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How to Choose the Best Lawn Fertilizer

How do you choose the best lawn fertilizer when there are literally hundreds of fertilizer products to choose from?

What do the fertilizer numbers mean?

Are organic lawn fertilizers safer and more eco-friendly than chemical fertilizer? Is there a pet safe lawn fertilizer?

The ideal way to choose the best fertilizer is to start by understanding your lawn's nutrient needs and then pick a product that can supply those needs.

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Nutrients for Grass Care

  • Nitrogen is the mineral element that affects turfgrass growth and development the most. It is required in the largest amounts and fertilizer recommendations are usually based on pounds of nitrogen per 1000 ft2.

  • If you are using a complete lawn fertilizer, it should have a nitrogen-phosphorus-potassium (N-P2O5-K2O) ratio around 4-1-2 (For example 16-4-8).

  • Use a complete NPK fertilizer when planting a new lawn. Established lawns rarely need phosphorus fertilizers and should only be used when recommended by a soil test.
Grass Types, the quality of lawn desired, length of growing season and soil type are factors that influence your lawn's nutrient needs.
Spreading Lawn Fertilizer

Don't Guess, Take a Soil Test

A good place to start is by having your soil tested. A soil test is a helpful tool that will tell you the percentage of organic matter, available nutrients and the pH of your soil.  The results will include customized recommendations for your site that will help you to pick the best lawn fertilizer and soil amendments. 

It's a good idea to have your soil tested every couple of years because the only way to effectively add amendments -- for example, lime to raise pH -- is by following recommendations included in the test results.

A soil test generally costs $20 to $30 depending on the service that you use.  I recommend the Soil Testing Kit from Yard Mastery or the MySoil Kits available on Amazon.  These are professional DIY kits that combine accurate soil testing technologies with an easy to use process.  The report includes fertilizer recommendations tailored to your soil, site, and grass types and the results are available online within 6-8 days.

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You can also contact a local cooperative extension agent, they will have soil testing information and might offer soil tests at lower costs from an affiliated testing laboratory.  Your extension agent will also have recommendations that will help you choose the best lawn fertilizer for your grass type and location. These can be customized according to the lawn quality you desire.

The maintenance level of your lawn is a big factor when determining your lawns nutrient needs. What is the level of quality that you desire? A high quality lawn will require slightly more nutrient inputs than low maintenance lawns. For example, Kentucky bluegrass lawns in Northern Idaho require between two to four pounds of nitrogen per 1000 square feet a year. A high maintenance lawn will require four pounds and a low maintenance lawn only two pounds of nitrogen.

Mulching or Composting Grass Clippings

How do you manage your grass clippings? Recycled clippings add organic matter to the soil and reduce the amount of fertilizer needed.

Sometimes, just plain grass clippings are the best lawn fertilizer. Older lawns that have regularly had clippings recycled during mowing will require less nitrogen -- and no additional phosphorus -- per year.

When you have to collect them, composting grass clippings is better than sending them to the land fill.

Compost can be used to improve the soil. Compost alone is not the best lawn fertilizer because it does not contain enough nitrogen, but it adds nutrients, organic matter and beneficial microorganisms.

Chemical vs. Organic Lawn Fertilizers

It is important to understand that mineral elements are available to plants only in certain forms and your lawn does not care where it comes from. Meaning your lawn does not care if it gets nutrients from a natural organic, synthetic chemical, liquid or granular source.

For example, your lawn will only absorb and use nitrogen in the chemical form of ammonium (NH4+) and nitrate (NO3-). So if you choose to use a natural organic fertilizer, the organic nitrogen must first be converted to one of the chemical forms of nitrogen before it can be used by the grass plants.

What is the best lawn fertilizer for the environment?

Fertilizer becomes a pollutant when it is misapplied or overapplied - it does not matter if the product is natural organic or synthetic.  Take care to use fertilizers according to their labels and instructions.  Proper rate and timing is important as well as basing lawn nutrient requirements on a reliable soil test. Protect our water sources!  Avoid getting fertilizer on sidewalks, driveways and roads where it can wash into storm drains and then into streams, lakes and rivers.

Fertilizers with a slow nitrogen release rate are usually the most eco-friendly and recommended over products with quick release rates. One of the benefits of natural organic fertilizers is they release nutrients slowly as they break down. Please visit Natural Organic Lawn Care for more information.

The percentage of slow release nitrogen is usually listed as WIN (Water Insoluble Nitrogen) on fertilizer labels. Slowly-available nitrogen sources release their nitrogen over extended periods of time. They are applied less frequently, at somewhat higher rates and less likely to leach nitrogen into groundwaters.

Proper fertilizer use will enhance the growth and health of your lawn without harming the environment. On the other hand, misuse pollutes our waters and damages landscape plants.

Pet Safe Lawn Fertilizer

What's the best lawn fertilizer to use if you have pets?

It's a good idea to keep your pets off of a lawn for a couple of days after it has been fertilized with any product.

Fertilizers can make pets sick if they eat them. Fertilizers -- synthetic and organic -- are smelly and attractive to pets...especially dogs. Unless the fertilizer contains a pesticide, such as weed killer or insecticide, it will not be poisonous and in most cases a pet that eats plain fertilizer just ends up with a bad case of diarrhea.

Major problems occur when pets get into fertilizer bags and eat a lot of it. If this happens, serious digestive tract problems may develop and they need to see a veterinarian for treatment.

Keep All Fertilizers Away From Pets! Even if it is labeled as "pet safe", they might still eat it and get sick, so store it where your dog or cat can't get into it.

Sunday's plant and soil nutrient products are made from food waste, seaweed, and molasses.  The natural additives stimulate plant growth and activate soil life.

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What do the Fertilizer Numbers Mean?

The numbers printed on the bag are called the fertilizer analysis.

The Fertilizer Analysis is the concentration of nutrients by percent. It is always printed prominently on the the product label. The analysis is printed in a three number sequence indicating the amounts of N - P - K (Nitrogen - Phosphorus - Potassium).

For example, an NPK Fertilizer labeled as 23-3-6, indicates 23% Nitrogen, Phosphorus equivalent to 3% P2O5, and Potassium equivalent to 6% K2O.

Choosing The Best Fertilizer Based on Cost Per Unit of Nutrient

Fertilizer costs per pound of nitrogen is an important factor to consider when shopping for the best lawn fertilizer.

Comparing two products - Product A and Product B: Your lawn is 15,000 ft2 and you want to apply 1 pound of nitrogen per 1,000 ft2. You are looking at two products, both are sold in 50lb bags and are priced at $20 a bag.

Product A: a natural organic fertilizer labeled 6-1-2 has 3 lbs of nitrogen per 50 lb bag. One bag of this product would fertilize 3,000 ft2 at your rate of 1 lb nitrogen per 1000 ft2. You will need five bags of this product and it will cost $100 to fertilize your lawn. Note: the actual cost of nitrogen is $6.67 per pound.

Product B: a manufactured synthetic product labeled 30-10-20 has 15 lbs nitrogen per 50lb bag. One bag will cover 15,000 ft2 and it will cost you $20 to fertilize your lawn. Note: the actual cost of nitrogen is $1.33 per pound.

Comparing the two products based on cost of actual nitrogen - since we know that plants do not care where the nutrients come from - Product B is the best lawn fertilizer. Product B is the better deal!

Use this fertilizer calculator to determine the cost per pound of nitrogen in a bag of fertilizer.

Lawn Fertilizer Calculator

Cost of Nitrogen Calculator

Calibrate Your Spreader

Drop spreaders are a good choice for homeowners with small lawns. They are very precise, perfect for small lawns and easy to calibrate. Click to learn how to calibrate your drop spreader.

Use this fertilizer calculator to determine how many pounds of fertilizer is needed to cover your lawn according to recommended rates. 


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