When it comes to fertilizing your lawn, it can be a bit of a science since some basic math and chemistry are involved. Monitoring the soil nutrient profile, pH level, and moisture content is part of an annual fertilizing schedule that will make for a healthier lawn.
The size of the yard is also factored into the equation of what kind and how much fertilizer is needed. Typically, the fertilizer’s product information will include the application rate and how much area the bag should cover.
There are many kinds of fertilizers with various NPK ratios, referring to the amounts of nitrogen (N), phosphorus (P), and potassium (K) in the mixture. The 19-19-19 formula is a popular all-purpose fertilizer that can be used for lawns as well as for trees, flower and vegetable gardens, grass fields, and food crops.
The numbers in the NPK positions refer to the percentage of the mixture that is the certain nutrient. 19-19-19 means 19% nitrogen, 19% phosphorus, and 19% potassium. Fertilizers also contain many other nutrients and organic matter that contribute to the soil’s profile.
How Do Plants Use 19-19-19 Fertilizer?
Different plants use fertilizer with different efficiency, which is why ratios can vary by plant type and use. Plants will absorb the 19-19-19 ratio at different rates:
- Fruits and flowers – Vegetables, fruit trees, and flowers all use phosphorus and potassium to produce fruit, seeds, and flowers, while nitrogen plays its normal role in photosynthesis.
- Trees and shrubs – Non-flowering and non-fruit trees also use phosphorus regularly to help build the roots, trunk, and branches, while nitrogen feeds the tree’s leaves.
- Lawns – Turf grasses use little to no phosphorus once they are mature, so grass fertilizers are usually high in nitrogen but low in the other two macronutrients.
- Fields and ornamentals – Pastures, like hay fields or ornamental grasses, will use more phosphorus than lawn grasses since they grow to flowering maturity.
Is 19-19-19 Fertilizer Good For Lawns?
The triple 19 ratio can be applied to mature lawns, but there are some accompanying notes to using this fertilizer balance. Regular maintenance fertilizers usually have NPK ratios with high nitrogen numbers, low potassium, and little to no phosphorus.
This is because phosphorus contributes to root growth, and turf with established roots will mostly need nitrogen to produce grass blades. For newly planted grass seeds, you should use a starter formula that is balanced for seed germination.
That being said, some grasses that spread by their roots may use some of the phosphorus put down with a triple 19 formula, including many of the warm-season grasses like Bermuda and Zoysia.
Much of the phosphorus may be leftover, however. If the soil profile isn’t monitored closely, the phosphorus may build up and make other nutrients like iron and zinc unavailable to plants, resulting in yellowing or dying off of grass blades.
Before applying 19-19-19 fertilizer, or fertilizer of any ratio, to your lawn, check the soil levels to make sure they aren’t already sufficient or too high in any nutrient. If you have a newly established lawn, the soil may be low in phosphorus and potassium after root development. In this case, the triple 19 fertilizer will replenish what was lost and provide the new grass blades with a nitrogen boost.
How Do I Calculate How Much Fertilizer I Need?
After establishing your soil’s nutrient profile and selecting a 19-19-19 fertilizer, you need to know the size of the area you’ll be fertilizing. The area of your property will be an important factor in whether you need just one or multiple bags.
To find the area of your yard, you can check your deed or any survey information you might have about the property. If you don’t have that, you can measure the yard in feet. Multiply the length times the width for the square footage of your yard. There are 43,000 square feet in an acre, and the average quarter of an acre yard is about 11,000 square feet.
This means if you have an average-sized yard, one bag of 19-19-19 should last for multiple applications. If you have several acres of lawn, you will need a few bags to be sure you get full coverage.
19-19-19 Fertilizer Application Rates
A 25-pound bag of triple 19 fertilizer will generally cover up to 2 acres depending on how thick or thin an amount is applied, using between 10 and 15 pounds per acre. For an established lawn, 19-19-19 should be used as a booster and not applied too thick.
A mature lawn usually needs between 3 and 6 pounds of nitrogen per year, and 19% of a 25 pound bag is 4.75 pounds. With even application potentially spread out over several months, a 19% nitrogen fertilizer is a significant nitrogen source for your lawn.
Dry Or Diluted Fertilizer?
The absorption rates of fertilizer will vary based on the type. Granular fertilizers can be applied dry and will dissolve into moist soil over a certain period of time. Liquid fertilizers, on the other hand, are available immediately for plants to absorb.
You can buy dry fertilizer and dilute it with water, following the ratio of one gallon per pound of dry fertilizer.