Fertilizer

Fertilizers or fertilisers are compounds given to plants with the intention of promoting growth; they are usually applied either via the soil, for uptake by plant roots, or by foliar spraying, for uptake through leaves.

Organic fertilizers

• Examples of naturally-occurring organic fertilizers include manure and slurry, urine, peat, seaweed and guano. Green manure crops are also grown to add nutrients to the soil.
• Examples of manufactured organic fertilizers include compost, dried blood, bone meal and seaweed extracts.

The decomposing crop residue from prior years is another source of fertility. Though not strictly considered "fertilizer", the distinction seems more a matter of words than reality.

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Although the density of nutrients in organic material is comparatively modest, they have some advantages. For one thing organic growers typically produce some or all of their fertilizer on-site, thus lowering operating costs considerably. Then there is the matter of how effective they are at promoting plant growth, chemical soil test results aside. The answers are encouraging.

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Implicit in modern theories of organic agriculture is the idea that the pendulum has swung the other way to some extent in thinking about plant nutrition. While admitting the obvious success of Leibig's theory, they stress that there are serious limitations to the current methods of implementing it via chemical fertilization. They re-emphasize the role of humus and other organic components of soil, which are believed to play several important roles:

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• Mobilizing existing soil nutrients, so that good growth is achieved with lower nutrient densities while wasting less
• Releasing nutrients at a slower, more consistent rate, helping to avoid a boom-and-bust pattern
• Helping to retain soil moisture, reducing the stress due to temporary dryness
• Improving the structure of the soil

Organics also have the advantage of avoiding certain long-term problems associated with the regular heavy use of artificial fertilizers;

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• the possibility of "burning" plants with the concentrated chemicals
• the progressive decrease of real or perceived "soil health", apparent in loss of structure, reduced ability to absorb precipitation, lightening of soil color, etc.
• the necessity of reapplying artificial fertilizers regularly (and perhaps in increasing quantities) to maintain fertility
• the cost (substantial and rising in recent years) and resulting lack of independence

In practice a compromise between the use of artificial and organic fertilizers is not uncommon, typically in the form of chemical use, supplemented with the application of such organics as may be readily available such as the return of crop residues or the application of manure.

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It is important to differentiate between what we mean by organic fertilizers and fertilizers approved for use in organic farming and organic gardening by organizations and authorities who provide organic certification services. Some approved fertilizers may be inorganic, naturally-occurring, chemical compounds, e.g. minerals.

Related Topics:
Organic farming - Organic gardening - Organic certification - Minerals

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