The Mid Klamath region encompasses a wide array of elevations, soils and topography that have given rise to one of the most diverse flora and fauna of any temperate zone on earth. This same complexity yields a range of opportunities and challenges for farming and gardening. The alluvial soils adjacent rivers and clay soils found upslope can be very fertile and productive, while ultramafic and serpentine soils that make this region unique are ill-suited for crop production and best left to the unique native plant communities adapted to them.
You can explore the Web Soil Survey website of the Natural Resources Conservation Service at http://websoilsurvey.nrcs.usda.gov/app/ , but you won't find many details on soils in the mid Klamath because of our remote location. At the risk of oversimplifying a complex science, we're going to break our soils into four simple groups and discuss them from the perspective of growing a garden or farm, the soil in your particular site may or may not fit precisely into one of these categories:
Alluvial Soils, River Bars - The soils on the river bars, known as alluvial soils, have been deposited by the river and are composed of a mix of the parent materials upstream. Some alluvial soils contain a lot of gravel and are low in fertility, but many are the best agricultural soils in the region, with lots of fertile silt from previous floods. Alluvial soils tend to be light in texture and easy to cultivate, they drain freely and will often leach out nutrients quickly so they require ongoing mineral fertilization and cover cropping.
Upslope Clay Soils - Many of the upslope soils of the mid Klamath area have a significant amount of clay; these soils are fertile, with good retention of water and nutrients, supporting the large conifer and hardwood forests our region is known for. From a gardening perspective, they can be sticky when wet and hard when dry, so be sure to cultivate only at the proper moisture level. You can tell it's time to cultivate if you can form a ball of soil in your hand that can be easily broken down with the push of a finger. These soils benefit from lots of organic matter to loosen them up and make them more tillable. Cover crops are a good way to introduce more organic material.
Decomposed Granite - or DG, is weathered granitic rock that forms a light or white soil that is very loose and highly erosive. While DG does contain some nutrients from the granitic parent material, it is still fairly low in fertility from a gardening perspective and will need a lot of amending with mineral fertilizers and organic matter to be productive (see chart). DG is not very good garden soil, if it is all you have then consider raised beds. Whenever possible, avoid disturbing DG on steep slopes (i.e. road building or extensive cultivation) as it will erode quickly.
Ultramafic and Serpentine Soils - One of the things that makes the Klamath region so unique is ultramafic soils - soils that are high in Magnesium (Mg) and Iron (Fe)and other micronutrients, sometimes occurring at levels that are toxic to plants. The collision of tectonic plates that formed the Klamath mountains brought lots of the earth's mantle material to the surface. The mantle is high in Magnesium, Iron, Nickel, and other micronutrients, and low in Calcium and Phosphorous. It's very common to find soils in our region with this particular imbalance of nutrients. When the Magnesium and Iron levels are very high the result is a serpentine soil, which yields a sparse vegetation, often consisting of Jeffrey Pine, Incense Cedar, and buckbrush (Ceanothus cuneatus). Trees growing on serpentine are likely to be dwarfed. While it is possible to amend some ultramafic soils to render them agriculturally productive, it is not advisable to try to garden on serpentine - these soils are best left undisturbed; they are highly erosive, host a high number of endemic species and tend to be so infertile that attempting a garden is futile.