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 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 and fertilizer you should add to your soil to best meet your plants’ needs.
What does the soil test measure?
For 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.
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 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. Here in Fairfield County, the Soil Nutrient Analysis Laboratory at UConn is a good option.
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 on the east coast (just because that’s where I live, not because there aren’t similar services in other states!).
CT – University of Connecticut - Soil Testing Program
NY - Cornell University Cooperative Extension (listed by County)
RI – University of Rhode Island Soil Testing Program (in conjunction with UMass)
MA – University of Massachusetts Soil Testing Program
NJ - Rutgers University Cooperative Extension Office Soil Test Program
PA - Penn State Soil Testing Services
MD – University of Maryland Co-Op Ext Soil Testing Services
DE - University of Deleware Soil Testing Program
VA - Virginia Cooperative Extension Soil Testing Services
NC – North Carolina Department of Agriculture - Soil Testing Services
SC - Clemson University Cooperative Extension - Soil Testing
GA - University of Georgia Cooperative Extension - Soil Testing
FL - University of Florida Cooperative Extension - Soil Testing Services
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 I recommend are:
A&L Laboratories
Woods End Laboratories
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?
The University of Connecticut Soil Nutrient Analysis Laboratory (SNAL) provides Standard Nutrient Analysis for only $8.00. Commercial labs are comparable for a basic soil analysis. Additional tests will add to the cost.
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.
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