Oklahoma State University Turfgrass Science


May turf management tips


Justin Quetone Moss


Homeowners often wonder how long they should irrigate their lawns, but the volume of applied irrigation water cannot be directly measured in units of time.  However, one can estimate how much irrigation water is applied to their lawn over time by following a few simple steps.

  1. Purchase a few short, plastic rain gauges from a local lawn and garden retail store.
  2. Strategically place the rain gauges approximately at turfgrass mowing height throughout the irrigated turfgrass areas in the lawn.
  3. Early in the morning, irrigate the lawn for exactly 20 minutes on a relatively non-windy day.
  4. After irrigating for 20 minutes, measure the volume of water in each rain gauge and calculate the average volume over 20 minutes, then multiply by 3 to calculate the average volume over one hour.
  5. Move the rain gauges to different areas/zones of the lawn and repeat the process as needed.
  6. After completing this process, you will have a very good estimate of average irrigation output in inches per hour for your lawn.

 Assume you complete this process and determine that your irrigation system delivers 0.5 inches of water per hour.  Assuming you water three times per week for 20 minutes, then your weekly irrigation output would be 0.5 inches of water per week.  For more information about lawn irrigation scheduling, visit the Oklahoma Mesonet SIP website at http://sip.mesonet.org/.  Now that you know the output of your irrigation system, you can use the SIP website to determine the daily and weekly irrigation requirements for your lawn.  In addition, many companies now have “smart” lawn irrigation controllers that have automatic rain “shut-off” sensors and capabilities to connect to local weather stations to help you determine your lawn irrigation needs.  For further information, contact your local OSU Cooperative Extension Service Office.




Justin Quetone Moss


Proper fertilizer spreader calibration and application is important for producing a healthy lawn and to reduce potential environmental impact by fertilizer misapplication. Non-calibration and misapplication of lawn fertilizers may result in applying too much or not enough nutrients to the turfgrass area. Even when properly calibrated, misapplication of fertilizers can result in unsightly lawn areas (Figure 1).  Although it is advised to conduct a complete fertilizer spreader calibration, the following tip can help homeowners properly apply fertilizer to turfgrass lawn areas without having to worry about weighing out fertilizers, measuring out test sites, or asking the nearest college or high school student for a mathematics refresher.

  1.  The first step is to conduct a soil test of the lawn by contacting your local OSU Cooperative Extension Educator and/or following the guidelines in OSU Cooperative Extension Fact Sheet PSS-2207 and PSS-2225.
  2. After completing the soil test, the simplest option for homeowners is to purchase a rotary fertilizer spreader (Figure 2) made by their favorite or preferred manufacturer A drop spreaders can be more precise and accurate than a rotary but may result in uneven application if not careful (Figure 1).
  3. Fertilizers have three numbers on the front of a bag which represent the percentage of nitrogen, phosphorus (phosphate), and potassium (potash).  The next step is to purchase the same brand of lawn fertilizer (made by the same manufacturer as the spreader), preferably with a “0” in the middle number which means 0% phosphorus. Only apply phosphorus to the lawn according to soil test results and recommendations as excessive phosphorus has the potential to runoff and degrade water quality.
  4. After purchasing the same brand of fertilizer spreader and fertilizer, read the fertilizer bag to find the proper fertilizer spreader setting for that particular fertilizer formulation. Most often, spreaders have a dial with numbers or letters corresponding to the width of the opening in the bottom of the fertilizer spreader. For instance, often a spreader setting of “1” will output a small amount of fertilizer while a spreader setting of “10” will output a larger amount of fertilizer.  Since you have a fertilizer bag and a fertilizer spreader made by the same manufacturer, by using the recommended spreader setting, you should be able to apply the proper amount of fertilizer to the lawn area.
  5. Note that the walking speed should be normal (1-2 MPH) and even during application of the fertilizer and that the fertilizer spreader should be closed when coming to a complete stop. Also the fertilizer spreader should only be opened after coming up to a normal walking speed.
  6. Lastly, make note of the distance that the spreader is throwing the fertilizer to the side (typically about 5 ft depending on product and spreader type) and make subsequent passes across the yard accordingly.

For a more detailed explanation of fertilizer calibration, contact your local OSU Cooperative Extension Office.  



Figure 1. Example of uneven fertilizer distribution with a drop spreader.




Figure 2. Example of a rotary fertilizer spreader.

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