| [Image: Selecting a Fertilizer] |
| [Image: Selecting a Fertilizer] |
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You will need a product that fulfills what’s lacking in your soil, supplies nitrogen and is right for your type of grass. Some soils may be too acid for good growth and nutrient availability; an acid soil will need lime. A soil test every few years will determine the nutrient status of your soil and any lime requirement. Contact your LSU AgCenter local county agent and ask about a routine soil nutrient analysis for your lawn. Without a soil test, you must assume you have a moderate level of nutrients, and this may not be correct.
When selecting fertilizer, look at the three numbers on the bag. They will read something like 15-0-15 or 16-2-8. The first number represents the percentage of nitrogen in the bag, the second refers to phosphorus, and the third number refers to potassium. For example, a 50 pound bag of 16-2-8 is 16 percent nitrogen, or eight pounds of nitrogen; two percent phosphate (P2O5), or one pound; and eight percent potash (K2O), or four pounds. The remaining weight is usually composed of inert ingredients. Nitrogen and phosphates cause the most problems with regard to water pollution. An average balanced turf fertilizer will have a high first number, low second number and a mid-strength third number. Some centipedegrass fertilizers will have little or no phosphate.
What fertilizer is safest to buy?
Look for slow-release fertilizers, or fertilizers that have a high percentage of slow-release nitrogen in them. These products have less potential than quick-release, water-soluble sources to leach or run off into Louisiana’s waterways. Nitrogen promotes shoot growth, so if you use slow-release nitrogen, you’ll have less growth surge. In lawns, that means less thatch accumulation and disease following fertilizer application — which ultimately means less work.
What indicates if a fertilizer is slow-release?
Look at the fertilizer sources listed on the back of the bag and find the amount of nitrogen that is water-insoluble or slow-release. This slow-release N is also listed as water-insoluble, WIN, controlled-release or slowly available. Not all the N will be slowly soluble. Urea, ammonium nitrate and ammonium sulfate are water-soluble nitrogen forms and give a quick, short-term green-up. With a blend of soluble and insoluble N, you will get some immediate greening and sustained feeding for five or six weeks. This feature is especially important in spring when soils are cool and growth is sluggish. The higher the percentage of slow-release, the less chance of leaching — and less thatch and mowing!
What is the right amount of phosphorus and potassium to look for?
A soil test is necessary to determine if you need to apply phosphorous and potassium. Contact your parish extension office to get a soil test form and learn how to take one. If you have ample phosphorus in your soil, look for a fertilizer with no more than two percent phosphorus (the second number). As for potassium, look for a fertilizer with about half as much potassium as nitrogen (16-2-8) or equal amounts of nitrogen and potassium (15-0-15), depending on the results of your soil test.
What is the right amount of fertilizer to apply?
How much to apply depends on three things:
1. Your desired level of maintenance.
2. The amount of nitrogen in the bag.
3. The percentage of nitrogen that is slow-release. To get the maximum points based on LYN guidelines outlined in The Louisiana Yardstick Workbook, apply the lowest of the fertilizer ranges recommended by the LSU AgCenter. Understand that at times an under-fertilized lawn may be less pest- or disease-resistant and unable to perform as well in preventing erosion. On the other hand, lawns receiving more fertilizer than recommended by LYN guidelines generally require more mowing and additional irrigation and may develop more pest problems. Regardless of the level of maintenance you desire, adhere to the following guidelines.
• Apply fertilizers to a dry lawn, and then lightly water it in.
• If in doubt, apply less fertilizer at any one time and reapply a little sooner. Regardless of the total nitrogen applied over a year, even at high maintenance levels, it is the amount of nitrogen applied at any one time, the type of nitrogen and the proper application and watering-in or rain that have the greatest effect on the potential for creating pollution.
What is the right way to apply fertilizer?
Follow these simple steps:
Step 1. Determine the annual fertility needs of your grass species by referring to Table 1.
Step 2. Measure the square footage of your lawn area. Do not include landscape plants in this area calculation.
Step 3. Determine how much slow-release nitrogen is in your fertilizer.
Table 1. Fertilization Guidelines for Established Turfgrass Lawns in Two Regions of Louisiana. (Nitrogen recommendations -- lb N/1,000 sq ft/year)*
| Species |
North |
South |
| Bermudagrass |
3-4 |
4-5 |
| Carpetgrass |
0-1 |
1 |
| Centipedegrass |
1 |
1-2 |
| St. Augustine grass |
3 |
3-4 |
| Zoysia |
2 |
2-3 |
Step 4. Refer to Table 2 to find out how much fertilizer to apply to your lawn area based on the percentage of nitrogen in your fertilizer product. These figures are based on one-half pound of N fertilizer per 1,000 square feet. If you are using one pound of N, double these amounts to apply one pound nitrogen per 1,000 square feet.
Step 5. Apply the fertilizer over the lawn with a drop spreader for most accuracy.
One of the main steps you can do to prevent pollution is to use caution when applying fertilizers.
• A drop spreader application is more precise and even than a rotary spreader. This allows superior control of granule dispersement. Read operational instructions carefully.
• Calibrate all spreaders to get an accurate delivery of fertilizer. The fertilizer bag may have a suggested opening setting for a particular model spreader. If using this number, try one notch less until you calibrate the spreader; you can come back a little sooner with the next application if spread too lightly, but you can’t take back an over-application.
• Fill spreaders on pavement where spills can be swept up. After prescribed application, remove extra granules from the spreader and return them to a proper container. Fill and clean liquid applicators and wash spreaders over turf where spills and water would be absorbed and not washed into the street.
• Do not spread fertilizer onto water bodies or impervious surfaces, such as driveways or sidewalks. Shut off the spreader when passing over hardscape walks or bare ground or when making a sharp turn. Particles on hard surfaces can wind up in waterways. Blow, sweep or wash sidewalk granules back into the lawn.
• Be careful using “weed-and-feed” products that contain herbicides and fertilizer together. These products can injure some trees and shrubs. Tree and shrub root systems can extend far beyond the visible foliage, intermingling with turf. In addition, pesticides should be applied only to affected areas, rather than broadcast over the entire yard as occurs with weed-and-feed products.
• Do not fertilize if heavy rain is forecast. This increases the potential for fertilizers to run off into storm drains or to leach through soil with the rainwater.
• In fall, when turf is slowly growing, apply an iron source instead of a nitrogen fertilizer to green the lawn without increasing growth. Use chelated iron or iron sulfate.
How do I water in fertilizer?
Most fertilizers need to be watered in to move fertilizer just below the soil surface to grass roots. This process requires only about ¼ inch of irrigation water. Do not over-water, or you will increase the potential to move fertilizer into the street or through the root zone and into groundwater. Follow the recommendations of your local LSU AgCenter parish extension office when fertilizing lawns.
Herbicide: a chemical that kills plants or inhibits their growth; typically intended for weed control.
Chelate: a complex organic molecule that surrounds certain trace elements, such as iron, and keeps them dissolved in a solution.