When your soil begins to dry up in spring, grab your spade and get going: It's time to prepare your garden for planting. Most gardeners know they should put good effort into soil prep, because it¹s the single most important thing one can do to grow a good garden.

The goal is to improve soil structure so that the soil is deep, loose, and well-drained. In friable soil such as this, plants can send roots into regions where the nutrients and moisture they need are located. Nutrients move more easily as water percolates between soil particles; and in addition, oxygen is available for the roots to use.

The overall effect is healthier, stronger plants that resist diseases and insects.

Whether you have clay or sandy soil, the best way to improve soil structure is to add organic matter such as compost, manure, completely decomposed sawdust or straw, shredded bark, or rotten leaves. Don't use fresh sawdust or straw because it uses up nitrogen, a major plant nutrient, while it is decomposing. The organic matter is fed upon by beneficial soil bacteria that then release nutrients into the soil and make them available for plant use. It¹s all part of the food chain, and it's pretty remarkable when you think about it.

Here's a quick guide to soil preparation.

Don't work on soil that's too wet or it will dry into large, hard clumps that are difficult to break down, and that turn into unplantable powder when they do. Test soil to make sure it's ready to work by forming a handful into a ball. The moisture content is OK when it forms a ball that clings together but still crumbles easily when squeezed or dropped to the ground.

Clear all weeds from the area.

Tillers and tractors are fast and easy -- essential for people with physical limitations. A drawback is that they loosen the soil to a depth of only 6 to 8 inches. They also tend to compact the soil just under the tines' reach.

With hand tools such as garden forks and spades you can prepare a deeper bed that¹s at least 12 inches deep.

For an even deeper garden, use a technique called double digging in which you dig down two forks deep. it makes more room where plants can reach out for nutrients and moisture. I personally think it's too much darned work, but I do agree it can improve plant performance. Of course my opinion could be influenced by the fact that I have barely 18 inches of top soil to work with here in Southern Oregon.

Spread 2 or 3 inches of compost or other organic matter onto the soil surface. With a spade or garden fork, turn the soil and dig the amendments into the top 12 inches.

Break up large clods of soil with a spade or the back of a rake, and then smooth the surface into a level bed ready for planting.

Don't walk upon your garden beds after they are prepared. If you must cut across an area, walk on a board to spread your weight over a larger area and minimize soil compaction.

Next growing season try another approach and do this work in the fall when your annual garden comes to an end. As beds are harvested, perform the same steps mentioned above and then take it one step further: Plant a cover crop to blanket the soil over the wintertime and add nutrients and organic matter next spring; or spread several inches of straw over the beds to protect them from rain and erosion. You'll be ready to plant weeks earlier the following year.

There are numerous cover crops good for over wintering. Check seed catalogs or local garden centers and farm supply outlets. My favorite is a mixture of crimson clover and annual winter rye. Other good cover crops include vetch, oats & peas, and fava beans.

One question that comes up if you¹re growing cover crops is: When do you turn them under? The latest you should let cover crops grow is two weeks before you intend to plant, although four weeks beforehand would be better. Cover crops need time to break down. If you¹re growing nitrogen-fixing legumes, such as crimson clover, turn them under or cut them just as they are coming into bloom, which signals that a peak of nutrients has been reached. You may turn everything under the soil surface, or you can cut off the green tops, put them in your compost pile, and then chop up and turn under the stubs and roots.

Good soil prep from the beginning will do more than nearly anything else you can do for your garden to guarantee successful plant growth.