There are two types of fertilizer: natural (organic) and chemical (synthetic).

Natural fertilizers are composed of organic materials such as plant or animal matter that has not been chemically processed (e.g. bone powder, fish emulsion and shrimp waste); or minerals, such as magnesium sulfate, potassium sulfate and mica. “Most natural fertilizers must be broken down by living organisms in the soil before they can release nutrients,” says Jean-Pierre Parent, a horticultural information agent at the Montreal Botanical Garden. Moreover, most natural fertilizers have a slow and prolonged action, which limits any risks of leaching or root burn. They are less harmful to the environment than chemical fertilizers.”

Chemical fertilizers (also called inorganic fertilizers) contain chemically processed substances (synthetic chemicals). “They are produced by using non-renewable fossil resources such as natural gas,” says Jean-Pierre Parent. “Unlike natural fertilizers, they dissolve quickly, releasing more nutrients than the soil can absorb. The surplus nutrients then seep through the water table or are swept by rain into waterways, polluting the environment, most notably drinking-water sources. Risks of root burn are higher than with natural fertilizers. What’s more, exclusive and repeated use of chemical fertilizers can wreak havoc on the soil, causing salinity problems and even killing beneficial microorganisms. That’s why we recommend that you use 100% natural fertilizers. But if you must use chemical fertilizers, we suggest you consider the coated variety (sulfur, for example), which dissolves more slowly.”

That said, remember that too much fertilizer (whether natural, but especially chemical owing to its high nitrogen content) in the soil can “burn” your lawn. Furthermore, plants that grow too rapidly are particularly vulnerable to insects and disease. So fertilize your lawn according to its special needs, as recommended by the manufacturer. A tip: practise grasscycling, in other words, leave grass clippings on the lawn when mowing. As they decompose, the clippings will release nutrients, thereby reducing your fertilizer need by 30%.

By Jacqueline Simoneau