As most of you are probably already familiar with, the University of Connecticut is home to the UConn Soil Nutrient Analysis Laboratory. This lab is staffed by Dawn Pettinelli, the manager, and myself, the technician. We also have a few part time and student employees throughout the year that help with the receiving, spreading, and sieving of soil samples; among other things. We offer an array of tests designed to help homeowners, community gardeners, farmers, etc… maximize the efficiency of their soil to produce the greatest yields in whatever plant or crop they are growing, from silage corn to turf. We can test for soil organic matter content, textural fractionation, soluble salts, Nitrogen, and Carbon. We also provide tests for plant tissues and corn stalks. However, our most vital and popular test is the Standard Nutrient Analysis. This is a relatively comprehensive test that allows us to make limestone and fertilizer recommendations. We check the pH, add a buffering agent and then retest the pH. From there we are able to determine the soils capacity to resist the change in pH, this allows us to make an accurate and precise limestone recommendation, in lbs/1000 square feet, or lbs/acre, depending on the desired crop production. The second part of the Standard Nutrient Analysis is the actual nutrient content. Soil samples are analyzed for micro and macro nutrients; Potassium, Calcium, Phosphorus, Magnesium, Aluminum, Boron, Copper, Iron, Manganese, Zinc, and Sulfur. Samples are also screened for Lead. Using the nutrient results, we are able to make fertilizer recommendations based on what is being grown. We give results in N-P-K format, and also provide organic alternatives.

We get calls year round from customers asking if they can submit a soil sample, and the answer is always yes! You can submit a soil sample any time of the year, we receive soils from throughout the country (although we have to be careful of areas under certain quarantines). Generally, it only takes around a week from when we receive a sample for us to send out the results. As you might imagine, Spring is an extreme exception. We are so busy and backed up with thousands of soil samples right now, we are expecting a 3 week turn-around time. We understand that everyone is eager to get their hands dirty and work on their lawns and gardens, but waiting until Spring to submit soil samples isn’t the best idea.


The current line of samples waiting for analysis. J.Croze

We often recommend that customers take and submit soil samples in the Fall! Soil sampling and testing in the Fall is better for all parties involved. For starters, we offer a discount on the Standard Nutrient Analysis, if you submit 10 or more samples we only charge you $8 per sample opposed to $12. However, there are more practical reasons to submit a Fall soil sample. It’s easier! The soil is generally going to be easier to work with in the Fall than after a wet Winter during the first few weeks of Spring. This will help you obtain soil samples that are a more accurate representation of the area you are interested in. Every year around this time we get dozens of zip-lock bags that are filled with soaking wet soil, dripping everywhere. A Fall soil test also allows you more time to think about what amendments you might want to use, and is the perfect time to apply limestone and fertilizers in preparation for a busy and productive growing season. Applying limestone in the Fall ensures that it has enough time to raise your soil pH to whatever the optimum range is for what you plan on growing. My personal favorite reason for submitting a Fall soil sample is that we are less busy! You’ll be happier because your results will only take a few days, and we’ll be happier because the phone won’t be ringing off the hook with customers wondering where their results are! You can obviously submit a sample whenever your heart desires, but I advise you to consider sampling in the Fall. For those of you currently waiting on results, I appreciate your patience! Happy gardening!


The UConn Soil Nutrient Analysis Lab tests for and analyzes multiple soil parameters; but none as critical, and as often overlooked, as pH. Soil pH plays a crucial role in the growth of vegetation planted, as well as ground water quality. Before we start talking about soil pH, I think it is a good idea to try to define what exactly pH is, and how it is determined.

When most of us think of pH, a pool probably comes to mind. I remember growing up, watching my mother apply different chemicals to our pool, and impatiently wondering why I had to wait to go swimming. She would tell me that she was adjusting the pH of the water to ensure it was safe to swim in. The basic understanding is that pH is tells us how acidic, neutral, or alkaline something is. To get a little more technical, pH is the measurement of the activity of Hydrogen Ions (H+) in an aqueous solution. The equation for determining and quantifying pH is:

pH = -log10 (aH+)

(aH+ = Hydrogen Ion Activity in Moles/L)

We express pH on a logarithmic scale of 0-14, where 0-6 is considered “acidic”, 7 is “neutral”, and 8-14 is “basic”.

pH range

(Image from:

Mineral soil pH values generally range from 3.0 – 10.0. There are numerous factors that determine soil pH including climate, parent material, weathering, relief, and time. Texture and organic matter content also influence soil pH. Most Connecticut soils are naturally acidic. Nutrient availability is directly influenced by pH with most plants (with some exceptions) thriving at pH values between 6 and 7. A majority of nutrients are available within this range.

pH vs nut avail-1

(Image from:

Our lab measures pH using an 1:1 soil-to-DI water ratio. The saturated soil paste is mixed, then is analyzed using a glass electrode and a pH meter. We calibrate our meter using 2 solutions with known pH values, 4 and 7. We use these values because we expect most Connecticut soils to fall within this range. Once the initial pH value is obtained, a buffering agent is added. In our lab we use the Modified Mehlich Buffer. A second pH reading is obtained, and from these two values plus crop information, we are able to make limestone and/or sulfur recommendations.

The Buffering Capacity of a soil is the resistance it has to change in pH. Soil buffering is controlled by its Cation-Exchange-Capacity, Aluminum content (in acidic soils), organic matter content, and texture. A soil with a lot of organic matter and clay will have a higher buffering capacity than one with little organic matter that is mostly sandy.

If the soil pH is lower than the target range for a particular plant, limestone would be recommended. Whether you use pelletized, ground or granular limestone, the application rate would be the same. Once the target pH is reached, a maintenance application of 50 lbs/1000 sq ft would be applied every other year to maintain it.

If the soil pH is higher than desired, sulfur recommendations are made. Typically only powdered sulfur is available locally but granular sulfur could be mail ordered. Aluminum sulfate can be substituted for sulfur and used at a higher rate. Check out this list of preferred pH ranges for many common plants.

Monitoring your soil pH is essential to ensure that it is falling within the range best suited for the vegetation you are growing. The Standard Nutrient Analysis performed at our lab gives you a pH value, a buffer pH value, a lime/sulfur recommendation, available micro & macro nutrient levels, and a fertilizer recommendation. For more information on pH, you can contact Dawn or myself (Joe) at the UConn Soil Nutrient Analysis Lab (!

Test, don’t guess!

Joe C.



Bag of Lime

Many Connecticut residents spread limestone on their garden beds and lawn as an annual ritual. Why do we do this? Some do it because their parents did it, or the guy at the garden center told them to and sold them the limestone. How much should be purchased and applied is another mystery to most. The real answers of limestone’s why, how much and when lies in the science of soil.

Soil is made up of sand, silt, and clay. The percentage of each of these three determine the soil’s texture, which will determine how the water will move through it, or hold on to moisture. More clay equals wetter soils; more sand, better drainage. The sand, silt and clay are tiny pieces of rock, broken off of bigger pieces over much time by weathering. The rocks that makes up much of Connecticut has a naturally low pH in the 4.5 to 5.5 range. Other areas of the country and world have different rocks with different pH ranges. Acid rain falling onto the ground lowers pH levels, as does the action of organic matter decomposing which produces organic acids. Even the normal function of respiration by plants mixing oxygen and water together produces carbonic acid in the soil. More acid equals lower pH. No wonder why we need to test, monitor and fight the natural tendency of our soil to stay in a low pH range.

Most plants we want to grow require a pH range of 6 to 7. This means we have to change the pH to grow plants like grass, tomatoes, peppers, squash or garlic by adding limestone which raises the pH level. The only plants consistently happy with our native range are native plants! They have evolved in the local soil. This is why blueberries, oak trees and mountain laurel fill our forests and wild areas. Pines are another tree preferring our lower pH.

Why do the grass and vegetables prefer the 6 to 7 pH range? Because more of the nutrients that these species of plants need are available when the soil pH is in that range. The easiest way to think of pH is it is a measurement of the amount of hydrogen ions in the soil. The more hydrogen ions, the more acidic the soil is. The pH of the soil affects the availability of all plant nutrients. Just as plants have ideal moisture and light requirements, they have a preferred pH range as well.

The pH range numbers 0 to 14. The middle is neutral at 7. Pure water has a pH of 7. 0 is acid or bitter; 14 is alkaline or sweet. Old time farmers used to taste the soil to determine if it was bitter (acid, low) or sweet (high, alkaline). I am glad we have pH meters and laboratory soil testing equipment now!

0_________________________________________7_____________________________________14 Acid (Bitter)                                                                           Neutral                                                                  Alkaline (Sweet)

Soil pH levels also affect other life in the soil such as insects, worms, fungi and bacteria. The soil is alive with more than just plants. It is an entire ecosystem sustaining many life forms all interacting with each other. The pH level is probably the most important place to start when trying to provide the best environment for whatever plants you are growing.

Have your soil tested for pH and nutrient levels at the UConn Soil Nutrient Laboratory Have the $12.00 basic test for Home Grounds and Landscapers done. Forms and directions are on the website. We will be offering free pH only tests at the CT Flower Show February 23-26, 2017. A half cup of soil is needed. If you don’t have snow covering your ground now, go gather some soil now and hold it until the show. Once you know the pH of your soil, we can tell you how much limestone to apply in the spring. Fall is the best time to put down lime as it needs about six months to fully react and change the soil pH. Never put limestone down on frozen or snow-covered soil to avoid it running off to areas you didn’t intend to lime, like the storm drain. Limestone will not soak into frozen soil.


pH Meter

-Carol Quish