Over the years, we’ve found that compost, worm castings, nitrogen fixing cover crops, and green manures
provide more than enough nutrients for our garden to thrive.
Today I’ll talk about why we prefer these organic practices over the use of synthetic fertilizers.
Like last week’s leaves versus rock dust comparison,
I’ll evaluate these two approaches from the perspective of a home gardener
who is looking for an approach that is environmentally friendly, gets great results, and is cost effective.
To help me evaluate the two approaches, I’ve created a report card with the following criteria:
environmental impact, nutrient availability and diversity, impact on soil and plants,
results in the garden, and cost.
I’ll grade each criterion on a scale from A, which is excellent, to F, which is failing.
The grades will admittedly be subjective, but I’ll do my best to be fair.
Let’s start with the environmental impact of our organic practices versus those of synthetic fertilizers.
All of our compost and worm castings are made from renewable resources, and our cover crops and green manures are renewable as well.
However, some of our compost and worm bins are plastic, which is not renewable.
So, I’ll give our organic practices an A- in this category.
Synthetic fertilizers are a different story.
Phosphorus and potassium are both non-renewable mined resources.
Phosphorus, in particular, is in short supply.
Though the nitrogen in synthetic fertilizers is derived from the air through the Haber Bosch process,
, this process uses natural gas as a hydrogen source
and requires a significant amount of energy, usually from fossil fuels.
I’ll give synthetic fertilizers an F because of their reliance on non-renewable resources.
Our compost and worm castings are made entirely from free local resources.
Here I consider locally generated waste products to be local regardless of where the original product came from.
For example, I consider used coffee grounds from the coffee shop to be local.
Even though the grounds were shipped from some distance, they were shipped in order to make and sell coffee,
and I consider the spent grounds to be a locally generated waste product.
Of the organic products under consideration,
only the cover crop seeds are not local. Some of the compost and worm bins are also not from local sources.
I’ll give our organic practices an A- in this category.
Grading synthetic fertilizers is a no brainer. They get an F.
Here in North America, rock phosphate is usually mined in Florida and North Carolina
and potash is mined in New Mexico, Utah, California, Michigan, and Saskatchewan.
Most countries don’t mine enough of their own and have to import them.
Given the wide ranging origins of synthetic fertilizer ingredients,
there’s no such thing as a local synthetic fertilizer.
Now let’s look at fossil fuel usage.
We do drive very short distances to pick up free resources like coffee grounds and wood chips,
but to minimize the impact we try to combine these trips with our grocery shopping or trips to Home Depot.
Our cover crop seeds are also shipped from California,
so I’ll give our organic practices an A- in this category.
The mining of rock phosphate and potash, on the other hand, require huge expenditures of fossil fuels.
And the Haber Bosch process, which fixes nitrogen from the air, requires natural gas as a hydrogen source as well as electricity,
usually from coal powered plants.
to create the high temperatures and pressures needed to fix nitrogen.
Again, synthetic fertilizers get an F.
I believe our organic practices have a very positive impact in terms of pollution.
By composting household organic waste as well as other free local waste products,
we reduce the amount of organic matter in landfills and instead use it to improve soil fertility
and grow our own food.
Similarly, planting nitrogen fixing cover crops is a very environmentally friendly way to increase nitrogen in the soil. I’ll give our organic practices an A in this category.
I’ll give our organic practices an A in this category.
Once again, the story is very different with synthetic fertilizers.
In addition to the pollution caused by the burning of fossil fuels described above, mining rock phosphate and potash destroys landscapes and wildlife habitats, and pollutes the air and water.
In addition to the pollution caused by the burning of fossil fuels,
mining rock phosphate and potash destroys landscapes and wildlife habitats, and pollutes the air and water.
In addition, nutrient leeching and runoff from soluble synthetic fertilizers
contributes to the eutrophication of bodies of water and the death of aquatic life.
Excessive use of compost can also contribute to eutrophication.
However, because nutrients in compost are tied to organic compounds,
nutrients are released more slowly into the environment and are less likely to pose a problem.
I’ll give synthetic fertilizers an F for their contribution to pollution.
One of the key benefits of synthetic fertilizers
is that their nutrients are in plant available form.
As a result, they can be used as a quick fix to address nutrient deficiencies.
If a plant has yellow leaves, a quick shot of nitrogen might just fix the problem.
So, synthetic fertilizers definitely get an A when it comes to nutrient availability.
That said, we’ve never actually encountered a situation in our garden
in which we’ve needed a quick nutrient fix.
Our compost, worm castings, cover crops, and green manures provide a slow release of nutrients that has been more than adequate.
In fact, we prefer the slow release of nutrients as microorganisms break down organic matter,
because a single application of compost and worm castings
can provide enough nutrients for our garden for an entire year.
Synthetic fertilizers, on the other hand, move through the soil quickly
and may have to be applied two or three times per year.
So, I’ll also give our organic practices an A in this category as well.
Another advantage of our organic practices is that they provide a broader range of nutrients.
Because organic matter comes from once-living things, it contains nutrients that are needed by living things.
So compost and worm castings, for example, contain a wide range of nutrients,
whereas synthetic fertilizers typically do not.
So, I’ll give our organic practices an A for nutrient diversity, but since synthetic fertilizers typically don’t have a wide range of nutrients, they get a D.
Our approach to gardening is to build a healthy soil food web of beneficial bacteria, fungi, earthworms, and other soil organisms.
And compost, worm castings, nitrogen fixing cover crops, and green manures all help to feed the soil food web and provide a slow release of nutrients into the soil.
Compost and worm castings improve soil structure, increases water retention in sandy soils, and increases air infiltration in clay soils.
And cover crops prevent erosions and fix nitrogen in the cleanest way possible.
Synthetic fertilizer, on the other hand, can disrupt the soil food web,
by harming beneficial soil organisms like bacteria, fungi, and earthworms.
Soluble phosphate fertilizers inhibit growth of mycorrhizal fungi
and the formation of mycorrhizal relationships
thereby limiting their ability to provide nutrients to plants.
All is not lost if synthetic fertilizers are used sparingly along with organic matter.
However, if synthetic fertilizers are used instead of organic matter, the nutrient holding capacity of the soil will be lost over time
as organic matter erodes,
resulting in the need to apply more synthetic fertilizers.
This can be extremely detrimental to crops and the soil.
So, I’ll give our organic practices an A for their impact on the soil.
The impact of synthetic fertilizers can vary a great deal, depending on how they’re used.
Used sensibly and in moderation they can have little negative impact,
but used to the exclusion of organic matter, they can have a very negative impact.
Given this wide range of possibilities and their potential to damage the soil food web,
I’ll give them a D for their impact on the soil.
Now let's take a look at how these approaches impact the plants themselves.
Our organic practices get an A for their impact on plants.
They provide a slow release of nutrients and won’t burn plants.
Care has to be taken with synthetic fertilizers, because the ammonia can burn plants.
However, once taken up by plants, the nutrients in synthetic fertilizers
are the same as those from organic sources.
I’ll give synthetic fertilizers a B.
But what about results? Here I’m talking specifically about plant size and yields.
We’ve always had excellent results using our organic practices and have never seen the need to use synthetic fertilizers.
Organic matter’s ability to hold nutrients and release them slowly during decomposition
has provided more than enough nutrients for healthy plants.
So, I’ll give our organic practices an A.
It’s tough to grade synthetic fertilizers,
because when used in moderation you can definitely get excellent results.
Since I’ve already penalized synthetic fertilizers for their improper use in previous categories,
I’ll grade this category based on their sensible use and give them an A.
Clearly many gardeners get excellent yields using synthetic fertilizers.
Finally, let’s look at cost. Our organic practices cost next to nothing.
We made a small initial investment in compost bins and worm bins,
and we buy a bag of cover crop seeds every year,
but that’s it.
So, our organic practices get an A for cost.
Synthetic fertilizers get a C because, though they’re not terribly expensive,
they do represent an ongoing cost that we’ve been able to avoid entirely
by relying on compost, worm castings, cover crops, and green manures.
So, from the perspective of a home gardener who is looking for a quality product that is environmentally friendly,
gets great results, and is reasonably priced,
I much prefer compost, worm castings,
cover crops, and green manures over synthetic fertilizers.
When I average the grades on the report card, our organic practices get an A
and synthetic fertilizers get a D.
Of course, I understand that some home gardeners who rely mostly on organic practices
also use synthetic fertilizers in emergency situations when a plant needs a quick fix.
I certainly wouldn’t grade this level of usage as harshly
as I would a total reliance on synthetic fertilizers.
As I said earlier, the grading is admittedly subjective.
If you would have graded differently, please let me know in a comment below.
Before closing, I should point out that not all organic products would get a final grade of A.
In fact, there are a number of products that would do quite poorly.
In the future, I hope to take on a number of these products
using the same approach I used here today.
Well, that's all for now.
Thank you very much for watching,
and until next time remember
you can change the world one yard at a time.