Soil plays a vital role in the nitrogen cycle, particularly through processes facilitated by the microorganisms living within it.
Soil's Key Contribution: Nitrification
One of the primary ways soil contributes to the nitrogen cycle, as highlighted by the provided reference, is through the process of nitrification. This essential step is carried out by soil organisms, specifically certain types of bacteria and archaea.
Nitrification involves a two-step conversion:
- Soil organisms first convert ammonia (NH₃) and ammonium (NH₄⁺) into nitrite (NO₂⁻).
- Subsequently, other soil organisms convert the nitrite (NO₂⁻) into nitrate (NO₃⁻).
Nitrogen Forms in Soil
The reference mentions different forms of nitrogen and their plant availability:
- Ammonia (NH₃) / Ammonium (NH₄⁺): Initial forms that are converted.
- Nitrite (NO₂⁻): An intermediate form produced in soil, referred to as Nitrite N. The reference states this form is not available for plant use.
- Nitrate (NO₃⁻): The final form produced by nitrification. The reference states this form is available for plant use.
Soil, therefore, acts as a crucial site where unavailable or less available nitrogen forms are transformed into the nitrate form, making it accessible for plants to absorb and utilize for growth. Without the soil ecosystem and its diverse microbial community, this critical conversion step would not occur effectively, significantly impacting plant life and the broader ecosystem.
| Nitrogen Form | Chemical Formula | Plant Availability (Based on Ref.) |
|---|---|---|
| Ammonia / Ammonium | NH₃ / NH₄⁺ | Converted by soil organisms |
| Nitrite N | NO₂⁻ | Not available |
| Nitrate N | NO₃⁻ | Available for plant use |
Soil's contribution is fundamental to making nitrogen, a critical nutrient, usable for the terrestrial ecosystem.
