Manure Spreader Calibration
Introduction
Manure spreader calibration and manure nutrient
analysis are beneficial to Nutrient Management
Planning in calculating the crop available nutrients
supplied by a manure application. Knowledge of
manure nutrients supplied by a manure application
allows the crop nutrient requirements to be better
met, lessening reliance on chemical fertilizers.
While application timing and incorporating manure
will ensure the best use of available nutrients.
Excessive manure application rates and chemical
fertilizer use can contribute to potential water
quality issues.
When calibrating manure spreaders, details such as
tractor gear, rpm, and manure spreader settings
should be recorded. Manure spreader settings can
include such things as: fast and slow settings on
some box spreaders, gate position on side delivery
spreaders and splash plate position on liquid tankers.
Before calibrating a manure spreader, the spreader
settings should be adjusted so that the spread pattern
is uniform. In some cases overlapping of adjacent
passes is required to make the overall application as
uniform as possible.
Figure 1. Plume from liquid tanker with top
mounted splash plate producing a uniform spread
pattern.
In order to determine manure spreader application
rates you need to know the amount of manure in a
spreader load and the area that each load covers.
There are several methods that can be used to
determine this. Two common methods are the loadarea method and the plastic sheet method. The
load-area method is the most accurate and can be
used for all types of manure. The plastic sheet
method can only be used with solid or semi-solid
manure.
Load-Area Method
The load-area method consists of three steps:
1) determine the amount of manure in a load,
2) determine the area covered by a load, and
3) calculate the application rate.
1) Determine the amount of manure in a load
The most accurate method of determining the
amount of manure in a spreader is difference in
weight between a full and empty manure spreader.
The Environmental Farm Plan has portable scales
which are used to weigh the tires and tow hitch on a
manure spreader. Alternately, spreader capacities as
listed by the manufactures can be used to determine
the amount of manure in the spreader. However,
depending on loading methods, manure type and
amount of bedding the capacity may vary
considerably from actual amounts for box and side
delivery manure spreaders. Spreader capacities for
liquid spreaders are accurate provided the tanker is
filled completely with no sludge buildup or foam in
the tank. Foaming can reduce tank capacity by as
much as 10 %. It is important to distinguish whether
the capacity is listed in US or Imperial gallons.
2) Determine the area covered by a load
The area covered by a load is determined by
measuring the length and width of the application
and multiplying to calculate the area. Overlapping
each pass is usually required to obtain a uniform
application. When overlapping, measure the width
of two adjacent passes and dividing by two to
determine the effective spread width. The area
should be converted to acres or hectares by using the
appropriate conversions. Measuring can be done
with a measuring wheel, measuring tape or by
pacing. The area covered in hectares (ha) can be
determined as:
Swath width (m) x distance traveled (m)
10,000 m2
The area covered with a load can also be determined
by dividing the field size, if accurately known, by
the number of loads of manure needed to cover the
field.
3) Calculate the application rate
The application rate is calculated by dividing the
amount of manure in the spreader (Tonnes or
gallons) by the area it is spread over (acres or
hectares).
Application rate =
Amount applied
Area covered
Plastic Sheet Method
Spreader application rates can be estimated by
laying a plastic sheet on the ground and driving the
manure spreader over the sheet. The plastic sheet
with the manure on it is folded and placed in a
bucket. The bucket, sheet and manure are then
weighed on a scale (bathroom scale will do) and the
sheet and bucket weight is subtracted to determine
the weight of manure. This procedure should be
repeated several times to get an average value. The
application rate is determined from the weight of
manure and area of the plastic sheet. Table 1
correlates application rates to the weight of manure
applied to different sized plastic sheets. If the sheet
size or the weight of manure on the plastic sheet is
different than the values listed than the application
rate can be determined by extrapolating.
Conversions
2
2
1 ha = 10,000 m = 2.47 ac = 107,642 ft
1 ac = 43,560 ft2 = 0.4 ha = 4,047 m2
1 L = 0.264 US gal = 0.22 Imp gal
1 Imp gal = 1.2 US gal = 4.55 L
1 US gal = 0.83 Imp gal = 3.79 L
1 Tonne (T) = 1,000 kg = 2,200 lb
1 ton (t) = 2,000 lb = 907 kg
Assuming 1 L of manure weighs 1 kg:
1 Tonne/ha = 0.445 ton/ac
= 107 US gal/ac
= 89 Imp gal/ac
Table 1. Manure application rates (T/ha) based on weight of manure
captured by four common plastic sheet sizes.
Pounds of
manure applied
to sheet
4
14
24
34
44
54
64
74
Sheet size (feet x feet)
6x6
5.5
19.1
32.8
46.5
60.1
73.8
87.4
101.1
8x8
3.0
10.7
18.3
25.9
33.5
41.1
48.7
56.4
10 x 10
2.0
6.9
11.8
16.8
21.7
26.6
31.5
36.5
For further information contact:
Rick Hoeg, Environmental Technical Support
Phone : (902)893-6577 Cell: (902)890-1894
E-mail: [email protected]
10 x 12
1.6
5.6
9.7
13.7
17.7
21.8
25.8
29.8