When Dawn Pettinelli was a little girl, she would trail her grandmother around her garden, marveling at the beautiful flowers she grew. But aside from planting seeds and searching for worms, she thought little about the soil that nourished those flowers. That changed when she took her first soils course in college. “I was bowled over by the complexity and intricacies of the soil ecosystem upon which all life is based,” she says. Today, the head of the University of Connecticut’s Soil Nutrient Analysis Laboratory (who has been a part of the lab for more than 22 years) “never takes soils for granted and tries to encourage folks to take a second look at the world beneath their feet.” In the interest of getting our spring flowers to look as pretty as, well, Pettinelli’s grandma’s (we like to aim high!), we asked Pettinelli to get down and dirty about just what we need to do to strengthen our own soil.
Your website says that a mere handful of soil can contain more than a billion microorganisms. What are we talking about here?
Without these microbes, our soils would be inert and incapable of supporting life. All of the organisms found in the soil are part of the soil food web. These organisms, like bacteria and fungi that you can’t see without a microscope, along with larger ones, like sowbugs and earthworms, are responsible for making the soil suitable for plant growth. They do this by providing nutrients to plants, aggregating the soil so water and air can move through it, decomposing organic matter and controlling pathogenic and disease-causing organisms, among other functions.
Is there one way to describe Connecticut soil as a whole?
The best description would be that soils in Connecticut are “variable,” because just about all of them were affected by the glacier that covered most of New England 15,000 years ago. In general, though, our native soils are predominantly acidic, sandy, rocky and low in organic matter and phosphorus. Our native plants have adapted to them. However, many people want to grow vegetables, flowers and lawns, and these species are not necessarily native, so we need to modify our soils by adding limestone or fertilizers to make them more amenable.
Why get a soil nutrient analysis done?
Soil testing is just another gardener’s tool. With the right tools, gardening is easier and your plants grow better. Since you can’t tell what the pH and nutrients are in the soil just by looking at it or feeling it, a soil test will let you know if your pH and nutrient levels are adequate or if you need to add something for better plant growth. Folks spend a lot of time and money on their plants, and when soil conditions are right for them, plants do best.
What exactly will the analysis tell us?
Our standard nutrient analysis provides the soil pH level, major plant nutrients (including calcium, magnesium, potassium and phosphorus), micronutrient levels and a lead scan. If the soil lead level is elevated (almost 20 percent of the samples we receive from Connecticut are) appropriate interpretation will be included with your results. As long as we know what folks are growing, we can also make limestone and fertilizer recommendations, if needed.
What are the key nutrients we should be focusing on?
The big three are nitrogen, phosphorus and potassium (NPK). These elements are contained in complete fertilizers. Nitrogen is for green, leafy growth, phosphorus promotes root growth and fruiting/flowering and potassium is an overall stress-buster.
How many soil samples does the lab process in an average year?
We usually process 10,000 soils per year with the majority of the samples coming in the spring. That is when we are the busiest and process up to 500 samples per week. As you can imagine, that does create a backlog and it takes longer to get results. We encourage people to send in their samples in the fall, which is a great time to soil test. Not only will you get your results back faster, if you need to amend your soil by adding limestone (to raise the pH) or sulfur (to lower the pH) you can do that in the fall, and since it takes six to 12 months to change the pH, your garden will be in better shape for planting come spring.
So are we talking “one and done,” i.e., just one soil analysis per yard?
To figure out how many soil samples to send in, decide whether or not your soils look different or if they have been treated differently in regard to how much fertilizer, limestone and/or other amendments have been added. For instance, if you have done nothing to your lawn but added compost and fertilizer to the veggie garden, you would sample these two areas separately. Sometimes if you have the same plant in two different locations and one is doing well and the other poorly and no obvious insect or disease problems are seen, you might want to have the soil tested as a comparison.
What other tests does the lab have available for home gardeners?
The standard nutrient analysis is a great test for about 95 percent of those seeking to have their soil tested. Other tests that are offered include a textural analysis, which determines the amount of sand, silt and clay in soils and puts them into a USDA Soil Textural Classification; percent organic matter (ideal would be between 4 and 8 percent for gardens); and soluble salts (to see if you’ve been a bit too heavy-handed with the fertilizer or in early spring to see if road salts have seeped into your plantings).
How does UConn’s analysis differ from at-home kits or those done at different labs?
You can also send soil samples to Agricultural Experiment Station labs in New Haven and Windsor, which use the “Morgan Soil Test.” (In fact, the “Morgan,” the world’s first widely accepted method for quickly estimating soil fertility, was devised by the New Haven station’s own Dr. M.F. Morgan in 1933.) Our test, a more complex variation of the original Morgan, is similar to those being done at both the universities of Massachusetts and Maine. We differ from home tests because our tests and interpretation are specific to the types of soils in our area. (The home tests can give you an average value but, since they are sold nationwide, the interpretation is not specific to one particular region of the country.) We also run our tests on analytical equipment using known calibration standards and quality controls.
We’ve got our results; now what? Do we make all the suggested amendments now?
As long as we know what you are growing, we can make limestone and/or fertilizer recommendations if they are needed. In the fall, you would add limestone (or sulfur to lower pH), but not add any fertilizer. The plants are ending their growing season, so fertilizer would be added in the spring before planting. If you added it now, most of the nitrogen and potassium would be leached out over the winter and you would have to reapply. In the spring, you would follow all instructions.
Get down to earth
To send samples to UConn’s Soil Nutrient Analysis Lab, head to soiltest.uconn.edu, print the sample questionnaire and fill in your name and mailing and/or email address, depending on how you’d like to receive results. You will then need to list the origins of each sample, i.e. front lawn, veggie garden, strawberry patch, pick from the list of crop codes or simply list the specific plants growing in the particular soil sample(s) for which you’d like recommendations. The cost for a standard nutrient analysis is $12 per sample; checks should be made payable to the University of Connecticut.
To collect a sample, use a spade, trowel or bulb planter to collect cores or thin slices of soil from six to 10 random, evenly distributed spots in your sample area to the appropriate depth — Pettinelli recommends from the top to about 3 to 4 inches down for grass, 6 to 8 inches down for flowers, vegetables and small fruits, and 8 to 10 inches down for trees and shrubs. Put these in a clean container, mix thoroughly and then remove one cup. Transfer to a zippered plastic bag and send, along with your questionnaire and check, to: UConn Soil Nutrient Analysis Lab, 6 Sherman Place, U5102, Storrs, CT 06269.