Nitrogen organic matter refers to the complex mixture of organic compounds that contain nitrogen, primarily found in soil and resulting from the decomposition of plant and animal residues. These compounds form a crucial part of soil organic matter (SOM).
Composition of Nitrogen Organic Matter
Nitrogen in organic matter isn't present as a single compound but rather within a variety of substances. These can be categorized as:
- Decomposing Plant and Animal Residues: Freshly added organic material from plants and animals undergoing breakdown. This material contains proteins, amino acids, nucleic acids, and other nitrogen-containing molecules.
- Products of Decomposition-Resistant Compounds: More stable and complex organic molecules formed during the decomposition process. These include substances less readily broken down by microorganisms.
- Humus: A relatively stable, amorphous, colloidal substance that is a product of decomposition. Humus contains complex nitrogen-containing organic compounds that are highly resistant to further breakdown.
Importance of Nitrogen Organic Matter
The nitrogen held within organic matter plays several key roles:
- Nutrient Reservoir: It serves as a reservoir of nitrogen that can be slowly released over time to plants and microorganisms. This slow release helps sustain plant growth.
- Soil Fertility: Contributes to overall soil fertility by improving soil structure, water retention, and nutrient availability.
- Environmental Impact: Influences nitrogen cycling in ecosystems and can affect greenhouse gas emissions and water quality.
Release of Nitrogen from Organic Matter (Mineralization)
The conversion of organic nitrogen to inorganic forms (like ammonium and nitrate) that plants can use is called mineralization. This process is carried out by soil microorganisms. The rate of mineralization depends on:
- Temperature: Higher temperatures generally increase microbial activity and mineralization rates.
- Moisture: Adequate moisture is essential for microbial activity.
- pH: Near-neutral pH is usually optimal for mineralization.
- Carbon to Nitrogen Ratio (C:N): Organic matter with a lower C:N ratio (more nitrogen relative to carbon) tends to mineralize more rapidly.
In summary, nitrogen organic matter is a vital component of soil, acting as a storehouse for nitrogen that is gradually released to support plant growth and overall ecosystem health. It is formed through the decomposition of organic materials and contributes to soil fertility and nutrient cycling.
