Plants Need a Little Vigor? How to Choose a Good Fertilizer
A walk down the fertilizer aisle at your local garden center or feed store can be incredibly anxiety-producing. Figuring out how to keep your crops growing vigorously and producing abundantly, without using questionable chemicals, is as complicated a subject to untangle as how to eat in a way that’s good for the body, the environment, and for farmers.
In an ideal world, we would grow food in a way that does not deplete the soil, thereby eliminating the need for boosting nutrient levels with fertilizer. We would also choose crops based on what our particular soil type—which might be higher in some nutrients and lower in others—is best suited for. And of course there are many biological methods to improve nutrient availability in the soil, from simply adding compost to growing cover crops, which are the backbone of any holistic approach to fertility management. The old adage that real farmers grow soil, not crops, is more important than ever in the age of high-input chemical agriculture.
But the world is not an ideal place, and most farmers and gardeners are reliant on fertilizers beyond just compost, which are more accurately described as a soil amendments. In the name of demystifying the marketing hype and technical jargon, here are a few tips to help you sniff out the products best suited to your unique horticultural circumstances, with as little negative environmental side effects or health hazards as possible.
Organic, All-Natural, or Synthetic?
First question: How do you tell what’s synthetic and what’s not? That’s fairly straightforward—usually. The ingredients in each fertilizer product should be listed on the container. Organic products contain natural substances like blood and bone meal, cottonseed meal, fish meal, rock dust, kelp, etc. On the contrary, if you see ingredients like “ammoniated super-phosphate” or “isobutylidene diurea,” you’re looking at a synthetic product.
The distinction is less clear with some terms, however. Phosphates are generally associated with synthetic fertilizers, but some organic fertilizer products may also list phosphates as an ingredient—if you see the term listed by itself or as “rock phosphate,” a naturally occurring mineral, it is generally an organic product, while most other forms of phosphate (products like diammonium phosphate and polyphosphate, for example) are synthetics.
“Urea,” a common source of nitrogen used by fertilizer manufacturers, is another confusing term. While it can be derived from animal urine, a natural source, the urea listed in fertilizer is almost always a synthetic form made from natural gas. Because it is a carbon-based compound, it can legally be described as an organic fertilizer (even if the urea is synthetic), and often is, though this is a highly misleading claim.
Natural vs Organic: Understanding Labels
This brings about an important point about fertilizer labels: “organic” does not mean the same thing in the fertilizer aisle as at the grocery store. There is no such thing as organic certification for fertilizers, so the word is often used in the broadest sense, meaning simply “carbon-based.” This is why it’s good to check the ingredients. The term “natural” is more relevant than “organic” on fertilizers—which is pretty much the opposite of food—as it indicates that the ingredients are derived from minimally processed (i.e. ground up and mixed with other natural substances that make them easier to apply or more effective in some way) plant, animal, or mineral sources, rather than artificially synthesized. The Organic Materials Review Institute maintains a list of fertilizers that are compatible with organic growing practices; look for the OMRI seal to be sure a product is not using the word “organic” in a misleading way.
The Ugly Truth About Synthetic Fertilizers
Why does it matter if fertilizer is natural or synthetic? As far as the plants are concerned there’s not much difference—a molecule of nitrogen is the same, whether it’s derived through natural or synthetic means. The biggest difference for plants is that synthetic fertilizers are usually in a form that’s easy to absorb, so they get a quick boost of the nutrient rather than a slow release.
But there are drawbacks. Synthetic nutrients do not feed the soil food web, which means biological life in the soil slowly ceases to function as it should, a process that is accelerated by the relatively high salts and acidity of chemical fertilizers. The result is powdery, crusted over, nearly lifeless soil, and thus greater dependency on fertilizers to provide nutrients, rather than biological processes. Plus, synthetic nutrients are highly water soluble and tend to run off into the watershed, where they cause toxic algae blooms and other environmental havoc. Not to mention that they require huge quantities of fossil fuels to produce and even contribute to greenhouse gases after they are applied—a double whammy on a warming planet.