Calibration of Fertilization for Home Lawns

Below is fill-out information for calibration of a drop spreader or rotary spreader. 

Print this page to complete the calibration. 

1. Measure the distance between the outside holes of the spreader: ____________ in. 

2. Convert this to feet by dividing by 12: ___________ feet

3. Measure off a convenient distance to run the spreader: __________ foot

   • The longer the distance, the more accurate the calibration  

4. Multiply the number in step 2 by the number in step 3 to calculate the area covered by the spreader: _______ square foot

5. Weigh a portion of the product and put into the spreader: ________lbs. 

6. Run the spreader over the area previously measured in step 3, being careful to shut the spreader on and off precisely at the beginning and end of the course. 

7. Weigh the amount of product left in the spreader: __________ lbs. 

8. Subtract the number in step 7 from the number in step 5. This is the amount of product applied to the area that you have measured: ___________ lbs. 

9. Divide the number in step 8 by the number in step 4 to give lbs. of product per square foot: _________ lbs/ square foot

10. Multiply the number in step 9 by 1000 to give lbs. product per 1000 square feet: __________ lbs./1000 sq. ft. 

11. Is the number close to the recommended rate listed on the bag? Adjust the spreader setting and repeat the process until the spreader is applying the recommended rate listed on the bag. 

1. Measure the width of the effective pattern of the spreader: This is simply the distance from the center of the spreader to the edge of one side of the pattern: _______ feet

2. Measure off a convenient distance to run the spreader. The longer the distance, the more accurate the calibration: _______ ft 

3. Multiply the number in step 1 by the number in step 2 to calculate the area covered by the spreader: ________ sq. ft. 

4. Weigh a portion of the product and duplicate into spreader: ______ lb. 

5. Push the spreader over the area previously measured in step 3, being careful to shut the spreader on and off precisely at the beginning and end of the course.

6. Weigh the amount of product left in the spreader: ________ lb.

7. Subtract the number in step 6 from the number in step 4. This is the amount of product applied to the area you have measured: _______ lb. 

8. Divide the number in step 7 by the number in step 3 to give lb. product per square foot: _______ lbs./ sq. ft. 

9. Multiply the number in step 8 by 1000 to give lb. product/1000 sq ft: ________ lbs./ 1000 sq. ft. 

10. Is this number close to the recommended rate listed on the bag? Adjust the spreader setting and repeat the process until the spreader is applying the recommended rate listed on the bag.