PO 7. Recognize the role of the following in supplying nutrients from the soil.

Soil minerals weather, break down, and dissolve, releasing nutrients that plants can take up.  Some also can retain nutrients by adsorption on their surfaces, much like CEC.  Soil minerals are divided into two categories based on the degree of weathering.

1.       Primary minerals persist with little change in composition.  Examples include: quartz, micas and feldspars.

2.       Secondary minerals are formed by the breakdown and weathering of primary minerals.  Examples include clay minerals, iron and aluminum oxides, dolomite, calcite and gibbsite.

Plant residues include contributions to the soil such as green manure or plowing down of cover crops.  As these break down, the nutrients contained are leached into the soil, where they become available to growing plants.  Nitrogen is one of the nutrients most commonly associated with residue, but the other essential nutrients will become available as well.