Soil Organic Matter, Carbon Cycling & Nitrogen Dynamics

A comprehensive set of flashcards outlining key concepts related to soil organic matter, carbon cycling, and nitrogen dynamics, aimed at aiding students in understanding soil processes essential for environmental and agricultural studies.

Soil Organic Matter (SOM)

The organic component of soil, consisting of plant and microbial biomass.

Litter

Dead plant material that contributes to fresh soil organic matter.

Carbon Inputs

Sources of carbon entering the soil, mainly from plant biomass and microbial activity.

Decomposition

The microbial breakdown of organic matter into simpler compounds.

Mineralization

The conversion of organic nitrogen into inorganic nitrogen forms, primarily NH₄⁺.

Nitrogen Mineralization

The process by which microbes convert organic nitrogen into inorganic nitrogen.

Nitrogen Immobilization

The uptake of inorganic nitrogen into microbial biomass, temporarily reducing its availability to plants.

C:N Ratio

The ratio of carbon to nitrogen in organic matter, influencing nitrogen cycling.

Biological Nitrogen Fixation (BNF)

The microbial conversion of atmospheric N₂ into ammonium (NH₃).

Nitrification

The aerobic microbial oxidation of ammonium (NH₄⁺) to nitrite (NO₂⁻) and then to nitrate (NO₃⁻).

Denitrification

The anaerobic microbial reduction of nitrate (NO₃⁻) to gaseous nitrogen forms (e.g., N₂O, N₂).

Reactive Nitrogen

Biologically available nitrogen forms including ammonium (NH₄⁺) and nitrate (NO₃⁻).

Labile Compounds

Organic compounds that are easily broken down by microbes, promoting rapid decomposition.

Stabilization of SOM

Processes that protect organic matter from decomposition, including chemical recalcitrance and physical protection.

High C:N Ratio

Organic matter with a high carbon to nitrogen ratio that tends to promote nitrogen immobilization.

N₂O

Nitrous oxide, a potent greenhouse gas produced during nitrification and denitrification.

Microbial Community

The diverse populations of microorganisms in the soil that drive processes such as decomposition and nutrient cycling.

Humic Substances

Large, heterogeneous organic compounds formed from the decomposition of plant and microbial materials.