There are so many choices at the stores these days, credit or debit, paper or plastic, and trying to select the best lawn fertilizer for your lawn. But how does it work? What will work best on your lawn? What do those numbers mean?
Our Guide To The Best Lawn Fertilizers
Let’s start by taking a look at what your lawn needs in the way of nutrients:
Macronutrients are the building blocks of plant life, the things that are needed in large quantity to keep a plant growing. Some are available through the air and water the plant is exposed to. The primary nutrients make up most multi-nutrient fertilizer formulas and are referred to in the field as NPK (Nitrogen, Phosphorus, Potassium). The secondary nutrients are often available from limestone applied to adjust soil pH, from polluted air or from household sources.
- Hydrogen – freely available from water
- Carbon – freely available from the air
- Oxygen – freely available from water and the air
- Nitrogen – a primary nutrient used in large quantities
- Phosphorus – a primary nutrient used in large quantities
- Calcium – a secondary nutrient, often received from quick lime or ground limestone
- Magnesium – a secondary nutrient, received from Epsom salts or dolomitic limestone
- Sulfur – a secondary nutrient, received from the air (sulfur dioxide, an air pollutant) or Epsom salts
These are elements needed in smaller quantities, though they can be just as important to plant development and growth. They are usually available in the soil, but if you have problematic growth, dead spots, yellowing or similar issues, it may be caused by a micronutrient deficiency.:
You can use general estimates of how much fertilizer to put on your lawn as a rule of thumb, but for the best lawn fertilizer, you’re going to need to do a soil test. Home tests are available from most garden centers, but are not terribly accurate. For not much more money, your best bet is a professional soil test from your county extension office.
Why is it important to have a quality soil test performed? If your soil has a high capacity to hold nutrients and you put a “rule of thumb” amount of fertilizer on, there can be unintended results. Excess nitrogen causes plants to grow not only very strong stems and leaves, but also a weak root system that can wash out during heavy rains or not provide sufficient water during drought, leaving your lawn barren. On the other side, if your soil can’t hold the nutrients you’re adding as a rule of thumb, the excess fertilizer can wash off into ponds and lakes, fertilizing algae and causing an algae bloom that can kill aquatic plants and fish.
A good soil test will also show what your soil pH is. High or low pH can limit how much of a nutrient is available for plants. A good range to try to stay in is from 6.0 to 7.0, slightly on the acidic side. You can alkalize (raise) the pH by adding quicklime or crushed limestone, or you can acidify (lower) it by adding sulfur. Both of these products are commonly available at farm stores and garden centers.
Fertilizer Lables and Calculations
Now that you know what your needs are, it’s time to pick the best lawn fertilizer! Most fertilizers have three numbers on the label, which refer in order to the percentage of each nutrient is in the bag. As an example, here’s what would be in a 50 pound bag of 8-4-16:
- 8% nitrogen x 50 pounds = 4 pounds of nitrogen per bag
- 4% phosphorus x 50 pounds = 2 pounds of phosphorus per bag
- 16% potassium x 50 pounds = 8 pounds of potassium per bag
Since 4+2+8=14 pounds, you may be wondering what the other 36 pounds has in it. Fertilizers have to use a form of the nutrient that the plant is able to take up, which it can’t do in a straight elemental form. The nutrients found in fertilizers have oxygen, carbon and other elements mixed in so the plant can put it to work. Lawns typically do best with a mixture that has no more than 10% of nitrogen or phosphorus, and no more than 24% potassium.
So now you know what mix you need; what forms does it come in? Some fertilizers can be watered in, which is helpful when you need a quick fix. For a long-term, more gradual change in your lawn, you may want to try slow-release pellets.