Did You Know? The Myth of Synthetic Fertilizers


In today’s Did You Know? post, I thought that we should look at synthetic fertilizers. In the next few weeks, people will be buying 10-10-10 and other fertilizers by the bags at home improvement centers and garden stores. While conventional wisdom dictates that a lawn or garden needs to be fertilized every year, you may be surprised to learn that you can save money and time by not applying them.

Let’s investigate a 50-pound bag of 10-10-10 fertilizer and see what it is really comprised of. 10-10-10 refers to the nitrogen (N), phosphorous (P) and potassium (K), or N-P-K for short, content. A 50-pound bag of 10-10-10 is made up of 5 pounds of N (10% of the 50-pounds), 5 pounds of P and 5 pounds of K. The other 35 pounds are inert ingredients that allow the fertilizer to be applied evenly.

Nitrogen in fertilizer is usually made from ammonium nitrate or urea. Either way, most of the nitrogen is readily available when it is applied and is therefore either quickly taken up by the plant or washed away with heavy rains. A good rule of thumb to remember is that the nitrogen is usually gone within a couple of weeks of being applied.

Phosphorus in fertilizer is generally made from phosphoric acid which is the end result of treating rocks containing phosphorus with sulfuric acid. Of course, there is much more to this process than I can explain here, but suffice it to say that it’s a chemical process that produces phosphorus that is in a bag of fertilizer.

Potassium in fertilizer is comprised of potash, which is a generic term that describes water soluble potassium in various salts. Again, I’m not attempting to give a chemistry lesson here…my main objective is to show you that all of these nutrients that we put down with the best of intentions aren’t naturally occurring in the form that they are applied.

If you’ve read any of my posts about soil building, you may have heard me say that we need to feed the SOIL not the plants. And that is my point here. By applying synthetic versions of nitrogen, phosphorus and potassium we are feeding the plants…it is the plants that need these nutrients, not the soil. The soil needs organic matter to feed the microbes and earthworms that in turn release these nutrients in their natural form. By applying chemical fertilizers, we are acidifying the soil and turning an environment that would otherwise foster the growth of our little friends into a barren, almost lifeless area of dirt. That feeds into the vicious cycle of having to apply more and more fertilizers to achieve the same result in subsequent years.


  1. Add compost, compost and more compost. While it’s true that you don’t want to apply a thick layer to an existing lawn, but in the vegetable garden I can’t imagine that you could ever apply too much. Just make sure if it is manure based, that it is well-composted. The only exception to this rule is rabbit poo. It can go straight from the rabbit to the garden without composting.
  2. Aerate the soil. I don’t really think that tilling is a good idea (I’ll do a post about that soon) but it is vitally important to make sure that there is enough air in the soil to sustain plant roots and soil organisms. If you are encouraging earthworms, they will do all of the aerating that you will ever need…remember, Ma Nature knows what she is doing.
  3. Don’t leave the soil barren. You can avoid crusting of the soil and erosion by making sure that there is always something actively growing on the land. Cover cropping is a popular technique in veggie gardens for the winter but even mulching with straw or leaves is far better than allowing the rain to beat the topsoil into a crust.


I hope that I’ve given you a little insight into synthetic fertilizers and more importantly, how to think of them differently. If you take the time to compost your scraps and look for other sources of compost like horse barns, you will be rewarded with the most beautiful plants and healthy soil. I’d love to hear what you have done to reduce your use of synthetic fertilizers. Leave me a comment below or e-mail me at stacey@midatlanticgardening.com. Happy gardening!

January 23, 2012Permalink 1 Comment

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