KENNEWICK, Wash. -- Eager first-time gardeners may be so anxious to start their garden that they fail to take the time to adequately prepare the soil.
The key to garden success starts with the soil. If you have bad soil, your success will be limited.
So what is considered a bad soil? Soils that are compacted, don't drain well or drain too well and don't retain moisture, or don't contain nutrients, are bad soils that need help to become productive.
Organic matter is the magic potion for creating a better soil from bad soil. Organic matter improves the drainage of compacted or heavy soils by increasing the porosity. It helps sandy soils retain water and nutrients. Organic matter also acts as a slow-release fertilizer over time, releasing nitrogen, phosphorus and sulfur.
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However, it can turn into "bad magic" if you add too much. Don't overload the soil by applying more than 1 to 2 inches of organic matter before tilling it into the soil. Fall is a good time to add uncomposted organic matter to your soil, especially when starting a new garden.
The wrong types of it also will can spell trouble. The microbes in the soil responsible for breaking down organic matter need nitrogen to reproduce. Materials with a high carbon to nitrogen ratio will tie up all the available nitrogen. The garden plants will suffer because they can't get enough nitrogen from the soil for healthy growth. That is why it is best not to use straw, straw bedding, sawdust, wood chips or bark as the source of organic matter because they all have a very high carbon to nitrogen ratio.
Organic matter with a low carbon to nitrogen ration, such as fresh manure and grass clippings, are a good source of nitrogen, but usually aren't as good in building the soil. Materials with a moderate carbon to nitrogen ratio, such as chopped tree leaves, compost and cover crops, don't provide as much nitrogen to plants, but do a better job of adding organic material to the soil.
More bad magic
When adding manure from a feed lot or dairy barn, be aware that these materials may be high in accumulated salts because of animal urine. Fall is a good time to apply manure so winter precipitation can leach salts away.
When adding manures to your vegetable garden, you risk exposing you and your family to E. coli bacteria and other pathogens in the manure. To reduce the risk, Washington State University recommends against using fresh manure. If you do use fresh manure, they recommend waiting 120 days after application before harvesting high risk crops and 90 days before picking harvesting for low risk crops.
High risk crops are those in direct contact with the soil and that often are eaten raw. This includes leafy greens, such as lettuce and spinach; as root vegetables, such as carrots and radishes; and vining crops left to sprawl on the ground, such as melons or cucumbers.
Low risk crops are those that don't touch the ground or that are typically cooked before eating, such as sweet corn, squash and eggplants.
To minimize the risk, it would be best to apply fresh manure to the garden in the fall of the year or use professionally composted manure from a commercial facility where hot composting was practiced.
Marianne Ophardt will be teaching a Backyard Composting Workshop on April 28 from 9:30 a.m. to noon inside the Highland Grange Hall, 1500 S. Union St., Kennewick.
Participants will receive a free composting bin and book for attending. Seating is limited. For more information or to register, call 509-735-3551.
* Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.