Photo Credit: Brendan Riley on Flickr
Many of us inherit gardens and yards that consist of lifeless or hardpan soil unfit for growing edibles. Good quality soil is essential for an abundant garden and reducing the incidence of pests. While there are many ways to improve soil quality for the purpose of growing food, these are the seven methods that have been the most successful for me.
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Improving Soil Tilth
Tilth refers to the physical condition of soil–how suitable it is for planting crops. Healthy soil with good tilth will include lots of organic matter. It will be well-aerated and well-drained, but retain enough moisture to feel like a wrung-out sponge.
To revive lifeless soil, we will aim to improve its tilth.
7 Ways to Improve Soil Quality
1: Create Permanent Garden Beds and Pathways
One rule that I learned early in my garden training is to never step in garden beds. Stepping on garden soil compacts it, which destroys tilth, beneficial soil organisms, and their habitat. Establish permanent beds and walkways so that the beds are clearly defined. This will keep foot traffic out. Beds can improve in time rather than starting each season in a compacted state from last year’s walkways.
In addition to keeping soil in the garden beds loose, permanent beds will also save time and money. Rather than applying costly amendments over a broad area, they need only be applied to the permanent bed areas, skipping the pathways. Irrigation installation is easier, too.
Permanent pathways of white clover or wood chips will attract beneficial insects and fertilize the garden.
2: To Till or Not To Till
Tilling is an agricultural method that uses mechanical means to quickly loosen and aerate soil in preparation for planting. Although tilling has its place on large farms where manual soil management would be impractical, a tiller is simply a quick fix in small gardens and on micro-farms, where it can have detrimental effects on the soil in the long run.
In some instances, tilling can encourage the soil to blow away in the wind and wash away in the rain. Losing almost three tons of topsoil per acre per year, topsoil is now America’s largest export. Since topsoil can take up to 500 years to form naturally, this is alarming news. Read 7 Ways to Prevent Soil Erosion.
Tilling can also destroy beneficial soil organisms.
Did you know that earthworms, fungi, and other beneficial soil organisms exude sticky substances as they build tunnels and networks throughout the soil? These sticky substances are nature’s way of holding soil together so it doesn’t wash or blow away even when it is loose and crumbly.
This is the reason why aerating and loosening the soil with a rototiller is different than using a digging fork: A rototiller chops up worms and other soil organisms, destroys the fungal networks and tunnels made by soil organisms, and disrupts the connections of sticky exudates. This activity kills soil fertility, requiring fertility to be added in the form of imported soil amendments.
What’s more, tilling can also expose dormant seeds to sunlight, causing more weeds to germinate where they aren’t wanted.
Fortunately, growing crops at a micro-farm or backyard garden scale doesn’t require tilling to produce a loose soil for planting. A digging fork is a useful tool for the no-till garden because it will easily loosen the soil without destroying the soil microorganisms.
A digging fork gently aerates and loosens the top few inches of soil before planting.
For soil to come to life, not only will we want to loosen and aerate it without destroying beneficial insects, but we will also need to add organic matter to help heal it. Fall is the best time to add organic matter to soil, since it will break down and become habitat for beneficial soil organisms over the winter.
3: Sheet Mulch
Sheet mulching is a no-till method for starting a new garden or reigning in a garden that has been overtaken with weeds. It consists of layering organic materials over cardboard. The cardboard smothers plant matter and weed seeds while simultaneously attracting worms and other soil organisms attracted to the decomposing cardboard and the plant residue underneath it.
First, cut back vegetation in the area to be sheet mulched. Leave as much of the cut plant matter as possible on the ground, but remove weed seed heads and vines. Dig up any woody plants in the area. Next, use a digging fork to aerate the area. Now cover the area with pieces of cardboard. To effectively smother weeds, the ends of the cardboard pieces should be overlapped. Next, layer organic matter on top of the cardboard.
Organic matter could consist of food scraps, grass clippings, or manure, followed by shredded leaves or straw, for example.
The top layer should be at least 6 inches of compost soil.
The organic material on top of the cardboard can reach as high as three feet. As it decomposes, the contents of the sheet mulch will shrink in size.
Sheet mulched areas should sit for at least two weeks before planting, and ideally for three months. This will allow the organic matter to decompose so that its nutrients are bioavailable to plants.
4: Add Organic Matter
We extract the soil’s nutrients when we harvest our nutritious, homegrown crops. It is important to replenish the soil each year so it doesn’t get depleted.
Gardens that need a boost of vitality will benefit from the addition of organic matter.
Organic matter has many benefits to soil depending on the specific material used. In general, it will help to improve soil structure, attract beneficial soil organisms, and make nutrients more bioavailable to your crops. Organic matter is a great place to start when improving soil quality, simply because it is inexpensive and because most garden soils are lacking in it.
Add organic matter in the fall (or two weeks before planting) to start the spring garden season on a good note.
Some Animal-based Amendments
- livestock manure (cow, pig, chicken, horse, rabbit, etc.)
- worm compost
- dried and powdered egg shells
Some Plant-based Amendments
- dried and powdered comfrey leaves
- homemade compost (made from yard and kitchen waste)
- leaf mold (shredded leaves aged for 3 or more years)
- wood chips (composted for 3 or more years)
- grass clippings
These are just some examples of the many kinds of amendments that can be found in large quantities for free or very inexpensively. Use a combination of animal- and plant-based amendments whenever possible, but don’t fret over specifics–just use what’s available to you.
Take a couple of years to add a heavy layer of organic material to your garden beds each fall. Use a digging fork each spring to aerate soil and turn in the amendments. After a couple of years, a soil test is a good next step. A soil test will inform you of any lacking nutrients that need to be supplemented through store-bought products. The organic matter and soil organisms that you’ve added can now help break down the store-bought nutrients and make them bioavailable to your crops, ensuring that you get your money’s worth.
After the second year, continue to add organic matter each fall. However, a high volume of organic matter will not be as essential once you are happy with the quality of your soil, unless you are market gardening and require intensive production.
Mulching protects healthy soil tilth by retaining moisture and nutrients. Mulching saves time by reducing the need for weeding, watering, and fertilizing.
The practice of mulching will be different depending on the climate. For example, heavier mulches will be beneficial in hot, dry climates where moisture evaporation is high, while lighter mulches will be more appropriate in cool, rainy climates where soil benefits more from the warmth of the sun.
For most gardeners, a heavy mulch in the off season will provide protection against the elements for beneficial soil organisms and reduce soil erosion from heavy rains. For gardens that sustained pest outbreaks, it is best to discard all affected plant material and NOT apply mulch over the winter. While protecting soil organisms is beneficial, providing winter protection for pests is not.
There are many ways to mulch and many types of materials that can be used. To learn more about mulching, read my post about mulching in the garden.
6: Cover Crops
Cover crops can provide organic matter and nutrients, improve drainage and aeration, attract beneficial soil organisms, and act as an overwintering mulch. While cover crops can be grown in rotation with other crops at any time throughout the year, they are most popularly planted in the late summer or early fall, growing over the winter. Many are killed by the winter cold making spring planting easy. Others are turned under before planting.
It is important to choose the right cover crop for the no-till garden because some cover crops are difficult to kill without tilling. I made the mistake of planting winter rye as a beginning gardener. Although I used my digging fork to turn it under before planting, it has continued to sprout in that same area of the garden every year since. This is because winter rye is a grass.
Other examples of grass-type cover crops are winter wheat, oats, barley, sorghum, corn, and millet. While beneficial to the soil, I would recommend skipping them if you do not intend to till.
Instead, choose legumes like crimson clover, alfalfa, hairy vetch, or sweet peas. Alternate legumes every other year with other cover crops such as buckwheat, daikon radish, forage turnip, or calendula, or try mixing a variety of cover crops together.
If cover crops aren’t winter-killed, use a digging fork (or chickens!) to turn them under about three weeks before planting in the spring. Many of these cover crops can be fed to livestock. Daikon radishes–if not winter-killed–can be harvested for human consumption.
7: Nutrient Accumulators
Nutrient accumulators are plant species that are often used in permaculture gardens. These accumulators reach into the soil and collect specific nutrients. We can take advantage of these nutrients by chopping the plants back and using the cuttings as mulch in garden beds, or planting them around perennial edible crops. This saves money by reducing the number of soil amendments you need to purchase. Growing them also improves biodiversity.
Some examples of nutrient accumulators are:
- Many kinds of “weeds”
- Black locust and other trees, shrubs, and herbs
- See more nutrient accumulators listed in How to plant a hedgerow
- Herbs like yarrow or chives
There are many ways to improve soil quality, but at the heart of it is reducing compaction, amending soil with organic matter, and taking advantage of the off-season.
I’m interested in hearing from you.
What methods have you used to improved your garden soil?