Earthworms do more than most of us realize to improve soil. As they tunnel through the soil, they bring virgin, nutritious soil from below the surface. And their castings are actually a nutrient-rich fertilizer, containing nitrogen, potassium, phosphorus and many other micro nutrients essential to healthy plant growth. But not all earthworms can be added to garden soil. Purchase an endogenic variety of earthworm like Lumbricus terrestris. Other types, like those used for vermicomposting are unlikely to survive for long.
Fertilize the soil. If earthworms are not present in your soil, it's likely the soil is too poor to support them. Till the soil to a depth of 6 inches with a pitchfork or hand tiller. Then spread 3 inches of compost over the soil and dig it in to a depth of 8 inches. Tilled, enriched soil can support up to 25 earthworms per cubic foot. Once your soil is fertilized, the earthworms will probably find your garden on their own.
Spread purchased earthworms over the surface of the soil. Space them out so that there are only two or three per every square foot of soil.
Spread a 1-inch layer of organic mulch (dried leaves are ideal) over the soil. It will keep the soil cool and moist and provide the worms with food.
see also: Green Manure Crops
Fall is a good time to till your garden soil, especially if there is sod to be turned under. This will reduce erosion, expose heavy soils to frost, kill exposed insects, aid the decay of organic matter, and enable earlier planting. Work in any organic matter you have available when you till. If you do this every fall you will find that your garden takes less time and work to prepare every year. It's best to wait until spring to fertilize, but the addition of granular (not pulverized) lime in the fall will help condition the soil for spring planting.
Organic material that can be tilled into the soil in autumn:
Never work wet soil, especially clay. You may ruin the soil structure for the entire season and end up with solid, sun-baked clods. Use these guidelines to determine if your soil is dry enough to till:
- If you pick up a handful of soil and can squeeze water from it, it's obviously too wet.
- If the soil compresses into a ball and stays that way, it needs more drying time.
- If it is dry enough to crumble in your hand, it is "friable" and is ready to be worked.
Rake dead leaves, sticks and debris that may have accumulated over the winter. Clearing the garden area before winter also reduces the chance of insects or bacteria filtering down into the top layers of the soil, which may result in poor soil nutrition in the spring.
Determine the health of your soil by taking a plug sample to your local nursery or agricultural school for testing. Most soil will benefit from plowing, no matter how healthy it appears. Plowing enables gardeners to evenly rake or shape the soil; it also makes the planting process easier.
Plow in early spring when the danger of frost has passed. Use a harrow pulled by a tractor, or for smaller areas use a rototiller.
You can tell if the area is ready to plow by digging up a chunk of soil with a shovel. If the soil stays clumped, the ground is still too wet to plow. The soil should break up and crumble easily. Run the plow length-wise and width-wise over the area to evenly distribute the nutrients.
To prepare the plot by hand, create a trench along one side of the garden area with a shovel. Then dig another row next to trench, turning the soil from the second trench into the first. Continue through the garden in this manner. After the entire area has been turned, sprinkle fertilizer and a soil amendment like compost over the surface. Turn the soil again to work in the material, then rake the area smooth.
Work the soil with a garden spade or fork to loosen it to a depth of about 6 inches.
Add at least 4 inches of aged compost or peat moss to the soil, spreading the compost in an even layer.
Spread 2 inches of coarse sand over the compost in an even layer.
Work the amendments into the soil with a garden spade or fork, working the soil until the ingredients are completely incorporated.
Rake the soil surface smooth to finish amending the soil.
Stand at one end of the area that you are working and dig the tines of the cultivator into the soil. You may have to break the soil up a bit to do this.
Draw the cultivator towards you, using your arm muscles (not your back) to pull against the soil.
Dig the tines into the soil and draw the cultivator towards you, keeping the head submerged, to loosen the soil.
Go over loosened soil repeatedly to break up any large clumps of dirt.
Amend the soil. Spread any soil amendments over the soil and mix them in by raking the soil with the cultivator, using the method in step 3.
Use the cultivator as a leveling rake to smooth the soil and prepare it for planting. Rake the planting area cross-wise, then length-wise and then diagonally.
Rent a core aerator from a heavy machinery shop or lawn care store. Select a walk-behind core aerator with large, closely spaced tines. Aerators of this sort are designed to break up heavily compacted soil.
Read the instructions that come with your core aerator. Most walk-behind core aerators are designed to operate similar to a lawn mower in that they have a pull cord or push button start and can be pushed in sections to aerate your soil. Specific operating instructions will vary.
Start the aerator and push it over your soil until the entire area you plan to seed has been aerated.
Leave behind the plugs that the aerator pulled up on the surface of your lawn. These plugs will break down in a short time.