Soil Cycling
Soil Cycling
Soil is very important for nutrient cycling and is an integral part of biogeochemical cycles. For each of the biogeochemical cycles you have learned (carbon, nitrogen, sulfur, phosphorus, hydrologic) answer/describe the following questions as it relates to soil and biogeochemical cycles.
1) In what forms (compounds/molecules/states/phases) does each exist within soil? (1 pt)
- Nitrogen
Ammonium (NH4+)
Nitrogen exists in soil as ammonium, a positively charged ion readily absorbed by plants. It forms through organic matter decomposition.
Nitrate (NO3-)
Nitrate, a negatively charged ion, is another key form of nitrogen. It results from nitrification of ammonium by soil bacteria.
Organic Nitrogen
Organic nitrogen is found in soil organic matter, including proteins, amino acids, and humus. It mineralizes into ammonium.
Nitrogen Gas (N2)
Nitrogen gas exists in soil air spaces. Soil bacteria convert it into usable forms through nitrogen fixation.
- Phosphorus
Phosphate Ions (H2PO4-, HPO42-)
Phosphorus in soil primarily exists as phosphate ions. Plants absorb these ions directly from soil solution.
Organic Phosphorus
Organic phosphorus resides in soil organic matter. Microorganisms decompose it, releasing phosphate ions for plant use.
Calcium Phosphate Minerals
Phosphorus also exists in insoluble minerals like calcium phosphate. These minerals slowly dissolve, releasing phosphate ions.
- Potassium
Potassium Ions (K+)
Potassium exists in soil as potassium ions. These ions are easily absorbed by plant roots from the soil solution.
Fixed Potassium
Fixed potassium resides in clay minerals. It becomes available to plants through weathering and soil microbial activity.
Organic Potassium
Organic matter contains organic potassium. Microorganisms decompose it, releasing potassium ions into the soil solution.
- Sulfur
Sulfate Ions (SO42-)
Sulfur primarily exists in soil as sulfate ions. Plants absorb these ions from the soil solution.
Organic Sulfur
Organic sulfur is found in soil organic matter. Microbial decomposition releases sulfate ions from these compounds.
Elemental Sulfur (S)
Elemental sulfur exists in soil, often from fertilizers. Soil bacteria oxidize it to sulfate, making it plant-available.
- Calcium
Calcium Ions (Ca2+)
Calcium in soil exists as calcium ions. These ions are readily absorbed by plant roots.
Calcium Carbonate (CaCO3)
Calcium carbonate is a common soil mineral. It neutralizes soil acidity and provides calcium ions upon dissolution.
Calcium Phosphate
Calcium also exists in calcium phosphate compounds. These compounds release calcium ions slowly as they dissolve.
- Magnesium
Magnesium Ions (Mg2+)
Magnesium exists in soil primarily as magnesium ions. Plants absorb these ions from the soil solution.
Magnesium Carbonate (MgCO3)
Magnesium carbonate is a mineral form of magnesium. It dissolves slowly, providing a steady supply of magnesium ions.
Organic Magnesium
Organic matter contains organic magnesium. Microbial decomposition releases magnesium ions for plant uptake.
2) What role or importance does each cycle play in regard to nutrient cycling? To organisms? (1.5 pts)
3) Describe what most plays a role in the cycling of each? (organisms? chemical reactions? other?; 1.5 pts)
4) Describe two different examples of how different cycles may interact with one another in the soil. (1 pt)
5) Describe South Florida soil. Particularly address the layers of soil (O-A-E-B-C-bedrock) present (or absent) and its constituents (what it is made of). Do not just copy and paste this answer from a website, even if you properly cite it…describe in your own words. (1 pt)
References
https://www.soils.org/membership/divisions/
https://sarep.ucdavis.edu/sustainable-ag
