Question: We have been raising a vegetable garden in the same place for many years. Last year, many of the vegetables did not grow as well as we thought they should. Our neighbor told us we should probably have our soil tested. How do we do that?

Answer: Taking a soil test is an excellent way of measuring soil fertility. It is a very inexpensive way of maintaining good plant health and maximum yields. Soil fertility fluctuates throughout the growing season each year. The quantity and availability of mineral nutrients are altered by the addition of fertilizers, manure, compost, mulch and lime or sulfur in addition to leaching. Furthermore, a large quantity of mineral nutrients are removed from soils as a result of plant growth and development, and the harvesting of crops. A soil test will determine the current fertility status. It also provides the necessary information needed to maintain the optimum fertility year after year.

Some plants grow well over a wide range of soil pH, while others grow best within a narrow range of pH. Most turf grasses, flowers, ornamental shrubs, vegetables, and fruit grow best in slightly acid soils which represent a pH of 6.1 to 6.9. Plants such as rhododendron, azalea, pieris, mountain laurel, and blueberries require a more acidic soil to grow well. A soil test is the only precise way to determine whether the soil is acidic, neutral or alkaline.

Most soil nutrients are readily available when soil pH is at 6.5. When pH rises above this value, nutrient elements such as phosphorus, iron, manganese, copper and zinc will become less available. When soil pH drops below 6.5, manganese can reach a toxicity level for some sensitive plants.

Question: How do I take a soil sample?

Answer: Remove the top debris, residue, or turf thatch from the soil surface before taking the sample. Sample gardens, trees, shrubs, flower beds, and orchards 6 to 8 inches deep. For the lawn, lift the sod and sample 3 inches deep. Take separate samples from soils that are distinguishable by color, drainage or other factors. Samples may be taken anytime in the spring, but preferably when soils are suitable for spading or tilling.

The test results are only as good as the samples taken. It is extremely important to provide a representative sample to the testing lab so that a reliable test and recommendations can be made for the entire area. This can be accomplished by submitting a composite sample. A good representative composite sample should contain 10 to 15 cores. Each core should be taken at the same depth and volume at each site. Sample at random in a zigzag pattern over the area and mix the sample together in a clean plastic bucket. Separate samples should be taken from areas with distinctive soil types or plant performances.

Question: Where do I send my soil sample?

Answer: There are a number of commercial laboratories that do soil testing. WSU Extension has published an excellent publication listing these laboratories titled: Analytical Laboratories and Consultants Serving Agriculture in the Pacific Northwest. The publication is available from the WSU publications office by dialing 1(800)723-1763 and asking for Extension Bulletin 1578E. You can also download it free of charge from:

Question: My son wants to drill a hole into our bigleaf maple tree with the intent of collecting sap to make maple syrup. Is this possible?

Answer: In theory, it would be possible, but more than likely enormously disappointing. Although sap to produce maple syrup can be collected from any native species of maple, our bigleaf maple is far less than ideal compared to the sugar maples grown in those areas of the country known for their syrup production.

Maple sap is made into syrup by boiling off water, which increases the sugar content to 66 percent and causes chemical changes that darken the syrup and provide its characteristic taste. The amount of sap required to produce a gallon of syrup depends on the sugar content of the sap. On the average sugar maples in the Northeastern part of the country have about 2 percent sugar content, requiring 43 gallons of sap to produce a gallon of finished syrup!

EDITOR'S NOTE: For answers to local gardening questions, contact Master Gardener Rachel Gana at 642-8723 or e-mail her at:

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