Preparing the soil for planting involves cleaning it up, solving any problems it poses, adding soil amendments, and then tilling them into the soil.
How much the soil needs to be improved depends on the condition it was in when the landscaping project began. If it was growing a healthy garden—or even a healthy weed crop—and water did not puddle up, the soil may not need much work.
A good first step, if you haven’t already done so, is to get a soil test. A soil testing laboratory will make recommendations about minerals and fertilizers to add to your soil to improve it, and will tell you a great deal about your soil. They might point out problems that aren’t readily apparent, such as a salinity or acidity problem.
If you have any soil problems, deal with them before planting. It’s very difficult to do things to the soil after it’s planted. See About Problem Soils for more information.
Soil is prepared differently for different plantings. Trees and shrubs are usually planted so far apart that it isn’t necessary to prepare the soil between them. In this case, the planting hole becomes a pocket of prepared soil, rather than the entire landscape being prepared. Flower and vegetable beds, and lawns, need the most careful preparation.
Clear Off Weeds
Get rid of any weeds first. This is done in different ways depending on the season. If it’s spring, The weeds are probably just sprouting. If no perennial weeds are present, young weeds can just be scraped off the surface with a hoe. If perennial weeds are present, or if the season is summer or fall, kill the weeds with Roundup before removing them. Roundup kills any weeds present, then breaks down in the soil within a few days.
Spread any materials to be tilled into the soil on the soil surface. Most minerals and chemicals are sprinkled on the surface. Organic matter is spread a few inches thick. Any of these amendments might be added.
Organic matter improves almost any soil. It increases the capacity of the soil to absorb water and nutrients; it separates soil particles by opening and loosening the soil; and, as it breaks down into humus, it forms glue-like materials that adhere soil particles together into little crumbs, making the soil soft and friable (easily crushed or crumbled).
Most organic materials are beneficial to the soil. Wood by-products such as sawdust and composted bark are widely available; so are ground corncobs and peat moss. Other materials—including the farmer’s standby, manure—may be available for the hauling. A home compost pile provides a continuing source of organic material.
Spread the organic matter on the surface of the soil between 1 and 4 inches deep. The effects of a single addition of organic matter can last for years.
If the organic matter does not already contain a nitrogen supplement, add a high-nitrogen fertilizer. This will prevent the organic matter from tying up the available nitrogen in the soil as it decomposes, a condition called Nitrogen Draft. Organic matter that does not need added nitrogen include compost, manure, and any commercial material that has been supplemented with nitrogen. Most other organic matter needs supplementary nitrogen, especially sawdust, leaves, and straw.
In many regions of the United States, including most areas east of the Mississippi River, the soil will benefit from the addition of lime. A soil analysis will reveal how much lime to use. If a soil analysis is unavailable, ask at a local nursery whether the soil needs lime.
Besides any nitrogen added to help organic matter break down, apply some fertilizer for the plants. If you got a soil test, the test results recommended fertilizer amounts. If not, apply a balanced, general-purpose fertilizer, according to the label instructions.
If the garden has a very sticky clay soil that drains slowly, gypsum might help to improve its structure. See Sodic Soils for more information.
Till the Soil
After these materials have been spread evenly over the ground, the next step is to till them into the soil. This process of loosening the soil not only mixes in amendments, but also increases aeration, which improves drainage and root growth.
You can till the amendments in with a rotary tiller or by hand. For more information, see Working the Soil.
After tilling, use a cultivator or garden rake to smooth the surface. A cultivator breaks up clods quickly, and a garden rake makes a fine seedbed.
A quick way to dispose of hard clods and rocks that you rake up is to dig a deep hole at the end of the planting bed and bury them. Make sure that they’re buried below tilling depth or you’ll have to deal with the rocks again next year.