Organic in that sense means fertilizers and pesticides that haven’t been chemically enhanced or changed. They are in their natural form (or at least they are supposed to be). It is a healthier way to grow food. The food doesn’t have hormones and chemicals in it.

Examples of naturally-occurring inorganic fertilizers include Chilean sodium nitrate, mined rock phosphate and limestone (a calcium source).
Examples of naturally occurring organic fertilizers include manure, slurry, worm castings, peat, seaweed, sewage , and guano. Green manure crops are also grown to add nutrients to the soil. Naturally occurring minerals such as mine rock phosphate, sulfate of potash and limestone are also considered Organic Fertilizers.
Examples of manufactured organic fertilizers include compost, bloodmeal, bone meal and seaweed extracts. Other examples are natural enzyme digested proteins, fish meal, and feather meal.

Inorganic fertilizers sometimes do not replace trace mineral elements in the soil which become gradually depleted by crops grown there. This has been linked to studies which have shown a marked fall (up to 75%) in the quantities of such minerals present in fruit and vegetables.[2] One exception to this is in Western Australia where deficiencies of zinc, copper, manganese, iron and molybdenum were identified as limiting the growth of crops and pastures in the 1940s and 1950s. Soils in Western Australia are very old, highly weathered and deficient in many of the major nutrients and trace elements. Since this time these trace elements are routinely added to inorganic fertilizers used in Agriculture in this state.

In many countries there is the public perception that inorganic fertilizers poison the soil and result in low quality produce. However, there is very little (if any) scientific evidence to support these views. When used appropriately, inorganic fertilizers enhance plant growth, the accumulation of organic matter and the biological activity of the soil, while reducing the risk of water run-off, overgrazing and soil erosion. The nutritional value of plants for human and animal consumption is typically improved when inorganic fertilizers are used appropriately.

There are concerns though about arsenic and cadmium accumulating in fields treated with phosphate fertilizers. Eventually these can build up to unacceptable levels and get into the produce. (See cadmium poisoning.)

Another problem with inorganic fertilizers is that they are presently produced in ways which cannot be continued indefinitely. Potassium and phosphorus come from mines (or from saline lakes such as the Dead Sea in the case of potassium fertilizers) and resources are limited. Nitrogen is unlimited, but nitrogen fertilizers are presently made using fossil fuels such as natural gas. Theoretically fertilizers could be made from sea water or atmospheric nitrogen using renewable energy, but doing so would require huge investment and is not competitive with today’s unsustainable methods. The present level of human population may not be sustainable without the use of the artificial fertilizers which we have gotten used to.

Organic fertilizers vs. Inorganic fertilizers.

There has been much controversy over organic versus inorganic fertilizers.

It is important to realize that plants do not recognize the difference between organic and inorganic fertilizers.

Their tiny root hairs can absorb only nutrients that have been broken down into inorganic, water-soluble forms.

It makes no difference to your tomato plant if the atom of nitrogen it is absorbing has come from a compost pile or a fertilizer factory.

There are, however, advantages and disadvantages to each form of fertilizer, organic and inorganic.

Organic Fertilizer

Advantages -

Organic nutrients include such things as cow, sheep, poultry and horse manure. (One should avoid using pig, dog or cat feces because of the problems involved with internal parasitic worms which may be transferred to humans.) Bonemeal, bloodmeal, compost, and green manures will also provide nutrients for your plants.

There is less danger of over-fertilization by adding decomposed organic material to a garden.

It provides a slow release of nutrients as micro-organisms in the soil break the organic material down into an inorganic, water soluble soluble form which the plants can use.

The addition of organic material improves soil structure or workability immensely. It also vastly improves the water-holding capacities of sandy soils, a distinct advantage in arid climates such as ours.

Disadvantages -

For the most part, organic fertilizer is not immediately available to the plants. As noted above, this slow- release feature can be an advantage.

However, if there is an immediate need for nutrients, organic fertilizer cannot supply them in a hurry. Furthermore, information on the amount of nutrients and the exact elements in an organic fertilizer such as manure is not readily available to the home gardener.

In contrast, when you apply manufactured inorganic ferilizer you know the kinds and amounts of the elements it contains, and this allows you to be more precise in meeting a plant’s nutritional needs.

The possibility of nitrogen depletion is another drawback of organic fertilizers.

Because of complex bacterial action, the addition of a large amount of organic material can cause a temporary nitrogen depletion in the soil and therefore in the plants.

Inorganic or Commercial Fertilizer.

Advantages -

The primary advantage of using packaged commercial fertilizer is that nutrients are immediately available to the plants. As well, the exact amounts of a given element can be calculated and given to plants.

Disadvantages -

Commercial fertilizer, especially nitrogen, is easily washed below the level of the plant’s root system through the leaching of rain or irrigation.

An application which is too heavy or too close to the roots of the plants may cause burning (actually a process of desiccation by the chemical salts in the fertilizer). As well, overly heavy applications of commercial fertilizers can build up toxic concentrations of salts in the soil, thus creating chemical imbalances.

If organic materials are readily available and cheap, the expense of the commercial fertilizer should also be considered.

Whether a gardener chooses to use organic, inorganic or a combination of both types of fertilizers, it’s important to follow the guidelines regarding timing of application, placement of the fertilizer, and the proper amount of fertilizer to be used.