KENNEWICK -- The "ideal" soil for vegetable gardening is one that is slightly acid, well-drained and fertile.
The ideal soil has sufficient levels of decayed organic matter and also is deep, loose and free of weeds and disease organisms.
Unfortunately for us gardeners, the "ideal" garden soil is just that, an ideal. Good garden soil is developed over time. There are no magic additives and no quick fixes that will instantly change regular or bad soil into the perfect garden soil.
However, even less-than-perfect soils can be coaxed into growing productive gardens.
First, I would recommend getting a soil test done at one of the local soil testing labs. A soil test gives you a starting point regarding soil fertility, pH and organic matter content. Based on past experience, I predict your soil will be slightly to moderately alkaline. This is typical for local home garden soils. One home garden soil test I recently reviewed revealed a pH of 8.2 and another had a pH of 7.9. Both soils were within a range where most vegetables will grow without any problem.
Your soil also will most likely be low (less than 1 percent) in organic matter and lacking nitrogen. Depending on the soil type and past fertilizing practices in the area, the soil may or may not be lacking phosphorus or potassium. Knowing your current nutrient levels will help you avoid adding unnecessary fertilizer and avert a buildup of excessive amounts of these nutrients.
Your best path to building a good garden soil is the addition of organic matter. In sandy soils, organic matter helps improve water and nutrient retention. In heavier soils, organic matter aids in aeration and drainage.
Organic matter may sound like that magic additive I mentioned earlier, but the improvement process is gradual. Only about two to three inches of organic matter should be added to the soil each year and mixed in with the soil to a depth of six to eight inches. Mulching with organic matter during the summer also is a great way to help add organic matter to the soil.
So what qualifies as organic matter? There are a variety of plant-derived materials that qualify such as compost, grass clippings, chopped leaves, coconut coir and peat moss.
It's not advisable to add woody materials, such as sawdust or wood chips, conifer needles, animal bedding or straw to your garden soil as sources of organic matter because they're considered high in carbon and low in nitrogen. It takes a long time to for them to decay. Soil microorganisms responsible for breaking down organic matter can use up all the available nitrogen in the soil when "eating" high carbon materials. With no available nitrogen, your garden plants will have a hard time growing without extra applications of nitrogen fertilizer.
Also, caution should be taken when using grass clippings if pesticides have been used on the lawn. Manures can cause problems because they often contain weed seeds.
My recommendation is to use quality compost you make yourself or purchase from a nursery supplier. Add organic matter to your garden soil every year, and you'll build a better soil.
* Marianne C. Ophardt is a horticulturist for the Washington State University Benton County Extension.