This article appears in Spring Home & Garden 2018 magazine.
Any seasoned gardener knows that soil matters for healthier produce, lawns and plants. Even novice gardeners can tell how good soil is simply by looking at and feeling it.
Most homes don’t have perfect soil, and soil conditions can change year to year. Doing simple tests before planting can help growers evaluate what they’ve got to work with.
“Most people without a science background can learn enough about their soil to grow a successful garden,” said Clay Robinson, associate professor of soil science, Department of Agriculture, Illinois State University. “Many are surprised at the things they learn when I teach a one- to two-hour lesson on soils, nutrients and water at local meetings and for Master Gardeners because sometimes the common lore does not jibe with science. The observation is correct, but the science of why it happens often gets misinterpreted.”
Know your soil
When it comes to soil, one of the first things to keep in mind is organic matter, which is a source of plant nutrients and energy for soil organisms. Organic matter acts like a sponge for holding water in the soil, said Nick Comerford, a soil scientist at the University of Florida.
“Soils with more organic matter are more fertile; they have more nutrients available,” Robinson said.
Generally speaking, the darker the soil, the more organic, Robinson said. Xeriscape- or drought-tolerant plants are a special case because they “evolved in environments with low organic matter, soil water and soil fertility. Some of these plants do not do well in soils with a lot of organic matter,” Robinson said.
Grab a handful of soil and smell it. Good soil should smell “like the fresh smell after a rain. A bad soil smells like rotten eggs — it is waterlogged, has bad drainage, and oxygen is limiting in the root zone, which will make it difficult for most plants to grow,” Robinson said.
Now, crumble the handful of soil between your fingers. Depending on where you live, soil texture is different because of its composition of sand, silt and clay particles.
“Whatever the texture, though, small clumps (composed of many individual particles) that break with little pressure between the thumb and forefinger are ideal. For some clay soils, this may not achievable because the clumps are too hard. And very sandy soils may not form clumps at all,” Robinson said.
Right way to dig
Now that you’re on friendly terms with your soil, it may be time to plant as long as the soil is not too wet or if it has rained recently.
“Do not dig/plant in a soil that is very wet. This can destroy soil structure, and may waterlog/drown some roots,” Robinson said.
There is actually a right way to dig a hole for planting, whether you’re transplanting a six-pack of flowers or a 5-gallon shrub, Robinson said.
— When digging a hole, do not pat the sides. Compacted soil is unhealthy for plants and plant microbes, which “are what mobilize nutrients for our plants, help decay mulches, etc. So, work carefully with your soil to protect your plants and your microbes,” said Susan Fisk, Master Gardener and spokeswoman for the Soil and Science Society of America.
— Use a small garden spade or trowel to rough up the sides so that you can see the cracks or soil pores where the roots can grow, Robinson said.
— Dig the hole about twice the diameter of the pot and 8 to 16 inches deep, depending on size of the plant. For plants in 1- to 5-gallon pots, dig a hole about one-and-a-half to two times the size of the pot and up to three times the width, Robinson said.
— Most plants benefit from the addition of compost, which improves water retention and provides energy and nutrients to improve soil and plant health. If you want to fertilize, now’s the time.
— Finally, add the plant and gently firm the soil around the plant roots, but avoid using too much pressure and compacting the soil.