United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-83-081 Dec. 1983
f/ERA Project Summary
A Comparison of Alternative
Manure Management Systems-
Effect on the Environment,
Total Energy Requirement,
Nutrient Conservation, and
Contributions to Corn Silage
Production and Economics
Rodney 0. Martin and David L. Matthews
This study compares alternative dairy
manure management systems operated
under full-scale commercial conditions.
The investigation included weight of
manure handled per cow per year, labor
and energy requirements, effect on the
environment, nutrient conservation,
corn silage production and total annual
operating costs.
The dairy production facility used to
study alternative manure management
systems was a 13.41 m x 43.89 m
confinement stall barn at the Agway
Farm Research Center, Tully, New
York. The insulated, mechanically
ventilated barn included 60 tie stalls
(cows positioned tail to tail) with rubber
mats and grates over the gutters. Wood
sawdust and shavings were used for
bedding over the rubber mats through-
out the study. Application rate averaged
0.027 m3 per cow per day, or approxi-
mately 5.9 kilograms.
Only lactating Holstein cows were
housed in the barn during the four year
study (average population of 47). Cows
were fed a total mixed ration with corn
silage the basic forage input. Average
milk production per cow was 27
kilograms per day, which equates to an
annual production of 9,855 kilograms.
A chain gutter cleaner was used to
collect and discharge manure at the
west end of the barn. To complement
the study, provisions were made to
handle the manure from the barn in
three ways: 1) directly into a spreader
for daily spreading, 2) by gravity into a
liquid manure storage tank for spring
application and immediate plow down,
3) by hydraulic ram to a roof-covered,
above-ground manure storage area for
spring and fall spreading and immediate
plow down.
Results of the study show that a
manure storage system can reduce
annual labor requirements by 65 percent
and fuel requirements by 60 percent or
more, compared to daily spreading.
Stored manure, applied in the spring,
and promptly plowed down produced
19 to 29 percent more com silage than
daily spread manure. The study shows
daily spreading of manure to be the
least cost system for herds up to
approximately 60 cows. A roof-covered
semisolid manure storage and handling
system is the lower cost system for
herds above 60 cows.
This Project Summary was developed
by EPA's Robert S. Kerr Environmental
Research Laboratory, Ada. OK, to
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announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Manure, as a by-product of milk
production systems, has significant
value. Each dairyman has a constant
supply of this valuable source of plant
nutrients, which represents a substantial
recovery of feed nutrient input. Over the
years, dramatic changes in dairy manure
management practices have impacted on
environmental quality, energy require-
ments, and crop production efficiency.
During the middle and late 1800s, the
popular dairy barn design in the Northeast
housed cows in a stable above a basement
manure storage. Manure was transferred
to the storage by gravity through a scuttle
located at the rear of the gutter. During
this period, cows were pastured in
summer, housed in winter. One hectare
of pasture was required to meet the
summer forage needs of one cow. At this
stocking rate, the manure dropped on
pasture posed no serious pollution hazard
in most situations. However, the full
fertilizer value of the manure dropped on
pasture was not realized because of poor
distribution and ammonia volatilization.
Manure dropped in the barn over
winter and stored in the basement below
the floor lost few nutrients in cold
weather, but did pose a potential pollution
problem in warm weather from run-off
and leaching. Odor and fly breeding were
also warm weather problems. The stored
manure was usually spring applied and
plowed down for corn. A popular rotation
was corn, spring grain, and three years in
hay or improved pasture. Limestone,
manure and rock phosphate would be
applied to the corn in this rotation.
This manure management scheme
conserved and returned most of the
organic matter, phosphorus and potassium
to the soil. Indeed, because most dairy
farms fed some purchased grain, there
probably was a modest net gain in plant
nutrients to the farm. Crop yield levels, by
today's standards, were marginal.
In the mid-to late-1930s, concerns
about milk quality prompted more strin-
gent sanitary regulations. Manure could
not be stored in the same building with
cows producing Grade A milk. The energy
efficient manure gravity flow from stable
to basement storage below was disallowed.
Over a thirty-year period, from the
1930s to the 1960s, many devices and
systems were developed to collect
manure and move it away from the barn.
Generally, these systems were labor
and energy intensive and most did not
work well during sub-freezing weather.
Following World War II, fertilizer and fuel
costs remained low for twenty years. The
use of manure as a fertilizer was minimal
during this period. Manure became not a
by-product to be used, but a waste to be
disposed of. Daily spreading evolved as
the most common method for disposing
of manure during this period. While it is
a burdensome chore, labor and energy
intensive, and the most costly method of
handling manure for most dairies, the
practice continues on the majority of
dairy farms today. Basic reasons for this
include: 1) historical practice, 2) natural
resistance to change, 3) mechanical
capability to perform the task with large
tractors and PTO spreaders, 4) low
investment required, and 5) lack of sound
alternatives supported by research data.
The use of animal manures as fertilizer
and soil conditioners was a focus of
research by the USDA and land grant
colleges during the 1920s and 1930s.
Following 1939, virtually no research
was directed at manure management
until the 1960s, when environmental
concerns prompted studies of the impact
of animal manures on streams, lakes, and
ground water.
The handling of dairy manure is one key
factor in determining dairy farm profit-
ability. Interest, depreciation and main-
tenance of equipment and structures,
labor input, and energy use associated
with the collection, storage and distribu-
tion of manure represents a significant
percentage of the total cost of milk
production. There are little reliable data
comparing complete manure management
systems in terms of influence on the
environment and total annual operating
costs. This study was undertaken to meet
the need for long-term research compar-
ing alternative manure management
systems over several operating seasons
in terms of a number of criteria important
both to commercial dairymen and to
society. Costs, energy use, nutrient
conservation, efficiency of nutrient
utilization and influence on the environ-
ment in terms of odor, nitrates in ground
water and the biological oxygen demand
(BOD) and pollution of streams were
measured over three years of dairy farm
operation.
In terms of environmental impact, it
seems clear that storing manure over
winter should be preferred to the alterna-
tive of daily spreading on frozen ground.
Further, it was theorized that a storage
and handling system that did not involve
the addition of water would overcome the
more objectionable features of liquid
manure handling. Such a system became
feasible with the development of a
hydraulic ram capable of moving manure
76 meters underground to bottom load a
roof-covered containment storage.
Three manure handling systems were
studied: 1) daily spreading of manure, 2)
liquid manure (water added) storage and
handling, and 3) semisolid (no water
added) storage and handling. Five field
treatments were used: 1) daily spreading
of fresh manure, 2) liquid manure stored
from October to April, spread in the spring
and immediately plowed down, 3) semi-
solid manure stored from October to
April, spread in the spring and immediately
plowed down, 4) semisolid manure stored
from April to October, spread in the fall
and immediately plowed down, 5) in-
organic fertilizer spring applied and
immediately plowed down as a control.
The alternative systems were compared
in terms of 1) influence on the environ-
ment and 2) total annual operating costs.
Conclusions
The following conclusions are drawn
from this research investigation compar-
ing alternative manure management
systems in terms of weight of manure
handled per cow per year, labor and
energy requirements, odor control,
nutrient conservation through storage,
effect on the environment, corn silage
production, and operating costs.
Weight of Manure Handled Per
Cow Per Year
Decreasing the weight of manure to
haul offers the potential of decreasing
labor, energy, and machine use require-
ments. Further, soil compaction will be
reduced by reducing the weight of each
load and/or the number of loads hauled
over the field. Weight of manure handled
per cow per year is influenced by several
factors including: breed and size of cow,
stage of lactation, level of production,
feeding program, bedding used, water
added, and drying which may occur in
storage.
Only lactating Holstein cows were used
in this study. Milk production averaged 27
kilograms per cow per day. Manure
production averaged 54.3 kilograms per
cow per day including 5.9 kilograms of dry
sawdust and shavings. Average dry
matter of the manure including the
bedding was 17.3 percent.
With daily hauling and spreading,
19.82 M tons of manure were handled
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per cow per year. Handling the manure as
a liquid required the addition of water to
create a 14 percent dry matter slurry
resulting in 24.5 M tons of manure
handled per cow per year. Had water
been added to create a 10 percent dry
matter slurry, 34.29 M tons of manure
would have been handled per cow per
year. Handling the manure as a semisolid
through a roof-covered manure storage
allowed natural drying and a reduction in
weight of 8.9 percent resulting in 18.06
M tons of manure handled per cow per
year.
Labor and Energy
Requirements
Daily spreading of manure is a labor
and energy intensive operation compared
to using a six-month storage system.
Based on a 100 cow lactating herd and a
round-trip haul of 2.4 kilometers, a
storage system can reduce annual labor
requirements by 65 percent and fuel
requirements by 60 percent or more
compared to daily spreading.
Nutrient Conservation Through
Storage
Agitating manure to create a pumpable
slurry in a liquid manure storage is a
primary cause of nitrogen loss through
volatilization of ammonia gas. Bucket
loading of semisolid manure does not
create the same conditions. Average
nutrient loss through the liquid manure
storage and unloading was 10.3 percent
nitrogen, 9.1 percent P20s and 7.9
percent K2O. Considerable agitation was
required to handle the high solids manure
which probably contributed to the nutrient
loss, particularly of the nitrogen. Average
nutrient loss through the semisolid
manure storage and unloading was 4.6
percent nitrogen, 6.4 percent P205 ad 6.7
percent K2O.
Environmental Impact
Animal manures impact the environ-
ment in a number of ways. Clearly, there
are positive benefits to the integration of
manure organic matter and soil. However,
poorly designed and/or managed systems
can cause a negative impact. A key
objective of this investigation was to
measure and document the impact of the
manure management systems studied on
the environment. Concentrations of
nutrients (nitrogen, phosphorus and
potassium) and coliform bacteria were
measured in the stream water adjacent to
the treatment field, run-off water from
the fields and percolation water. Odor
was measured by a panel made up of
equal numbers of farm and non-farm
persons.
Stream Water
The concentration of nitrogen, phos-
phorus, and potassium in stream water
appeared related to the stream flow rate.
The highest concentrations were mea-
sured in late summer when stream flow
is minimal. At no time during the study
did stream water levels of ammonium or
nitrate nitrogen exceed the maximum
limits considered safe for potable water
(0.5 mg/l NH3 and 10 mg/l N03).
Coliform counts in stream water
collected downstream from the experi-
mental site never exceeded those of
samples taken upstream from the site.
Thus, it seems safe to conclude that the
performance of this experiment had no
adverse effect on the stream water. The
site is well suited to continuing studies of
the environmental impact of crop man-
agement practices.
Run-off Water
Run-off water provides the best single
measure of the inf I uence of the treatments
studied on the environment. The treat-
ments can be listed in declining order of
merit (from least run off to most run off) as
follows: semisolid spring, liquid spring,
daily spread, semisolid fall, inorganic
fertilizer. These findings are in agreement
with reports that the organic matter in
manure has a profound effect on reducing
run off and subsequent loss of soil. Of the
twelve storms resulting in measurable
run off, one occurred in July, three in
August, six in September, and two in
October. Since it is known that organic
matter in the soil diminishes over time
and that manure organic matter reduces
run off, then it is logical to expect that the
soils to which manure was spring applied
and plowed would have the highest
manure organic content and least run off
while those to which manure had been
applied earlier or not at all would have the
lowest manure organic matter content
and greatest run off.
Percolation Loss of Nutrients
It was observed that the highest
concentration of nitrate nitrogen in
percolation water occurred shortly after
the application and incorporation of each
treatment. All treatments contributed
levels of ammonium and nitrate nitrogen
to percolation water in excess of estab-
lished safe limits for drinking water (0.5
mg/l NH3 and 10 mg/l NO3). There is
reason to believe that in most situations
these concentrations will be reduced to
safe levels as a result of plant and
microorganism uptake, soil retention and
dilution by the time the percolate reaches
the ground water table.
Odor Control
Common sense management in han-
dling and spreading manure can minimize
the odor impact on the environment.
Manure storages loaded through the
bottom usually form a crust over the top
during warm weather and a frozen top
layer during cold weather. These condi-
tions prevent the release of any significant
odors during the storage period. Odors
are released from manure during the
loading and spreading operations. Reduc-
ing the amount of agitation of liquid
manure at the storage will lower the odor
level. Loading semisolid manure with a
bucket loader disturbs the manure only
slightly, thus minimizing odor release.
Field spreading for uniform coverage
breaks up the manure, thus increasing
the release of odor. Early incorporation of
the manure into the soil by harrow or
plow will control the duration of odor
release. Same day incorporation of
manure into the soil is not practical with a
daily spreading system.
Contribution To Corn Silage
Production
The relative efficiency of the several
manure management systems is com-
pared in the most meaningful way to dairy
farmers in Table 1.
Here, the corn silage produced by
3,472 kilograms per hectare of manure
dry matter or 129 kilograms per hectare
of inorganic fertilizer nitrogen is recorded.
Table 1. Effect of Treatment on the Yield of 32% Dry Matter Corn Silage
Three Year Average 1977-79
Treatment Yield. Metric Tons/Hectare
Spring applied liquid
Spring applied semisolid
Fall applied semisolid
Daily spread
Spring applied inorganic fertilizer
35.13
38.20
31.92
29.60
41.90
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On average, over the three years of the
study, the five treatments can be listed in
declining order of merit (from most
efficient to least efficient): spring applied
inorganic fertilizer, spring applied semi-
solid manure, spring applied liquid
manure, fall applied semisolid manure
and daily spread manure.
Daily spreading of dairy manure
remains the most common practice in the
Northeast. Assigning a value of 100 to
daily spread it is possible to calculate the
relative value of the other manure
management systems as shown in
Table 2.
On this basis, storing manure, applying
it in the spring, and promptly plowing was
19 to 29 percent better than daily
spreading. Storing manure in the semi-
solid form (without added water) was 9
percent more efficient than a liquid
storage system to which water is added.
Semisolid manure was applied in both
spring and fall treatments. The fall
application was consistently inferior to
spring applications, producing just 84%
as much corn silage when averaged over
the three years of the study. However, the
fall application of stored semisolid
manure produced more corn silage than
the daily spread treatment.
Chemical Analysis of Corn
Silage
Both the nitrogen and the phosphorus
content of corn silage showed a positive
linear relationship to yield (R = .77 and R =
.65 respectively). This supports the use of
corn silage yield as a reliable and
practical measure of the economic impact
of manure management systems com-
pared in terms of nutrient utilization
efficiency when the rate of application is
less than that needed to produce the
highest yield the growing season will
support.
Annual Operating Costs and
Returns
A key focus in this study was analyzing
annual costs and returns of the three
manure management systems used,
based on actual performance data
generated through the conduct of the
project.
Annual costs are partitioned between
fixed costs for equipment and facilities
and operational costs for labor, electrical
and tractor use costs. Generally, as fixed
costs increase operational costs decrease,
which underscores the importance of
analyzing total annual costs when
comparing systems. While tax implica-
tions have a significant effect on annual
Table 2.
Treatment
Relative Efficiency of Three Manure Management Systems Compared to Daily
Spread, 1977-79
Relative Efficiency
Compared to
Daily Spread.
percent
Yield of 32% DM
Corn Silage,
metric tons/hectare
Daily spread
Spring applied liquid
Spring applied semisolid
Fall applied semisolid
29.60
35.13
38.20
31.92
100
119
129
108
costs, favoring systems with higher fixed
costs, no attempt was made to factor
them in. The actual effect of investment
tax and depreciation tax credits on annual
operating costs will vary widely from farm
to farm, depending on the overall
profitability of the farm enterprise.
An economic life was established for
each piece of equipment and structure
based on experience at the Agway Farm
Research Center and generally accepted
practice. The depreciation term and/or
loan term was considered to be the same
as the economic life. Residual value of all
equipment and structures was assumed
to be zero.
Investment costs are fall 1982 costs of
equipment and structures delivered and
installed in central New York. Interest
rates of 14% and 12% were established
for equipment and structures, respec-
tively. Annual level payments for principal
and interest were calculated using Com-
prehensive Mortgage Payment Tables
published by Financial Publishing Com-
pany, Boston, Massachusetts.
Gutter cleaners, pumps, rams, spreaders
and storages were totally assigned to the
respective manure management system
investment costs. Tractors were not
treated as part of the system investment
because only a fraction of their annual
operating hours are required for manure
handling. An hourly use cost, including
fuel, was determ i ned for tractors requ i red
for each system. This cost remains
constant when calcuated on a kw hour
basis. A cost of $0.221 per kwH was used
for all systems.
Annual costs for insurance and taxes
were taken at 1.5% of the original
investment. Annual costs for repairs
were taken as a percent of original
investment and varied from 2% to 10%
based on generally accepted practice.
A labor rate of $5 per hour was
established for all labor functions.
Electrical costs were calculated for each
motor, using recorded kilowatt draw and
annual hours used. An electrical rate of
6C/kilowatt hour was applied.
Table 3 compares in summary the
fixed, operating, tola I and per cow costs of
handling daily manure with three different
manure management systems. Cost data
are presented for three herd sizes to show
the effect of herd size on per cow cost of
handling manure. Table 4 summarizes
the potential annual improvement to farm
enterprise profit with a manure storage
system considering fertilizer nutrient
recovery as measured by crop yield in this
study.
Table 3.
Summary of Total Annual Costs for Three Manure Management Systems and Three
Herd Sizes
Annual Costs
Type of System
Fixed
Operating
Total
Per
Cow
Daily spreading of manure
from barn
50 cows $ 5,867 $ 4,680 $10,547 $211
100 cows 7,915 9.099 17,014 170
150 cows 9,576 14.578 24,154 161
Handling liquid manure
through an above-ground
tub silo storage
50 cows 12,814 2,131 14.945 299
100 cows 16,257 3,790 20.047 200
150 cows 20,183 5,476 25.659 171
Handling semisolid manure
through a roof-covered
storage
30 cows 10.337 1,652 11,989 240
100 cows 12,083 3.107 15,190 152
150 cows 74,762 4.618 19,380 129
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Table 4. Potential Annual Improvement to Farm Enterprise Profit with a Manure Storage
System
Per Cow
Total
Fixed &
Operating
Type of System Costs
Fertilizer
Nutrient
Recovery
Net
Costs
Profit
Gain or Loss
Over
Daily
Spreading
Daily spreading of manure
from barn
50 cows $211
100 cows 170
150 cows 161
Handling liquid manure
through 6 months tub
silo storage
50 cows 299
100 cows 200
150 cows 171
Handling semisolid manure
through 6 months roof-
covered storage
50 cows 240
100 cows 152
150 cows 129
$ 68
68
68
81
81
81
88
88
88
143
102
93
218
119
90
152
64
41
-75
-17
3
-9
38
52
The study shows daily spreading of
manure as the least cost system for herds
up to approximately 60 cows. A roof-
covered semisolid manure storage and
handling system is the lower cost system
for herds above 60 cows. A liquid manure
storage and handling system will improve
profit potential over a daily spreading
system with herds above 150cows, but is
not as cost effective as semisolid manure
handling. Calculating annual costs of
manure handling systems can be done
with a high degree of reliability if
performance data and investment data
are at hand. Projecting the dollar return
through nutrient recovery as crop fertilizer
is subjective. Variations in existing soil
fertility, soil type, rate of manure applica-
tion, crops grown and climatic conditions
are some of the factors which will
influence actual dollar return through
fertilizer nutrient recovery. In this study,
nutrient recovery from each manure
handling system as measured by corn
silage yield can be listed in declining
order of merit as follows: 1) semisolid
manure storage and handling, 2) liquid
manure storage and handling, 3) daily
spreading.
Recommendations
1. Manure from dairy production facilities
should be stored in containment
structures, loaded from the bottom,
unloaded and field spread when field
and environmental conditions are
favorable and incorporated into the
soil the day of application. This
management practice will have a net
favorable impact on the environment.
2. Dairy manure should be handled as a
semisolid (as produced manure with
no water added) through a roof-
covered storage to attain least cost
operation and minimum soil compac-
tion.
3. Transfer manure into the bottom of
storages to minimize odors, nutrient
loss, freezing and fly problems during
the storage period.
4. Agitation of liquid manure (as pro-
duced manure with water added)
should occur below the surface of the
stored manure to decrease release of
objectionable odors and nitrogen loss
through volatilization of ammonia
gas.
5. Further work is recommended on:
a. developing practical equipment to
bottom load storages, which will
minimize stratification of manure
in storage,
b. methods of unloading manure
storages, which will reduce release
of odors and nutrient loss, and
c. design of lower cost containment
manure storages, particularly for
small herds.
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Rodney O. Martin and David L Matthews are with Agway, Inc., Syracuse, NY
13221.
Lynn R. Shuyler is the EPA Project Officer (see below).
The complete report, entitled "A Comparison of Alternative Manure Management
Systems—Effect on the Environment. Total Energy Requirement, Nutrient
Conservation, and Contributions to Corn Silage Production and Economics."
(Order No. PB 83-258 765; Cost: $16.00, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penafty for Private Use $300
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