Emily recently asked for a detailed post on Soil Building -that is a fabulous idea, so here goes!
I live in a new Subdivison. Besides good insulation and resale values, I also got a denuded yard with no topsoil. I am no different than hundreds of thousands of households out there. Growing things organically on what starts as essentially subsoil takes some doing, but it is very possible. Here are some of the things I learned in the past 3 years getting my gardens to produce 500#’s + on 500 sq ft in Zone 5 on what what started as soil that not even weeds grew on.
First off the main difference between “Topsoil” and “Subsoil” revolves around two critical aspects: Organic Matter and the Soil Ecosystem. Organic Matter creates air channels and holds water between rains, but most importantly it supplies the raw materials that the Soil Ecosystem (bacteria, fungus, nematodes, protozoa, worms, etc) use to make nutrients accessible -be it from minerals or dead plant debris- to plants. Subsoil is essentially dead -Organic Matter levels below 1% and virtually no soil life to speak of. Luckily it often has rich levels of minerals and trace nutrients, so all is not lost. To make Top Soil from the Subsoil (or dead denuded soils post industrial Ag) you will need to restore both Organic Matter and foster a thriving soil ecosystem.
Here at our home we have trucked (ok, trailered) in literally TONS of organic matter. If you want to build soil, you have to find the raw materials. Here is a short list of things I have scrounged here on the fringes of Suburbia:
- Coffee Grounds from local Coffee Shop
- Resturaunt Waste
- Woodchips and Compost from the Municipal Yard
- Straw Bales from garden shops and local farmers
- Leaves from ALL my neighbors
- Grass Clippings and other yard waste
The thing to remember is that the soil isn’t picky, in fact a diverse mix is better than one particular source. But SOMETHING is better than nothing. Some of the above list should be composted first-notably any animal manures, and kitchen and resturaunt wastes. The others can be applied to the soil as mulches to feed the soil from the top down, as nature intended. More on that in a bit. Wood chips are for my numerous paths which I rebuild annually -the bottom 25% of each path decomposes nicely providing me with almost a yard of compost annually -with very little work and no bins! The coffee grounds are a great system I have worked out with a local shop. I pick up 3-5 5 Gallon Buckets of restaurant “gorp” every week, and compost it. They save on garbage fees, and I get an extra 3 yards of compost! Less formally, any Starbucks has bags of grounds behind the counter they will gladly give you.
When we started our gardens, just three years ago, I double dug the beds ala John Jeavons’ Biodynamic techniques. This was necessary as the soil was horribly compacted from the Heavy Equipment used in the home construction. As I went to turn the “top” soil back in, I added compost in with the original soil in a 1:1 ratio. This took ALOT of compost-more than I had, but our Village has a compost pile the size of a small house. This also inoculated the soil with a living batch of decomposers to get things going-more about this later as well. I also mixed in a few bags of grass clippings to give the critters something to munch on. Careful to mix it well -large clods of grass will spoil in the soil due to lack of air. Once this was mixed in I planted the gardens, but as the soil was still pretty dead it wasn’t a great year. As my compost batches finished (I turned them very aggressively to speed it up to about 2 months) I side dressed the rows 1″ thick with the compost.
After the growing season, I added chopped leaves (run them over with a power mower with a bag on) and composted manures/kitchen wastes in a thick 4-6″ blanket for the winter. By May the next year, this was about 50% composted and I turned it in with a single pass with a garden fork and then topdressed with whatever compost I had ready from the fall piles -even if it was only 75% done, it goes on. After seedlings are up, more straw mulch between the row to feed the soil. Rinse and Repeat!
The truly depressing thing about my “soil” was it was dead. There was almost no life in it at all. Topsoil is a living thing- actually it is hundreds of trillions of livings things, but you get the picture . It (they?) needs air to breathe, water to drink, and food to eat. A compacted soil effectively removes the first two, and as I already discussed, without organic matter you don’t have the third. To fight compaction, I double dug the beds to aerate them down 18″ which opens the soil to air and water passages. Adding the organic matter gets food into the cycle. But you still really don’t have many critters at this point. Given time, simply having air, water, and food will be enough to attract a thriving soil system, but we are a frenetic society and have issues even waiting for a You Tube movie to start, let alone giving our soil 2-3 years to begin to wake up.
So to speed things up: inoculate the soil. If you noticed above, I added compost… alot. In fact I added about 3″ of compost per sq ft per year for 3 years now. That is about a cubic yard of compost annually per 100sq ft. That may seem excessive, and I have toned it down now as it served its purpose. See, compost is alive. That is not some Earthy Granola Get-in-touch-with-your-Mother talk …it is literally true. When your compost heats up it is due to the metabolic heat from bacteria reaching critical mass. In the cooler sections of the pile are billions of protozoa, fungi, and thousands and thousands of larger critters like pill bugs, worms, millipedes, etc that are all doing their part to decompose your kitchen and yard wastes. When you load your finished pile into your barrow and trundle it into your beds, all those buggers come with and they will continue to decompose the wastes of your garden soil and multiply in the process. Congratulations! Your soil is now alive! Now lets keep it that way:
The dying roots of your garden plants each season supply some of this food, but continual mulching will help even more. Nature feeds the top of the soil, and immediately under your mulch the soil will be alive with the Front Line decomposer’s that take some sustenance, and in turn break down the material further to allow even more and varied critters to further complete the work. In time the material will be completely broken down and distributed through the top 6-12″ of the soil by worms and other animals. This is how all the leaves in the forest are gone by the time the next season’s Fall approaches. The previous year’s leaves have fed the soil, which in turn fed the trees and allowed them to make more leaves… which in turn feed the soil. Perfect and Beautiful. Since we harvest much of the surplus of our gardens we must ensure we add back those nutrients in the form of compost or mulches.
It should go without saying that spraying and “-cide” on the garden -plants or soil- will take you back to Step #1 in a very real way and is to be avoided like the plague. A Dairy Farmer would never take a shotgun to his herd and hope to stay in business. We are all ranchers, it is just that the Vegetable Garden’s herds live underground!
3 years ago I had to water my “soil” to even be able to get a sharpened spade into it, and ended up using a pickaxe (literally) to break it up. Now I can stick a 2×2″ stake in 6″ deep by hand when I string my pea trellis and I expect further fertility gains for at least 3-5 more years. Nature wants healthy soil, and has a gazillion tools to help create it. All you have to do is rebuild a suitable environment, and either wait for the magic, or help it along with compost. Re-Building our soils is one of the most important legacies we can leave to future generations. Be the Change!
Good luck and Great Gardening!