Soil Knowledge and Testing to Support Healthier Home Gardens

Many Minnesotans (including yours truly) are eager to get into the garden and grow their own feast (but hold on, frost may still be coming!), so it seemed like a good time to talk soil with Master Gardener Sarah Green Toews. She shared with me her knowledge about soil, and how a simple soil test can make a world of difference in your garden.

Gardeners are just as guilty as anyone else of being distracted by shiny objects. When the catalogs arrive, we start to select our seeds, and as we gaze at photos of giant sunflowers and heirloom tomatoes, we forget all about the bug bites, dirty knees, and weeding that awaits us. One of the most overlooked and least shiny components in our backyard vegetable gardens is the soil. It’s messy and mysterious. It gets dragged throughout the house, and has a habit of sticking to everything. But it’s crucial in plant development, and should be given some serious attention.

Why is Soil Important?
Soil gives your plants the nutrients they need to grow. Taking care of your soil will help your plants stay healthy, which could mean a better crop of goodies from your garden. Taking care of your soil means you can cut down on excess fertilizer, which can be bad news for the environment. University of Minnesota Master Gardener Sarah Green Toews shared some basic information with me about how we can build better soils for our gardens at home. 

Toews directed me to a soils guide on the University of Minnesota Extension website, where I read a summary of important soil nutrients by some researchers in the Department of Soil, Water, and Climate: “Optimum growth of turf, flowers, fruits, and vegetables depends on many management factors, one of which is ensuring a sufficient supply of plant nutrients. There are at least 17 essential elements required for plant growth: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, zinc, copper, boron, molybdenum, chlorine, and nickel. Plants obtain carbon, hydrogen, and oxygen from air and water. The remaining elements are derived from the soil. When the soil cannot supply the amount of these nutrients required for adequate growth, supplemental fertilizer applications become necessary. Many urban soils are disturbed during the construction process. Top soil is often scraped off and removed and, as a result, nutrient and organic matter levels are often lower in these disturbed sites than in native soils. Adding organic matter as well as fertilizer may be necessary to improve the growth of plants on these sites.”

Toews said the first thing to do when planning your garden is to have your soil tested, because soil health plays a big role in plant health. Soil tests will let you know if your soil has a sufficient supply of nutrients, and they can also look for not-so-nice elements, such as lead (from lead paint that chipped off your garage). 

How Do I Take a Soil Test?
Towes recommends using the University of Minnesota Soil Testing Laboratory to test your garden soil. They provide routine soil testing and fertilizer recommendations to homeowners. Conducting the test basically involves you heading out to your garden to collect five samples of soil from throughout the garden plot. You mix those five samples together to create a composite sample, and label the composite sample with your name, address, and a sample ID. Once you’ve done that, you fill out this form, and then mail your sample(s) and a check for fees to the lab. You can also drop it off, but they recommend mailing due to traffic congestion. The test takes three-to-five days, so plan a couple weeks in advance in order to collect the sample, send it in for testing, and get the results.

If you’ve never tested your soil, or haven’t done so for more than three years, now’s the time. Soil tests can be taken throughout the year, but this week makes sense, since the soil isn’t covered with snow, and you still have time to amend your soil before you put your plants in the ground.