A Procedure for the Determination of
Storage Period for Manure Storages in Oregon
Donald L. Stettler,
Environmental Engineer
USDA, NRCS, National Water and Climate Center
Portland, Oregon
Stefanie G. Aschmann, Agroecologist
USDA, NRCS, Watershed Science Institute, Lincoln, Nebraska
Bruce D. Wilson, Conservation Planning Engineer
USDA, NRCS, Portland, Oregon
Abstract
Determining an appropriate storage period for sizing manure storage
facilities is of great importance in planning and designing agricultural waste management
systems that will successfully protect the resource base. However, because of the wide
variation of environmental conditions throughout the United States, the Natural Resources
Conservation Service practice standards and handbook guidance are necessarily vague on how
storage period is determined. Oregon NRCS has adopted a procedure for determining storage
period that takes into account the wide variation of Oregon climatic conditions as well as
farm variables including the level of management, soils, field location, nutrient loading,
and application method. This procedure may be adaptable to other regions the United
States.
Introduction
The NRCS Practice Standard 313, Waste Storage Facility, defines the
storage period as "... the maximum length of time anticipated between emptying
events." The criteria for its determination is that it "...shall be based on the
timing required for environmentally safe waste utilization considering the climate, crops,
soil, equipment, and local, state, and Federal regulations." The necessary vagueness
of this criteria requires that individual States supplement the criteria or provide
guidance on its determination based on the local conditions.
Oregon NRCS uses a procedure for determining storage period that
considers the level of management, soils, location, nutrient loading, and method of
application. Oregon's climate is highly varied from its coastal area with mild winters and
high precipitation to its eastern high desert with cold winters and snow. As such, the
Oregon procedure may serve as a model for other parts of the country.
Oregon NRCS's procedure begins with the determination of a basic
storage period that is based on the period of time between when three-fourths of crop's
evapotranspiration (ET) has occurred and when evapotranspiration become equal to or
greater than precipitation the next spring. The premise of using three-fourths of the ET
is that at this point the crop has absorbed the majority of the nutrients that it will
use. Nutrients in manure applied after this time will be available for runoff and
leaching. It is assumed that runoff ceases when ET becomes equal to precipitation the next
spring. The procedure allows for adjustment of the basic storage period based on the
assumption that management can take advantage of times within the basic storage period to
apply wastes to reduce the storage requirement. The Oregon NRCS procedure involves
methodology for evaluating first, the level of management, and then availability farm
variables that are conducive to winter time manure applications. These include
availability of suitable soils and buffered land application areas. Also evaluated are the
method of application and nutrient loading in terms of percent of the crop requirement.
Procedure for Determining Storage Period
1. Determine the basic storage period
(SPb). Determine the day of the year (L) when 3/4 of annual evapotranspiration
has accrued. Determine earliest day of the year (E) when evapotranspiration is equal to
precipitation by interpolation of month averages SPb =
365 - (L - E)
2. Determine adjustment factor for level of management (Fm).
The basic storage period is adjusted on
the assessed level of management that will be provided.
![](20524/ManureMgmt/Image50.gif)
3. Determine adjustment factor for availability of suitable soils
for land application (Fs). An adjustment to basic storage period based on
soils can only be made if the application area does not have any of the severe limitations
given in Table 5-3 of the NRCS Agricultural Waste Management Field Handbook.
Hydrologic Soil Group |
Manure Consistency |
Liquid |
Slurry |
Semi-Solid |
Solid |
A |
1.00 |
0.95 |
0.90 |
0.80 |
B |
0.80 |
0.75 |
0.70 |
0.65 |
C |
0.90 |
0.85 |
0.80 |
0.75 |
D |
1.00 |
1.00 |
0.95 |
0.90 |
4. Determine adjustment factor for availability of
land application area buffered from water bodies and free of concentrated flow areas (Fl). Buffered application areas are not subsurface drained,
have a 0 to 5 percent chance of flooding from adjacent water bodies, and are at least 50
feet from water bodies, ground water sources, and areas of concentrated flow.
![](20524/ManureMgmt/Image51.gif)
5. Determine adjustment factor for nutrient loading (Fn). In order for the nutrient loading factor, Fn, to be
less than 1, the location factor, Fl, must be 0.95 or
less. The percent of annual nutrient requirement (%ANR) is determined by taking the total
nutrients applied annually (TNA) and dividing it by the total nutrient requirement
(TNR)
of all the crops grown.
%ANR = TNA/TNR x 100%
![](20524/ManureMgmt/Image52.gif)
6. Determine the adjustment factor for the method of land
application (Fa)
Method |
Fa |
Solid manure, surface applied, no
incorporation |
1.0 |
Liquid manure, surface applied, no
incorporation |
0.8 |
Injection or immediate incorporation |
0.7 |
7. Compute the adjusted storage period (ASP)
ASP = SPb x Fm x Fs x Fl x Fn
x Fa
8. Compute adjusted earliest calendar day for application (Ea)
Ea = ASP - (365 - L)
9. Check adjusted storage period, ASP, to ensure it spans seasonal
periods of flooding. Also check to ensure the adjusted storage period spans frozen
ground and snow conditions where the application areas slope is greater than 5% and buffer
strip of 100 feet or more cannot be maintained between the application area and open water
courses.
Determine the calendar day when seasonal frozen ground, snow or flooded
conditions are first anticipated for application area (Lf).
If Lf comes
before L (Step 1) then the ending
date for manure application (Lsp) =
Lf
If Lf
comes after L or there is no seasonal frozen ground, snow or flooding then Lsp = L
Determine the calendar day when frozen ground, snow or flooding
conditions are no longer anticipated for the application area (Ef).
If Ef comes
after Ea (Step 8) then the
beginning date for manure application (Esp) = Ef
If Ef
comes before Ea or there is no
seasonal frozen ground, snow or flooding then Esp = Ea
10. Compute Storage Period (SP)
SP = 365 - (Lsp - Esp)
References
Stettler, D.L. Aschmann, S.G. 1995 Demonstrating the Water Quality Consequences of
Organic Waste Application Using the GLEAMS Model. Proceedings of the Seventh International
Symposium on Agricultural and Food Processing Wastes, American Society of Agricultural
Engineers, St. Joseph, MI.
United States Department of Agriculture. 1996. Waste Storage Facility, NRCS
Conservation Practice Standard, Code 313. Natural Resources Conservation Service,
Washington, DC
United States Department of Agriculture. 1992. Agricultural Waste Management Field
Handbook. Natural Resources Conservation Service, Washington, DC
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