A top most mineral horizon - varying levels of organic matter - .5 to 4% in Missouri zone of maximum leaching/weathering - clay along with iron & aluminum oxides - light in color E zone of maximum accumulation - clay along with iron & aluminum oxides B
zone where the soil forming processes that are active in the A, E, & B horizons are essentially non-existent
Classes based on relative proportions of sand, silt and clay Moderately Fine sandy clay loam, clay loam & silty clay loam Fine sandy clay, silty clay & clay Coarse sand and loamy sand Moderately Coarse Sandy Loam Medium silt, loam and silt loam
The "exchange" between a cation in the soil solution and another cation on the surface of negatively charged material such as clay or organic matter.
Negatively Charged Colloids Attract Positively Charged Ions Cations K + Ca +2 Na + Ca +2 H + Mg +2 - - - - - - - - - soil colloid H + H + K + Ca +2 NH 4 + soil solution soil solution soil solution Fe +2 - - - Al +3 H + H +
pH Preferences of Some Common Plants Alkaline loving >7.0 Pin Oak, Magnolia Pine, Juniper Holly, Birch Sweet Gum, Spruce Ash, Beech Dogwood, Maple Spruce, Yew Cedar, Elm Juniper, Poplar Redbud, Willow Tuliptree Poplar, Willow Black Walnut Junipers, Redbud Elm, Maple Hickory Medium Range 6.0 - 7.0 Acid Loving <6.0