Soil

Greetings readers. After a short winter hiatus, I am back and eager to sink my hands in the earth and get growing.

Though some of us began starting seeds indoors in January or February, I consider the true start of the growing season to be the last frost date. This date is determined using historical climate data and your garden’s location. The Farmer’s Almanac is a reliable resource for finding your last frost date. Although this date does not guarantee frost-free days ahead, I use it as a benchmark for when the soil may be worked, spring amendments added and early seeds sunk.

The last frost date in our growing zone is predicted to be May 1. With this date as a guide, a grower starts the season’s growing journey with thoughts of soil preparation. So let’s take a short (yet deep) dive into the medium that makes growing possible.

What is soil?

Soil is the top layer of the earth’s crust. It’s composed of organic matter, minerals, gases, liquids and organisms. Soil supports life, thanks to a magical balance of ingredients, and we depend on it for our survival.

Deep, established soil has five layers. The topmost layer is organic matter such as grass, trees, flowers, vegetables, etc. The second, or surface layer, is made up of some live, but mostly broken-down organic matter and small mineral particles. The surface layer is often dark brown or black, and its texture is fairly soft and crumbly, which allows the roots of plants to penetrate and absorb nutrients.

Next comes the subsoil. Subsoil is lighter in color and is composed of sand, silt or clay. Its texture is more dense than the surface layer, a result of less organic matter and fewer live organisms crawling through it creating air pockets and tunnels. Dig a little further and your shovel will really start to ring as it hits the rocky substratum layer, composed of parent rock (another term for rocks of varying sizes which have broken away from the bedrock layer beneath them). Finally, there is bedrock which is just as it sounds, a bed of solid, unweathered rock.

Types of soil

There are four primary types of soil: sand, silt, loam and clay. Soil types are determined mainly by the size and percentage of the particles in them. Compound soils are composed of larger amounts of one particle or another. Ex: Loamy sand, sandy clay, silty clay, and so on. Soil may also be classified by its color, which provides a clue to the minerals it contains or the percentage of organic matter, clay or other particles.

Loamy soil is the preferred soil type for growing a wide variety of fruits and vegetables. It provides a well-balanced diet of nutrients and minerals with an adequate amount of water, thanks to its mixture of clay, sand, silt, organic matter and air. Tiny roots can spread and grow in the spaces or ‘pores’ between soil particles. These pores also allow loamy soil to hold water and air.

What type of soil do I have?

Determining your soil type is easy. Pull a golf ball-sized sample of soil from two to three inches deep in your growing area. The sample should not be drenched in water, so wait until two or three days after a rain to perform this test. Next, pinch the soil between your fingers and gradually roll the soil into a ball. If the soil is dry and crumbly, add enough water to moisten it. If the soil balls up easily and stays in a tight ball, you have clay soil. If the soil won’t form a ball or falls apart at the slightest touch, you have sandy soil. If the soil forms a ball that barely keeps its shape and is easily pulled apart, you have loamy soil.

Take this test a step further by rubbing a small amount of soil into your palm. Soil with a high percentage of clay will leave a solid streak. Sandy soil will crumble easily and feel gritty while leaving little to no mark on your palm. Loamy soil will mark your palm lightly and you will feel some grit.

Finally, take a moment to observe your growing area. What thrives there? Loamy soil can support a wide range of plants while sandy or clay soil supports a narrower range of species. Observe the soil’s color. Loamy soil often has a dark, rich color. Poor soils are often lighter in color, and you may see evidence of sand on the surface or a tight, flat crust, which signifies a high percentage of clay or silt.

The key is to get up in there and get familiar with the texture, color, feel and even smell of your soil. This accomplished, you are ready to move on to the next step, soil building/amending.

Building/Amending Soil

Let’s say you discover an abundance of sand in your soil. Not to worry. Sand is actually tiny particles of rock that allow water and air to move freely though soil. However, a lot of sand renders soil unable to hold water for very long, and thirsty crops will suffer as a result. This is where compost comes in. Compost is organic matter that has been broken down by living organisms like worms, nematodes and tiny microorganisms such as bacteria. All these little beings digest food scraps, grass clippings, leaves and tiny particles of rocks and minerals to create a more stable form of carbon, which we call compost.

For sandy soil, heap about three inches of compost on top of your growing area. Then, gently fork the compost into the soil, walking backward to avoid soil compaction. Finish by top dressing with another inch or two of compost. Cover with a mulch of leaves or straw.

Clay soil is very tight and sticky. Adding sand and compost will really help to loosen it. Just like sandy soil, start by topping the soil with a few inches of compost. Spread enough sand over the compost to just cover it and work both in, walking backwards. Repeat this process until you start to see smaller clumps of clay. Be sure to top with compost and mulch when you are done working the soil.

Loamy soil benefits from a compost treatment once or twice a season. The beneficial microbes it contains act like a serving of yogurt, re-establishing the gut of your soil, which helps your plants uptake nutrients more efficiently.

What if I’m buying soil and growing in pots?

Choose a bagged soil that is all natural and organic. The last thing you want is unwanted chemicals or additives leaching into the plants you will later consume. You don’t need to spend a fortune. Look for potting soil, which is made to hold water and not compact easily. Some potting soil has compost already in the mix, but adding a few cups of fresh compost will only help to enliven your soil and allow it work more efficiently.

One final tip before you sink your seeds or starts: Find a tree that looks hale and hearty. Dig a hole near its base, about six inches deep, and grab a few handfuls of the luscious rich soil you find there. Add this to your potting mix for a boost of fertility and microorganisms.

That’s it for this go around, readers. Don’t forget to send in your questions, and, by all means, get out there and experiment. Growing is a process of discovery. We learn a lot from our successes, but even more from our failures.

This article was published in the March/April 2023 print edition of Katonah Connect.

Artwork by Carol Bouyoucos.