Soil Testing for the Home Gardener
Why should I test my soil?
Soil testing takes the guesswork out of keeping your soil in optimum condition for plant growth and development. Soil testing is inexpensive when compared to investments in your plants, amendments, time, and effort.
A basic soil test assesses the levels of major plant nutrients, soil pH, and micronutrients in your garden. Based on that, you get recommendations about the amounts of limestone, fertilizer or compost, and other amendments you should add to your soil to best meet your plants’ needs.
What does the soil test measure?
For many home gardeners, the Standard Nutrient Analysis is probably all that’s needed. It measures plant available calcium, magnesium, phosphorus, potassium, iron, manganese, copper, zinc, aluminum and boron; soil pH; estimated total lead; estimated soil textural class, and amount of soil organic matter.
You can also go beyond available plant nutrients and look at the quantity and balance of microbial life, such as bacteria, fungi, and protozoa. When you hear people talking about the soil food web, these tiny critters are a big part of it. Some are beneficial – they help to build healthy soil and support healthy plant life. Others are pathogens – they cause a range of problems, such as root rot, blight, mold, and mildew.
What areas of my garden should I test?
For home gardeners, you should test soil in lawns, as well as beds with fruits and vegetables, flowers, and/or woody ornamentals. Generally, you should test areas separately if you believe they will be different. For example, your lawn may have been treated quite differently than the vegetable garden and so should be sampled separately.
When/how often should I test my soil?
Fall is a good time to collect soil samples, especially if you suspect a soil pH problem. This will give any amendments time to affect soil pH and fertility over the winter so they will be at or close to target levels by spring. However, soil samples can be collected any time of year that the ground is not frozen. Many people collect their soil samples in the early spring before planting. Be aware, however, that some reported nutrient measures could be low in the early spring simply because microbial activity isn’t yet underway and so the nutrients haven’t yet been ‘released’.
Soil testing should be done about every three years to monitor soil pH and fertility levels. However, if a large correction in soil pH or fertility is called for by the initial soil test, it is a good idea to retest your soil one year after amendments or fertilizer additions to see if the situation has been corrected.
How do I know what kind of soil I have?
Soil can come in many different types, from sandy to clay or loam, or a combination of these (for example, sandy loam).
It’s easy to find out what kind of soil you have by performing a simple “jar test”. You can find instructions in this easy-to-follow how-to article from Horticulture magazine.
You can also find some really interesting information about the “health” of soil in your state and what’s being done to improve it. Check out this clickable map from the USDA.
How do I test the soil?
Soil Sampling Tools – You can collect soil samples using a shovel or spade, a soil sampling tube, or a soil auger. Tubes and augers should be stainless steel or chrome plated. A wooden rod will be helpful for removing soil from a sampling tube. If using a shovel or spade, make sure it’s clean and rust-free.
Amount of Soil Needed – You’ll need to collect enough soil for the lab to run the necessary tests – usually about 1 to 1 ½ cups. Many labs will send you a special bag in which to place your soil sample; just fill the bag to the marked line.
How to Collect Soil Samples – Each soil sample consists of small amounts of soil collected from a specified area. For example, if you’re testing the lawn, you’ll take small samples of soil from 10 to 20 random spots across the lawn. If you’re using a sampling tube or auger, simply withdraw as many core samples as you need. With a spade or shovel, dig a V-shaped hole to sampling depth and then remove a thin slice from one side. In all cases, remove vegetative matter from the surface before you sample.
You will be able to affect only about the top 6 inches of soil by adding amendments. For that reason, it’s best to take your soil samples from the top 6″ only.
As you remove the soil samples, mix them together in a clean container. Because soil will vary in color, texture, and consistency throughout the garden, soil testing is usually done on a ‘composite’ sample. If you’re using a pail to collect the soil, it should be plastic to avoid contamination from any trace metals. For example, soil will pick up zinc from a galvanized pail.
Remove 1 to 1 ½ cups of mixed soil from the container and place it in the sampling bag.
And that’s it – soil sample collected!
Where do I get my soil tested?
There are many soil testing companies found in the Yellow Pages or online. However, for most homeowners, the local Cooperative Extension offices provide all of the analyses needed, and at a very reasonable cost.
Cooperative Extension Offices – The Cooperative Extension offices of most state universities provide an excellent and affordable soil testing service. Most provide both testing and recommendations for adding fertilizer or amendments. Here are links to the soil testing services for state universities across the country. In cases where the university doesn’t provide soil testing, there’s information about alternative options that they recommend. You’ll find a lot of useful information on these pages!
- See our state-by-state list of Soil Testing Labs associated with Cooperative Extension offices.
Commercial Labs – You may prefer to get your soil tested at an independent lab. Prices are often comparable to those offered through the Cooperative Extension offices and these labs may also offer additional tests, such as for pesticide or herbicide residue, nematode analysis, and plant tissue analysis. Bear in mind that many of these labs are focused on agricultural soil testing so be sure to use the right form when submitting your samples (i.e., a form for home gardeners). Some of the labs we recommend are:
- Waypoint Analytical (formerly A&L Laboratories)
- Logan Labs
- Earthfort (for soil food web analyses)
- Woods End Laboratories (for soil food web analyses)
How do I submit a soil sample?
Complete instructions are found on the websites of the various Cooperative Extension offices or commercial labs. Generally, the lab will provide a bag in which you will submit the sample. Some labs will even provide the shipping labels and boxes. Be sure to complete the order form with all the correct information. The lab will need to know what you’re growing in the area being tested (e.g., flowers, lawn, specific crops) so that they can provide accurate fertilizer and amendment recommendations.
How much does soil testing cost?
A basic soil test (e.g., Standard Nutrient Analysis) performed through a Cooperative Extension office generally costs around $10.00. Commercial labs are comparable for a basic soil analysis. Additional tests will add to the cost. Commercial soil food web analyses are in the $50 to $75 range.
How soon will I receive my soil testing results?
The typical turn-around-time for soil testing results is 3 to 4 business days from time of sample receipt except during April and May when it may take 1 to 2 weeks due to heavy sample load. Check with your local provider before sending in your soil sample, as times may vary.
Last update on 2021-01-17 / Affiliate links / Images from Amazon Product Advertising API