Spreader Calibration Improves Fertilizer Applications (5-2-11)

Poor application of fertilizer can cause strange patterns of growth in lawns. Streaking or burning is quite common when fertilizer is applied by hand or with spreaders that do not distribute the fertilizer evenly.

Most spreaders come with instructions or charts for calibration, but fertilizer formulations differ in nutrient analysis and particle size so care should be taken to be sure you are applying fertilizers not only evenly but also at the recommended rates.

A simple way to calibrate a spreader is to weigh out a small amount of fertilizer prior to putting it in the spreader, make a pass or two and then measure (in square feet) the area covered. Weigh again the remaining fertilizer left in the spreader and subtract this amount from the original weight to give you the amount actually applied to the measured square footage. Using this ratio you can determine the amount being applied per 1,000 square feet or amount per acre.

Open or close the spreader opening to release more or less fertilizer and repeat this process until the spreader disperses the amount of fertilizer you desire. It is good practice to apply only one-half of the desired amount of fertilizer in one pass, then move over one-half the distance of the spreader’s throw width and apply the remaining recommended fertilizer.

Different particle sizes, particularly of blended fertilizers, will then be distributed more uniformly. This will help avoid streaking and will allow an opportunity to readjust the spreader if needed to increase or decrease the rate.

Fertilizers are corrosive, so it is important to thoroughly flush the spreader with plenty of water and dry it soon after use to prevent rust and corrosion.

The foliage of the turf should be dry when applying fertilizer to prevent wheel tracking from the spreader and potential leaf burn from fertilizer particles sticking to the leaves. Watering immediately after applying fertilizer will help dissolve the fertilizer particles and move the nutrients into the soil to the roots.

Published May 2, 2011

Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. wwells@ext.msstate.edu