We made our first batch of potting soil this week. Like lots of small farmers, we start our plants in greenhouses (or windowsills!) to have young plants ready for planting outdoors as soon as frost danger has passed. This means you need potting soil, and although good quality potting soils suitable for organic production are on the market, we prefer make our own. It’s a control thing. We have ideas about how things ought to be, and taking a do-it-yourself approach helps ensure that the farm we make resembles the ideas we have.
It is also, arguably, a sustainability thing. “Sustainability” is many-splendored, but we can anchor ourselves in the definition of “sustainable development” from the 1987 Brundtland Commission report, entitled “Our Common Future,” and published in 1987: “sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” Over the interceding 25 years this has been elaborated upon in numerous ways. Sustainability is now generally recognized as having three pillars—environmental quality, economic vitality, and social equity (this “triple bottom line” often appears as environment, economy, and equity; also as planet, profits, and people). “Meeting needs” is sometimes re-construed as “flourishing” or “continuing to evolve.” Metrics and indices have come online. Sustainability is a rapidly-growing academic specialty. And so forth.
It is also, arguably, a sustainability thing. “Sustainability” is many-splendored, but we can anchor ourselves in the definition of “sustainable development” from the 1987 Brundtland Commission report, entitled “Our Common Future,” and published in 1987: “sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” Over the interceding 25 years this has been elaborated upon in numerous ways. Sustainability is now generally recognized as having three pillars—environmental quality, economic vitality, and social equity (this “triple bottom line” often appears as environment, economy, and equity; also as planet, profits, and people). “Meeting needs” is sometimes re-construed as “flourishing” or “continuing to evolve.” Metrics and indices have come online. Sustainability is a rapidly-growing academic specialty. And so forth.
Adding sand to peat moss and compost.
So here is a look at our potting soil with sustainability in mind. We began a few years back with Eliot Coleman’s blocking soil mix from The New Organic Grower, and have revised it in light of our experience. Our recipe has two components: the base, and the fertilizer mix.
Potting Soil Mix
30 units peat moss
20 units sand (or perlite)
20 units compost (or worm castings)
10 units garden soil
1/8 unit limestone
3/4 unit fertilizer mix
And here’s the fertilizer mix:
1 unit feathermeal (or other nitrogen source, e.g. alfalfa meal, cottonseed meal)
1 unit Tennesse Brown phosphate
1 unit kelp meal
1 unit Menefee humates
In the background, the scale we use to portion out potting soil ingredients.
Let’s start with peat moss. It is a natural substance, needing no lab synthesis. Horticulturally, it a light, weed-free medium, making a nice home for germinating seeds and tender young plants. When seedlings are transplanted into our garden beds the potting soil comes with them; the peat moss leavens the clay, encouraging the bug, worm and microbial life so beneficial to gardening soils.
However, peat moss production entails destruction or degredation of peat bogs. Peat bogs are slow-developing bits of biota—they lay on about .03” per year, and most in existence today (ranging from 3 to 30+ feet deep) formed over the 15,000 years since the last Ice Age. A typical harvesting method involves ditching and draining to dry upper layers, milling and loosening of the upper layers, and then vacuuming them off. How long the ditching and drying takes will vary, but with diesel-powered hydraulic machinery and vacuum harvesters that can suck 4” off 100 acres in a day, rest assured it goes at an astonishing pace relative to the pace of the peat’s production in the first place. So we see why peat bog harvesting is often called “mining.”
Peat bogs play locally important roles in biodiversity and water quality and, globally, they sequester enormous amounts of carbon dioxide. The approximately 5% of global terrestrial surface occupied by peat bogs is estimated to contain about one third of terrestrial carbon. So, as peat bogs are dessicated and destroyed (as is happening quickly—all natural peat bogs in the Netherlands and Poland are now gone; they are nearly gone in Switzerland, Germany and the U.K.; they are rapidly going in Eastern Europe, etc.) they dump loads of carbon dioxide, a key greenhouse gas, into the atmosphere.
Phoebe considers the mixing ahead of her.
Now, our peat moss comes from Canada. Canadian peat moss production is often described as sustainable, because of national and industrial regulations and practices controlling the harvest process. The Canadian process involves setting bogs aside for preservation and recording their flora and fauna; leaving buffer zones and leaving unharvested layers of peat moss; and post-harvest ecological restoration. It appears that this does substantially retard the rate of bog loss.
Or, maybe not. Once their hydrology and living physiology has been so substantially disrupted, it is unclear whether they can be restored to a substantially similar condition.
And of course rate of bog loss is only one consideration. Greenhouse emissions and waste production is implicated all along the chain, from harvest to packaging to transport. As we see in this lively discussion within the gardening community quite a few gardeners figure locally available stuff like compost, leaf mould, and rotted wood chips is preferable.
There are debates to be had about other components of the base, such as the sand and limestone. While their source materials are quite abundant, significant mining, refinement (including combustion) and transportation is necessary to get bags of them into our Vanagon. Any of those processes, depending on how they happen, is subject to critique as causing environmental damage or social inequity
Phoebe settles into work.
The fertilizer mix component of our potting soil raises further questions. Like most folks who grow produce for sale, we add nitrogen to our soils. The nitrogen sources for our potting soil have varied over time, but tend to be byproducts of already-extant agricultural/industrial processes. So, on the one hand, using feathermeal (as we did this year) helps to recover a byproduct (feathers) of the poultry industry (billions of chickens every year!) that would otherwise be wasted. Unlike petroleum (or, maybe, peat moss) the feathers are not mined—they are a renewable resource.
But on the other hand, getting from feather to feathermeal is a fairly intense process, with cooking and grinding, boxing and bagging, and transport. And the poultry industry itself is, well, not exactly a poster child for sustainability. Issues ranging animal cruelty to antiobiotic overuse to environmental dumping to dessimation of genetic diversity spatter the record.
But, then again, the meat industry is hardly sitting on the sustainability sidelines, with various sectors of it changing practices, sometimes radically. Maybe knowing that they've got some small organic growers buying in will encourage more progress in the sustainability direction. And we are very careful in maintaining healthy nutrient balances, as well as overall soil management. This is about as far a cry from the kind of agricultural fertilizer application implicated in such travesties as soil poisoning, massive marine dead zones, or drinking water contamination and acid rain as one might imagine. But, still, we are importing fertility, which according to sustainable ag superstars like Ecology Action is a no-no.
The mixing goes ever on.
One of the more interesting ingredients in our fertilizer mix is the Menefee Humates, a pre-coal product of the Cretaceous ooze found in the Menefee Formation in northwest New Mexico. Horticulturally, it is good stuff—natural, carbon-rich material that increases availability of nutrients to plants and injects intense “organic matter” into the soil, encouraging the life of the dirt so important for organic/sustainable agriculture.
But the humates are—like the peat (perhaps)—being mined. The Menefee Formation in northwestern New Mexico is the exclusive source of Menefee Humates, and once they’re all dug up and gone…well, it took the Cretaceous swamps plus millions of years to get them there in the first place. It appears to be mostly surface mining, but it is mining nevertheless. When getting the humates gets harder, mining techniques will presumably become more intense and invasive, as we’ve seen with fossil fuels. As it happens the Menefee Formation is also a key source for the North American fossil record—the specific site of the current humate mining may not be important, fossil-wise, but it’s hard to know. To top it off, the Menefee Mining Corporation (source of the humates brand popular with small growers like us) had to cough up $100,000 to the state of NM in 2009 for violating the state’s air quality laws.
Potting soil this nice deserves a good presentation.
I could go on, and am sure you are glad that I won’t but will instead return to the question: is our potting soil sustainable? Economically, it surely makes sense for us. We made ours for about $0.15 per quart, whereas purchasing a comparable product would run around $0.85 per quart plus shipping. And we had fun doing it.
Environmentally, our potting soil is part of a larger picture--a small family farm using practices that exceed USDA National Organic Program standards, while incorporating additional sustainable agricultural (e.g., biointensive) practices. We provide a source of good produce that doesn't have to travel hundreds, or even dozens, of miles to make its market. Isn't that a pretty picture, sustainably speaking?
Is it good for social equity? Well…it does certain sectors of certain industries that are arguably on the wrong side of that equation--note comments about peat moss and feathermeal above. But it also supports sectors on the right side. Several companies retailing these products, such as Fedco, are leading the entrepreneurial front of sustainable ag. And, perhaps more importantly, it supports us, and we’re on the good side, right?!? I mean, if an enterprise such as ours isn’t on the brighter side of sustainability…then what is?
