indeed contain free-and bananas, are dependent on mycorrhiza living (as opposed to symbiotic) microbes that arefungi. Others that benefit from having them are known to fix nitrogen in certain circumstances.artichokes, melons, tomatoes, peppers, and Those species, however, work best in wet,squash. oxygen-poor conditions that most farmers and their crops would prefer to avoid. Rice paddiesRoots colonized by mycorrhizae are less likely to are a notable exception. In the vast majority ofbe penetrated by root-feeding nematodes since cropping situations other than rice production,the pest cannot pierce the thick fungal network. the amount of nitrogen fixed by such free-livingMycorrhizae also produce hormones and microbes is not generally consideredantibiotics, which enhance root growth and economically significant (3). In other words, theprovide disease suppression. The fungi benefit value of any fixed nitrogen may be less than the cost of the product. Far greater nitrogen fixation, // ALTERNATIVE SOIL AMENDMENTS Page 8
  9. 9. for example, can be obtained via symbiotic surface is necessary. On most soils this wouldRhizobia on a legume sod or cover crop, for much require irrigation.lower cost. Where weed management is a concern, aSoil microbes, like all living things, will thrive traditional cover crop will be more effective thanonly in the presence of their preferred algae. The algal mat is very thin and will notenvironmental conditions—moisture, oxygen, suppress weeds adequately. The constant surfacetemperature, pH, food, and shelter. When moisture required by the algae tends toconditions are not within favorable ranges, the encourage weed seeds to sprout. It can alsomicrobes cease reproduction or die. Natural encourage disease problems in the crop.microbial populations will be abundant if soilconditions are right. Adding a microbial Enzyme-Based Amendmentsamendment in such circumstances may not becost-efficient, because the naturally occurring Enzymes are involved in a number of soilindividuals will typically outnumber the same reactions, particularly as catalysts in thespecies supplied in a product by 10,000 to 1, or microbial breakdown of organic matter, but verymore (4). little research has been done on the effects of adding enzyme products to the soil.If soil conditions are not right, inoculant Nevertheless, commercial enzyme treatments fororganisms will reproduce just as slowly as their soils are often advertised as having a largenaturally occurring colleagues, which is to say, number of beneficial effects, including improvednot at all. The consensus among agronomists soil structure, nutrient "activation," greaterappears to be that these products perform best nutrient availability, "detoxification" of the soil,when the soil is at or near optimum conditions to better drainage, better water retention, andbegin with. greater microbial activity.Algal mats In nature, the microorganisms that process soil organic matter produce the enzymes they need toAnother group of inoculants, sold as "cover do the job. Those enzymes, being proteins, arecrops," are commercial preparations of themselves broken down by microbial action (5).soil-inhabiting algae advertised as providing Enzymes added to the soil would probably suffermany benefits, including reduced soil crusting, a similar fate in short order.improved soil structure, increased soil organicmatter, improved drainage, and better moisture As with free-living soil organism products, theretention. A solution of the algae mixed with circumstances where enzyme products are likelywater is sprayed on the soil surface. In theory it to perform the best are in soils, that are alreadythen establishes itself to form a continuous mat well-balanced and in good condition.over the soil surface. If natural algae populationshave not been observed to populate a particular Vitamin products are also sold as soil treatmentssoil already, management practices will have to on occasion, but more often as sprays for thebe adjusted to get successful growth of an algal plants themselves. Plants might absorb some ofcover crop. the vitamin through leaves or roots, but much of the applied vitamin is broken down into simpleAlgae are susceptible to the vast majority of components before being absorbed by the plantherbicides in use today and would therefore be (6, 7). Generally, plants in favorableessentially incompatible in a conventional row environments synthesize all the vitamins theycrop system. Mat establishment could only occur need from the resources at hand. The most likelyin the absence of soil disturbance. Therefore, benefit of applying a vitamin product would beapplication would need to be made only after a as a “quick fix” measure for plants grown underfinal cultivation. Lastly, a continuously moist poor conditions, provided it is possible to // ALTERNATIVE SOIL AMENDMENTS Page 9
  10. 10. determine just which vitamins happen to be structure. Note, too, that many wetting agentsdeficient. are not acceptable in certified organic production.Soil Conditioners Evaluate Products CarefullyWetting agents and surfactants break the natural Some non-traditional soil treatments are based onsurface tension of water, overcoming its tendency sound biological or scientific form droplets, and allowing it to penetrate a Unfortunately, a number of studies cited in thevariety of materials. Common clothes-washing Compendium (9, 10) and in the Rodale reportsolutions, shampoos, and detergents rely on Novel Soil Amendments (2) show that using manywetting agents or surfactants to function of the non-traditional products mentioned hereeffectively. Similar compounds are also sold as results in negative net income for the farmer. Thesoil conditioners and are heavily promoted as supposed beneficial effects of the products testedimproving water penetration, drainage, and soil in these studies do not increase yields sufficientlystructure. They are also advertised as aids in to offset the cost of applying the product. Incontrolling erosion and reducing compaction or many studies, the product tested had nohardpans as a result of increased water measurable effect on either the crop or the soil.penetration of the soil. Advertisements for these products often citeIn general, wetting agents are effective where a studies which the sellers claim prove thesoils water-repellency is caused by turf or effectiveness of their products. Those results,grassland cover, by ash from the burning of however, are usually taken out of context,organic matter, or by single-grain soil structure obscuring the fact that the claimed yield increase(soil particles all of one size and not aggregated, is due not to the tested product, but to normalas occurs in some sands). Conditions random fluctuations in yield caused byin which wetting agents have little or no effectinclude poor drainage due to hardpans, environmental conditions within the study.compaction from tillage or traffic, and “tight” or In other words, the product doesnt really dofine-textured soils that have very small pores what the vendors claim it does. Though(such as some clays). In other words, wetting governments do require companies to guaranteeagents are likely to have some effect where water analyses and to back up sales claims forinfiltrates a soil slowly because the soil surface conventional fertilizers, alternative products are,repels water, but not where water penetrates for the most part, unregulated and uncontrolled.slowly because there are no large pore spaces (8).Most soils with good structure have good At the same time, prejudice against alternativeinfiltration rates. Soil structure can be products and practices has often resulted inmaintained and improved by a good rotation, testing that has been less than honest, and someregular additions of organic matter, and normal off-the-cuff rejections by researchers andconservation practices. Beneficial effects shouldnot be expected on soils that are already wetable. Extension. As a result, farmers benefit the most by evaluations done within the context of theirCommercial wetting agents can be quite own farm operations. On-farm research trialsexpensive, especially when used to treat large take some effort but are not difficult to perform.areas, and any results may not justify the cost of Contact ATTRA for a copy of the Sustainablethe product. Some farmers attempt to economize Agriculture Networks publication entitled Howby applying something like dishwashing soap or to Conduct Research on Your Farm or Ranch.shampoo instead of commercial wetting agents, Referencesbut caution is advised since other ingredients inhousehold products may be detrimental to plant 1) Mumptom, Fredrick A. 1985. Using zeolitesgrowth or may cause a breakdown of soil in agriculture. p. 125–158 In: Innovative // ALTERNATIVE SOIL AMENDMENTS Page 10
  11. 11. Biological Technologies for Lesser Developed 7) Allison, F.E. 1973. Soil Organic Matter and its Countries. Congress of the United States, Role in Crop Production. Elsevier Scientific Office of Technology Assessment. Publishing Co., New York, 639 p. Washington D.C. 246 p. 8) Sunderman, H. D. 1983. Soil Wetting Agents:2) McAllister, J. 1987. A Practical Guide to Their Use in Crop Production. North Central Novel Soil Amendments. Rodale Press, Regional Extension Publication 190, 4 p. Emmaus, Pennsylvania. 124 p. 9) NRC-103 Committee. 1986. Compendium of3) Huang, P. M. and M. Schnitzer, (eds.) . 1986. Research Reports on Use of Non-Traditional Interactions of Soil Minerals with Natural Materials for Crop Production, Cooperative Organics and Microbes, Special Publication Extension Service, Iowa State University, 17. Soil Science Society of America, Madison, Ames. Varied pagination. Wisconsin. 606 p. 10) Ibid. Supplement 1.4) David Patriquin Department of Biology, Dalhousie Univ. Halifax, Nova Scotia By Bart Hall, July 1998 Revised by Preston Sullivan, April, 20015) Stevenson, F. J., (ed.) . 1982. Nitrogen in Agricultural Soils. American Society of NCAT Agriculture Specialists Agronomy. Madison, Wisconsin. 940 p.6) Vitosh, M. L. 1984. Biological Inoculants and Activators: Their Value to Agriculture. North Central Regional Extension Publication. 168. 4 p. The electronic version of Alternative Soil Amendments is located at: The ATTRA Project is operated by the National Center for Appropriate Technology under a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. ATTRA is located in the Ozark Mountains at the University of Arkansas in Fayetteville at P.O. Box 3657, Fayetteville, AR 72702. ATTRA staff members prefer to receive requests for information about sustainable agriculture via the toll-free number 800-346-9140. // ALTERNATIVE SOIL AMENDMENTS Page 11
  12. 12. Notes: Notes:// ALTERNATIVE SOIL AMENDMENTS Page 12