Spring is here, which means your TV and social media feeds are probably filled with lawn care ads hawking fertilizer, weed killers, and the like, often with the promise of golf course quality results. I don’t have anything against these products, and in fact, I use them in my own yard.
Here’s the thing, though: spreading nutrients and other additives onto your lawn is pointless if you don’t know the underlying soil conditions — kind of like taking medicine before getting an accurate diagnosis from the doctor. That’s why my first, and most important, tip to anyone looking to improve their lawn this season is to do a soil test.
What is a soil test?
A soil test is a method for determining two key factors: the relative acidity of the soil (known as “pH”) and the level of essential nutrients present, including phosphorus and potassium. The results of a soil test are critical for preparing the soil at the start of the growing season and figuring out how much, if any, fertilizer to apply.
Without this information, many homeowners end up overfertilizing their lawns, which harms the root system by stimulating excessive plant growth. “What soil testing does well is tell you what you don’t need to add, saving you money and protecting local waterways from runoff,” explains Frank Rossi, associate professor of horticulture at Cornell University’s School of Integrative Plant Science. That’s because excess fertilizer from the lawn can run off into surface waters during storms or leach into groundwater.
What is the right way to get your soil tested?
While DIY soil tests are available at home centers and online, they tend to be inaccurate. That’s why our lawn experts in Good Housekeeping’s Home Improvement & Outdoor Lab recommend sending soil to your local cooperative extension, which are operated by land-grant schools throughout the U.S. (as a New York resident, my local is the Cornell Cooperative Extension).To find the nearest extension to your home, go to the website of the U.S. Department of Agriculture Extension Service.
How does the soil test work?
Soil tests can be done at any time. After completing the online submission form and paying the small fee (usually around $10), you’ll receive cardboard soil sample boxes from the extension, or instructions on where to find them in your area.
The ideal tool for collecting samples is a core soil sampler probe, though a standard garden trowel will do the trick. Take 8 to 10 samples from random locations across the lawn and garden, digging down about 4 inches. Avoid wet soil, which can damage the cardboard box during shipping. Mix and break up the samples in a plastic bucket, fill each box to the designated line, and label them with their respective section of the yard (front lawn, back lawn, garden, etc.). Then ship them off to the extension.
How to read your soil report
You should receive the results of your soil test within a couple of weeks. Though the details will vary from region to region (and even from yard to yard), the following information is typically included:
- Soil pH: This indicates the acidity of your soil. Soil with a low pH is too acidic for healthy lawns and plants. Adding lime to the soil will balance its acidity; the report will provide guidance on how much to apply, ideally using a mechanical spreader, which you can buy or rent at the home center. If you have high alkaline soil, the report will call for adding elemental sulfur; it can also be applied in pellet form with a mechanical spreader. Spring is the perfect time for both applications, since frequent rains will help with the absorption of whichever soil amendment you’re putting down.
- Phosphorus Index (P-I) and Potassium Index (K-I): These two results will tell you what kind of fertilizer is needed to bring your soil into nutritional balance. Fertilizer recommendations are given as pounds per 1,000 square feet of lawn. If the P-I and K-I levels are found to be adequate, a nitrogen-only fertilizer will be recommended. If the levels are off, a mixed fertilizer will be recommended. Every bag of fertilizer lists a N-P-K number, short for Nitrogen, Phosphorus, and Potassium. For example, a 50-pound bag with an N-P-K of 10-20-10 contains 10% nitrogen, 20% phosphorous, and 10% potassium, with the remainder being filler or inert material.
All those numbers and percentages might seem confusing, but soil test reports provide clear instructions, and you can always contact the extension with any follow-up questions.
Other spring lawn care essentials
“A soil test is a smart tool, but it’s not a magic wand,” says Rossi. While giving your soil the nutrients it needs is the first step towards maintaining a lush, healthy lawn, here are a few extra measures that will help bring about that result.
- Aerate and dethatch: Over the course of the year, the soil in your yard can become compacted and covered with a dense layer of living and dead plant material, known as thatch. These two tasks will allow vital water and air to reach the root system. Dethatching can be done with a rake if you have a small yard. For large lawns, it’s worth renting or buying a mechanical dethatcher, which looks and functions much like a walk-behind lawn mower. A core aerator, available for rent from home centers, is a walk-behind piece of equipment with a studded drum that pulls small plugs of soil from the ground.
- Reseed Bare Spots: Nature abhors a vacuum, the saying goes. When it comes to bare spots in the lawn, crabgrass and other invasive weeds will quickly take over. Putting down turfgrass seed (or “overseeding,” to use the technical term) in early spring will fill the spots with fresh lawn before the weeds have a chance to move in.
- Sharpen Your Mower Blade: Never start the season with a dull blade, since it will create ragged cuts that not only look bad, but also expose the grass to pests and disease just when it’s coming back after the dormant winter. Our experts recommend sharpening the blade a few times throughout the season, so it’s good to have a second blade for when the first one is in the shop getting a fresh edge.
Having written thousands of product reviews and how-to articles on all aspects of home ownership, from routine maintenance to major renovations, Dan (he/him) brings more than 20 years of industry experience to his role as the director of the Home Improvement & Outdoor Lab at the Good Housekeeping Institute. A one-time roofer and a serial remodeler, Dan can often be found keeping house at his restored Brooklyn brownstone, where he lives with his wife and kids.
