Multnomah County has about fifty different kinds of soil. While most of these soils are very good for growing a variety of crops, many are subject to erosion. Knowing the characteristics of your soil is very important for learning how best to use and manage your land.
The Soil is Alive
Every cubic inch of topsoil contains millions of creatures – mostly bacteria, fungi, and other microbes. These tiny creatures recycle dead plant matter back into nutrients that support plant growth. When the upper 8 inches of soil stays put, this living layer produces:
Studies show a healthy soil has up to 200 percent more nitrogen and phosphorus and 20 percent more potassium than an eroded soil.
High Plant Yields
In general, healthy, protected soils have 25 percent higher yields than severely eroded soils. Studies have shown 31 percent higher alfalfa yields and 86 percent higher barley yields on protected soils versus eroded soils.
Clean Waterways and Fish Habitat
Studies show that we can save $1 for each ton of soil that stays on the land. With erosion control, clean gravel beds produce healthy fish populations, cities reduce filtration costs for drinking water, and harbors can lower their dredging costs.
Know Your Soil
Soils vary in texture, drainage, susceptibility to erosion, and water holding capacity. These characteristics and how they affect the potential of a soil are described in the soil survey for each county. Printed copies are available at both the West Multnomah and East Multnomah SWCD offices, but we recommend you use the online version at http://websoilsurvey.nrcs.usda.gov. This site allows you to create a soil map of your property and gives you access to loads of information about your soils.
A good soil test is essential to understanding the chemistry of your soil. A basic test will give you the levels of nutrients present and the acid level or pH. Many soils in Multnomah County are somewhat acidic and may need additives like lime to increase the pH level.