In the last ten years, we’ve seen an explosion in demand for organic fertilizers as alternatives to synthetic fertilizers. But is one really superior to the other? Let’s take a moment to explore this question.
Undoubtedly, there are some environmental concerns with the production of synthetic fertilizers, but purely in the context of what is best for our gardens, the short answer is no. Each type of fertilizer serves a different purpose, and by understanding these differences we can use both to the advantage of our gardens and the environment.

Using Synthetics
The main advantage to using synthetic fertilizers (especially liquid or water-soluble ones) is that they give your plants the nutrients that they need immediately. In synthetics, nitrogen, phosphorus, and potassium exist in a purer form that can be taken up quickly by your plants. If your plant has a nutrient deficiency, synthetics will give you a noticeable improvement in a matter of days. Synthetic fertilizers are also carefully proportioned – the numbers indicated on the package are very accurate, and synthetics tend to be less expensive than many organic options.

In summary, synthetics give your plant exactly what it needs, right now, for less money.

Conversely, the nutrients in organic fertilizers are often bound to other substances, and cannot be taken up by plants until a healthy microbial population breaks down the fertilizer into its contingent parts. It can take weeks or months to see a noticeable improvement, though warm, moist weather will speed the process considerably. As well, the nutrient ratios on many organic fertilizers may not be an accurate reflection of what will actually be available to your plants.

Using Organics
Organic fertilizers have their own important advantages, too. Over time, they will improve the health of your garden in ways that synthetics never will. As organic fertilizers break down, they improve the overall soil structure of your bed and will increase the soil’s ability to hold moisture and nutrients on its own. In contrast, synthetic fertilizers do almost nothing to improve overall soil fertility – they’re a once-and-done kind of treatment. Synthetics often lack many micronutrients that are available in organic fertilizers.

Their other advantage is that it is hard to over-fertilize with organic fertilizer, since the nutrient ratios are often low and the nutrients take a long time to release into the soil. On the other hand, the over-application of synthetic fertilizer in the short-term can harm your plants. In the long-term, it can even negatively affect your soil pH, allow for a build-up of undesirable compounds in the soil, and can upset delicate microbial balances in the soil that many plants rely on.

So, in short, organic fertilizers are better for the long-term health of your garden, and introduce important elements to the soil that synthetics do not.

So, now we’re left the question: which one do we use? The answer is of course contextual. A helpful way to decide is to ask yourself why you’re fertilizing in the first place. Are you troubleshooting a specific problem or perhaps trying to give a burst of growth to a short-lived annual? Use a synthetic fertilizer. If you’re instead trying to generally improve the overall health and vigour of your garden, consider organic fertilizers.

Have a tricky spot in your garden where just about nothing seems to grow? Consult our Tip Sheets on Difficult Planting Locations.