By Daryle Thomas
Once you know where you are, it’s easy to get to where you want to be. And that, dear reader, is why you need to test your garden soil.
A bit of a leap? Not really. Garden soil is not just dirt. You have sand, silt, a little bit of clay, and some organic material. The percentage of each determines the type of soil.
You know that good garden soil has a certain pH, which is the acidity or alkalinity of the planting medium. Too acid, and you can only grow blueberries. If the soil is a bit alkaline, asparagus and cucumbers are happy. With a pH of 6.4, just about everything can grow well. What makes soil fertile? Minerals. The right minerals in the right proportion, is what gives your carrots incredible sweetness and a delicate crunch.
Plants need zinc and copper. They need calcium, magnesium, boron, manganese, nitrogen, potassium, iron and a handful of other treats. Cation exchange capacity determines what minerals will be available to feed the plant. Cations are positively charged ions which are held by negatively charged soil particles. Imagine an Argyle sock stuck to your backside by static cling. The sock is not part of your pants, just temporarily attached. Cations – calcium, magnesium, potassium and sodium – grab onto clays and organic matter in a similar way as static electricity does. Free hydrogen shows up and is attracted to the same clays and organic material. In doing so, the cations are freed to nourish the plant. In a similar way, a dryer sheet would make the Argyle sock fall off before you spend the day carting it around on your tail. Dryer sheet equals hydrogen. Calcium, magnesium, potassium, and sodium equal Argyle socks.
In the 1940s, Professor William Albrecht determined the format for 11 minerals, plus aluminum, free hydrogen, pH, exchange capacity and base saturation ratio. How these elements react with each other is what a soil test will tell you. When your soil test comes back from the lab, some amount of interpretation may be necessary.
How do you get your soil tested? Obtain a test kit. Garden centers sell them. I’m sure Amazon offers something. UVM has them. A call to 1-800-639-2230, Monday through Thursday from 9 a.m. to noon will get the ball rolling.
Your best bet is to call me at 802-259-2299. I keep UVM soil test kits available for nearly instant gratification. You may not need help with interpretation, so any soil test kit may do. When you get a UVM kit from me, I will help you understand the test results when they come back from the testing facility. Or answer any other questions. Free!
Fall is the best time to test your garden soil. Amend the soil as needed. Let it sleep through the winter and be ready for planting in the spring. It may take a year or more to fully balance the soil minerals. Patience! Doing so will give you the tastiest and most nutritious fruits and vegetables you can grow. And, perhaps, the admiration of a secretly jealous friend or two.
Daryle Thomas is a volunteer with the UVM Master Gardener Program