Page 202 - Nutrient Management Planning Guide

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Calibrating Manure Application Equipment

Using Calibration Results to Plan Manure Applications

Calibrating will provide an application rate that was achieved when travelling at a constant speed and equipment settings. Altering the travel speed of the spreader according to the relationship below will change the application rate:

Desired Application Rate

= Calibration Test Speed × Calibration Application Rate ÷ Target Speed

This equation can be rearranged to yield the target speed to achieve the desired application rate:

Target Speed

= Calibration Test Speed × Calibration Application Rate ÷ Desired Application Rate

If applying solid manure, a correction must be made for differences in density between the manure to be applied versus the manure used during the calibration:

Corrected Target Speed

= (Calibration Test Speed × Calibration Application Rate × Present Manure Density) ÷ (Desired Application Rate × Calibration Manure Density)

Calculating Ground Speed to Achieve a Target Application Rate

A calibrated solid spreader was found to apply manure with a density of 923 kg/m 3 , at a rate of 12.5 t/ha when traveling at a speed of 4 km/h. The target application rate for a field is 9 t/ha. The travel speed necessary to apply manure with a density of 794 kg/m 3 at a rate of 9 t/ha using the calibrated setting for this applicator is:

Corrected Target Speed (km/h)

= (4 km/h × 12.5 t/ha × 794 kg/m 3 ) ÷ (9 t/ha × 923 kg/m 3 )

= (39,700) ÷ (8,307)

= 4.8 km/h is the approximate corrected target speed

Developing Calibration Graphs

Spreaders with multiple settings (e.g., PTO-driven) offer the advantage of being able to achieve multiple application rates through variable setting and ground speed combinations to accommodate field conditions. Considerable time can be saved in the future by developing calibration “curves” for each of the settings on the spreader. To do so, use the following procedure:

Use either the load-area or weight-area method to 1.

determine the application rate at a low and high speed for a specific setting (if applicable). Record the density of manure used during the calibration (for solid manure), the setting (e.g., PTO speed) and the travel speed of the spreader. On a piece of graph paper, plot the application rate 2.

for the setting at low and high speeds on a graph with application rate on the vertical axis and speed on the horizontal axis (Figure 4.6.4).