Page 24 - Nutrient Management Planning Guide

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Soil Nutrient Cycling

Important Terms

Table 2.1.1 Key Terms and Definitions

Term Definition

Adsorption

Is the physical adherence or bonding of ions and molecules onto the surface of another molecule.

Denitrification

The process where soil micro-organisms obtain their oxygen from nitrates and nitrites, resulting in the release of nitrogen or nitrous oxide. This can happen in waterlogged soils when oxygen is limited and anaerobic decomposition occurs.

Eutrophication The natural ‘aging’ of aquatic systems caused by the introduction of limiting nutrients.

Fixation (nitrogen)

The conversion of atmospheric nitrogen by soil micro-organisms, such as rhizobia, into organic forms, which can be released into a form plants can use.

Humus Any organic matter that has reached a point of stability and breaks down very slowly.

Immobilization

The absorption by micro-organisms of nutrients released from organic matter decomposition, preventing these nutrients from being available to plants. The opposite to mineralization. Labile Nutrients or organic material that is constantly changing or susceptible to rapid changes. Leaching The downward movement of substances, such as nutrients, in water through soil pores.

Macronutrient

An essential chemical element, such as nitrogen or phosphorus that is needed by plants in large quantities for it to function normally.

Micronutrient

An essential chemical element, such as boron or zinc that is needed by plants in small quantities for it to function normally.

Mineralization

In biology, this is the process where an organic substance is converted to an inorganic substance.

Nitrification

The biological addition of oxygen to (oxidation of) ammonia creating nitrite that can be further oxidized into nitrate.

Precipitation In chemistry, this is the condensation to a solid from a solution during a chemical reaction. Salinity The accumulation of free salts in the soil solution.

Sorption

The action of either absorption or adsorption. It is the effect of gasses or liquids being incorporated into material of a different state and adhering to the surface of another molecule.

Stomata

Is a pore or opening in plant leaves (plural term for stoma). Guard cells close and open the stoma, controlling the loss of water vapour and other gasses from the plant. Transpiration The process of evaporation of water from above ground parts of plants.

Volatilization

Gaseous loss to the atmosphere. In a nutrient management context, it is the loss of ammonia gas to the atmosphere.