Manure Spreader Calibration Calculator

Application rate from spreader settings and speed.

Load weight (tons)

Distance to empty (ft)

Spread width (ft)

N content (lbs/ton)

P₂O₅ content (lbs/ton)

K₂O content (lbs/ton)

N availability (%)

Target N (lbs/acre)

Tab to move between fields

Application rate (tons/ac)

5.45

Available N (lbs/ac)27.2

P₂O₅ applied (lbs/ac)27.2

K₂O applied (lbs/ac)43.6

Optimal rate for target N (tons/ac)30

Speed adjustment (%)-82

Loads Per Acre For Target N5

How to Use This Calculator

Enter Load Weight (tons), Distance to Empty (ft), and Spread Width (ft) for your spreader configuration.
Enter N, P₂O₅, and K₂O content (lbs/ton) from a manure nutrient analysis.
Set N Availability (%) — surface-applied liquid averages 25–50%, injected 50–75%.
Enter Target N (lbs/acre) for the crop to calculate the optimal application rate.
Read Application Rate (tons/ac), Available N (lbs/ac), and Speed Adjustment (%) — positive means slow down to increase rate.

How the result changes with Distance to empty (ft)

Load weight (tons): Weight of manure per spreader load in tons.
Distance to empty (ft): Distance traveled to empty one load in feet.
Spread width (ft): Effective spread pattern width in feet.
N content (lbs/ton): Nitrogen content per ton. Dairy: 8-12, Swine: 10-18, Poultry: 20-30 lbs/ton.
P₂O₅ content (lbs/ton): Phosphorus (as P₂O₅) per ton. Dairy: 3-6, Swine: 7-12, Poultry: 15-25.
K₂O content (lbs/ton): Potassium (as K₂O) per ton. Dairy: 7-12, Swine: 5-9, Poultry: 8-15.
N availability (%): First-year N availability. Surface: 25-50%, injected: 50-75%, poultry: 50-70%.
Target N (lbs/acre): Desired plant-available nitrogen per acre for the crop.

Application rate (tons/ac): Actual manure application rate in tons per acre at current settings.
Available N (lbs/ac): Plant-available nitrogen delivered per acre.
P₂O₅ applied (lbs/ac): Phosphorus applied per acre (total, not adjusted for availability).
K₂O applied (lbs/ac): Potassium applied per acre.
Optimal rate for target N (tons/ac): Application rate needed to deliver the target nitrogen.
Speed adjustment (%): Positive = slow down (rate too high), negative = speed up (rate too low) to hit target.

Identify Input Parameters
4 parameters
Load weight (tons) = 6, Distance to empty (ft) = 1200, Spread width (ft) = 40, N content (lbs/ton) = 10 = 8 input(s) provided
Calculate Application rate
5.45 = 5.45
Calculate Available N
Available N = appRateTonsAcre * nContentLbTon * nAvailFactor
27.2 = 27.2
Calculate P₂O₅ applied
P₂O₅ applied = appRateTonsAcre * pContentLbTon
27.2 = 27.2