Recently the popularity of organic fertilizers has been on the rise. More and more people use cracked corn, alfalfa or soy bean meal as their main source of nutrients for their lawn. Proponents of organic fertilizers often claim that the use of organic fertilizers brings has great benefits. Let’s analyze each claim:
- Hard to overdose vs. synthetic. This is true. While application instructions on fertilizer bags are generally clear and easy to follow, some novices may feel more at ease knowing they can’t really over-apply and hurt the lawn. Synthetic fertilizers are fairly forgiving as well though, I have applied synthetic fertilizer at double the rate with no ill effects except to my back from all the extra mowing.
- Slow release. This is also true. Organic fertilizers have to be broken down by bacteria before nutrients becomes available to the plant, resulting in a slow trickle of nitrogen. However, synthetic options such as coated urea and UMAXX exists at a cost up to 7 times lower per pound of nitrogen.
- Feeds the soil microbes. This is true, but the need for an over-inflated microbial population in the soil beyond what grass clippings and bugs and normal natural processes can sustain is unclear.
- Increases organic matter/improves soil structure. This claim is false. Studies have shown little to no long term contribution to soil organic matter content from materials applied on the surface. In pastures studies have shown grass roots to be the major contributor to organic matter – up to 80%. Other studies have show shoot restitution programs to have zero or negative effects of soil organic matter.
- Safer for kids and dogs. This claim is also false, both are equally safe. No child is going to pick granules of fertilizer out of lawn, and if they did, it’s unclear which one would be worse, a granule of urea or a piece of rotting corn coated in bacteria and fungus.
Organic fertilizers do come with some clear disadvantages over synthetic fertilizers:
- Cost. Organic fertilizer is up to 11 times more expensive per pound of nitrogen than urea and up to 7 times more expensive per pound of nitrogen that coated urea.
- Cumbersome. It takes 13-20 pounds of organic material per thousand square feet vs 2 pounds of urea per thousand square feet to apply one pound of elemental nitrogen. That can literally add up to truckloads of corn per year for larger lawns.
- Slow to act. Since the organic matter has to be broken down by bacteria and fungi before nutrients become available to the plant, it takes a while before you see any results, generally 3-4 weeks.
- Unpredictable. No one can say for sure when the nitrogen is going to be available to the plant. Availability of nitrogen also changes with temperature since bacterial activity slows once it gets cooler.
- Unsustainable. Plant derived organic fertilizers are the equivalent of using a gas engine to power a generator which is then used to release hydrogen from water through electrolysis which is then burnt to power a car via steam. Also, a lot more carbon is spewed into the atmosphere for the production and delivery of 20 pounds of corn than for the equivalent 2 pounds of urea.
So with very little benefit backed by mostly anecdotal evidence and a lot of disadvantages, what place does organic fertilizer have in the average lawn? There are situations where organic fertilizers are needed, such as fertilizing an area where nitrogen runoff must be avoided. For most homeowners, synthetic fertilizers work faster, are less work to apply and are significantly less expensive than organic fertilizer. Give your grass the nutrients it needs and the grass will always be greener on your side.