Publications
Calibrating Liquid Manure Tank Spreaders
 Printer Friendly (PDF)
Importance of Calibration •
Calibration •
Calibration Procedures
Importance of Calibration
You can avoid the potential adverse effect on ground and surface
water caused by overfertilization by applying only the amount of waste and wastewater
necessary to maintain soil fertility for crop production.
The calibration of liquid manure spreading equipment is important because it lets you know
the amount of waste and wastewater you are applying to an area.
The calibration rate and the nutrient concentration level of the liquid manure lets you
know the amount of plant nutrients you are putting on the soil. Then you can adjust your
fertilization rate to avoid overfertilization.
Calibration
The calibration procedure in the example on the following page is
a load-area method. The principle is to apply a known volume of manure over a known area.
The application rate is then calculated as the volume divided by the area. This
application rate is then multiplied by the nutrient concentrations of the manure to
determine the amount of nutrients applied to the area. This information can then be used
to adjust the manure application rate to meet the crop’s requirements.
Cubic
feet =
0.79 x D x D x L
Example: If D = 7 ft, L
= 10.4 ft
cubic feet = 0.79 x 7 x 7 x 10.4 = 400
cubic feet
Figure 1. Calculating the volume of a full cylindrical tank
Calibration Procedure
1) Determine the spreader’s tank capacity in gallons by
using the conversion of 7.5 gal per cuft. If the tank’s capacity in cubic feet or
gallons is unknown, refer to Figure 1.
Example: 400 cuft x 7.5 gal/cuft = 3000 gal
Your Numbers: ______ cuft x 7.5 gal/cuft = ______ gal
2) Spread one or more loads of manure to the field. The manure should be applied using the
same equipment settings, ground speed, swath width and pattern overlap that will be used
in normal application practices.
Example: 1 load applied at 1.5 mph
Your Numbers: ______ load(s) applied at ______ mph
3) Measure and calculate the land area to which the manure was applied. The application
area should be square or rectangular so you can multiply the length and width to calculate
the land area. The distances can be determined by measuring or pacing.
Example: 100 ft wide x 200 ft long = 20,000 sqft
Your Numbers: ______ ft wide x ______ ft long = ______ sqft
4) Convert the area from Step 3 to acres using the conversion rate of
43,560 sqft per acre.
Example: 20,000 sqft ÷ 43,560 sqft/ac = 0.46 ac
Your Numbers: ______ sqft ÷ 43,560 sqft/ac = ______ ac
5) The application rate is calculated as the tank capacity from Step 1
times the number of loads from Step 2 divided by the application area in
acres from Step 4.
Example: 3,000 gal x 1 load ÷ 0.46 ac = 6,522 gal/ac
Your Numbers: ______ gal x ______ load(s) ÷ ______ ac = ______ gal/ac
6) The pounds of nutrients applied per acre is calculated by multiplying the gallons per
acre applied from Step 5 by the pounds of nutrient per 1,000 gallons of
wastewater1 and then dividing by 1,000.
Example: 6,522 gal/ac x 20 lb N/1000 gal ÷ 1000 = 130 lb N/ac
Your Numbers: ______ gal/ac x ______ lb N/1000 gal ÷ 1000 = ______ lb
N/ac
Authors: Karl
VanDevender - Extension
Agricultural Engineer
Phil Tacker - Extension Agricultural Engineer
John Langston, Extension Agricultural Engineers
This publication was funded in part by the University of Arkansas
Cooperative Extension Service, the Environmental Protection Agency and the Arkansas Soil
and Water Conservation Commission.
DR. KARL VANDEVENDER,
PHIL TACKER and JOHN LANGSTON are Extension agricultural
engineers, Cooperative Extension Service, University of Arkansas, Little Rock.
FSA1021-PD-4-02R |
