BIOL 317 1st Edition Lecture 4 Outline of Last Lecture - SoilOutline of Current Lecture - Soil HorizonsCurrent Lecture- Soil Subordinate Horizons - Oi - organic fibric horizon - one is able to identify all the constituents of the soil- Oe - organic hemic horizon - half the constituents are identifiable - Oa - organic sapric horizon - decomposed constituents that are unidentifiable Five Drainage Classes - Well Grain Soil - Moderately Well Grain - Somewhat Poorly Drained Soil - Poorly Drained Soil - Very Poorly Drained Soil Depending on where the soil develops determines how many layers and type of drainage class of soilCatena - sequence of soil that are the same age and derived from similar parent material. They occur under similar climatic conditions, but have different characteristics, because of a variation in topographical relief and drainage Loam - soils made up of equal amounts of sand, silt, and clay. Typically the most fertile soils- 50% are all pore space- 45% are minerals - 5% are organic materialSoil Texture - Soil is negatively charged - Sando Largest mineral particle in soil o 2.0 to .05 mm- Silt o .05 to .002 mm- Clay o Smallest particle in soilo Less than .002 mm o High cation change capacity - will hold more nutrients Entisols - Young in age and have little profile development Histisols - Young in age and are organic soils that exist in medium to high rainfall areasInkeptisols - Embryonic soil that lead to the B horizon Andisols - Soil that develops from volcanic ejections (volcanic soil)- High in base cations, which means they are good for plant