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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.
Table of Contents
Introduction
Livestock manure is traditionally a key fertilizer in organic and
sustainable soil management. It is most effectively used in combination
with other sustainable practices. These include crop rotation, cover
cropping, green manuring, liming, and the addition of other natural
or biologically friendly fertilizers and amendments.
In organic production, manure is commonly applied to the field
in either a raw (fresh or dried) or composted state. This publication
addresses the advantages and constraints of using manure in either
form, but with particular focus on raw manure; it does not discuss
the specific circumstances and challenges associated with handling
and applying slurry manure.
There are clear restrictions on the use of raw manure in organic
farming. These restrictions are detailed in the National Organic
Program (NOP) Regulations, which constitute the federal standard
for organic production. Details will be discussed later in this
publication.
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Raw Manure Use: Problems and
Solutions
Raw manure is an excellent resource for organic crop production.
It supplies nutrients and organic matter, stimulating the biological
processes in the soil that help to build fertility. Still, a number
of cautions and restrictions are in order, based on concerns about
produce quality, food contamination, soil fertility imbalances,
weed problems, and pollution hazards.
Contamination
Some manures may contain contaminants such as residual hormones,
antibiotics, pesticides, disease organisms, and other undesirable
substances. Since many of these can be eliminated through high-temperature
aerobic composting, this practice is recommended where low levels
of organic contaminants may be present. Caution is advised, however,
as research has demonstrated that Salmonella and E. coli
bacteria appear to survive the composting process much better than
previously thought. (1) The possibility of transmitting
human diseases discourages the use of fresh manures (and even some
composts) as preplant or sidedress fertilizers on vegetable crops—especially
crops that are commonly eaten raw. (2)
Washington State University (3) suggests that
growers:
- Apply animal manures at least 60 days prior to harvest of any
vegetable that will be eaten without cooking. (Note: The NOP's
specific requirements on the timing of manure applications are
discussed later in this publication.) If possible, avoid manuring
after planting. Fall spreading is advised.
- Do not use dog, cat, or pig manures (fresh or composted). These
species share many parasites with humans.
- Wash all produce from manured fields thoroughly before use.
Persons especially susceptible to food-borne illnesses (children,
the elderly, those with compromised immune systems, etc.) should
avoid uncooked produce.
In February 2000, the issue of manure use on organic farms was
highlighted on the television news program 20/20. The segment
suggested that fertilization with livestock manures made organic
foods more dangerous than other food products in the marketplace.
(4) The show's producers arranged for a sampling
of various organic and nonorganic vegetables from store shelves
and tested for the presence of E. coli. The samples of
both organic and nonorganic produce were generally free of serious
contamination. The exceptions were bagged sprouts and mesclun salad
mix. Of these, more E. coli contamination was observed
on the organic samples. It was largely on this basis that the news
program challenged organic farming.
The attack was embarrassing to the organic industry and forced
its membership to undertake a lot of "damage control,"
despite the fact that the allegations were contrived and based on
poor science. The sampling was not statistically significant (i.e.,
the same sampling done today might produce the opposite result).
The show failed to point out that the specific test used does not
distinguish between pathogenic and benign forms of E. coli.
Also ignored was the obvious fact that conventional farmers use
manure, too! Furthermore, the reporter failed to disclose the vested
interests of the individual bringing the charges (Dennis Avery of
the Hudson Institute—a "think tank" heavily funded
by conventional agriculture interests), presenting him instead as
a former official with the Agriculture Department. (5)
John Stossel—the journalist responsible for the 20/20
report—subsequently issued an apology and a correction. (6)
Unlike conventional farmers, who have only safety guidelines regarding
manure use, certified organic farmers must follow stringent protocols.
Raw manure may NOT be applied to food crops within 120 days of harvest
where edible portions have soil contact (i.e., most vegetables,
strawberries, etc.); it may NOT be applied to food crops within
90 days of harvest where edible portions do not have soil contact
(i.e., grain crops, most tree fruits). Such restrictions do not
apply to feed and fiber crops. (7)
Organic substances are not the only contaminants found in livestock
manures. Heavy metals can be a problem, especially where industrial-scale
production systems are used. Concerns over heavy-metal and other
chemical contamination have dogged the use of poultry litter as
an organically acceptable fertilizer in Arkansas, where it's readily
and cheaply available. (8) This matter is discussed
in more detail under "Composted Manures."
Heavy-metal contamination is also a concern with composted sewage
sludge (biosolids)—a major reason for its being prohibited
from certified organic production.
Under federal organic standards, certifiers may require testing
of manure or compost if there is reason to suspect high levels of
contamination.
Produce Quality Concerns
It has long been acknowledged that improper use of raw manure can
adversely affect the quality of such vegetable crops as potatoes,
cucumbers, squash, turnips, cauliflower, cabbage, broccoli, and
kale. As it breaks down in the soil, manure releases chemical compounds
such as skatole, indole, and other phenols. When absorbed by the
growing plants, these compounds can impart off-flavors and odors
to the vegetables. (9) For this reason, raw
manure should not be directly applied to vegetable crops; it should
instead be spread on cover crops planted the previous season. In
the Ozark region, for example, poultry manure is sometimes used
to fertilize winter cover crops that will be incorporated ahead
of spring vegetable planting.
Fertility Imbalances
Raw manure use has often been associated with imbalances in soil
fertility. There are several causal factors:
- Manure is often rich in specific nutrients like phosphate or
potash. While these nutrients are of great benefit to crops, repeated
applications of manure can result in their building to detrimental
levels. A good example is the overuse of broiler litter in the
mid-South, which has put excessive phosphate in the soil and polluted
surface waters. Nutrient excesses also "tie up" other
minerals. Excessive phosphate interferes with plant uptake of
both copper and zinc; excessive potash can restrict boron, manganese,
and even magnesium. (9)
- Continual manure use tends to acidify soil. As manure breaks
down it releases various organic acids that assist in making soil
minerals available—a benefit of manure that is often unrecognized.
Over time, however, this process depletes the soil of calcium
and causes pH levels to fall below the optimum for most crops.
Manures do supply some calcium, but not enough to counterbalance
the tendency toward increased acidity. (9)
Possible exceptions include caged-layer manure (when oyster-shell
or similar calcium supplements are fed) and manure from dairy
operations where barn lime is used.
- When fresh manure containing large amounts of nitrogen and salts
is applied to a crop, it can have the same effects as excessive
applications of soluble commercial fertilizers—it can burn
seedling roots, reduce immunity to pests, and shorten produce
shelf life. Excessive salinity is often associated with heavy
applications of feedlot manure in regions where little leaching
naturally occurs—as in most western states. (10)
For example, growers in southwestern states like Arizona are advised
to apply gypsum and leach the soil with about 4 inches of irrigation
water following incorporation of dairy or feedlot manures. (11)
To avoid manure-induced imbalances, continually monitor soil fertility,
using appropriate soil tests. Then apply lime or other supplementary
fertilizers and amendments to ensure soil balance, or restrict application
levels if needed. A soil audit that measures cation base saturation
is strongly advised. If this service is not provided through your
state's Cooperative Extension Service, use of a private lab is suggested
(see the ATTRA publication Alternative
Soil Testing Laboratories for a listing).
Understanding the soil's needs is only part of the equation. You
must also know the nutrient content of the manure you're applying.
Standard fertilizer values (such as those shown in Table
1) should be used only for crude approximations. The precise
nutrient content of any manure is dependent not only on livestock
species, but also on the ration fed, the kind of bedding used, amount
of liquid added, and the kind of capture and handling system employed.
Also, some traditional assumptions about manure composition may
need to be updated. Because of the abundance of sulfur in rations,
manure has long been recognized as a good source of sulfur. However,
less sulfur is applied to crops in contemporary high-analysis fertilizers,
and atmospheric deposition has been decreased by pollution controls.
Sulfur deficiencies are appearing in many soils, and levels in manure
may also be diminished. (9) It is advisable
to test manure as you would test the soil, in order to assess its
fertilizer value.
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 |
Cooperative Extension is an excellent source of guides to manure
use. These are often tailored to the region and provide useful information
not mentioned in more general publications.
Weed Problems
Use of raw manures has often been associated with increased weed
problems. Some manure contains weed seed, often from bedding materials
like small-grain straw and old hay. High-temperature aerobic composting
can greatly reduce the number of viable weed seeds. (12)
In many cases, however, the lush growth of weeds that follows manuring
does not result from weed seeds in the manure, but from the stimulating
effect manure has on seeds already present in the soil (as demonstrated
through studies at Auburn University using broiler litter). (13)
The flush of weeds may result from enhanced biological activity,
the presence of organic acids, an excess of nitrates, or some other
change in the fertility status of the soil. Depending on the weed
species that emerge, the problem may be related to the sort of fertility
imbalances described above. Excesses of potash and nitrogen in particular
can encourage weeds. (9) Monitor the nutrient
contents of soil and manure and spread manure evenly to reduce the
incidence of weed problems.
Pollution
When the nutrients in raw or composted manure are eroded or leached
from farm fields or holding areas, they present a potential pollution
problem, in addition to being a resource lost to the farmer. Leached
into groundwater, nitrates from manure and fertilizers have been
linked to a number of human health problems. Flushed into surface
waters, nutrients can cause eutrophication of ponds, lakes, and
streams. Excess nitrates from farms and feedlots in the Mississippi
Basin are deemed the primary cause of the Gulf of Mexico Dead Zone—a
hypoxic (oxygen deprived) area about the size of New Jersey that
now threatens the shrimp, fishing, and recreational industries off
the Louisiana and Texas coasts. (14)
The manner in which manure is collected and stored prior to field
use affects the stabilization and conservation of valuable nutrients
and organic matter. Composting is one means of good manure handling
and is discussed in more detail below.
Reducing manure run-off and leaching losses from fields is a matter
of both volume and timing. Manure application far in excess of crop
needs greatly increases the chances of nutrient loss, especially
in high-rainfall areas. Manure spread on bare, frozen or erodible
ground is subject to run-off, especially where heavy winter rains
are common. Under some conditions, however, winter-applied manure
can actually slow run-off and erosion losses from fields, likely
by acting as a light organic mulch. (15)
Sheet-composting manure (tilling it into the soil shortly after
spreading) or applying it to growing cover crops are two advisable
means of conserving manure nutrients. Grass cover crops, such as
rye and ryegrass, are especially good as "catch crops"—cover
crops grown to absorb soluble nutrients from the soil profile to
prevent them from leaching. (All cover crops function as catch crops
to a greater or lesser degree.) It is a sound strategy, therefore,
to apply manure to growing catch crops or just prior to planting
them.
Note that both sheet composting and applying to cover crops have
trade-offs. Sheet composting improves the capture of ammonia nitrogen
from manure, but requires tillage, which leaves the soil bare and
vulnerable to erosion and leaching losses. Surface-applying to cover
crops (with no soil-incorporation) eliminates most leaching and
erosion losses but increases ammonia losses to the atmosphere. More
details on these trade-offs will be provided below in the section Field-applying Manures and Composts.
Back to top
Composted Manures
An effective composting process converts animal wastes, bedding,
and other raw products into humus—the relatively stable, nutrient-rich,
and chemically active organic fraction found in fertile soil. In
stable humus, there is practically no free ammonia or soluble nitrate,
but a large amount of nitrogen is tied up as proteins, amino acids,
and other biological components. Other nutrients are stabilized
in compost as well.
Composting livestock manure reduces many of the drawbacks associated
with raw manure use. Good compost is a "safe" fertilizer.
Low in soluble salts, it doesn't "burn" plants. It's also
less likely to cause nutrient imbalances. It can safely be applied
directly to growing vegetable crops. Many commercially available
organic fertilizers are based on composted animal manures supplemented
with rock powders, plant by-products like alfalfa meal, and additional
animal by-products like blood, bone, and feather meals.
The quality of compost depends on the feedstuffs used to make it.
Unless it is supplemented in some way, composted broiler litter—though
more stable than raw litter—will be abundant in phosphates
and low in calcium. Continued applications may lead to imbalanced
soil conditions in the long term, as with some raw manures. Soil
and compost testing to monitor nutrient levels is strongly advised.
While composting can degrade many organic contaminants, it cannot
eliminate heavy metals. In fact, composting concentrates metals,
making the contaminated compost, pound for pound, more potentially
hazardous than the manure it was created from. Broiler litter and
broiler litter composts have been restricted from certified organic
production in the mid-South largely for this reason. Arsenic—once
used in chicken feed as an appetite stimulant and antibiotic—was
a particular concern. Since the precise composition of commercial
livestock feeds is proprietary information, arsenic may still be
an additive in formulations in some regions. (16)
A more recent concern is the inclusion of additional copper in
poultry diets and its accumulation in the excreted manure. While
copper is an essential plant nutrient, an excessive level in the
soil is toxic. This concern is most relevant to organic horticultural
producers, who often apply significant amounts of copper as fungicides
and bactericides, increasing the hazard of buildup in the soil.
Whenever you import large amounts of either composted or raw manure
onto the farm, it is wise to inquire about the feeding practices
at the source or have the material tested.
The NOP has put no specific restrictions on when farmers can apply
composted manure to crops; however, it is very specific about manure
composting procedures. According to the NOP Regulations, compost
must meet the following criteria:
- An initial carbon : nitrogen ratio of between 25:1 and 40:1
must exist for the blend of materials in the "pile";
and
- Temperatures between 131° F and 170° F must be sustained
for three days using an in-vessel or static aerated pile system;
or
- Temperatures between 131° F and 170° F must be sustained
for 15 days using a windrow composting system, during which period
the materials must be turned a minimum of five times. (17)
The National Organic Standards Board—the advisory body to
the NOP—has recommended a more flexible interpretation of
the compost rules, but this has not yet been incorporated into the
legislation. (18)
ATTRA offers information on various composting methods in the publications
Farm-Scale Composting
Resource List, Worms
for Composting (Vermicomposting), and Biodynamic
Farming and Compost Preparation. We can also provide
information on the more exacting processes of controlled microbial
composting (also known as CMC or Luebke composting).
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About Guano
Guano is the dried excrement of various species of bats and seabirds.
It has a long history of use as an agricultural fertilizer. It was
apparently highly prized by native Peruvians well before the Spanish
conquest. Before the development of chemical fertilizers, there
was U.S. Government support for entrepreneurs who discovered and
developed guano deposits. (19, 20)
The nutrient content of commercial guano products can vary considerably
based on the diet of the birds or bats. Seabirds subsist largely
on fish; depending on the species, bats may thrive largely on insects
or on fruits. Another major factor is the age of the source deposit.
Guano products may be fresh, semi-fossilized, or fossilized. (21)
A quick check of several commercial products provided the range
of analyses shown in Table 2.
Table
2: NPK Analysis by Guano Type |
Guano Type/Product |
N-P-K Analysis |
Source |
Desert Bat |
8 - 4 - 1.0 |
|
Dry-Bar Cave Bat |
3 - 10 - 1.0 |
|
Fossilized Sea Bird |
1 - 10 - 1.0 |
|
Pelletized Peruvian Sea Bird |
12 - 12 - 2.5 |
|
Old Thyme Sea Bird |
13 - 8 - 2.0 |
|
Jamaican Bat |
1 - 10 - 0.0 |
|
Peruvian Seabird |
11 - 13 - 3 |
|
Jamaican Bat |
3 - 8 - 1.0 |
|
As a nutrient source, guano is considered to be moderately available,
as are most manures. (24) One source (20)
suggests that guanos are rich in "bioremediation microbes"
that assist in cleaning up soil toxins. If true, this would make
guano an excellent amendment to use when transitioning from conventional
to more sustainable production systems. ATTRA, however, has not
reviewed the documentation to substantiate this claim.
Guano is advertised as being quite safe and non-burning to plants;
"foolproof" is the term sometimes employed. There does
not appear to be any evidence to the contrary. There is, however,
one serious human illness connected with guano. Histoplasmosis,
caused by the fungus Histoplasm capsulatum, produces symptoms
similar to influenza in mild cases, or pneumonia when severe. In
persons with compromised immune systems, histoplasmosis can produce
complications leading to death. (25, 26,
27)
Accumulations of both bird and bat guano can contain the Histoplasm
spores, as can manure from old poultry houses. The problems are
most severe in piles that have aged for two or more years, as the
fungus has additional time to proliferate and produce spores. In
a fresh state, bat guano is more hazardous than bird guano because
infected bats can "shed" the organism and rapidly inoculate
the manure. (27)
It appears that those who spend time in caves, and those who harvest
and package guano, are at the greatest risk of infection. Cases
of infection through later handling are apparently not common, though
if they have occurred, they may well have been misdiagnosed as influenza
or a similar ailment.
Infections come about when dust and other aerosols bearing the
fungal spores are inhaled. Therefore respirators and masks are recommended
when handling guanos. Also, clothing should be removed carefully
afterwards to avoid inhaling accumulated dusts. If possible, wet
down the pile of dried guano to reduce dust. (25,
26, 27)
At the present time, the NOP regulations treat guano as raw, uncomposted
manure. It is therefore subject to the same 90- and 120-day application
restrictions. It is relatively safe but rather expensive for organic
production. Its use is best justified on high-value crops.
Back to top
Field-applying Manures and
Composts
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 scheduling 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 agronomic crops commonly apply them to the most nitrogen-hungry and responsive crops. In midwestern organic rotations (see Figure 1), this would likely be corn. While the small-grain crop shown here would respond positively to manure, it is a relatively low-value crop and therefore resides at the bottom of the pecking order when manure resources are in short supply.
Figure 1:
The circumstances are a bit more complex with vegetable crops.
According to experienced market gardener and author Eliot Coleman
(28), crops like squash, corn, peas, and beans
do best when manure is spread and incorporated just prior to planting.
The same holds true for leafy greens, though only well-composted
manure should be used. Cabbages, tomatoes, potatoes and root crops,
on the other hand, tend to do better when the ground has been manured
the previous year. Obviously, crop rotations that feature non-manured
crops following manured crops would be ideal.
To achieve maximum recovery of the nutrients in spread manure,
sheet composting—plowing or otherwise incorporating the manure
into the soil as soon as possible after spreading—is the best
option. Research has shown that solid raw manure will lose about
21% of its nitrogen to the atmosphere if spread and left for four
days; prompt soil incorporation reduces that loss to only 5%. (10)
However, since excessive tillage is discouraged in sustainable
systems, options for sheet composting may be limited on some farms.
The next-best option appears to be spreading onto growing cover
crops. This reduces the chances of loss through surface erosion
and cuts leaching significantly. However, it does little to control
ammonia losses to the atmosphere.
How . . .
One of the weakest links in the use of manure as
a fertilizer appears to be the actual process of field spreading.
According to some researchers, the conventional box spreader is
an "engineering anachronism"—an outdated piece of
equipment designed principally to dispose of a waste product, not
to manage a nutrient resource. Many machines are built to "dump"
as much material as possible in a short time and are difficult to
calibrate if you want to distribute manure accurately and according
to crop needs. (29) (Instructions for calibrating
compost and manure spreaders are provided in Table
3.) Still, the basic box spreader is the only technology available
and affordable to most farmers.
Table
3: Field Calibration of Manure & Compost Spreaders
You will need a:
- Scale (capable of accurate measurement in 1-2 lb. units)
- 10'x10' plastic sheet
- 5-gallon bucket
- Spreader load of manure or compost
Begin by weighing and recording the weight of the plastic
sheet and bucket. Next, spread the sheet over the ground in
the path of the spreader and drive over it as you unload at
normal speed. Carefully fold the sheet in on itself to capture
the spread manure or compost and place back into the bucket.
Weigh the bucket, sheet, and captured material. Subtract the
weight of the bucket and sheet to find how much manure was
captured. The amount of manure or compost applied per acre
can be estimated using the figures provided below. The exercise
should be repeated several times and the results averaged
to increase accuracy.
|
Pounds of manure or compost
captured by a 10'x10' sheet |
Tons of manure or compost
applied per acre |
8 |
1.74 |
10 |
2.18 |
12 |
2.61 |
14 |
3.05 |
16 |
3.48 |
18 |
3.92 |
20 |
4.36 |
22 |
4.79 |
Characteristics to consider when purchasing a spreader (used or
new) include:
- Condition of chains, gears, and sprockets.
It is common knowledge among farmers that manure spreaders only
break down with a full load. Naturally, it is the floor chain—buried
under the manure—that is the first item to go.
- Condition of the floor. Acids and moisture
in manure corrode and rot metal and wood flooring long before
the sides decay. Some manufacturers now make models featuring
a plastic floor that is highly resistant to deterioration. Millcreek
Manufacturing (30) sells several with flooring
made from recycled milk jugs. (31)
- Condition of paddles. Paddles are designed
to shred and break up wads of manure and bedding materials. They
also provide some lateral spreading. Since this is rather crude
technology, the resulting distribution is generally less even
than desired. (32)
- Power drive. Box spreaders are either powered
through the tractor PTO or ground-driven. PTO-driven spreaders
have more flexibility and can also be used to create windrows
for composting.
Box manure spreaders are poor compost spreaders—especially
when well-made granular composts are used. Well-made compost is
fine, relatively flowable, and is better handled with spreaders
suited to broadcasting lime and bulk granular fertilizer. This equipment
is much easier to calibrate and provides a more uniform distribution
of material. (32)
Application rate recommendations for guano are usually provided
by the supplier. These rates appear somewhat lower than those for
other dried manures. (21) As the cost of guano
is relatively high compared to livestock manures, much lower application
rates are advised. Apparently, there is also some use of guano as
a base for fertilizer "tea."
Back to top
Summary
Both raw and composted manures are useful in organic crop production.
Used properly, with attention to balancing soil fertility, manures
can supplant all or most needs for purchased fertilizer, especially
when combined with a whole-system fertility plan that includes crop
rotation and cover cropping with nitrogen-fixing legumes.
The grower needs to monitor nutrients in the soil via soil testing,
and learn the characteristics of the manure and/or compost to be
used. The grower can then adjust the rates and select additional
fertilizers and amendments accordingly.
Back to top
References
- Anon. 1997. Agriculture issues
that affect our health. S.W. Organic Gardener. May. p. 3.
- Pederson, Laura. 1998. Prevent
pathogens. American Agriculturist. May. p. 26.
- Williams, Greg, and Pat Williams.
1994. Manure: Is it safe for your garden? HortIdeas. February.
p. 23.
- Stossel, John. 2000. How good is
organic food? ABC News 20/20. February 4.
- Rodale, Maria. 2000. Will the real
Dennis Avery please sit down? Organic Gardening. May-June. p.
2.
- Stossel, John. 2000. An Apology:
John Stossel Discusses Organic Produce Report. ABC News 20/20.
Aug 11. http://more.abcnews.go.com/onair/2020/2020_000811_stossel_apology.html
(Link is no longer active.)
- U.S. Department of Agriculture.
2000. Section 205.203(c)(1). National Organic Program Standards.
www.ams.usda.gov/nop/NOP/standards.html.
- Troop, Don. 1989. Is chicken litter
really organic? Ozark Cooperative Warehouse Market News (Fayetteville,
AR). November. p. 12.
- Kinsey, Neal. 1994. Manure: The
good, the bad, the ugly & how it works with your soil. Acres
USA. October. p. 8, 10, 11, 13.
- Huhnke, Raymond L. 1982. Land
Application of Livestock Manure. OSU Extension Facts No. 1710.
Oklahoma State University, Stillwater, OK. 4 p.
- Abbott, J.L. 1977. Manure in
the Home Garden. Publication Q66. University of Arizona, Tucson,
AZ. 2 p.
- Eghball, Bahman and Gary W.
Lesoing. 2000. Viability of weed seeds following manure windrow
composting. Compost Science & Utilization. Winter. p. 46–53.
- Williams, Greg and Pat Williams.
1994. No viable weed seeds in broiler litter. HortIdeas. March.
p. 28.
- CAST. 1999. Gulf of Mexico hypoxic
zone is largest in Western Hemisphere. Council for Agricultural
Science and Technology, Ames, IA. June 18.
- Young, R.A. and R.F. Holt. 1977.
Winter-applied manure: Effects on annual runoff, erosion, and
nutrient movement. Journal of Soil and Water Conservation. September-October.
p. 219–222.
- Haapala, JJ. 1997. Risks of chicken
manure as fertilizer. In Good Tilth. June. p. 10, 12.
- U.S. Department of Agriculture.
2000. Section 205.203(c)(2). National Organic Program Standards.
www.ams.usda.gov/nop/NOP/standards.html.
- Anon. 2002. Compost controversy.
Acres U.S.A. June. p.20.
- Anon. No date. Guano. Encarta
Encyclopedia. http://encarta.msn.com
(member only).
- Keleher, Sara. No date. Guano:
Bats' gift to gardeners. www.batcon.org/batsmag/v14n1-7.html
- Anon. 2000. Guano—the 100%
natural organic soil amendment.
Home Harvest Garden
Supply, Inc.
3712 Eastern Ave.
Baltimore, MD 21224.
410-327-8403
- Bloomington
Wholesale Garden Supply
800-316-1306
- Nitron
Industries
P.O. Box 1447
Fayetteville, AR 72702
800-835-0123
- Anon. No date. Guidelines for
Organic Fertilization. Cooperative Extension, University of Vermont,
Burlington, VT. www.uvm.edu/~pass/PSS161/problem/handout.html.(web
page no longer active)
- Greenhall, Arthur. 1982. Housebat
Management. Resource Management Publication 143. U.S. Fish and
Wildlife Service. Condensed version found at: BCM's Bat Central.
www.batmanagement.com/Batcentral/eviction/health.html
- Smith, Garry K. 1994. Are you
exposing yourself to histoplasmosis? Australian Caver. No. 36.
p. 6–8. Reprinted at http://wasg.iinet.net.au/histo.html
- Anon. 1997. Bird and bat guano
= histoplasmosis risk. Nebraska Veterinary Extension Newsletter.
March. www.ianr.unl.edu/ianr/vbs/extension/oldnews/mar97txt.htm
- Coleman, Eliot. 1995. The New
Organic Grower. Chelsea Green Publishing Co., White River Junction,
VT. p. 54.
- Gutknecht, Kurt. 1997. Examining
manure myths and misconceptions. Wisconsin Agriculturist. September.
p. 10–12.
- Millcreek
Manufacturing Co.
2617 Stumptown Road
Bird In Hand, PA 17505
800-311-1323
717-556-0279 (fax)
- Byczynski, Lynn. 1998. Find the
right manure spreader for your farm scale and budget. Growing
for Market. August. p. 6–7.
- Canales, Eugene. 1997. Spreading
soil amendments. Biodynamics. May–June. p. 18–19.
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Recommended Resources
The August 2000 issue of Acres USA features four articles on bats
and guano:
* Bat Guano & Its Fertilizing Value, by William Albrecht
* Advice on Fertilization—The Uniqueness of Guano, by Malcolm Beck
* Bats, IPM & Guano, by Lorie Evans
* The Bounty of Bats, by Chris Walters
The March 2002 issue of Acres USA includes the following article:
* Manure Management, by Robert Gerard
Back issues of Acres USA are available from:
Acres
USA
P.O. Box 91299
Austin, TX 78709
512-892-4400
512-892-4448 FAX
info@acresusa.com
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 online from the website www.soilassociation.org.
Goldstien, Jerome. 1998. Composting for Manure Management. JG Press,
Emmaus, PA. 77 p. Available for $39 postage paid from:
Biocycle
419 State Ave.
Emmaus, PA 18049
610-967-4135
biocycle@jgpress.com
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 Agricultural Commission, Seattle,
WA. 25 p. http://agsyst.wsu.edu/manure.html.
Miller, Laura. 2000. Basics of manure management. Small Farm Today.
July. p. 28-30.
Organic Trade Association. No date. Manure Use and Agricultural
Practices. Organic Trade Association, Greenfield, MA. www.ota.com
Patriquin, David G. 2000. Reducing risks from E. coli 0157 on the
organic farm. Canadian Organic Growers. www.cog.ca/efgsummer2000.htm
Pederson, Laura. 1998. Prevent pathogens. American Agriculturist.
May. p. 26.
Manures for Organic Crop Production
By George Kuepper
NCAT Agriculture Specialist
David Zodrow and Paul Williams, Editors
Cole Loeffler, HTML Production
CT 127
Slot 43
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