LSU AgCenter Horticulturist
Fertilizing lawns in most of Louisiana is best done in early to mid-April. At that time our warm-season lawn grasses have begun active growth and established a strong root system and are ready for the extra nutrients fertilizer provides.
In many situations fertilizing your lawn is optional. If your lawn has generally been healthy and attractive over the years with only occasional fertilization, you may choose to leave well enough alone this year.
Lawns that should definitely be considered for fertilization are those that have sustained some damage in the past and need new growth to fill in bare spots, those that are thin or are poor in vigor and those whose owners desire a high degree of quality.
Research shows that in March our turfgrasses undergo what experts call “spring root decline.” At that time, much of the old root system dies and the plants grow new roots. So, during March, turfgrasses don’t have substantial root systems even though the grass blades are beginning to grow.
If fertilizer is applied during this time, it can stimulate the grass to put its efforts into early leafy growth when it needs to be growing roots.
What type of fertilizer should you use? There is no one “best” fertilizer; just about any commercial lawn fertilizer would do a good job fertilizing your grass. Check the label of whatever fertilizer you buy and make sure that one-third to one-half of the nitrogen is slow-release for extended feeding.
The ratio of a fertilizer’s analysis – the three numbers on a fertilizer package that tell you the percentages of nitrogen, phosphate (phosphorus) and potash (potassium) in that order – is found by dividing each number in the analysis by the smallest number of the analysis.
A fertilizer with an analysis that has about a 3:1:2 ratio, such as 15-5-10 would work fine. Fertilizers with similar analysis such as 16-4-8, 12-4-8 or 19-5-9 also would be suitable.
Most fertilizers formulated specifically for lawns, such as 18-0-18, or high-nitrogen fertilizers, such as 27-3-3, will produce good results with turfgrass but may not be as suitable for general landscape use.
It’s a good idea to apply fertilizer to a lawn that has been recently mowed. It is best to use a fertilizer applicator to get even coverage.
Remember that fertilizing turfgrass is something we do to increase the quality and vigor of our lawns and is not a matter of life and death. One additional application in July will be adequate.
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