FERTILIZER: APPLICATION (ORGANIC VS INORGANIC)

Sara was a graduate student with the Department of Horticulture Science. This column is offered as a service of the Division of Extension and Community Relations and the Department of Horticulture Science, University of Saskatchewan.

When and When Not to Fertilize

Lawns should be fertilized on approximately May 15 with 2 to 2.5 kg of 27-14-0 or 26-13-0 per 100 m2. Six weeks later apply 2.0 kg of 34-0-0 per 100 m2. Six weeks later apply 2 kg of 34-0-0 per 100 m2.

Trees and shrubs generally do quite well on Saskatchewan soils without the addition of chemical fertilizers. Most problems associated with trees and shrubs are due to lack of proper watering or insect problems and are seldom attributed to lack of nutrition. Excess fertility in the soil promotes excess succulent foliage which is more susceptible to winter injury.

Vegetable and flower beds usually require 11-48-0 or 16-20- 0 applied in spring at the rate of 2 lb per 100 m2.

Do NOT apply fertilizer in late summer or fall. It will cause lush, succulent growth which may not "harden off" in time for winter and therefore be more susceptible to winter kill or fungal or bacterial problems.

Never put granular fertilizer or fresh manure in the planting hole. The chemical salts within the fertilizer may desiccate or "burn" plant roots.

How to Apply Commercial Fertilizer

On lawns, to apply granular fertilizer, first divide the total amount needed in half. With a fertilizer spreader adjusted to the lowest possible setting, walk north-south over the lawn area with half the amount, and then east-west with the other half. This will give an even distribution and reduce the possibility of "burning." If you are hand-broadcasting, follow the same procedure.

In vegetable gardens and annual flower beds, fertilizer may be applied in several ways: (1) fertilizer can be broadcast and thoroughly incorporated into the upper 7 to 8 cm of soil in spring prior to planting; (2) or it can be side-banded that is, incorporated along the sides of each row and about 5 cm deep. This involves more work but is more efficient because less fertilizer is used; or (3) fertilizer can be placed around each plant, 5 cm away and 5 cm deep. This last method is even more "labor intensive" than side- banding but it is also more efficient, in that all of the fertilizer is placed where it can be used by the plants. In perennial borders or other permanent plantings, fertilizer should be incorporated around each plant, 5 cm deep and 5 cm beyond the roots.

Organic vs. Inorganic

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 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.
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