Manure Spreader Calibration

Calibration is a way of checking and/or making adjustments to manure application equipment to ensure that a nutrient source is being applied uniformly and at the desired rate. It is important to properly calibrate manure application equipment to minimize the potential for over or under applying nutrients to a crop.

There are two methods for calibrating manure application equipment:

1. Weight-area method - This method, which is appropriate when dealing with heavier solid manure, involves spreading manure on a collection surface of known dimensions, weighing the manure on the collection surface, and calculating the application rate. The application rate is then converted to a per-acre basis. 
2. Load-area method - This method, which is appropriate for liquid and solid manures and poultry litter, involves spreading several loads of manure on the field, measuring the area, and then calculating the manure application rate for that area. The application rate is then converted to a per-acre basis. 

For more information on calibration, including uniformity of spread pattern and examples of worksheets, refer to the following University of Maryland Extension Soil Fertility Guide publications:

• EC-1 "Calibration of Manure Spreaders: Uniformity, Spread Patterns and Effective Swath Width"
• EC-2 "Calibration of a Manure Spreader Using the Weight-area Method"
• EC-3 "Calibration of a Liquid Manure Spreader Using the Load-area Method"
• EC-4 "Calibration of a Manure Spreader Using the Load-area Method (with Drive-on Scales)"
• EC-5 "Calibration of a Manure Spreader Using the Load-area Method (with Estimation of Density and Load Weight)"

For more information about operating and calibrating many types of nutrient application equipment, consult the NRAES-57 "Fertilizer and Manure Application Equipment" publication. 

Nutrient Management Advisors in University of Maryland Extension offices can provide instruction and assistance with manure spreader calibrations. Please visit our Nutrient Management Advisors web page to find your local Extension advisor.