a tractor pulling a toolbar applicator with swingarm and hose through a field with the overlaid title Calibrating Liquid Manure Application
January 29, 2020

Calibrating Liquid Manure Application

With drag hose application, there are a lot of different factors and conditions that affect the application rate out in the field – such as tractor speed, operating pressure, friction loss from hoses, etc. By calibrating your equipment, you’ll be able to better match the application rate to the nutrient requirements of the field’s pre-determined Nutrient Management Plan. This will help you avoid misapplication issues that are brought on by under and over application. 

Proper calibration of drag hose equipment requires the measurement of tractor speed, spread width, and flow rate through the hose. Many drag hose systems – such as Puck Enterprises’ Swing Arms – incorporate the use of flow meters to present an accurate measurement of liquid flow rates while in the field. Once you have those three measurements, you can use the 495 Rule to determine the desired ground speed or desired application rate for a job. Below are a few calibration formulas that can be used to figure out the optimal ground speed and flow rate, as well as formulas to help calculate the time required for an operation.

Note: additional helpful formulas for calculation can be found in this simple PDF from Daniel Ess and Stephen Hawkins from Purdue University and Charles Gould and Lee Jacobs from Michigan State University.

Calculating Desired Ground Speed

Ground speed plays a big part in the application rate. The faster you go, the lower the application rate. To achieve a higher application rate, you decrease speed. The following formula will assist you in determining the preferred ground speed when the application rate is known. 

For example: An applicator uses a 35FT wide Puck Toolbar. The applicator measures a flow rate of 3,000 gallons per minute and wants to apply manure at a rate of 15,000 gallons per acre. With those three values, what would be the needed ground speed?

3,000 gpm × 495 ÷ 15,000 gpa × 35ft = 2.83 mph

Calculating Optimized Flow Rate for Maximized Time 

If you need to check to see if your current flow is meeting the target rate, you use the following formula to figure the current flow rate. If the rate does not meet the target, adjust either the ground speed or flow to reach the ideal flow rate. 

Example continued:

15,000 gpa × 3 mph × 35ft ÷ 495= 3,182 gpm

Calculating the Required Horsepower

If you know the desired output of your operation, which includes the flow and total pressure, as well as the percentage of your pump's efficiency, you can calculate the horsepower required by using the following formula.

For example: If we know we need to generate 180 PSI with a pump efficiency of 76.5%, we can use the formula to figure out the required horsepower.

3000 gpm × 180 PSI ÷ 1714 × .765 = 411 HPr

Calculating the Value of Time

When utilizing the aforementioned 495 Rule, there are three factors that you have the power to adjust; your speed, your toolbar width, and your flow rate. We will refer to this iteration of the 495 Rule as the Value of Time.

Calculating Value

After figuring out your Value of Time, the next step when quoting an operation is to find the Value. This can be done by accounting for 60 minutes in an hour and your own application rates charged to a customer.

Calculating Time Required

To estimate the time it will take to apply your liquid manure to a job site, you will need the overall value and how many gallons you know you need to pump.

If the required time is too long, try changing one of the three variables in the Value of Time formula, or adjust what you charge customers.

With these formulas, you’ll be able to better stay in line with the application requirements on a particular job and make adjustments to your drag hose systems while in the field. If you are still curious about how dragline calibrations work, or would like to go into more detail, check out our Pump School. The Puck Pump School is an in-depth, two day event that helps you understand how to make your operation more efficient and make the most money. Experienced Puck pumpers lead the class and questions are always encouraged. For upcoming Pump School classes, explore our events calendar.