/ December 1991
Strategies for Recycling Nutrients
S to Recover Fertilizer Value and
Avoid Environmental Pollution
H.H.Van Horn, R.A.Nordstedt,
A.V. Bottcher, E.A. Hanlon,
D.A. Graetz, C.F. Chambliss
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T Woeste, Dean for Extension
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Introduction .............................................. 1
How much of Individual nutrients are excreted by dairy cows? ... 1
How does the manure management system affect nutrient flow? .4
Types of manure handling systems
Liquid manure handling
Anaerobic lagoon system
Removal of suspended solids from flushed manure
What Is the potential nutrient uptake by plants? ................ 8
How do you develop a manure nutrient budget? .............10
What steps help to document environmental accountability? .... 15
Summary ........................................... 16
Selected References ......................................16
About the authors: All are from departments in the Institute of Food and Agricultural Sciences, University of Florida. H.H. Van Horn
is Professor of Nutrition and Management, Dairy Science; R.A. Nordstedt is Associate Professor, Waste Management, Agricultural
Engineering; A. V. Bottcher Is Professor of Water Resources and Non-Point Pollution, Agricultural Engineering; E.A. Hanlon is As-
sociate Professor, Soil Fertility and Management, Soil Science; D.A. Graetz Is Professor, Environmental Chemistry, Soil Science;
and C.G. Chambliss Is Associate Professor, Forage Production, Agronomy.
Introduction are based on body weight of cows; however, they do
not account for the large variation among dairies in
Concerns regarding nutrient losses from the ma- feeding levels and consequently excretion levels.
nure of large dairy herds to ground water or surface The variation is caused by differing voluntary feed
runoff have been extremely acute in Florida. These intake, differing supplemental levels, and differing
widely publicized concerns have been with phos- amounts of nutrients harvested in the milk. For ex-
phorus (P) contamination of Lake Okeechobee, ample, a recent University of Florida experiment
probably washing off the farms in surface runoff (Morse, 1989) showed that P excretion by dairy
during the summer rainy season, and with nitrogen cows varied dramatically with level of P intake.
(N) losses in the form of nitrate into the ground wa- These data confirm that excretion estimates based
ter through the deep sandy soils of the Suwannee on dietary intake of a nutrient minus the amount
River basin. Florida is not unique. All states are secreted into milk is a good method of predicting
starting to monitor farms where large numbers of total excretion of minerals by mature dairy cows.
food producing animals are maintained on small The following milk composition, typical of Hol-
acreage to avoid nutrient "leakage" to the environ- steins, was used along with pounds of milk to deter-
ment. Similar concerns exist with overapplication mine recovery of fed nutrients in milk:
of commercial fertilizer which might lead to leakage
of nutrients to surface or ground water. Protein 3.30% (N content .512%)
Phosphorus (P) 0.10%
Nutrients in manure are recyclable in many Calcium (Ca) 0.12%
ways which can be utilized to avoid nutrient losses Potassium (K) 0.15%
to the environment. All these methods involve ap- Magnesium (Mg) 0.01%
plications of manure nutrients in some form to Sodium (Na) 0.05%
plants that benefit from nutrient fertilization. How- Chlorine (Cl) 0.11%
ever, to avoid excessive concentration of these nu-
trients at inappropriate points, it is helpful to bud- Phosphorus excretion estimates in Table 1 illus-
get nutrient flow through the total dairy farm sys- trate that dietary P of 0.40%, 0.45%, or 0.60%
tem. If there is a problem concentration at some causes changes in estimated annual excretion of ac-
point, then corrective measures can be taken which tual P from 40 to 46 to 69 pounds per cow per year.
are environmentally accountable. To do this, quan- Thus, dairy farmers have considerable control of
titative information is needed on nutrient flow mineral excretion through control of mineral con-
through all segments of the system. Critical ques- tents in the diets they feed. Feeding adequate P is
tions are: important for animal health and performance but
S. .40% of total diet dry matter or slightly more is very
1. How much of individual nutrients are excreted near the estimated requirements for lactating cows
by dairy cows? (NRC). Although these data do not lead us to rec-
2. How does the manure management system affect ommend lowering feeding levels for P for dairy cows
nutrient flow? below standard feeding recommendations (NRC),
the data point out that future committees which de-
3. What is the potential nutrient uptake by plants? velop NRC feeding standards need to review recom-
4. How do you develop a manure nutrient budget? mended feeding levels for N and environmentally
sensitive minerals with an objective to keep excre-
5. What steps help to document environmental ac- tion of these nutrients as low as possible and still
countability? maintain optimum animal performance.
This publication is designed as a guide to dairy
farmers and planners to help develop answers to Table 1 shows excretion estimates for N from two
these questions for an individual dairy farm. different diet formulation procedures proposed by
NRC. One is for cows consuming diets formulated
How much of individual nutrients to supply NRC crude protein standards (NRC,
are excreted by dairy cows? high). The other (NRC, low) minimizes dietary N
by providing minimal nonprotein N and ruminally
Currently, the nutrient excretion standards most degradable protein for optimum rumen microbial
often used in the design of manure management fermentation and provides for remaining animal
systems are those of the American Society of Agri- requirements with ruminally undegraded protein.
cultural Engineers (ASAE, 1989). These standards Numeric estimates of yearly N excreted by high
producing 1400 Ib cows were 260 Ibs per cow per achieving, most dairies with lower milk production
year when fed according to the NRC crude protein choose to feed as much protein as was used in this
standards and 223 Ibs N per year when diet protein example (e.g. up to 17.5% crude protein of total
was formulated for minimum needs for undegraded diet dry matter for their high producing group).
and degraded protein. As with P, these data sug- Excretion estimates for cows eating enough to pro-
gest that some diet control over N excretion is pos- duce more than 20,000 pounds of milk per year
sible. Figure 1 shows graphically some of the daily were used because most herds will be feeding the
excretion estimates in table 1. kind of diets to support that level of production in
the future and consequently those nutrient excre-
Although yearly excretion estimates in Table 1 tion levels should be considered in manure man-
are based on diets designed to support higher milk agement planning. Individual farms, however,
production than most dairymen are currently should develop their management plan based on
Table 1. Dally and yearly excretion estimates of various fractions and nutrients by Holstein cows.'
Daily milk and dry feed intake for: Total
30 days 70 days 205 days 60 days year
Milk, lbs/cow 100 70 50 Dry 21750
Dry feed intake, Ibs/cow 55.8 46.3 39.2 25.2 14462
Excretion for cow described in column above
Fraction or Nutrient Lb/day Lb/day Lb/day Lb/day Lb/yr/cow
Raw manure (feces + urine) 195.0 160.0 125.0 80.0 47475
Feces (wet) 125.0 100.0 75.0 45.0 28825
Urine 70.0 60.0 50.0 35.0 18650
Total solids (38% of DMI) 21.2 17.6 14.9 9.6 5496
Volatile solids 17.7 14.7 12.4 8.0 4580
BOD, 5-d, Ib 2.82 2.34 1.98 1.28 732
COD, lb 19.4 16.1 13.7 8.8 5038
Total N, Ib (NRC, low)' 0.899 0.727 0.601 0.364 223
Total N, Ib (NRC, high)1 1.030 0.846 0.698 0.439 260
Urea + ammonium N, (NRC, low) 0.408 0.308 0.249 0.125 92
Urea + ammonium N, (NRC, high) 0.500 0.391 0.319 0.178 118
P (diet.40% P) 0.123 0.115 0.107 0.101 40
P (diet.45% P) 0.151 0.138 0.126 0.103 46
P (diet .60% P) 0.235 0.208 0.185 0.151 69
K, Ib, diet .8% K 0.296 0.265 0.239 0.201 88
K, Ib, diet 1.2% K 0.519 0.450 0.396 0.302 146
Ca, Ib, diet .65% Ca 0.242 0.217 0.195 0.164 72
Ca, Ib, diet .90% Ca 0.382 0.333 0.293 0.227 108
Mg, Ib, diet .20% Mg 0.102 0.086 0.073 0.050 27
Mg, Ib, diet .35% Mg 0.185 0.155 0.132 0.088 49
Na, Ib, diet .35% Na 0.145 0.127 0.112 0.088 42
CI, Ib, diet .55% CI 0.197 0.178 0.161 0.138 60
'Data are from Van Horn (1990). Crude protein percent of total diet dry matter used in calculations for cows producing 100, 70,
50, and dry cows for "NRC, low" diets were 16.0, 14.8, 13.8, and 11.0%. Respective crude protein percent for "NRC, high"
diets were 17.5, 16.4, 15.3, and 12.0% of total diet dry matter.
excretion estimates for their cows: for example, if Table 2. Annual manure production and nutrient value for 100
their herd averages 50 lbs of milk per day for all cows (1400 Ib cows).
milking cows, use excretion estimates for cows pro- Manure constituent Lbs/year/ Initial
during 50 lbs milk (Table 1) and multiply by the av- 100 cows value1
erage number of days in milk per year, e.g. 305,
plus the average excretion for dry cows times the Raw manure (feces + urine) 4,747,500
average days dry, e.g. 60. This level of production Total solids 611,000
was near the average for Florida in 1991. Volatile solids 549,600
BOD, 5-d, Ib 73,300
Information in Table 1 can easily be extrapolated COD, lb 503,800
to any herd size by multiplying the number of cows
by the appropriate factor. For example, a herd with Total N, lb (NRC, low) 22,300 $6,690
100 cows would be estimated to excrete 100 times P (diet dry matter .45% P) 4,600 2,760
as much as the yearly excretion estimates in Table K (diet dry matter .80% K) 8,800 1,320
1 (see Table 2).
TOTAL VALUE of N, P, and K $10,770
Although the value of N, P, and potassium (I1 'Based on assumed values of $.30/Ib N, $.60/lb P, and $.15/Ib K.
fertilizer nutrients in manure will usually not be as
62% dies 75-125 50-70
dieI bs.feces Ibs.urine
40-55 I bs. Ibs.DM
.87-1.56 Ibs.N 50 -100 Ilbs.milk .60-1.03 Ibs.N
.16-.25 Ibs.P .11-.15 Ibs.P
Figure 1. Daily Input-output of dry matter (DM), nitrogen (N), and phosphorus (P) for a lactating cow producing 50 to 100 Ibs of milk
per day. Data from Table 1.
great as the total costs of the waste management spread fresh on land, or spread in some form at
system, it does help minimize the net cost of waste some later time. The longer the time in storage, the
handling. However, this will happen only if the nu- greater the potential for N losses to the air as am-
trients in dairy manure are used to displace the monia. The greater the dilution with water, the
purchase of inorganic fertilizer nutrients. Also, greater the potential for nutrient losses to surface
these values do not take into account losses from and ground waters unless included as part of an
the system that decrease the amount actually ap- irrigation program to distribute water and nutri-
plied to crops. For example, data from Table 2 im- ents to growing crops. Few manure systems on
ply that fresh dairy manure will contain: farms actually collect all of the feces and urine at
one location for application to one particular unit of
* N 9.4 lbs actual N/ton wet manure land.
* P 1.9 lbs actual P/ton wet manure (equivalent
to 4.4 lbs P20,) Separations or losses occur in many ways:
* K- 3.7 lbs actual K/ton wet manure (equivalent
to 4.5 lbs K20) a Flushed manure from the milking parlor and
a Total solids 12.8% feed barn may go through a sand trap and be
pumped over a separator screen before irrigation
Even if this were the composition when excreted, of land with the effluent.
composition when scraped and loaded usually is
quite different due to change in moisture content Manure is dropped in different areas such as
and volatilization of some of the N. It is impor- pasture, milking parlor, cooling barns, and the
tant to take samples of manure or wastewater primary feeding area and some these "separa-
applied to cropland and have these samples tions" may not be collectible for land-spreading.
analyzed at a commercial laboratory. The
analysis should include total Kjeldahl N and not a Some gaseous loss of ammonia occurs (volatiliza-
just nitrate N since the nitrate form of N does not tion) which returns a variable but often control-
occur in manures. Nitrification does not occur until lable portion of the N to the air.
after manure is incorporated into the soil. The ma-
jor forms of N in dairy manure are either organic N Other possibilities include some surface runoff
or urea N which is easily converted to ammonia and loss to the groundwater. Management practices
and can be lost to the air as gaseous ammonia. must control all of these components so that surface
-"" runoff and losses of nutrients to the groundwater
/ are minimized and do not cause violations of state
S.water quality standards (Holloway et al., 1990).
SThe choice of a manure management system will
S. depend on existing facilities. For example, if the ex-
Si isting buildings were designed for flushing, then a
J I dry handling system would not be possible without
A. ,? ~'* major structural modifications. If a new dairy is be-
S- 'i ing planned, then other factors can be considered.
In both cases, changes in the system must be com-
patible with other management practices on the
Sdairy and the manure nutrients must be spread in
a way to recover nutrients in harvested crops or
stockpiled in a way which will not pose environ-
Figure 2. Potential for Imbalance of nutrient flow through the mental risks before being spread.
dairy farm Is directly related to the percent of feed
nutrients which are Imported from off the farm.
Regulatory requirements may influence the
How does the manure manage- choice of a waste management system. For ex-
ment system affect nutrient flow? ample, if surface runoff must be collected, stored,
and dispersed on cropland, then a liquid handling
After excretion by the cow, manure may be system would be necessary. However, other compo-
stored wet, stored after being allowed to dry, nents could still be handled as a solid or as a
flushed with water to a lagoon or holding pond, slurry.
Types of manure handling systems Slurry manure
Manure management systems can be catego- This is basically the mixture of excreted feces
rized in many ways with options within each type and urine with only enough water added to facili-
of system. The types of systems can be outlined as tate handling. This results in a solids content of
follows: greater than 5 percent which is too wet to handle
with a front end loader but not dilute enough to
a solid or conventional manure handling handle in a conventional irrigation system. Storage
a slurry manure handling could be in pits or in tanks either above or below
a liquid manure handling ground. Transport would probably be in a tank
" anaerobic lagoon truck or wagon or in a flail spreader. Utilization
" composting would be on cropland. If knifing or soil injection of
a combinations of the above manure nutrients is desired, this is the system of
Each system can be broken down into five major
components: Use of slurry requires purchase of a tank truck
or wagon, special pumps that will handle the high
" collection solids content, and construction of storage tanks
a storage that may be quite expensive. Loading, transporting,
a processing or treatment and spreading the slurry also has a high labor re-
" transport quirement but the system can result in low nutri-
a utilization ent losses.
Liquid manure handling
Conventional or solid manure handling systems Lii nr nin
are not common in Florida. Normally high rainfall This usually involves flush tanks to move ma-
Snure and thus dilutes manure to a solids content of
and humidity make it difficult to keep manure dry less than 5 percent. In most Florida dairy systems,
enough to be handled with a front end loader. Also, ess thn 5 eent n most Florda dairy systems
the warmer climate permits the use of water for the content is less than 2 percent and can be
handled in specially designed irrigation equipment.
flushing on a year-round basis, as well as the utili- handled specially designed irrigation equipment.
zation of wastewater on cropland in multiple crop- Rqir storage ty ee type
ping systems. Use of water for flushing of manure the gat fieldthe tie between ir-
rigation applications, and the amount of
also has low labor requirements and is a clean way rato a atos a the amount of
to handle manure. stormwater runoff which the system must be ca-
pable of retaining. Some distinct advantages of this
Solid manure handling must employ some type ype of system are that it has low labor require-
Solid manure handling must employ some type
ments and can result in relatively few nutrient
of dry scraping for collection and every effort must losss whn irrigatn requent and growing
be made to keep out excess water. The manure can losses when irrigaton is frequent and growing
be hauled and spread on cropland on a daily basis crops are available to utilize the nutrients.
or the manure can be placed in storage. The stor- Anaerobic lagoon system
age facility will require a roof or a provision must This system has been the most popular type of
be made for capturing any liquid leachate or runoff manure handling on Florida dairy farms during the
in a pit or lagoon. Normally there would not be any 1970s and 80s. It actually is a specific type of liquid
processing or treatment of the manure. Transpor- handling in which the flushed manure is directed
station would probably be in a conventional box ma- into an anaerobic lagoon. The first stage of the a-
nure spreader, and utilization would be on crop- .
land goon system is designed with a constant liquid level
to overflow into a second lagoon or pond designed
for liquid storage capacity. Effluent from the stor-
In Florida, a dairy farm would rarely attempt to ae pod stbe dispersed on cropland through
employ a solid manure handling system for all of
the manure. However, part of the manure can be some type of irrigation system. Although seepage
the manure. However, part of the manure can be
irrigation and sheet flows have been used for efflu-
handled as a solid in some cases. In the design of e d, s
ent dispersal, pivot irrigation systems are becoming
new or modified facilities, it is recommended that m me popular ecau t n istrib
provision be made for both scraping and/or flush- tion of the manure nutrients.
ing, if possible.
In addition to the effluent, sludge accumulates in
the anaerobic lagoon which contains a significant
amount of P and a small amount of the N. The I '
amount of time before the lagoon fills with sludge -
to a point where it needs to be cleaned out varies
depending on loading rates and design volume.
Cleanout of smaller, more heavily loaded lagoons r
.... -- ".
Figure 4. Flushed manure Is pumped over stationary screens
S. .-".to remove fibrous matter, enabling effluent to be
S. pumped through Irrigation systems.
water is an easy and clean way to handle manure.
Variations of this method have been adopted across
much of the United States in dairy, poultry, and
swine operations. Separation of solids from flushed
-. .. manure by some manner is potentially important in
Figure 3. Water Is used to flush manure from cattle housing most of these systems for several reasons:
areas because It is labor saving and dean.
To remove large particles and sand that would
every 2 to 5 years is common while larger lagoons plug or damage distribution nozzles in irrigation
may function much longer before cleanout is neces- systems used to evenly spread the liquid over the
sary. Separation of larger manure solids is often cropping area.
done prior to the wastewater entering the lagoon in
order to permit accommodation of manure from n To reduce the biological loading on aerobic and
more cows or to extend the time until cleanout is anaerobic lagoons.
Composting a To capture a fibrous product and some of the N
and mineral nutrients which might be utilized in
Composting systems have recently received other products such as bedding for free stalls,
much attention to enable exporting nutrients from part of the feed for cattle on maintenance diets,
dairy farms. A composting system is a modification compost for potting material for plants, etc.
of a conventional or solid manure handling system
with the composting (treatment) process applied to Many systems exist which will remove a portion
the manure. Types of composting systems include of the solids from manure slurries. The stationary
window, bin, static pile, and aerated static pile. screen is most common with many new dairies ex-
Major factors to be considered are the desired qual- perimenting with settling basins of various shapes,
ity of the final product, space requirements, labor depths, and capacities.
requirements, and availability of a diluent to mix
with the raw waste. Before a composting system is Stationary screen separators take out 20% to
initiated, careful attention must be given to a mar- 30% of the organic matter from flushed dairy ma-
ket or outlet for the composted manure. Do not as- nure. With very dilute flushed dairy manure, an es-
sume that there will be a line of people waiting to timate of 20% removal of organic solids is probably
buy the product. most appropriate. Dilution also assures that almost
Removal of suspended solids from all of the soluble nutrients will stay with the water
portion. Most of the minerals and N are in soluble
flushed manure form (more than 80%).
Moving manure from animal pens with flushed
The expected composition of dairy manure fiber
recovered from a screen and squeezed with a screw Thus, land-spreading of these solids is the most
press is about 72.0% moisture (28% dry matter) likely method of disposal.
with a nutrient content as follows (data on a 100%
dry matter basis): Moore (1989) suggested that settling basins
should have a concrete bottom to allow a wheel
Nutrient' % of DM tractor access to remove the settled solids. A slot or
"V" notch outlet will allow the basin to drain dry
Ash 13.3 13.4 and still not "overtop" in high rainfall events.
Nitrogen 1.2- 1.6
NDF 77.7 83.5
ADF 50.5 52.7
Cellulose (ADF-ADL) 35.4
Hemicellulose (NDF-ADF) 32.0
'Moisture content usually about 72.0%/ (dry matter, 28%).
NDF=neutral detergent fiber, ADF=acid detergent fiber, and
ADL=acid detergent lignin.
The feeding value of this product will not sup-
port acceptable daily gains in growing animals.
However, the manure solids could be fed as an ap-
preciable percentage of diets for cattle which need .
only to maintain themselves and sustain a slow .. .
rate of gain; for example, dry cows. Figure 5. The best recycling method for liquid effluent Is Is rri-
gation of fields planted year-round with a series of
Screened manure solids have been used exten- different crops.
sively for bedding in free stalls. However, manage-
ment to prepare the product properly is critical. An
accepted practice seems to be to compost the solids .
so that internal temperatures within the pile be-
come high enough to kill coliform bacteria. Re-
search has shown that even though bacteria decline
to low or undetectable numbers during the .,
composting period, bacteria often return in the bed-
ding material in the free stalls unless there is op-
portunity to dry the solids in sunlight. Even when
researchers found higher bacterial counts in
composted dairy waste solids bedding than on rub- "
ber mats, there was no difference in bacterial
counts on teats or in the milk of cows using the two
types of bedding. They concluded that with "ad-
equate" composting, dairy waste solids were a suit-
able bedding in free stalls. Many dairymen with ex- Figure 6. Use of a manure spreader to spread fertilizer
cellent mastitis control programs are using dry, nutrients on cropland can be used Instead of a flush
system or to complement it.
screened manure solids for bedding in free stalls.
Moore mentioned a settling basin design which he
An alternative to removing solids from flushed observed in Taiwan that he felt could be used in
manure with screening or centrifuging equipment dairies. Four basins were used, each 75 feet long,
is to design holding ponds for gravity separation 25 feet wide and 18 inches deep. All the flow from
(settling basins). More solids can be removed with the operation, which markets 40,000 pigs annually,
well- designed sedimentation basins (40 to 60%)
than with stationary screens. The key is the reten- was diret Continuing through the second and third
tion time of the water carrying the solids. However, day th liquid draing tro the slope and exit
day, the liquids drain down the 11150 slope and exit
the sedimented solids have a much higher moisture the basin through a stainless steel, 5 mesh screen.
content and are not as useful as screened solids if
bedding for free stalls or composting is desired.
Table 3. Yields of forage dry matter and recycled N from crops fertilized with flushed manure through center pivot.'
Crop, Tons of dry matter or Ibs N/acre
application of N T-44 Abruzzi Corn Total
Lbs/acre bermuda rye silage2 (Tons) (Lbs)
DM N DM N DM N DM N
340 1.82 95 1.90 125 7.97 157 11.69 377
440 2.30 122 2.26 154 7.54 176 12.10 452
660 2.06 112 2.78 222 7.70 190 12.54 525
880 2.03 115 2.48 219 8.00 209 12.51 543
'Data from Johnson et al. (1991). Fibrous solids of flushed manure were removed before irrigation with stationary manure solids separating
'Mean bushels of grain/acre in silage were 175, 163. 161, and 169.
The fourth day, they empty the basin and land- mm hole size) to facilitate irrigation of the effluent.
spread the solids, The settling basin removed 81% The liquid portion was applied to the cropping area
of the suspended solids in swine waste. at four different rates. Actual dry matter and N
yields of the three crops in their rotation in re-
What is the potential nutrient sponse to different rates of liquid manure applica-
uptake by plants? tion are shown in Table 3. Harvests of all crops
yielded 11.69 tons or more of dry matter per acre
One generally acceptable philosophy of land ap- (23,380 Ibs) when N application was 340 lbs. N/
plication of manures is that nutrients can be ap- acre.
plied to land slightly above the level of the nutri-
ents removed by the crops harvested. When animal Due to luxury consumption of N in plants with
numbers are high in relation to the amount of land higher N applications, particularly in the rye, total
readily available, we need to know the maximum N harvested in the three crops continued to in-
application rates for given soil types and crops that crease after dry matter yields plateaued. The N ap-
can be efficiently utilized by different cropping sys- plication rate reported (340, 440, 660, 880 lbs N/
teams and use cropping systems which will take up acre) is the amount of N pumped to the irrigation
the maximum amount of environmentally sensitive sprinklers. Losses of N through volatilization dur-
nutrients such as N and P. ing irrigation (e.g. 20%), surface runoff, and accept-
able losses to the groundwater potentially make the
A long-term research project at Tifton, Georgia application of 660 lb N/acre in environmental bal-
was designed to identify the maximum application ance with a total harvest of 525 lbs N. These data
rate of flushed dairy manure nutrients when a do not show what happened to the excess N with
triple cropping system was used. The flushed dairy the 880 lb N application. From personal communi-
manure nutrients were applied through a center cation with Dr. Johnson, preliminary data show
pivot irrigation system. The cropping system in- that the nitrate level in drainage water underneath
eluded Tifton 44 bermudagrass sod in which corn the center pivot area was similar to levels under
was sod-planted for silage in the spring and abruzzi many corn fields fertilized with commercial fertil-
rye was sod-planted in the fall. Harvests included izer but was slightly above the environmental stan-
rye for grazing from about December 1 until Febru- dard of 10 ppm of nitrate N required for safe drink-
ary 15, rye for silage about March 20 (corn being ing water. Due to the close proximity of the plots,
planted the day following), corn for silage in mid- they could not differentiate between application
July, low-quality bermudagrass hay about 10 days rates but presumably most of the excess came from
later, and high quality bermudagrass hay or graz- the 880 lb N/acre applications.
ing until rye was planted again about November 1.
Data in Table 3 show that it is possible for N re-
In the Georgia experiment, large-particle ma- moval in crops to be greater than that applied, e.g.,
nure solids were separated from the liquid with an 377 lbs N harvested with 340 lbs N applied. For
inclined stainless steel separating screen (1.0 x 6.0 this to happen, N must have originated from soil
Table 4. Comparison of annual estimated uptakes of nutrients by different cropping systems with excretion rates by dairy cows.
Estimated Ibs harvested/acre:
Crop DM N P K Ca' Mg Na S
DM and N data from Johnson
et al., 1991; others estimated:
#1 (340 N/acre) 23390 377 55 284 61 43 12 33
#2 (440 N/acre) 24200 452 57 302 63 44 13 34
#3 (660 N/acre) 25080 525 60 317 66 45 14 35
Corn silage 16000 208 35 154 37 31 5 24
Sorghum silage 16000 154 42 163 46 43 5 23
Alfalfa 14000 448 41 358 216 34 21 43
Perennial peanut 10000 240 22 153 125 31 11 27
Bermudagrass 18000 346 40 306 58 29 24 22
Perennial peanut/rye 14000 329 30 197 131 35 22 30
Bermudagrass/rye 20000 403 43 306 57 29 23 22
Bahiagrass pasture 10000 200 25 145 46 27 10 10
Giant Elephantgrass 40000 499 100
(39.7 in. rain)1:
0 N/acre 2160 30
100 N/acre 7920 132
300 N/acre 14220 323
600 N/acre 17460 442
900 N/acre 18900 554
(from Table 1):
Lower estimate 223 40 88 72 27 42 26
Higher estimate 267 46 146 108 49
'From data cited by Staples, C.R. 1989. Proc. West Florida Dairy Prod. Seminar. FI. Coop. Ext. Serv., Dairy Science Dept., Univ. FI.,
reserves of N carried over from previous years, lbs N application rate. However, it could explain
from N in rainfall (often estimated at about 15 lbs much of the difference in the 452 lbs N harvest
N/year), or from N fixation from the air (not likely with the 440 lbs N application.
without legumes in the system). For N budgets de-
veloped in this publication, N in rainfall is esti- Although, Johnson et al. (1991) did not report P
mated to be offset by gaseous loss of N from the soil application rates, P recoveries and recoveries of
and, thus, neither are included in calculations, several other minerals were estimated from feed
However, with a deficit of N in the soil, gaseous composition tables (NRC, 1988). These data and
losses from the soil might be reduced appreciably data for several other example crops and systems
permitting the gain from rainfall to make a posi- are in Table 4. P recoveries were 55 to 60 lbs per
tive contribution. This gain might not be enough to acre. The P harvests are of particular interest since
make up the difference in the plots with the 340
more acres would appear to be required to accom- Table 5. Nitrogen volatilization oasses In handling and storage.1
modate manure P than manure N. Although it is
tempting to compare data in this table directly with Nitrogen loss
estimated excretion rates to estimate acreage System (percent)
needed for manure disposal, factors such as volatil-
ization of N, surface and groundwater runoff, ex- Solid
port of some manure fractions off the farm, etc. Daily scrape and haul 15 35
must be considered in the budgeting procedure. Open lot 40 60
Other forage crops, even legumes, like alfalfa Liquid
and perennial peanut, have been proposed as being Anaerobic pit 15 -30
good crops for consuming large quantities of ma- Above ground storage 10 30
nure nutrients since legumes take up soil N in pref- Earthen storage 20 40
erence to fixing N from the air when free N is avail- Lagoon 70 80
able in the soil to "scavenge." Giant elephantgrass
which has been used in field studies in Okeechobee Application (losses are % of that remaining after
County, Florida gives the highest estimated P up- storage)
take. Although there may be potential for greater Broadcast (solid) 15 30
recovery of P in the enormous quantity of biomass Broadcast (liquid) 10 25
harvested in giant elephant grass than from other Broadcast
crops, the estimated digestible energy value of the (solid, immediate incorporation) 1 5
harvested forage would be low. Broadcast
(liquid, immediate incorporation) 1 5
The Georgia cropping system would seem to Knifing (liquid) 0- 2
have tremendous potential for Southern United Sprinkler irrigation (liquid) 30 40
States because a large part of the harvest is corn
silage, a high-energy forage that fits the feeding 1Data taken from Structures and Environment Handbook, Midwest
management that most dairymen use for high pro- Plan Service, 1983.
during cows and the sod base is bermudagrass which plants recover from application of fresh ma-
which grows well in a warm season. The alfalfa, pe- nure are much greater than when manure is stored
rennial peanut, and giant elephantgrass systems anaerobically before application due to gaseous
are more hypothetical at this point and need fur- losses of N to the air. If storage conditions are al-
ther testing. lowed to become aerobic, there is substantial addi-
tional reduction in amounts of N available to
One of the major strengths of using flushed ma- plants.
nure systems along with irrigation, is that addi-
tional water can be applied along with fertilizer nu- Even with a "tightly" managed system, there is
trients so that full response to added nutrients is considerable N loss through ammonia volatiliza-
possible. tion. The amount volatilized is influenced by level
of N in the manure (particularly the part originat-
How do you develop a manure ing in the urine) and by the method of application.
nutrient budget? Nitrogen in urine is originally excreted in the form
of urea. Urease enzyme of bacterial origin is
After designing the essential components of the present almost everywhere so that N in urea is
manure management system and estimating total readily converted to ammonia which will be lost to
manure nutrient excretion, the next step necessary the air as free ammonia unless the conditions of
is to account for what happens to nutrients on the storage are acidic. In Table 1, it is estimated that
farm. If needed, alternatives can be developed to nearly half of the manure N from dairy cows is in
avoid nutrient leakage to the environment. This urea or ammonia form (mostly from the urine). This
includes utilization of a cropping system and a land portion is potentially volatilized very rapidly. Most
application system that are in nutrient balance. If of the fecal N from cattle is in a more stable form.
land with an appropriate cropping system is avail- Table 5 gives estimates of N losses through volatil-
able to utilize all nutrients, it is important to apply ization.
manure onto cropland soon after it is produced to
recover the maximum amounts of N. Amounts of N
flush water for a much longer time than temporary
Leaching losses may also occur. Application of holding ponds have been used extensively in
manures outside the growing season or in amounts Florida. Losses of N from lagoon systems where the
which exceed crop needs may result in nitrate effluent is applied through overhead irrigation
leaching losses of 25% or more of the applied N. A would work out similar to the dirt lot system (#3)
high utilization of N by crops can be achieved with because the loss of N to volatilization is similar.
lowered environmental risks when manures are ap- The uncertain part with respect to lagoons is how
plied at a time so that crops can absorb the min- much of the P and other minerals accumulate in
eral-N and at rates which do not exceed crop needs, the sludge at the bottom of the lagoon. In this ex-
ample, it was estimated that 50% of the P and 10%
Several example systems to illustrate how nutri- of the N are completed in the sludge which needs to
ents might "flow" through manure management be periodically removed from the lagoon. Although
systems and the acreage needed to utilize the ma- lagoons reduce acreage needed for day-to-day P
nure are illustrated in Tables 6 and 7. The manure budgets, the P must be eventually distributed on
excretion data for Systems 1, 2, and 3 are for 100 acres needing P applications, e.g. every 3 to 10
cows producing 50 pounds of milk per day. System years depending on the size of the lagoon. Finding
4 is for 100 dry cows. Yearly totals were obtained suitable acreage on which to spread these nutrients
by multiplying daily data by 365. The example sys- may present a problem unless the sludge is spread
teams are: on other farm land than that used for regular ma-
nure spreading. Better quantitative data are
1. Milking cows producing 50 lbs milk per day and needed to show how much P and other minerals are
fed diets based on "NRC Low" standards for pro- retained in lagoons so that acreage requirements
tein and .40% P are confined in concrete lots so for regular manure disposal can be adjusted accord-
that all of the manure can be flushed into a hold- ingly. However, it is well documented that sludge
ing pond for frequent irrigation of cultivated accumulates and therefore it needs to be included
crops taking up 400 lbs N and 50 lbs P per acre. in the nutrient budget in those dairies with anaero-
Solids are screened from the flushed manure to bic lagoons.
facilitate irrigation but are spread on the land.
In the four example manure management sys-
2. Milking cows are producing, fed, confined, and teams, these assumptions were made:
managed as in System #1 except that all of the
manure is flushed into a large anaerobic lagoon 1. Manure is applied year after year to the same
with the effluent from the second stage of the la- land at the same rates so that carryover ofnutri-
goon system used for frequent irrigation of the ents from previous applications, if any, can be
same cultivated crops. assumed to be equal each year.
3. Milking cows producing and fed as in Systems 1 2. Assumed losses of N through volatilization were:
and 2 are maintained in dirt lots where 75% of
manure is dropped; manure is scraped and a 2% of N dropped on concrete before daily flush-
hauled every three months. Twenty-five percent ing or scraping,
of the manure from milking parlor, holding ar- m 10% of N from flushed manure being held only a
eas, etc. is flushed and managed as in System #1. short time before irrigation,
Surface runoff water from dirt lots is put into the 50% of N dropped in dirt lots for clean-up and
holding pond with the flushed water. spreading every 3 months,
40% of runoff from dirt lots which was estimated
4. Dry cows fed to meet "NRC Low" protein stan- as 10% of N dropped on dirt,
dards and .40% P are maintained on pasture. It 20% of N applied in the field after land-spread-
was assumed that cows harvest 5.0 ton of dry ing or irrigation, and
matter/acre/year of nonirrigated bermudagrass a 50% of total N dropped in pasture.
or bahiagrass which recovers 200 lbs N (12.5%
crude protein of the forage) and 25 lbs P. Addi- 3. Runoff from flushed or scraped concrete lots was
tional feed was supplemented to provide captured in a holding pond for frequent irriga-
amounts for dry cows shown in Table 1. tion and that from diit lots was captured in a in
a separate holding pond which was also added to
Anaerobic lagoons (System #2) which detain the irrigation but after longer time in storage.
Table 6. Manure worksheet for nitrogen: needed acreage for 100-Cow groups
Diet N (NRC.low): System: Worksheet for
1 2 3 4 your dairy
Category MY=50 MY=50 MY=50 Dry
Number of cows per group 100 100 100 100
% to be flushed to holding pond 100 0 25 0
% to be flushed to anaerobic lagoon 0 100 0 0
% to be scraped from concrete daily 0 0 0 0
% scraped from dirt lot quarterly 0 0 75 0
% dropped in pasture 0 0 0 100
Lbs daily N excretion/cow 0.601 0.601 0.601 0.364
Lbs yearly N excretion/group 21937 21937 21937 13286
Lbs Lbs Lbs Lbs
Volatilized N on flush floors (2%) 439 439 110 0
N flushed for weekly irrigation 21498 0 5374 0
N removed by solids separator screen 1306 0 326 0
N to holding pond-irrigation weekly 20192 0 5048 0
Volatilized N from holding pond (10%) 2019 0 505 0
N irrigated from short-term holding 18173 0 4543 0
N flushed to anaerobic lagoon 0 21498 0 0
N retained in sludge (10% of N) 0 2150 0 0
Volatilized N from lagoon (60%) 0 12899 0 0
N irrigated from lagoon-2nd stage 0 6449 0 0
N runoff from dirt lot (10% of original) 0 0 1645 0
Volatilized N from dirt lot holding (40%) 0 0 658 0
N irrigated from dirt lot holding 0 0 987 0
Total N applied through irrigation 18173 6449 5530 0
Volatilized N during irrigation (20%) 3635 1290 1106 0
Volatilized N on scraped floors (2%) 0 0 0 0
Volatilized N, pastures (50% of original) 0 0 0 6643
Volatilized N, dirt lot (50% of original) 0 0 8226 0
Yearly Ib N hauled daily from concrete 0 0 0 0
Yearly Ib N hauled quarterly from dirt 0 0 6581 0
Volatilized N, land-spread from concrete 0 0 0 0
Volatilized N, land-spread from dirt lots 0 0 1316 0
Surface runoff (5% of crop applications) 909 322 606 332
Irrigated N available to plants 13630 5837 4148 0
Screened solids, N available to plants 1306 0 326 0
From concrete, N available to plants 0 0 0 0
From dirt lots, N available to plants 0 0 4936 0
Pasture N available to plants 0 0 0 6311
Summary: Total N in lagoon sludge 0 2150 0 0
Summary: Total N volatilized 6093 14627 11921 6643
Summary: Surface runoff 909 322 606 332
Summary: Applied N available to crops 14935 4837 9410 6311
Total N managed (= yearly excretion) 21937 21937 21937 13286
Acres needed/100 cows for manure for: acres' acres' acres' acres'
Irrigation if N/acre = 400 + 20 32.5 11.5 9.9 0
Scrapings from concrete, N/acre=400+20 0 0 0 0
Scrapings from dirt lot, N/acre =400+20 0 0 11.8 0
Screened solids, N/acre = 400 + 20 3.1 0 0.8 0
Pasture if N/acre = 200 + 20 0 0 0 28.7
Future: Lagoon sludge, N/acre=400+20 0 5.1 0 0
Total acres needed, N basis 35.6 16.6 22.4 28.7
'Acres calculated by dividing nutrients available to plants by estimated uptake of 400 Ibs N/yr for cultivated crops (pasture=200) + 20
Ibs/acre groundwater passage.
Table 7. Manure worksheet for phosphorus: needed acreage for 100-cow groups
P (.40% of diet): System: Worksheet for
1 2 3 4 your dairy
Category MY=50 MY=50 MY=50 Dry
Number of cows per group 100 100 100 100
% to be flushed to holding pond 100 0 25 0
% to be flushed to anaerobic lagoon 0 100 0 0
% to be scraped from concrete daily 0 0 0 0
% scraped from dirt lot quarterly 0 0 75 0
% dropped in pasture 0 0 0 100
Lbs daily P excretion/cow 0.107 0.107 0.107 0.101
Lbs yearly P excretion/group 3901 3901 3901 3675
Lbs Lbs LEs Lbs
P flushed for weekly irrigation 3901 0 975 0
P removed by solids separator screen 326 0 82 0
P to holding pond-irrigation weekly 3575 0 894 0
P irrigated from short-term holding 3575 0 894 0
P flushed to anaerobic lagoon 0 3901 0 0
P retained in sludge (50% of P) 0 1951 0 0
P irrigated from lagoon-2nd stage 0 1951 0 0
P runoff from dirt lot (20% of original) 0 0 585 0
P irrigated from dirt lot holding 0 0 987 0
Total P applied through irrigation 3575 1951 1479 0
Yearly Ib P hauled daily from concrete 0 0 0 0
Yearly Ib P hauled quarterly from dirt 0 0 2341 0
Surface runoff (5% of crop applications) 179 98 191 184
Irrigated P available to plants 3396 1853 1405 0
Screened solids, P available to plants 326 0 82 0
From concrete, P available to plants 0 0 0 0
From dirt lots, P available to plants 0 0 2224 0
Pasture P available to plants 0 0 0 3491
Summary: Total P in lagoon sludge 0 1951 0 0
Summary: Surface runoff 179 98 191 184
Summary: Applied P available to crops 3722 1853 3710 3491
Total P managed (= yearly excretion) 3901 3901 3901 3675
Acres needed/100 cows for manure for: acres' | acres' acres' acres'
Irrigation if P/acre = 50 + 2 65.3 35.6 27.0 0
Scrapings from concrete, P/acre = 50 + 2' 0 0 0 0
Scrapings from dirt lot, P/acre = 50 + 2 0 0 42.8 0
Screened solids, P/acre = 50 + 2 6.3 0 1.6 0
Pasture if P/acre = 25 + 2 0 0 0 129.3
Future: Lagoon sludge, P/acre = 50 + 2 0 37.5 0 0
Total acres needed, P basis 71.6 73.1 71.4 129.3
'Acres calculated by dividing nutrients available to plants by estimated uptake of 50 Ibs P/yr for cultivated crops (pasture= 25) +
groundwater passage of 2 Ibs/acre.
teams. The predicted manure disposal acreage
4. Surface runoff losses from crop fields of N and P needed per 100 cows varied from 17 to 36 acres.
were assumed to be 5% of nutrients applied. Similarly using a P budget in Table 7, the manure
disposal acreage needed varied from 71 to 129
5. To account for normal and acceptable losses to acres. It is important to note that 38 of the 73 acres
groundwater, it was estimated that 20 lbs N/acre estimated with 100% use of a anaerobic lagoon sys-
and 2 lbs P/acre/year pass with the water moving tem were future acres needed when the sludge will
through the soil into the groundwater. This be removed from the lagoon. Acres for sludge appli-
amount was added to the estimated uptake of N cation, however, might very well be acres on an-
or P by the crops harvested. Estimated uptake of other farm to which the sludge could be hauled or
N was 400 lbs/acre for cropping systems and 200 sold to other farmers for fertilizer.
for pasture; for P estimated uptake was 50 lbs/
acre for cropping systems and 25 for pasture. Al- If the same cows had been fed to meet NRC
though groundwater standards have not been set crude protein standards and a more typical level of
for P, it was assumed that 1.0 ppm P would be P (.45% of diet dry matter), the acreage require-
acceptable and that this level would be obtained ments would vary from 19 to 41 acres for N budgets
from 2 lbs P/acre/year. and 84 to 133 acres for P budgets. Direct acreage
comparisons are in Table 8.
Table 6 shows a N budget generated from a com-
puter spreadsheet for the four 100-cow groups man- Regardless of the manure management sys-
aged according to the scenarios described previ- ter, more acres are needed to dispose of ma-
ously and fed minimal dietary levels ofN (NRC nure with plant uptake of P as the application
Low, Table 1). Note that the N produced yearly by criterion than with plant uptake of N. Level of
the cow groups flowed somewhat differently feeding (level of production) also has a signifi-
through the four hypothetical management sys- cant effect. Remember the manure management
S15 in rainfall
15 from soil
126 Volatilized 31 surface
during Irrigation runoff
Harvested from 1 acre
Corn silage 176
---503 Bermudagrass 122
630 to 1.0 ACRE Rye silage 154
70 irrigation 1
Volatilized recycled feed
during holding 20
53 groundwater 653 purchased feed
15 for compost
Volatilized sold off farm 3.5 cows
7m7u total feed
milk, 7,364 gallons 3 newborn calves
Figure 7. Example of a dairy manure system where N Is environmentally balanced. Numbers represent Ibs nitrogen. Crop N Is from
Table 3, excretion and losses are calculated as in Table 6, System 1.
system differed between groups 1, 2, and 3 and lbs N passed through to the groundwater. The net
both feeding level and system were different for the recovery of 452 lbs N in the harvested feed was re-
dry cow group, group 4. cycled to the dairy cows in the feed harvested from
the acre to which the flushed manure effluent was
Many more scenarios are possible than those il- applied. Purchased concentrates and supplements
lustrated here. Because of the large variation from (53% of the estimated dry feed the cows were esti-
dairy to dairy in the systems used and in feeding mated to consume) imported 653 lbs N to the farm.
and production levels, it is essential that each farm In this system, it is estimated that the 53 lbs N in
be permitted to develop its own budget for nutrient screened manure solids (separated to facilitate irri-
flow. The tables are presented only to help indi- gation) were exported from the farm after
viduals make estimates which are appropriate for composting. Note, in this system it is estimated
an individual farm. that 15 lbs N available to the crops per acre in an-
nual rainfall is directly offset by an equal amount
Table 8. Acres needed per 100 cows with N or P criteria, of gaseous N loss from the soil.
N based P based What steps help to document
NRC NRC .40% .45%
100 Cow-Group Low High P P Even -with good management, there is potential
100 -- -- Hh -P- for trouble spots or "leaks" in the manure system
Milking cows: that might be judged as violations by regulatory
100%, rapid irrigation 36 41 72 85 agencies or as nuisances by citizens. After develop-
100%, anaerobic lagoon' 17 19 73 87 ing the plan, dairy farmers should take precaution-
25% flushed, 75% dirt lots 22 26 71 84 ary steps to monitor and verify that their plan
Dry cows on pasture 29 35 129 133 meets environmental standards. Helpful steps are
'Includes future acres at
annul a icati eq alent Have a copy of the manure management plan
annual application equivalent available for review. This should include:
for sludge of: 5 6 38 44
Maps showing locations of barns, pastures,
cropland, production wells, monitoring wells,
The principles of nutrient budgets can best be etcc
summarized by visualizing the total nutrient cycle
necessary to achieve environmental balance. Figure Engineering drawings of waste management
7 illustrates a system balanced for N which is con- system components.
structed from data presented in previous tables.
For this system, average Florida dairy cows produc- The nutrient management budget and
ing 50 lbs milk/day were chosen in which the ma- recordkeeping system which details available
nure was flushed to a holding pond for frequent ir- land area, application rates on specific crops
rigation (System 1, Table 6). Irrigated N was uti- including nutrient analyses of manure and
lized in the triple crop system of corn silage, wastewater applied, amount of inorganic fer-
bermudagrass hay, and rye silage reported by tilizer applied, yields and nutrient analyses of
Johnson et al. (1991) in which 452 lbs N were re- cr harvested, and quantities of manure nu-
covered in harvested crops (Table 3). To achieve trients sold or exported from the dairy farm.
balance, manure from 3.5 cows was flushed and the
effluent from the solids separating screen was irri- Obtain a water permit and install a water meter
gated with sprinkler irrigation heads on one-acre of or meters to monitor water use.
land. The cows consumed feed containing 1105 lbs
N, produced milk (7420 gallons) containing 327 lbs Install groundwater sampling wells and analyze
N and 3 newborn calves with 10 lbs N. The 3.5 cows samples regularly to monitor groundwater qual-
excreted manure containing 768 lbs N: 15 lbs N ity for use in deciding if changes are needed in
volatilized before flushing; 53 lbs N were recovered some components of the manure management
in the screened manure solids; 70 lbs N volatilized tm
during holding; 126 lbs N volatilized during irriga-
tion; 31 lbs N were lost to surface runoff. Twenty
If complaints are received about the dairy, the
above documentation makes it easier to refute in- Johnson, J. C., G. L. Newton, and J. L. Butler.
correct accusations. There will be increasing compe- 1991. Recycling liquid dairy waste to sustain an-
tition for water in the future and a valid water use nual triple crop production of forages. Proc.
permit will help to justify a farmer's claim for con- Florida Dairy Production Conf., Dairy Science
tinued use of water. The installation of one or more Dept., Univ. Fl. Coop. Ext., Gainesville, FL.
water meters will also help tremendously by en- 32611.
abling better estimates of water used in flushing
manures and applying wastewater to cropland. If Moore, J. 1989. Dairy manure solid separation.
fan and sprinkler cow cooling systems are installed, NRAES Publication 31, Proc. Dairy Manure
they require large volumes of water. The presence Management Symposium, Syracuse, N.Y., Feb.
of a water meter can help in conservation efforts 22-24, 1989. Northeast Regional Agricultural
and to minimize costs associated with handling ma- Engineering Service, Cornell University, Ithaca,
nure. N.Y. 14853
Summary Morse, D. 1989. Studies of modification of phospho-
1. Manure is unused nutrients from feed that need rus concentration in diets, hydrolysis ofphytate
to be captured and directed to plants that benefit bound phosphorus, and excretion of phosphorus
from fertilization, by dairy cows. PhD Thesis, Dairy Science De-
2. Water use in dairies to flush manure is efficient apartment, University of Florida, Gainesville
and environmentally sound if combined with an 32611.
effective crop irrigation and fertility program.
3. Developing total farm nutrient budgets to bal- NRC. 1988. Nutrient Requirements of Dairy Cattle
ance utilization of manure nutrients through (6th Ed.). National Academy Press, Washington,
crops with excretion by the cattle is an essential DC.
step toward environmental accountability.
4. Because of large variation from dairy to dairy in Sweeten, J. M. 1989. Groundwater quality protec-
systems used and in feeding and production lev- tion for livestock feeding operations. Texas Agri-
els, each farm should develop its own budget for cultural Extension Service Publ. L-2348, Texas A
nutrient flow. & M Univ., College Station, TX 77843-2121.
5. Dairy farmers need to monitor their nutrient
management system even after theoretical nutri- Sweeten, J. M. 1983. Dairy manure handling sys-
ent balance is achieved in order to avoid point tems and equipment. Texas Agricultural Exten-
sources of nutrient leakage to the environment. sion Service Publ. B-1446, Texas A & M Univ.,
College Station, TX 77843-2121.
ASAE Standards. 1989. Manure production charac- Van Horn, H. H. 1990. Achieving balance of nutri-
ASAE Standards. 1989. Manure production charac-
ent flow through animal production systems.
teristics. Developed by the Engineering Practices et fw rough animl dustry Assoc. Nutri
Subcommittee of the ASAE Agricultural Sanita- Proc. American Feed Industry Assoc. Nutrition
Subcommittee of the ASAE Agricultural Sanita- o su, S. L M N. 19p.
tion and Waste Management Committee. ASAE Symposium, St. Louis, MO, Nov. 5-6, 1990; pp.
tion and Waste Management Committee. ASAE 15-32
Holloway, M. P., A. B. Bottcher, and K. L.
Campbell. 1990. BMPs for mitigating nitrate
contamination of groundwater under North
Florida dairies. Research grant report to Florida
Department of Environmental Regulation, Talla-
hassee, FL 32399-2400.
"Manure nutrients are a
natural part of the envi-
ronment, they are build-
ing blocks to be used
again in nature's cycle of
COOPERATIVE EXTENSION SERVICE,UNIVERSITYOFFLORIDA,INSTITUTE OF FOODANDAGRICULTURALSCIENCES,JohnT.Woeste,
Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8 and June
30,1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and institutions that
function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding 4-H and youth
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is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida32611. Before publicizing
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