It is time to fertilize your fescue lawn! If you plan to do the job yourself, take the time to calibrate your fertilizer spreader first. It doesn’t take a long time, and it could save you money while helping the environment.

Calibrating a Fertilizer Spreader

By Michelle Wallace

There are several reasons to take the time to calibrate your fertilizer spreader before applying fertilizer: economics, environment, and plant health. Fertilizer prices are high. The cost to produce fertilizer is directly related to the cost of natural gas, so when natural gas prices are high so are fertilizer prices. It therefore makes economical sense to make sure the equipment you use to spread fertilizer is properly calibrated so that you don’t waste money and spread more than you need. From an environmental perspective, excess nitrogen fertilizer leaches into the watershed affecting the limited drinking water supply and potentially creating algae blooms downstream. The over application of fertilizer can be detrimental to plants. Fertilizer is a salt. Excessive salts in the soil can cause fertilizer burn. Too much salt causes reverse osmosis to occur in plants. Water instead of being taken up by the plants, is drawn back from the plant and into the soil. Ever swallow salt water at the beach? That’s a good way to get dehydrated. The end result is death for the plant. Conversely, the under application of fertilizer will affect plant health and vitality. Calibrating a fertilizer spreader is the process of measuring and adjusting the application equipment in order to make it more accurate.

There are two common types of fertilizer spreaders: rotary spreaders and drop spreaders. The different spreader types require a slightly different method of testing calibration. There are several methods to choose from to calibrate your spreader: Pan Method, Sweep and Weigh Method, Catch Pan Method. Regardless of the method you choose all require that you weigh out the material collected in grams and divide that weight by (spreader width x distance traveled) then multiply that number by 1000 to get grams material per 1,000 sq.ft. The equation is below:

Grams Material per 1000 sq. ft = 1,000 x Grams Material Collected

Spreader width x distance traveled

Fertilizer spreaders are used for multiple applications including spreading of seeds, lime, and pesticides. Prior to calibrating your spreader make sure that it is clean and in good working order. When using the spreader make sure the distribution lever is closed before filling the hopper. Don’t overfill the hopper and make sure the filter is in place. Push the spreader as close to the calibrated speed as possible and only open the spreader lever after you have begun walking, closing it before you stop. Walk in straight lines keeping the impeller level.

Since you may find one method easier than another method you can find a complete explanation and examples by going to http://www.turffiles.ncsu.edu/PDFFiles/004613/AG628CalibrationofTurfgrassBoomSprayersandSpreaders.pdf or requesting a printed copy of WQWM-152 Water Quality and Sprayer and Spreader Calibration.

For more information on Gardening contact the Durham Extension Master Gardeners at 919-560-0528 or email mastergardener@dconc.gov