Nutrient Availability to Plants
Outline of the section from "Home Gardener's Guide to Soils and Fertilizers" EB1971
- Plants can take up only nutrients that are in solution.
- Most soil nutrients are tied up in soil mineral and organic matter in insoluble forms.
- These nutrients must be converted to soluble forms and dissolved into the soil solution.
- This process occurs through weathering of mineral matter and biological decomposition of organic matter.
- Weathering of mineral matter is a very slow process that releases small amounts of nutrients each year.
- The rate of nutrient release from soil organic matter is somewhat faster and depends on the amount of biological activity in the soil.
- Nutrient release from soil organic matter is fastest in warm, moist soil and nearly nonexistent in cold or dry soil.
- Seasonal pattern of nutrient release is similar to the pattern of nutrient uptake by plants.
- About 1 to 4 percent of the nutrients in soil organic matter are released in soluble form each year.
- Soluble, available nutrients are in ionic form.
- K, Ca, Mg = cations. Cl = anion.
- Clay and organic matter surfaces have negative charges and can attract cations.
- "They hold nutrient cations in a ready reserve form that can be released rapidly into soil solution to replace nutrients taken up by plant roots. This reserve supply of nutrients contributes to a soil's fertility."