The Soils of Western Colorado
Mesa, Delta, Montrose and Ouray Counties


Curtis Swift, Ph.D.
Colorado State University
Extension
Tri River Area Agent (Horticulture)

  • Soils of Western Colorado The valleys in Mesa, Delta and Montrose counties were carved by rivers from material laid down by the Mancos sea. This page discusses the geological history of these valleys and the soils (problems and advantages) created.
  • Acid-Loving Plants - a listing
    Soils in Western Colorado are typically high in pH (above a pH of 7) yet many gardeners new to the area attempt to raise acid-loving plants. Hence the reason for this list.
  • Alkaline Soils and the Buffering Affect of Calcium Carbonate
    Soils in the valleys of Western Colorado typically have a pH of 7.5 to 8.5 creating a basic/alkaline condition. With up to four thousand feet of calcium-based Mancos shale under these valley soils and with irrigation water containing calcium carbonate, the possibility of reducing pH in gardens and lawns is highly unlikely.
  • Soil Reaction (pH)
    Soil reaction or pH is a measure of the `active' hydrogen ions in the soil water (solution). Changing the pH of the soils in Western Colorado is extremely difficult if not impossible.
  • Cation Exchange Capacity - CEC The ability of a soil to hold cations is termed its cation exchange capacity (CEC). Since many cations are plant nutrients the cation exchange capacity is a measure of the soil's ability to hold such nutrients.
    • The Gunnison Basin selenium Task Force is a group of private, local, state, and federal interests committed to finding ways to reduce selenium in our locally affected waterways, while maintaining the economic viability and lifestyle of the Lower Gunnison River Basin of Western Colorado.
  • Sodium Adsorption Ratio (SAR)
    Elevated concentrations of sodium ions in soil create a plant growth hazard. The Sodium Adsorption Ratio (SAR), a measure of the proportion of sodium (Na) ions compared to the concentration of calcium (Ca) plus magnesium (Mg), is a common method of estimating this sodium hazard. SAR is discussed and a quick and easy conversion chart to determine the SAR is provided.
  • Soil phosphorus levels and mycorrhizae-forming fungi
    Mycorrhiza are an integral part of most plants. Very high and very low phosphorus levels may reduce mycorrhizal infection and colonization. This literature review provides details on the mycorrhiza and phosphorus relationship. References are listed.
  • Soil Reaction (pH)
    Soil reaction or pH is a measure of the `active' hydrogen ions in the soil water (solution). Changing the pH of the soils in Western Colorado is extremely difficult if not impossible.
Soil Salts
  • Mancos Shale
    • The soils throughout the valleys of Western Colorado originated from Mancos shale. The white deposits seen throughout the area are a salt (gypsum).
  • Manures as Soil Amendments and Mulches for Vegetables & Ornamental Plants
    • Manures contain salts and may increase the soil salt level when used as mulch or soil amendments. This elevated salt level can be a serious problem when the resulting soil salt level is greater than the salt tolerance of the plant.
  • Methods Plants use to Tolerate & Avoid Salts in Soil and Water
    • This paper provides an abbreviated listing of methods higher plants use to avoid/tolerate salts. References are provided.
  • Salt Tolerance of Temperate Zone Plants - a listing
    • Soluble salts can cause harm to plants if they are in high enough concentration in water or soil. Salt levels of up to 139 mmhos/cm have been recorded for our soils, an impossible situation when attempting to grow plants. This listing should be considered a guide when recommending trees, shrubs, vines and herbaceous plants for salty sites.
  • Soil Salt Problem Areas - A Photograph
    • Many salty areas are visible in Mesa, Delta and Montrose counties - Western Colorado. The accumulation of these salts on the soil surface are due to insufficient precipitation to wash these salts below the root zone of plants.
  • Soil Testing Procedures
    • Soil testing can provide answers to many of the questions related to pH, salts and plant nutrient availability that are so necessary for the successful growth of plants. The way the soil sample is collected and cared for, as well as the soil testing laboratory selected can make a difference in the accuracy of the results.
  • Soluble Salts of Soil
    • The soluble salts in soils are mostly combinations of the cations (+ charged ions) sodium, calcium, and magnesium potassium, and the anions (- charged) bicarbonate, chloride and sulfate.