How to Create Soil for a Garden
Easy Ways to Improve Soil Quality
HOW TO MAKE RICH, CRUMBLY GARDEN SOIL
Garden soil isn't just—well, dirt. Soil is a dynamic ecosystem made up of four things plants really, really like: minerals, organic material, water and air.
Although there's at least one thing about soil that you can't change (its texture), there are several aspects of your garden's soil that you can improve.
Soil Texture v. Soil Structure
The texture of garden soil— that unalterable mix of clay, silt and sand-sized minerals in soil—is often a gardener's bugaboo. How often have you heard a would-be gardener say, "Nothing will grow in this soil!"
If you live in the U.S., you probably have either sandy soil that leaches nutrients or clay soil that's hard as a rock.
The soil in my garden is sandy clay but, like most gardeners, I'd prefer rich, crumbly loam. However, soil texture is what it is, and my garden's soil will always be sandy clay, no matter what I do it or what I add to it.
EVERYBODY ♥s LOAM
Loam is the growing medium most home gardeners can only dream about, a combination of clay, sand & silt that drains well while retaining nutrients & allowing plants to root easily. Loam is a welcoming environment not only to plants, but also to the organisms that live in soil as part of its healthy ecosystem.
Typical garden soil isn't loam, but ... that's okay. With a little hard work, you can fake it!
That doesn't mean, however, that I can't make my soil better. I can.
And so can you.
Soil structure can be improved.
From Crummy to Crumbly
Soil structure refers to the way particles of soil are arranged. The best arrangement is a "crumbly," friable one anywhere from 1 to 2-feet deep that holds onto nutrients while easily allowing water and roots to pass through. This sort of soil provides a welcoming home to decomposers and other friendly organisms.
When creating (or rather, re-creating) the soil in your garden, that's what you should strive for: organically and biologically-rich, "crumbly" soil—a sort of faux loam.
So how can your soil go from crummy to crumbly? Through the addition of organic material.
Increasing the amount of organic matter in garden soil not only improves its structure, but it also increases its fertility. Most organic matter tends to bring soil pH to a neutral level, making nutrients in the soil more accessible to plants.
HOW TO USE COVER CROPS TO IMPROVE SOIL
Green manure refers to low-maintenance cover crops gardeners can dig into the ground.
Green manures add nutrients to the soil, attract beneficial insects, reduce erosion, smother weeds and improve the soil's physical state (tilth).
Because I mix vegetables, flowers and ornamental plants within my home landscape, I plant cover crops over small areas in my flowerbeds and raised beds. They're a pretty way to fill up the "blank" spots, and they're a great way to add nitrogen to the soil and improve its structure.
To give soil the biggest boost, crimson clover should be turned under before it blooms, but ... the flowers are so pretty, that may be tough to do!
How to Make Green Manure
Using green manure in the home garden isn't difficult. Here's an easy way to go about it:
- Purchase seeds of the cover crop of your choice. You'll need about a quarter pound of seed for every 100 square feet of planting area.
- Scatter the seeds over soil that you've prepared by working in compost and removing weeds and debris.
- Rake the seeds into the soil and moisten the planting area.
- If where you live is experiencing drought or drought-like conditions, water the germinating seeds occasionally. (You could even spread straw over the growing area.) But you really don't have to baby cover crops. They're low maintenance and should sprout and grow easily.
- Before the cover crop sets seeds (and in some cases, before it flowers) mow it down. If, like me, your cover crops are in a mixed bed or potager, cut them down with garden shears, pruners or a hedge trimmer. Then cut the felled plants up into smaller pieces and allow them to dry where they fall for a few days.
- Once the bits of cover crop have dried up, gently work them into the soil with a cultivating fork.
- In about a month, you'll be able to replant the freshly green-manured area.
HOW TO IMPROVE SOIL WITH COMPOST, CHOPPED WEEDS & OTHER ORGANIC MATERIAL
A Selection of Green Manures
Likes warm weather. Sow in spring or summer.
Biennial cover crop. Likes cooler weather. Has deep taproots that aerate soil.
A quick grower. Sow in spring or summer.
Annual crop cover. Fast growing. Aerates soil. Also called blackeyed pea.
Sow in spring, summer or fall. Turn it under before it blooms.
Prefers cooler weather. Somewhat drought tolerant. Has pretty purple flowers.
Fast grower. Sow in winter & turn under in mid-summer.
Sow in late summer or fall. Turn it under when it blooms.
Sow in spring, summer or fall. Let frost kill it, & then turn it under in the spring. If you've ever grown "cat grass" from the pet store, you've probably planted oats.
Quick grower that suppresses weeds.
Perennial. Sow in autumn or early winter & turn under spring. Leaves may be used to make liquid fertilizer.
Rye (Annual & Winter)
Sow in later summer or fall. Hardy grower & weed suppressor. Till under annual rye when about 10" high.
Suppresses weeds. Easy to grow.
May use foliage as mulch. Sow in fall or early winter.
Incorporating Other Organic Matter into Soil
Adding organic matter to garden soil sort of "opens it up," improving the soil's air flow and increasing its ability to retain nutrients and moisture while simultaneously improving drainage.
Rather than adding organic matter all at once, apply it twice a year— once in the fall and once in early spring.
If you're starting a new garden or your soil is especially poor, add 4 to 8 inches of organic matter to it each year for 2 years. By the third year, 1 to 2 inches should be enough.
Green manure is one simple way to add organic matter to your soil, but there are many others that are just as easy.
Whether it's store-bought or homemade, compost is one of the best ways to improve garden soil. You can work it into your soil any time of year, so long as the ground isn't frozen. You can also use compost as a mulch around vegetables and herbs, or apply it as a top dressing over your entire garden. So that it doesn't wash away, a light covering of 1 to 2 inches of compost at a time is usually best.
Shredded bark & wood chips
Wood chips and bark are good additions in ornamental flowerbeds as mulch. Not only are they decorative, but they also decompose slowly.
Spent plants, annual weeds, grass clippings & leaves
When plants reach the end of their life cycle, you can chop them up and dig them into your soil or use them as a mulch. (Just be sure that you don't use diseased plants. If you do, you'll spread the infection.)
You can add chopped up annual weeds that haven't gone to seed to your soil as well.
Common annual weeds that make good organic additions to soil include chickweed (Stellaria media), henbit (Lamium amplexicaule), red deadnettle (Lamium purpureum), carpetweed (Mollugo verticicillata), horseweed (Conyza canadensis), common purslane (Portulaca oleracea), prostrate spurge (Eurphorbia supina), knawel (Scleranthus annuus), hairy bittercress (Cardamine hirsuta), common groundsel (Senecio vulgaris), common ragweed (Ambrosia artemisiifolia), redroot pigweed (Amaranthus retroflexus), common pokeweed (Phytolacca americana) and Asiatic dayflower (Commelina communis).
Grass clippings and chopped leaves may also be added to your soil. Pine needles make a particularly good mulch for acid-loving plants like blueberries, azaleas and rhododendron.
When annuals die down, rather than pulling them out of the ground, cut them off at the base, leaving the roots behind to decompose and enrich the soil.
Like compost, aged manure can be worked lightly into the soil, used as a light top dressing or applied more heavily as mulch.
Many experts recommend that composted manure comprise no more than 25 percent of the total organic matter applied to a garden within the course of year. (Dog and cat manure, which contain harmful pathogens, should not be used, especially in an edible garden.)
Often gardeners use straw to protect plants from cold weather, but it's also a good mulch for improving tilth because it aerates the soil as it rots. Hay will do the same; however, it often contains weed seeds, and who wants that?
HOW TO IMPROVE SOIL THROUGH DIGGING
PROBLEMS WITH pH
Usually, adding organic matter to soil eventually brings the pH level at or near neutral, which is where it should be for most plants.
If, despite diligent applications of organic matter, your garden soil's pH is still too high (alkaline), amend it with sulfur. If the pH is too low (acidic), add lime.
Loosening the Soil
For the most part, a no-till garden that's regularly mulched with organic matter and/or planted with cover crops will have the healthiest, richest, most productive, loamiest, crumbliest soil—the soil you want.
However, unless you practice raised bed gardening and/or container gardening exclusively, sometimes you may need to dig down deep into the soil in order to improve tilth.
Although recent research shows that tilling and/or digging deeply into an established garden is counterproductive, it's still appropriate for new gardens as well as old ones that are in very poor condition.
Digging and tilling will allow you to remove debris and loosen the soil, preparing the way for future plantings. In most cases, working the soil to a depth of 12 inches is adequate.
In cool climates, digging heavy clay soil in the fall is particularly effective. Over the winter, frosts and freezes will break it down, improving its tilth.
Clay & Sandy Clay Soil
If you have heavy clay or sandy clay soil, dig manure into your garden in the fall.
If the soil is very heavy, dig it first and then cover it with a thick layer of composted manure. Over the winter, earthworms will work the manure into the ground, improving the soil's drainage and fertility.
If your garden soil is sandy, lightly turn it in the fall and cover it with composted material or plant it with green manure. Either one will help to prevent the leaching out nutrients over winter.
Digging Potagers, Flowerbeds & Raised Beds
If you're like I am, you actually enjoy digging in the garden. Fortunately, you can do so (even in an established garden) without disrupting the soil's ecosystem too much by trench or hole composting.
It's also okay to dig into the empty areas of your garden that are left when plants die or are removed. That's the perfect time to work compost or composted manure into the ground before replanting.
Copyright © 2012 by The Dirt Farmer. All rights reserved.
ABOUT THE AUTHOR
The Dirt Farmer has been an active gardener for over 30 years.
She first began gardening as a child alongside her grandfather on her parents' farm. Together, they would plant acres of vegetable gardens, setting tomato, eggplant and bell pepper plants; sowing row after row of beans and corn; and building up mounds of soil for white squash, pumpkin, cantaloupe and potatoes.
Today, The Dirt Farmer gardens at home, volunteers at community gardens and continues to learn about gardening through the MD Master Gardener program.