In most of our area, April 1-15 is the time when most everyone begins fertilizing lawns. A good way to know when to fertilize is to wait until you have mowed the predominant turf grass twice. If you fertilize too early, you will be fertilizing the winter weeds! It is always a good idea to have your soil tested so that you do not over apply nutrients on your lawn and you know exactly what fertilizer to purchase. The next step would be to base your fertilizer applications on the soil test report and split the annual nitrogen (N) requirement into 1 lb increments. (Never apply more than 1 lb. of N at a time.) If you do not have a current soil test and need to make your applications most warm season turf grasses respond best to a 3-1-2 or 4-1-2 ratio fertilizer at 6-8 week intervals during the growing season. Apply about half a pound to one pound of actual nitrogen per 1000 sq. ft. at each fertilization interval. This means that if you buy a 16-4-8 (4-1-2 ratio) then you would apply about 6 pounds of fertilizer per 1000 sq. ft. A fertilizer calculator can be found on the Aggie Turf website at http://aggieturf.tamu.edu. Click on “Turf Answers 4 You” and you will find the fertilizer calculator that will help you determine how much fertilizer to apply based upon the ratio of the fertilizer you have purchased.
If rain is not expected within 2-3 days after you apply fertilizer then you need to water your lawn. You can use a slow release N fertilizers which will work well will last longer and help prevent N runoff and leaching. Slow release fertilizers are also excellent fertilizers for shrubs and trees. There are also several organic fertilizers on the market that can be used as well as compost. However, if you choose to use compost make sure it is a finely-screened well-composted mixture so that it can spread evenly and does not have an odor. Continue to monitor soil nutrients with a soil test when utilizing organics as well. Organics can be over applied just as easily as synthetics and an oversupply of nutrients can lead to problems with our turf.
Regardless of how well you fertilize and how well you manage weeds mowing is the most important step in quality turf grass. I have seen people do more to improve their lawns with mowing than I have with either fertilizer or water. Mowing at the proper height and often enough makes a turf thicker and even more drought tolerant and it sure helps control weeds. Bermudagrass should be mowed to 1.5 inches and St. Augustine should be mowed at 2.5 inches. When the grasses have added 1/3 of their height we would mow again. Mowing even more frequently than that is better, just remember to never take off more than 1/3 of the blade at a time. The more you mow (at least once every 5 days) when grass is actively growing will increase your turf density tremendously and help choke out weeds.
Whit Weems is an Erath County extension agent. His column appears weekly and online at yourstephenvilletx.com.