Usually three trials at a given setting are enough to obtain a reliable application rate. Weigh the material and record the information on each trial run for future use. One of the calibrated settings will approximate the correct rate of material. Since the area for calibration trials in only 100 square feet, apply one-tenth of 10 pounds or one pound of fertilizer per 100 square feet. The spreader setting should be 11 for this example if you obtain the following results shown in Table 1 from your calibration trials with your spreader.
Careful calibration is suggested for the complete spreader range.
Settings are not necessarily linear, therefore, half of a particular application rate may not necessarily be obtained by using a setting number half the original. The same calibration procedure is used for any material you want to apply. Since the quantity applied depends upon the physical properties of the material, the same settings cannot be used for different materials, even if the ratios are the same. Once the spreader is calibrated and set for the proper rate, any size area can be treated accurately. Example of calibration trial results from No. 7.