As the cold season begins, the attention to the garden usually wains. Fall and winter, however, are some of the most important times for thinking about building soil health.
Soil maintenance and improvement is the cornerstone of any agricultural system. As Franklin Delano Roosevelt once said, “A nation that destroys it’s soil destroys itself.” As such, let’s go through a whirlwind tour of how to protect your soil during winter and how to initiate some strategies for fast-action soil improvement.
The garden plot pictured below constitutes part of the yard my parents use to grow food. The inputs to the system were only those which were readily available and mostly free. Remember, the exact management strategies and inputs you should use are dependent upon a host of factors including soil type and parent material, climate, pH, moisture retention, intended crops to be grown, and past use. In other words, there’s no universal strategy that’s going to work for every circumstances and, in fact, creative and novel strategies that respond to specific situations should be tried whenever possible.
STEP 1: REMOVE RESIDUES TO BE APPLIED LATER
The picture below is a soil bare and denuded–not a good situation! If left in this condition, the soil would be exposed to significant erosional processes over the winter; will likely become infested with weed seed; and is likely to have nutrient loss from mineralization and leaching of key plant nutrients. Like a wound, the vegetative cover and epipedon–the skin of the soil–has been cut away and is prone to loss of vital nutrients and infection. Thus, our goal is to speed up the healing process while directing the use of the soil to a sustainable surplus for human consumption.
Step 1: Here I have removed all residues from the plot, but don't worry I'll return them shortly. Try not to pull up plants which disturbs the soil and removes potential nutrients and carbon in the form of root biomass; instead, cut them at the base of the plant thereby leaving roots intact.
STEP 2: APPLY NUTRIENTS
The reason why I’m using the amendments pictured below was because they are free (sitting in my parent’s basement). I would have liked to also include some long-lasting rock dust fertilizers. There are many gravel mines located nearby that harvest glacial outwash plains. I’m not sure how difficult it is to get “fines” (the dust fraction from the gravel) from the mines or how much it would cost, but this is a very nutrient rich and heterogeneous product that would be perfect for such application.
Step 2: The next step is applying soil amendments that will boost soil health, biota, and productivity. Here I have chosen to add lime in order to decrease the acidity of the soil to a pH of between 6.5 and 7, and I have also added a fertility input (4-4-5) that includes bonemeal, bloodmeal, fish residue and mycorrhizal fungi.
Close-up of application by hand: a liberal handfuls of both fertilizer and lime are used.
The garden plot after application of lime and fertilizer + mycorrhizal fungi innoculant.
STEP 3: ADD RECALCITRANT CARBON SOURCE
Adding as many different types of carbon sources provides the soil food web with a diverse assortment of food sources. Some are like simple carbohydrates (sugar monosaccharides) that are rapidly consumed. Others are like more complex carbohydrates (cellulose polysaccharides.) Here I’m adding bark that was chipped off of cordwood when splitting wood for my dad’s soapstone stove. Some of the bark I soaked in a trash can full of water with a little bit of the mycorrhizal fungi added to innoculate the wood. I’m not sure that the particular strain of fungi will take to breaking down the cellulose/lignin. It’s probably good to have innoculant containing a host of fungal communities that are native the local region.
Step 3: Bark that chipped off of cordwood when splitting for my dad's soapstone stove are put down to provide a long-lasting recalcitrant feedstock for microbial decomposition. The stable lignin complex will take a while for the microbes to breakdown and bark tends to concentrate nutrients, so we're providing a nice lasting carbon source to the system. Note I put down quite a bit more than what is pictured.
STEP 4: ADD SOME MORE CARBON
Next I add a layer of leaves to the garden bed. My dad had these all raked into a nice neat pile–great for the taking. And then I add some paper bags that were about to be recycled. Note that the thin layering of bags isn’t going to smother out weeds. If you’re goal is to mulch out weeds I recommend having a uniform and multi-layered cover preferably using cardboard which is nearly impenetrable. Lastly, I’m adding garden “waste”–the “trash” from a perennial sunflower provides another source of high-lignin microbe feed.
Step 4: The oak tree in the front of the house has finally lost all of its leaves and my dad's raked them into a huge pile--perfect for the taking. Don't put all your leaves in a single plot, though! Leaves often wet to form large impenetrable masses that block water penetration. Thin layering is preferable.
An accumulation of paper bags about to be sent to the curb for recycling are--in my opinion--better used to build up my soil organic carbon (SOC) levels. Hey, if you've got them, you might as well use them! Another, this-time-more-decomposible source of carbon for the soil food web.
My mom loves to grow large flowers. These are a perennial sunflower variety that the birds have already pecked most of the seed out of. I give them a little additional threshing over the area they are planted to ensure I won't be adding a bunch of unwanted weed seed to the soil. More and more nutrients and carbon for the system.
An upclose shot of the now-dead flower stocks going into the garden.
STEP 5: Cover with Rough Compost
The next step is to smother everything in a nice rich compost. I’ve got a good amount of somewhat rough compost (not fully decomposed) that’s been steeping in the backyard that I’ll use. It’s ok if it’s somewhat rough–it will break down over winter as leachate and microorganisms move down the profile to help break down the rest of the material. After applying the rough compost, I’ll again cover the whole bed with a layer of leaves to protect the compost from possible wind or water erosion.
A super-rich, but still quite rough compost has been made from leaves, grass clipping, kitchen scraps, hair cuttings, and sundry decomposible materials.
Here the rough compost has been applied and a layer of leaves have been scattered on top to prevent any possible wind or water erosion.
STEP 6: Seed with Cover Crop
Just prior to adding the leaves in the previous step, I spread annual rye grass seed. The seed will germinate to produce a thick mat of winter hardy rye that will further protect and aggregate the soil together through the dense rhizome layer (roots). The rye grass should be killed before it seeds so that it doesn’t scatter unwanted seed in the garden. In order to do this you could simply chop or mow it down with a hoe or scythe and/or mulch over it with a thick layer of newspaper or cardboard.
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STEP 7: Add Ash
We’ll be adding ash to this garden regularly as we burn through our wood pile. The ash will provide plant-available nutrients for the coming growing season.
Step 7 : Ash from the wood-burning soapstone heater will be scattered on the plot throughout the winter heating season.
Note that practically all things we just looked at are either fairly inexpensive or free. Most of the materials (save the store-bought fertilizer and lime, and rye seed) came right from on-sight and cost nothing at all (though having them hauled away may have). Systems can be changed, adapted, and regionalized based on your needs, climate, budget, and time. Most gardeners and farmers agree that regenerating healthy soil is incredibly rewarding and enjoyable. Best of luck!
-Ryan
Ryan Hottle has run several market farms, worked in a commercial orchard and is currently a PhD student at Ohio State’s Carbon Management and Sequestration Center in the Ohio Agricultural Research and Development Center.
