Manures for Organic Crop Production
SOIL SYSTEMS GUIDE
Abstract: Livestock manures are an important resource in sustainable and organic crop production. This publication addresses the problems and challenges of using both raw and composted manures and discusses some of the solutions. It also deals with guano, a similar material.
By George Kuepper Table of Contents NCAT Agriculture Specialist Introduction ...... 1 March 2003 Raw Manure Use: Problems & Solutions ...... 2 Contamination ...... 2 Produce Quality Concerns ...... 3 Introduction Fertility Imbalances ...... 3 Livestock manure is traditionally a key fer- tilizer in organic and sustainable soil manage- Weed Problems...... 4 ment. It is most effectively used in combination Pollution ...... 4 with other sustainable practices. These include crop rotation, cover cropping, green manuring, Composted Manures ...... 5 liming, and the addition of other natural or bio- About Guano ...... 6 logically friendly fertilizers and amendments. In organic production, manure is commonly Field-applying Manures & Composts ...... 7 applied to the field in either a raw (fresh or dried) Summary ...... 9 or composted state. This publication addresses the advantages and constraints of using manure References ...... 9 in either form, but with particular focus on raw Recommended Resources...... 10 manure; it does not discuss the specific circumstances and challenges associated with handling and applying slurry manure. There are clear restric- tions on the use of raw ma- nure in organic farming. These restrictions are de- tailed in the National Or- ganic Program (NOP) Regulations, which consti- tute the federal standard for organic production. Details will be discussed later in this publication.
ATTRA is the national sustainable agriculture information service operated by the National Center for Appropriate Technology, through a grant from the Rural Business-Cooperative Service, U.S. Department of Agriculture. These organizations do not recommend or endorse products, companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville, AR 72702), Butte, Montana, and Davis, California. sible, avoid manuring after planting. Fall spread- ing is advised. •Do not use dog, cat, or pig manures (fresh Raw Manure Use: or composted). These species share many para- sites with humans. Problems & Solutions •Wash all produce from manured fields thor- oughly before use. Persons especially suscep- Raw manure is an excellent resource for or- tible to food-borne illnesses (children, the eld- ganic crop production. It supplies nutrients and erly, those with compromised immune systems, organic matter, stimulating the biological pro- etc.) should avoid uncooked produce. cesses in the soil that help to build fertility. Still, In February 2000, the issue of manure use on a number of cautions and restrictions are in or- organic farms was highlighted on the television der, based on concerns about produce quality, news program 20/20. The segment suggested that food contamination, soil fertility imbalances, fertilization with livestock manures made or- weed problems, and pollution hazards. ganic foods more dangerous than other food products in the marketplace (4). The show’s pro- ducers arranged for a sampling of various or- Contamination ganic and nonorganic vegetables from store shelves and tested for the presence of E. coli. The Some manures may contain contaminants samples of both organic and nonorganic produce such as residual hormones, antibiotics, pesticides, were generally free of serious contamination. disease organisms, and other undesirable sub- The exceptions were bagged sprouts and stances. Since many of these can be eliminated mesclun salad mix. Of these, more E. coli con- through high- tamination was temperature observed on the aerobic organic samples. It composting, was largely on this this practice is basis that the news recommended program chal- where low lev- lenged organic els of organic farming. contaminants The attack was may be present. embarrassing to Caution is ad- the organic indus- vised, however, try and forced its as research has membership to un- demonstrated dertake a lot of that Salmonella “damage control,” and E. coli bacte- despite the fact ria appear to that the allegations survive the composting process much better than were contrived and based on poor science. The previously thought (1). The possibility of trans- sampling was not statistically significant (i.e., the mitting human diseases discourages the use of same sampling done today might produce the fresh manures (and even some composts) as pre- opposite result). The show failed to point out plant or sidedress fertilizers on vegetable crops— that the specific test used does not distinguish especially crops that are commonly eaten raw (2). between pathogenic and benign forms of E. coli. Washington State University (3) suggests that Also ignored was the obvious fact that conven- growers: tional farmers use manure, too! Furthermore, the •Apply animal manures at least 60 days prior reporter failed to disclose the vested interests of to harvest of any vegetable that will be eaten the individual bringing the charges (Dennis without cooking. (Note: The NOP’s specific re- Avery of the Hudson Institute—a “think tank” quirements on the timing of manure applications heavily funded by conventional agriculture in- are discussed later in this publication.) If pos- terests), presenting him instead as a former offi-
PAGE 2 //MANURES FOR ORGANIC CROP PRODUCTION cial with the Agriculture Department (5). John Stossel—the journalist responsible for the 20/20 Fertility Imbalances report—subsequently issued an apology and a correction (6). Raw manure use has often been associated Unlike conventional farmers, who have only with imbalances in soil fertility. There are sev- safety guidelines regarding manure use, certified eral causal factors: organic farmers must follow stringent protocols. •Manure is often rich in specific nutrients like Raw manure may NOT be applied to food crops phosphate or potash. While these nutrients are within 120 days of harvest where edible portions of great benefit to crops, repeated applications have soil contact (i.e., most vegetables, strawber- of manure can result in their building to detri- ries, etc.); it may NOT be applied to food crops mental levels. A good example is the overuse of within 90 days of harvest where edible portions broiler litter in the mid-South, which has put do not have soil contact (i.e., grain crops, most excessive phosphate in the soil and polluted sur- tree fruits). Such restrictions do not apply to feed face waters. Nutrient excesses also “tie up” other and fiber crops (7). minerals. Excessive phosphate interferes with Organic substances are not the only contami- plant uptake of both copper and zinc; excessive nants found in livestock manures. Heavy met- potash can restrict boron, manganese, and even als can be a problem, especially where industrial- magnesium (9). scale production systems are used. Concerns •Continual manure use tends to acidify soil. over heavy-metal and other chemical contami- As manure breaks down it releases various or- nation have dogged the use of poultry litter as ganic acids that assist in making soil minerals an organically acceptable fertilizer in Arkansas, available—a benefit of manure that is often un- where it’s readily and cheaply available (8). This recognized. Over time, however, this process matter is discussed in more detail under depletes the soil of calcium and causes pH levels “Composted Manures.” Heavy-metal contami- to fall below the optimum for most crops. Ma- nation is also a concern with composted sewage nures do supply some calcium, but not enough sludge (biosolids)—a major reason for its being to counterbalance the tendency toward increased prohibited from certified organic production. acidity (9). Possible exceptions include caged- Under federal organic standards, certifiers layer manure (when oyster-shell or similar cal- may require testing of manure or compost if there cium supplements are fed) and manure from is reason to suspect high levels of contamination. dairy operations where barn lime is used. •When fresh manure containing large amounts of nitrogen and salts is applied to a crop, Produce Quality Concerns it can have the same effects as excessive applica- tions of soluble commercial fertilizers—it can It has long been acknowledged that improper burn seedling roots, reduce immunity to pests, use of raw manure can adversely affect the qual- and shorten produce shelf life. Excessive salin- ity of raw vegetable crops such as potatoes, cu- ity is often associated with heavy applications of cumbers, squash, turnips, cauliflower, cabbage, feedlot manure in regions where little leaching broccoli, and kale. As it breaks down in the soil, naturally occurs—as in most western states (10). manure releases chemical compounds such as For example, growers in southwestern states like skatole, indole, and other phenols. When ab- Arizona are advised to apply gypsum and leach sorbed by the growing plants, these compounds the soil with about 4 inches of irrigation water can impart off-flavors and odors to the vegetables following incorporation of dairy or feedlot ma- (9). For this reason, raw manure should not be nures (11). directly applied to vegetable crops; it should in- To avoid manure-induced imbalances, con- stead be spread on cover crops planted the pre- tinually monitor soil fertility, using appropriate vious season. In the Ozark region, for example, soil tests. Then apply lime or other supplemen- poultry manure is sometimes used to fertilize tary fertilizers and amendments to ensure soil winter cover crops that will be incorporated balance, or restrict application levels if needed. ahead of spring vegetable planting. A soil audit that measures cation base saturation
//MANURES FOR ORGANIC CROP PRODUCTION PAGE 3 is strongly advised. If this service is not provided nure contains weed seed, often from bedding through your state’s Cooperative Extension Ser- materials like small-grain straw and old hay. vice, use of a private lab is suggested (see the High-temperature aerobic composting can ATTRA publication Alternative Soil Testing Labo- greatly reduce the number of viable weed seeds ratories for a listing). (12). In many cases, however, the lush growth Understanding the soil’s needs is only part of weeds that follows manuring does not result of the equation. You must also know the nutri- from weed seeds in the manure but from the ent content of the manure you’re applying. Stan- stimulating effect manure has on seeds already dard fertilizer values (such as those shown in present in the soil (as demonstrated through Table 1) should be used only for crude approxi- studies at Auburn University using broiler lit- mations. The precise nutrient content of any ter) (13). The flush of weeds may result from manure is dependent not only on livestock spe- enhanced biological activity, the presence of or- cies, but also on the ration fed, the kind of bed- ganic acids, an excess of nitrates, or some other ding used, amount of liquid added, and the kind change in the fertility status of the soil. Depend- of capture and handling system employed. Also, ing on the weed species that emerge, the prob- some traditional assumptions about manure lem may be related to the sort of fertility imbal- composition may need to be updated. Because ances described above. Excesses of potash and of the abundance of sulfur in rations, manure has nitrogen in particular can encourage weeds (9). long been recognized as a good source of sulfur. Monitor the nutrient contents of soil and manure However, less sulfur is applied to crops in con- and spread manure evenly to reduce the inci- temporary high-analysis fertilizers, and atmo- dence of weed problems. spheric deposition has been decreased by pollu- tion controls. Sulfur deficiencies are appearing in many soils, and levels in manure may also be Pollution diminished (9). It is advisable to test manure as you would test the soil, in order to assess its fer- When the nutrients in raw or composted tilizer value. manure are eroded or leached from farm fields Cooperative Extension is an excellent source or holding areas, they present a potential pollu- of guides to manure use. These are often tailored tion problem, in addition to being a resource lost to the region and provide useful information not to the farmer. Leached into groundwater, ni- mentioned in more general publications. trates from manure and fertilizers have been
TABLE 1 Approximate NPK Values of Various Animal Manures*
Animal % nitrogen % phosphoric acid % potash
Dairy cow 0.57 0.23 0.62 Beef steer 0.73 0.48 0.55 Horse 0.70 0.25 0.77 Swine 0.49 0.34 0.47 Sheep/goat 1.44 0.50 1.21 Rabbit 2.40 1.40 0.60 Chicken 1.00 0.80 0.39
* Adapted from: Anon. 1998. Fertilizer values of some manures. Countryside & Small Stock Journal. September-October. p. 75
linked to a number of human health problems. Weed Problems Flushed into surface waters, nutrients can cause eutrophication of ponds, lakes, and streams. Use of raw manures has often been associ- Excess nitrates from farms and feedlots in the ated with increased weed problems. Some ma- Mississippi Basin are deemed the primary cause
PAGE 4 //MANURES FOR ORGANIC CROP PRODUCTION of the Gulf of Mexico Dead Zone—a hypoxic fertile soil. In stable humus, there is practically (oxygen deprived) area about the size of New no free ammonia or soluble nitrate, but a large Jersey that now threatens the shrimp, fishing, and amount of nitrogen is tied up as proteins, amino recreational industries off the Louisiana and acids, and other biological components. Other Texas coasts (14). nutrients are stabilized in compost as well. The manner in which manure is collected and Composting livestock manure reduces many stored prior to field use affects the stabilization of the drawbacks associated with raw manure and conservation of valuable nutrients and or- use. Good compost is a “safe” fertilizer. Low in ganic matter. Composting is one means of good soluble salts, it doesn’t “burn” plants. It’s also manure handling and is discussed in more de- less likely to cause nutrient imbalances. It can tail below. safely be applied directly to growing vegetable Reducing manure run-off and leaching losses crops. Many commercially available organic fer- from fields is a matter of both volume and tim- tilizers are based on composted animal manures ing. Manure application far in excess of crop supplemented with rock powders, plant by-prod- needs greatly increases the chances of nutrient ucts like alfalfa meal, and additional animal by- loss, especially in high-rainfall areas. Manure products like blood, bone, and feather meals. spread on bare, frozen orerodible ground is sub- The quality of compost depends on the ject to run-off, especially where heavy winter feedstuffs used to make it. Unless it is supple- rains are common. Under some conditions, how- mented in some way, composted broiler litter— ever, winter-applied manure can actually slow though more stable than raw litter—will be abun- run-off and erosion losses from fields, likely by dant in phosphates and low in calcium. Contin- acting as a light organic mulch (15). ued applications may lead to imbalanced soil Sheet-composting manure (tilling it into the conditions in the long term, as with some raw soil shortly after spreading) or applying it to manures. Soil and compost testing to monitor growing cover crops are two advisable means of nutrient levels is strongly advised. conserving manure nutrients. Grass cover crops, While composting can degrade many organic such as rye and ryegrass, are especially good as contaminants, it cannot eliminate heavy metals. “catch crops”—cover crops grown to absorb In fact, composting concentrates metals, making soluble nutrients from the soil profile to prevent the contaminated compost, pound for pound, them from leaching. (All cover crops function more potentially hazardous than the manure it as catch crops to a greater or lesser degree.) It is was created from. Broiler litter and broiler-litter a sound strategy, therefore, to apply manure to composts have been restricted from certified or- growing catch crops or just prior to planting ganic production in the mid-South largely for this them. reason. Arsenic—once used in chicken feed as Note that both sheet composting and apply- an appetite stimulant and antibiotic—was a par- ing to cover crops have trade-offs. Sheet ticular concern. Since the precise composition composting improves the capture of ammonia of commercial livestock feeds is proprietary in- nitrogen from manure, but requires tillage, which formation, arsenic may still be an additive in for- leaves the soil bare and vulnerable to erosion and mulations in some regions (16). leaching losses. Surface-applying to cover crops A more recent concern is the inclusion of (with no soil-incorporation) eliminates most additional copper in poultry diets and its accu- leaching and erosion losses but increases ammo- mulation in the excreted manure. While copper nia losses to the atmosphere. More details on is an essential plant nutrient, an excessive level these trade-offs will be provided below in the in the soil is toxic. This concern is most relevant section “Field-applying Manures & Composts.” to organic horticultural producers, who often apply significant amounts of copper as fungicides and bactericides, increasing the hazard of Composted Manures buildup in the soil. Whenever you import large amounts of either composted or raw manure onto An effective composting process converts the farm, it is wise to inquire about the feeding animal wastes, bedding, and other raw products practices at the source or have the material tested. into humus—the relatively stable, nutrient-rich, The NOP has put no specific restrictions on and chemically active organic fraction found in when farmers can apply composted manure to
//MANURES FOR ORGANIC CROP PRODUCTION PAGE 5 crops; however, it is very specific about manure cies of bats and seabirds. It has a long history of composting procedures. According to the NOP use as an agricultural fertilizer. It was appar- Regulations, compost must meet the following ently highly prized by native Peruvians well be- criteria: fore the Spanish conquest. Before the develop- •An initial carbon : nitrogen ratio of between ment of chemical fertilizers, there was U.S. Gov- 25:1 and 40:1 must exist for the blend of materi- ernment support for entrepreneurs who discov- als in the “pile”; and ered and developed guano deposits (19, 20). •Temperatures between 131° F and 170° F The nutrient content of commercial guano must be sustained for three days using an in-ves- products can vary considerably based on the diet sel or static aerated pile system; or of the birds or bats. Seabirds subsist largely on •Temperatures between 131° F and 170° F fish; depending on the species, bats may thrive must be sustained for 15 days using a windrow largely on insects or on fruits. Another major composting system, during which period the factor is the age of the source deposit. Guano materials must be turned a minimum of five products may be fresh, semi-fossilized, or fossil- times (17). ized (21). A quick check of several commercial The National Organic Standards Board—the products provided the range of analyses shown advisory body to the NOP—has recommended in Table 2. a more flexible interpretation of the compost As a nutrient source, guano is considered to rules, but this has not yet been incorporated into be moderately available, as are most manures the legislation (18). (24). One source (20) suggests that guanos are ATTRA offers information on various rich in “bioremediation microbes” that assist in composting methods in cleaning up soil toxins. If the publications On-Farm true, this would make guano Composting Resource List, an excellent amendment to Vermicomposting, and Bio- use when transitioning from dynamic Farming & Com- conventional to more sustain- post Preparation. We can able production systems. also provide information ATTRA, however, has not re- on the more exacting pro- viewed the documentation to cesses of controlled micro- substantiate this claim. bial composting (also Guano is advertised as be- known as CMC or Luebke ing quite safe and non-burn- composting). ing to plants; “foolproof” is the term sometimes em- ployed. There does not ap- About Guano pear to be any evidence to the contrary. There is, however, Guano is the dried ex- one serious human illness WWW.CLIPART.COM crement of various spe- connected with guano. His- toplasmosis, caused by the TABLE 2 NPK Analysis by Guano Type fungus Histoplasm Guano Type/Product NPK Analysis Source capsulatum, pro- duces symptoms Desert Bat 8-4-1 Home Harvest (15) similar to influ- Dry-Bar Cave Bat 3-10-1 “ “ enza in mild Fossilized Sea Bird 1-10-1 “ “ cases, or pneu- Pelletized Peruvian Sea Bird 12-12-2.5 “ “ monia when se- Old Thyme Sea Bird 13-8-2 “ “ Jamaican Bat 1-10-0 Bloomington Whse. (22) vere. In persons Peruvian Seabird 11-13-3 with compro- Jamaican Bat 3-8-1 Nitron Industries (23) mised immune systems, histo-
PAGE 6 //MAUNURES FOR ORGANIC CROP PRODUCTION plasmosis can produce complications leading to would likely be corn. While the small-grain crop death (25, 26, 27). shown here would respond positively to manure, Accumulations of both bird and bat guano it is a relatively low-value crop and therefore re- can contain the Histoplasm spores, as can manure sides at the bottom of the pecking order when from old poultry houses. The problems are most manure resources are in short supply. severe in piles that have aged for two or more The circumstances are a bit more complex years, as the fungus has additional time to pro- with vegetable crops. According to experienced liferate and produce spores. In a fresh state, bat market gardener and author Eliot Coleman (28), guano is more hazardous than bird guano be- crops like squash, corn, peas, and beans do best cause infected bats can “shed” the organism and when manure is spread and incorporated just rapidly inoculate the manure (27). prior to planting. The same holds true for leafy It appears that those who spend time in caves, greens, though only well-composted manure and those who harvest and package guano, are should be used. Cabbages, tomatoes, potatoes at the greatest risk of infection. Cases of infec- and root crops, on the other hand, tend to do tion through later handling are apparently not better when the ground has been manured the common, though if they have occurred, they may previous year. Obviously, crop rotations that well have been misdiagnosed as influenza or a feature non-manured crops following manured similar ailment. crops would be ideal. Infections come about when dust and other To achieve maximum recovery of the nutri- aerosols bearing the fungal spores are inhaled. ents in spread manure, sheet composting—plow- Therefore respirators and masks are recom- ing or otherwise incorporating the manure into mended when handling guanos. Also, clothing the soil as soon as possible after spreading—is should be removed carefully afterwards to avoid the best option. Research has shown that solid inhaling accumulated dusts. If possible, wet raw manure will lose about 21% of its nitrogen down the pile of dried guano to reduce dust (25, to the atmosphere if spread and left for four days; 26, 27). prompt soil incorporation reduces that loss to At the present time, the NOP regulations treat only 5% (10). guano as raw, uncomposted manure. It is there- However, since excessive tillage is discour- fore subject to the same 90- and 120-day applica- aged in sustainable systems, options for sheet tion restrictions. It is relatively safe but rather composting may be limited on some farms. The expensive for organic production. Its use is best next-best option appears to be spreading onto justified on high-value crops. growing cover crops. This reduces the chances of loss through surface erosion and cuts leach- ing significantly. However, it does little to con- Field-applying Manures trol ammonia losses to the atmosphere. & Composts FIGURE 1
When...
The 90- and 120-day restrictions on manure application are mainly intended to prevent food contamination with manure pathogens. Beyond these timing constraints, however, additional agronomic considerations are involved in sched- uling manure applications. Generally, manures and composts have their strongest effect on a crop or cover crop if applied just in advance of planting. Growers of agro- nomic crops commonly apply them to the most nitrogen-hungry and responsive crops. In midwestern organic rotations (see Figure 1), this
PAGE 7 //MAUNURES FOR ORGANIC CROP PRODUCTION TABLE 3 Field Calibration of Manure & Compost Spreaders •Condition of chains, gears, and sprockets. It is You will need: common knowledge among Begin by weighing and recording • Scale (capable of accurate farmers that manure spread- the weight of the plastic sheet and measurement in 1-2 lb. units) ers only break down with a bucket. Next, spread the sheet over • 10’x10' plastic sheet full load. Naturally, it is the the ground in the path of the • 5-gallon bucket floor chain—buried under spreader and drive over it as you • Spreader load of manure or compost the manure—that is the first unload at normal speed. Carefully item to go. fold the sheet in on itself to capture the spread manure or compost •Condition of the floor. and place back into the Pounds of manure or Tons of manure or Acids and moisture in ma- bucket. compost captured by compost applied nure corrode and rot metal a 10’x10' sheet per acre Weigh the bucket, sheet, and and wood flooring long be- captured material. Subtract the fore the sides decay. Some 8 1.74 weight of the bucket and sheet manufacturers now make 10 2.18 to find how much manure was models featuring a plastic 12 2.61 captured. The amount of floor that is highly resistant 14 3.05 manure or compost applied per to deterioration. Millcreek 16 3.48 acre can be estimated using Manufacturing (30) sells sev- 18 3.92 the figures provided. The eral with flooring made from 20 4.36 exercise should be repeated recycled milk jugs (31). 22 4.79 several times and the results averaged to increase accuracy. •Condition of paddles. Paddles are designed to shred and break up wads of manure and bed- ding materials. They also provide some lateral spreading. Since this is rather crude technology, How... the resulting distribution is generally less even One of the weakest links in the use of ma- than desired (32). nure as a fertilizer appears to be the actual pro- cess of field spreading. According to some re- •Power drive. Box spreaders are either pow- searchers, the conventional box spreader is an ered through the tractor PTO or ground-driven. “engineering anachronism”—an outdated piece PTO-driven spreaders have more flexibility and of equipment designed principally to dispose can also be used to create windrows for of a waste product, not to manage a nutrient composting. resource. Many machines are built to “dump” Box manure spreaders are poor compost as much material as possible in a short time and spreaders—especially when well-made granular are difficult to calibrate if you want to distrib- composts are used. Well-made compost is fine, ute manure accurately and according to crop relatively flowable, and is better handled with needs (29). (Instructions for calibrating com- spreaders suited to broadcasting lime and bulk post and manure spreaders are provided in granular fertilizer. This equipment is much easier Table 3.) Still, the basic box spreader is the only to calibrate and provides a more uniform distri- technology available and affordable to most bution of material (32). farmers. Application rate recommendations for guano Characteristics to consider when purchas- are usually provided by the supplier. These rates ing a spreader (used or new) include: appear somewhat lower than those for other
PAGE 8 //MANURES FOR ORGANIC CROP PRODUCTION Discusses Organic Produce Report. ABC dried manures (21). As the cost of guano is rela- News 20/20. Aug 11.
Both raw and composted manures are useful 8) Troop, Don. 1989. Is chicken litter really or- in organic crop production. Used properly, with ganic? Ozark Cooperative Warehouse Mar- attention to balancing soil fertility, manures can ket News (Fayetteville, AR). November. p. supplant all or most needs for purchased fertil- 12. izer, especially when combined with a whole- system fertility plan that includes crop rotation 9) Kinsey, Neal. 1994. Manure: The good, the and cover cropping with nitrogen-fixing le- bad, the ugly & how it works with your soil. gumes. Acres USA. October. p. 8, 10, 11, 13. The grower needs to monitor nutrients in the soil via soil testing, and learn the characteristics 10) Huhnke, Raymond L. 1982. Land Applica- of the manure and/or compost to be used. The tion of Livestock Manure. OSU Extension grower should adjust the rates and select addi- Facts No. 1710. Oklahoma State University, tional fertilizers and amendments accordingly. Stillwater, OK. 4 p.
11) Abbott, J.L. 1977. Manure in the Home Gar- den. Publication Q66. University of Arizona, Tucson, AZ. 2 p.
12) Eghball, Bahman, and Gary W. Lesoing. References 2000. Viability of weed seeds following ma- nure windrow composting. Compost Science 1) Anon. 1997. Agriculture issues that affect & Utilization. Winter. p. 46–53. our health. S.W. Organic Gardener. May. p. 3. 13) Williams, Greg, and Pat Williams. 1994. No viable weed seeds in broiler litter. HortIdeas. 2) Pederson, Laura. 1998. Prevent pathogens. March. p. 28. American Agriculturist. May. p. 26. 14) CAST. 1999. Gulf of Mexico hypoxic zone is 3) Williams, Greg, and Pat Williams. 1994. largest in Western Hemisphere. Council for Manure: Is it safe for your garden? HortIdeas. Agricultural Science and Technology, Ames, February. p. 23. IA. June 18.
6) Stossel, John. 2000. An Apology: John Stossel 16) Haapala, JJ. 1997. Risks of chicken manure
//MANURES FOR ORGANIC CROP PRODUCTION PAGE 9 as fertilizer. In Good Tilth. June. p. 10, 12. Newsletter.March.
21) Anon. 2000. Guano—the 100% natural or- 31) Byczynski, Lynn. 1998. Find the right ma- ganic soil amendment. Home Harvest Gar- nure spreader for your farm scale and bud- den Supply, Inc., 3712 Eastern Ave., Balti- get. Growing for Market. August. p. 6–7. more, MD 21224. Tel: 410-327-8403/
23) Nitron Industries P.O. Box 1447, Fayetteville, AR 72702 Tel: 800-835-0123 Website:
24) Anon. No date. Guidelines for Organic Fer- tilization. Cooperative Extension, University Recommended Resources of Vermont, Burlington, VT.
PAGE 10 //MANURES FOR ORGANIC CROP PRODUCTION Tel: 512-892-4400 Fax: 512-892-4448 E-mail: [email protected] http://www.acresusa.com/magazines/ magazine.htm
Anon. 2001. Fair price for neighbor’s manure? New England Farmer. November. p. LP.
Anon. 2001. Manure Management in Organic Farming Systems. Soil Association. July. Available at website
Goldstien, Jerome. 1998. Composting for Ma- nure Management. JG Press, Emmaus, PA. 77 p. Available for $39 postage paid from: Biocycle 419 State Ave. Emmaus, PA 18049 Tel: 610-967-4135 E-mail: [email protected] http://www.jgpress.com/BioCycle/ Books.html
Miles, Carol, Tanya Cheeke, and Tamera Flores. 1999. From End to Beginning: A Manure Resource Guide for Farmers and Gardeners in Western Washington. King County Agri- cultural Commission, Seattle, WA. 25 p.
Miller, Laura. 2000. Basics of manure manage- ment. Small Farm Today. July. p. 28-30.
Organic Trade Association. No date. Manure Use and Agricultural Practices. Organic Trade Association, Greenfield, MA.
Patriquin, David G. 2000. Reducing risks from E. coli 0157 on the organic farm. Canadian Organic Growers.
Pederson, Laura. 1998. Prevent pathogens. American Agriculturist. May. p. 26.
//MANURES FOR ORGANIC CROP PRODUCTION PAGE 11 By George Kuepper NCAT Agriculture Specialist
Edited by David Zodrow and Paul Williams Formatted by Ashley Hill
The electronic version of Manures for Organic Crop Production is located at: HTML http://www.attra.ncat.org/attra-pub/manures.html PDF http://www.attra.ncat.org/attra-pub/PDF/manures.pdf
PAGE 12 //MANURES FOR ORGANIC CROP PRODUCTION