What’s the Difference Between Compost and Fertilizer?

When it comes to fertilizing your garden and flower beds, many options are available. Sure, composts and fertilizers are materials that enrich the soil and feed your plants, but wouldn’t you like to know which one to use to get the best results and provide your vegetables, flowers, and shrubs with what they truly need? Here are the main differences between composts and fertilizers and how you should use them.

The difference between compost and fertilizer

Composts

Composts are the result of the decomposition of organic matter. They fall into two main categories: plant compost and animal compost, more commonly known as composted manure.

As its name suggests, plant compost is the result of the controlled decomposition (composting) of plants, including but not limited to food waste, dead leaves, and lawn clippings. Composted manure, on the other hand, is the result of composting the excrement of herbivorous animals such as cows, horses, sheep, and chickens. A plant portion (sphagnum peat moss) is added so that the manure can compost (oxygen supply). The aim is to make the product drier, less odorous, and, most importantly, easier to spread. Composted manure is therefore a combination of animal and plant compost.

Generally speaking, composts have the following benefits and functions:

Improve soil structure and fertility on a long-term basis by enriching it with beneficial microorganisms.
Provide plants with a natural source of essential nutrients for growth.
Increase soil organic matter content to facilitate water and nutrient retention.

However, it’s important to know that composted manure is generally more nutrient-rich than plant compost. While both contain a full range of minerals, composted manure contains macronutrients (nitrogen, phosphorus, and potassium) in higher concentrations, making it a more appealing soil amendment. Composted manures available on the market are enhanced with ingredients that bring added value to your vegetable garden and flower beds. Take Biofor Composted Manure with Peat and Bark, for instance. This blend contains bark that breaks up compacted soil particles, improving drainage in heavy, clay soils and promoting root system development. Another example is the Biosol Composted Manure with Peat, Seaweed and Shrimp, which is enriched with seaweed and shrimp, an excellent source of micronutrients (calcium, magnesium, sulfur, iron, zinc, etc.). These micronutrients help boost plants’ immune systems, making them more resistant to stresses such as frost, drought, disease and pests.

Fertilizers

Unlike composts, which enrich and improve soil structure over time, fertilizers are designed to feed plants directly and quickly. In fact, a fertilizer is a concentrate of organic and/or mineral substances intended to provide additional nutrients to plants to improve their growth and favors abundant bloom and/or harvest. Its formulation includes a combination of predetermined percentages of nitrogen, phosphorus, and potassium (N-P-K) as well as other micronutrients.

Natural or synthetic fertilizers

There is a wide range of fertilizers on the market (water-soluble powder, granular, liquid, etc.). These are grouped under two main categories: natural and synthetic fertilizers.

Synthetic fertilizers, such as ammonium nitrate, ammonium phosphate, and potassium sulfate, come from a mineral source (nonliving) and have undergone chemical or mechanical processing. Nutrients are easily absorbed by the plants to provide fast and striking results.

As for natural fertilizers, they are composed of organic (animal or vegetable) and/or mineral sources that have only undergone mechanical transformation (drying, crushing, or sieving). They include bone meal, blood meal, feather meal, sodium nitrate, sulfate of potash, and seaweed. Their action is generally slow and long-lasting because they must first be transformed by soil microorganisms to be assimilated by the plants, which makes the risks of leaching and root burn almost nonexistent. They are also less concentrated than synthetic fertilizers. Indeed, you will notice that the numbers on the packaging are always smaller.

How to use composts

Composted manures are an excellent soil amendment for flower beds, vegetable gardens, lawns, and planters. They can be used basically anywhere at any time. Once a year, spread a few millimeters evenly on your lawn to nourish it, apply a few centimeters at the bottom of your planters, or spread a thin layer on top of your flower beds and vegetable garden and mix it to ensure growth and abundant flowering.

How to use fertilizers

Synthetic granular fertilizers are generally applied about every six to eight weeks. Slow-release fertilizers work for months, so one application is generally all that is needed for a growing season. Water soluble or liquid fertilizers are fast-acting. They should be applied every two weeks to compensate for nutrient loss due to leaching. Natural fertilizers should be applied every four weeks as they release the nutrients progressively. Fertilizers should always be applied throughout the growing season according to the manufacturer recommendation on the packaging since their formulation varies.

Compost or fertilizer? Use them together!

To sum it up, your garden and flower beds need a balanced supply of nutrients throughout the year. It is important to understand that compost and fertilizer are complementary and that each one plays a crucial role in the growth of your plants. Composts nourish the soil and improve its quality (structure, microbial life), while fertilizers nourish plants. Compost alone is not enough, as its nutrient supply is slowly depleted over the course of the season. This is where fertilizers come into play, as they contain a greater amount of nutrients. They will complement the work of composts by supporting the healthy, vigorous growth of your plants throughout the season (see graphic).

Hopefully, we’ve demystified the use of compost and fertilizer and answered all your questions. Visit your local garden center to find all the products you need to carry out your gardening projects!

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Compost and Fertilizer: Differences and Applications