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We often hear the soil in our Yampa Valley gardens is somewhat alkaline, as opposed to the acidic soils of places such as Georgia and the Carolinas, where acid-loving azaleas and rhododendrons flourish. What exactly does that mean, and what should we do about it?

The acidity or alkalinity, or pH level, of your soil will affect plant growth by controlling how easily nutrients can be taken up from the soil by your plants. For instance, in acidic soils, nitrogen - a very important nutrient - is not easily converted to a form plants can use. The same holds true for phosphorus and potassium in varying degrees and for micronutrients in lesser degrees.

Soil pH ranges from a scale of 0 (strongly acid) to 14 (strongly alkaline) with a reading of 6.5 to 7.0 indicating that the soil is neutral, or good, for most plants. Most Colorado soils tend to have pHs greater than 7, though my soil-test report from Colorado State University indicated a pH of 6.2 for my garden soil located a few miles north of town.

If soil has a pH value higher than 8.5, it means the soil contains too much sodium, making it difficult to grow most plants. To reduce soil alkalinity, you can apply sulfur or aluminum sulfate. For acidic soil, gardeners often apply wood ash or limestone.

The only way to determine the pH level of our garden soil is to have a soil test conducted. This is done at testing laboratories such as the lab at Colorado State University, available at (970) 491-5061. Once you know your soil pH, you can make adjustments as needed.

The master gardeners at the Routt County Cooperative Extension Office can help you determine which amendments to use and how much to add into your soil to make your garden more fertile. You can speak with a master gardener from 9 a.m. to noon Thursdays, or call anytime and leave a message for a master gardener to call you back or come out for a site visit.

As a garden goes through several seasons, the soil tends to become more acidic, especially when commercial fertilizers are used as opposed to using compost and tilling in old plant material to add nutrients. That's because most fertilizers contain salt that can build up in your garden soil.

When you have a soil test conducted, the lab will analyze your soil for pH, salts, lime and organic matter, and for nutrients such as nitrate, phosphorus, potassium, zinc, iron, manganese and copper. The report will make recommendations for the addition of organic matter, nutrients or other improvements if needed. The cost is minimal, and it takes about a week for results, depending on how busy the lab is at the time you send your sample in.

Consider having a soil test conducted every three or four years since your soil composition and pH level can change as the garden matures.

Deb Babcock is a master gardener through the Colorado State University Cooperative Extension office in Routt County. Questions? Call

879-0825.