This week I am researching the environmental costs and impacts of the amendments and products that are often used in organic farming, including here at the Pomona College Organic Farm.
Peat moss is a common soil amendment in organic gardens because it is a sterile and long-lasting medium that helps the soil retain moisture and airflow. Peat is the decomposed, dead layer under the living moss in a peat bog; it takes about 1,000 years for a 1-meter deep layer of peat to form. Although peat moss is often considered a renewable resource, we should understand that, like an old growth forest, these bogs take centuries to form and will take centuries to regrow (further, just because something can eventually regrow, that does not mean it will return with the same cultural significance or ecological intricacy as before).
When declaring things ‘renewable resources’, I think we need to take much more into account, like the time it will take for the resource to return, if it will be able to return with the same complexity and individual/cultural relationships to the being. Further, peat bogs store more carbon than even heavily forested areas and harvesting the moss releases this carbon into the atmosphere.
Coco coir is a soil amendment used interchangeably with peat moss, lauded for its water retention capacities. Coir is made out of the part of the coconut between the kernel (the part we eat) and the outer husk (which is used to make products), meaning that it is made out the part of the coconut that would otherwise be a waste product. Despite the fact of coco coir being made out of a waste product, there are still various environmental concerns: processing the coir requires chemicals and creates more waste products; the process requires a lot of water and pollutes that water; people that work in coir factories are exposed to an unhealthy environment (excess dust); because the coir is being sold the coconut fields have to import fertilizer to replenish their own soils.
In short, it seems like if coco coir was being made in small quantities for local consumption, it would be a sustainable resource, but the current scale of production (with transportation, energy consumption, chemical consumption and negative effects on human health) is not at all.
Perlite is a soil amendment used for aeration and drainage; it is the product of volcanic glass being heated to 1,600 degrees Fahrenheit and consequently popping and expanding 13 times its size, making it extremely lightweight. Similarly, vermiculite is a mined mineral that also greatly expands when heated and is used for water and nutrition retention in gardening.
Perlite is a non-renewable resource; to date, less than 1 percent of our global perlite has been mined. There are no chemicals involved in processing perlite, it is non-toxic, and it does not biodegrade, meaning its benefits to soil are permanent. All of that said, I am inclined to think that we should avoid mining at all possible opportunities.
Fish emulsion/fertilizer is (at least supposed to be) made out of the byproducts of fish industries that normally go to waste (bones, scales, skin, fluid, etc.) and is used to feed our plants nitrogen, vitamins and protein. Like all fertilizers, fish fertilizer can negatively impact waters of body that it runs off into with its high levels of nitrogen and phosphorous, causing eutrophication (aging of freshwater bodies by nutrient enrichment) and dead zones (areas unable to sustain aquatic life).’
I do not think that fish fertilizer is inherently unsustainable at all, but because so much commercial fish farming is so detrimental to our waterways and because it is hard to know if companies are actually using byproducts rather than entire fish, I would stick to seaweed fertilizer (renewable and very easily extracted).
Neem oil is pressed out of the neem trees fruits and seeds, which is a tree native to India, Pakistan and Myanmar that has been used for a very long time, showing up in ancient ayurvedic texts and practices. It is used in agricultural contexts as an organic, non-toxic biopesticide, nematicide and bactericide. It does not affect ground water or beneficial insects like bees, lady buys and butterflies.
Neem oil seems to be considered a very safe and sustainable option.
Diatomaceous earth is a fine powder made out of fossilized remains of diatoms (ancient, small, aquatic organisms) that is mined from lakebed deposits; it has many uses in the garden, especially in the realm of pest control (it should be noted that DE is a broad spectrum pesticide, meaning it also negatively impacts beneficial insects).
Although diatoms still exist and serve an important role in carbon sequestration, the fossils of diatoms that we are mining from lakebed deposits are millions of years old, so it’s hard for me to consider this a sustainable resource, as it is not being renewed at the same rate as it is being used. This is compounded by the fact that DE is easily made ineffective by getting at all wet or is often carried away on the wind.
In conclusion, as far as the soil amendments go, I am inclined to simply use healthy compost and crop rotations to provide the nutrients and proper aeration/water retention to plants as much as possible. For heavy feeders, I will use seaweed emulsion. In using neem oil and DE as natural pesticides, I have always found neem oil to be more effective and after this brief research, I plan to use neem oil going forward.