The 7-Step Soil Improvement Plan

If your garden doesn't seem the same lately, your soil might be suffering. Here's how to give it a kick-start.

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Gardeners know they need to weed, water, and prune for a healthy, vibrant garden. What they might forget, says Gary Heilig, horticulture educator at Michigan State University Extension, is some soil TLC.

"When we grow something in the soil and harvest it, we're always taking nutrients out," he says. The changes may be imperceptible initially, but eventually you'll find your plants are smaller, more susceptible to problems, and maybe discolored and misshapen. If your garden goes downhill and other problems like pests aren't too blame, you could have poor soil quality. Keep your soil healthy and fertile with this seven-step soil-improvement plan.

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1. Get Your Soil Tested

This is nonnegotiable: Get a soil test to find out its nutrient levels. Check with your local extension office, which probably offers testing services. There are also private companies that offering soil testing. You'll get know the status of what Heilig calls the big three—nitrogen, phosphorus, and potassium—as well as the pH level of the soil and possibly the organic-matter levels.

2. ID Your Soil Type

Soil consists of a mixture of sand, silt, and clay particles, along with organic matter. As part of the soil test, Heilig says, have a soil-texture test run to show what you're dealing with.

Or, try this quick test: Rub some soil in your hands, and if it's sandy, you'll feel the sand particles. If it's heavy clay, it will feel very slippery when wet because clay particles are the smallest. Heavy clay soil also is slower to drain and takes longer to warm up and dry off in the spring. Silty soil is usually found on land near water that may have flooded and left the silt sediment.

The preferred soil, says Heilig, is a sandy (but not too sandy) loam—it's easier to work with and drains quickly.

3. Soil Adjustment

It takes a while to change the texture of your soil, but it is possible. Heilig advises working 6 to 8 inches of organic matter, such as leaves, into the soil. Spread leaves on your garden, use your lawnmower to chop them up, and then spread liquid nitrogen on top to speed up the decomposition process. Let this sit for about a month, then turn it into the soil. The earthworms will do the rest. (Ideally, you want to do this in the fall before it gets cold.)

4. Choose the Right Fertilizer

"Every time you harvest something out of your garden, it's like making a withdrawal from your soil, like a withdrawal from the bank," Heilig says. "If you want to have a healthy situation at the bank, you have to make some deposits too. It's the same thing in the garden. You need to put something back if you want to keep the soil healthy."

This is why a soil test is important—so you can choose the fertilizer with the correct ratio of nutrients. "What you need to do is put it down in the amounts you need and not apply stuff that you don't need," Heilig says. For instance, nitrogen often has to be added. Find a fertilizer with the correct phosphorus and potassium ratio and add nitrogen separately.

5. Choose Between Organic and Conventional Fertilizer

Organic will do more for the soil overall, and some types, such as manure, also add valuable fungi that help improve the till and water-holding capacity. The downside: It's more expensive, and you'll need to apply more.

Conventional fertilizers are cheaper and easier to apply, but you won't get the same soil-building benefits. You can mix organic and conventional. One example: If you need to up potassium levels, use potassium sulfate or potassium, then revert to organic.

"You need to look at things in a holistic way," Heilig says. "There are about 16 nutrients that plants need, and the majority of fertilizers only give you about three or four." The best way to get the remainder is by composting. A simple method: Dig a hole in your garden about 16 inches deep and throw in your kitchen scraps. Cover it, and let the earthworms do their thing. You can do this in several areas of your garden where the soil needs help, both before you plant in the spring and after garden season.

6. Choose Between Liquid and Granular

Liquid fertilizer is valuable for its secondary benefits and extra micronutrients. However, because it's diluted with water, you'll need to apply it more often—around every two weeks.

With granular fertilizer, you'll need only about two applications, but you won't get the extra nutrients. Before you plant, put down all of phosphorus, potassium, and two-thirds of the nitrogen, and till into the soil. Put the remaining one-third of the nitrogen six to eight weeks after the garden is growing.

7. Choose Plants for Your Soil

Particularly for ornamentals, selecting plants that grow well in your soil will save you time and work. This is another job for your local extension office, which ought to have a list. Native plants are always a good idea, as they're acclimatized to your area.

If you have poor-quality topsoil, heavy clay content, and a lot of rocks, some root crops, such as carrots, will be tricky. You can select varieties with shorter roots, and some of the many varietals that grow well in poor soil, such as these carrots and cabbage.

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