NOTHING TO DO? SEQUESTER CARBON?
Agriculture: Good or Bad for Our Planet?
I’m enjoying this farmdening interlude, with essentially nothing to do, farmdenwise, for a few weeks. No planting, no pruning, no weeding. Seeds have been ordered and the greenhouse, full of lettuce and kale and chard and other fresh stuff, is cold enough to require no more than weekly waterings, if that. Even then, watering involves nothing more than a quarter turn of the mechanical timer to start water running through the drip irrigation lines.
I’m going to use this lull as an opportunity to ruminate — on rumens and other relationships between agriculture and global warming.
Deb, first time herding some very big cattle
Let’s get started right away with the rumen, that part of the digestive system of a cow, steer, or other ruminant where cellulose is fermented. With a capacity of more than 50 gallons, a cow’s rumen is a veritable factory, one whose byproduct is a lot of gas, more than 200 gallons a day, belched out by the cow. No small thing, that collective burp of agricultural ruminants. It’s good for the cow (when you consider the alternative) but not so good for the environment. A significant portion of the effluvia is methane, a carbon compound which is 20 times more heat-trapping in the atmosphere than carbon dioxide.
Let’s leave the cows alone and drop down to the soil. Global warming from the agricultural soils? Yes. Harvest a crop, any crop, and you’re removing nutrients from the site. So those nutrients need to be replaced, and that’s usually done with fertilizer. Fertilizer, unlike money, does, or can, grow on trees (such as honeylocust and others in the pea family, which garner nitrogen from the air a put it in the soil) but most fertilizer is synthetic. Synthetic fertilizer must be cobbled together using energy derived from fossil fuels, which then release carbon dioxide into the atmosphere.
That’s not all. The soil itself is a large reservoir of carbon tied up in complex, organic compounds as well as in living and dead organisms. Stir that soil up with a plow, a tiller, or a garden fork, and you charge it with oxygen, just what bacteria, fungi, and other microorganisms are waiting for so that they can gobble up that carbon, grow and extract energy, then release carbon dioxide to the atmosphere.
Of Tillage and Biochar
“Sequestration” isn’t only something done with our money by a bunch of mostly men in a big room (Congress) in Washington. It’s also done by farmers to save, not money, but carbon. The idea is to keep carbon in the soil rather than letting it “burn” to carbon dioxide, waft into the atmosphere, and contribute to global warming.
Me, a long time ago, burning carbon
Minimizing, or eliminating, tillage is one way to sequester carbon, something that can be done on a home or small farm scale, even on a large scale. I haven’t tilled my garden in over 20 years, and 22 percent of Midwestern farmland is no-till. Minimal tillage or no-till also brings other benefits, such as reduced weeds, a friendlier environment for earthworms and fungi, more efficient plant water use, more organic carbon in the soil for livelier biological activity and improved soil aeration, and, of course, the benefit of not having to till.
Biochar is another proposed savior in these carbon-burning times. Biochar is, basically, charcoal, which is mixed into the soil. Charcoal starts out as wood which, when left in or on the ground, rots, the carbon within turning to carbon dioxide. Charring the wood drives off much of what makes up wood, leaving only black carbon, a poor food for soil microorganisms, so it does not rot. The wood’s carbon has been locked up, sequestered, changed from organic carbon to inorganic, or elemental, carbon.
Hold that Carbon, But Not Too Tightly
When it comes to agriculture, keeping too tight a grasp on carbon is not a good thing. Agriculture, whether farming or gardening, isn’t Nature, or else my garden and yours would be all weeds (some of which would be edible and, hence, technically not “weeds”).
Carbon is energy, fueling growth of fungi, earthworms, and other creatures, and as it’s “burned,” nutrients associated with it are released into the soil in forms that plants can use. That’s a good thing, to a degree. Fermentation microorganisms within cattle rumen make cellulose available for energy and growth even as they release methane. That’s also a good thing, to a degree.
Good gardeners and farmers strike a congenial balance, emulating Nature without giving her a free hand. Too many cows belching methane is not good for the planet. Too much tillage “burning” up soil organic matter and releasing carbon dioxide also is not a good thing.
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A final word, about radishes, for no reason except that I am enjoying them right now. Winter radishes are large, variable in shape and color, and store well. Today, as I’ve done every few days since late fall, I sink my hand into a cold, wooden box full of wood shavings to pull out yet another Watermelon radish. Sliced open, this variety of winter radish looks much like watermelon and tastes — no, not like watermelon — but crisp, sharp, and slightly sweet. Highly recommended; sow seeds July 15th.
FRESH-PICKED SALADS ALL WINTER
Greenhouse, Coldframe, Hotbed = Fresh Lettuce, Mâche, & other Salad Fixings
You can’t beat the luxuriousness of entering a greenhouse on a sunny, cold winter day, and hitting that welcome wall of moist, warm air. Once you get through that soft wall, you drink in the redolence and visual vibrancy of green, growing plants. All this is possible even with a relatively inexpensive greenhouse, such as mine, which is, basically, 2 layers of plastic film supported by sturdy, steel hoops (plus thermostats, a propane heater, a cooling fan, and a “squirrel cage” fan to inflate the space between the layers of plastic for better insulating value).
Fresh greens in the greenhouse
Still, a greenhouse — my greenhouse, at least — isn’t for virtual trips to Puerto Rico; It’s for growing edible plants, mostly fresh lettuce, celery, mâche, claytonia, and arugula to fill the salad bowl every day from late fall through early spring.
This same benefit, though, can almost be achieved much more simply and much more cheaply with a coldframe. A coldframe, in its most basic incarnation, is a box frame covered with glass or some other transparent material and within which plants are grown or protected through the coldest months.
I have both a greenhouse and a coldframe. The coldframe came first. With a greenhouse full of greenery, I admit to usually neglecting the coldframe, which is unheated and only 25 square feet in contrast to the greenhouse’s heated 750 square feet. Still, last fall I had an extra 25 lettuce transplants and lacked even a square foot of extra space in which to plant them in the greenhouse. So I spread an inch of compost in the coldframe, firmed the transplants into holes there, and then gave the whole bed a good watering before replacing the cover.
Cold frame with cover closed, and Sammy
Except for one subsequent watering, I’ve pretty much ignored the coldframe. The polycarbonate (‘Exolite’) cover is translucent so the coldframe’s innards are hidden from view unless the cover is lifted. Today, mostly out of curiosity, I lifted the cover to see what was going on inside. The lettuce was alive and had grown. Fall weather was admittedly relatively mild although temperatures here did drop below 10°F at least one night — pretty good survival for plants growing in little more than a covered box outdoors.
With short days and cold weather, lettuce is growing very slowly. Individual leaves, perhaps whole heads, probably will not ready for harvest until towards the end of February. That’s if the lettuce survives that long, which it might not even in the coldframe, depending on the length and depth of winter cold. Spinach would more likely make it through winter; mâche and claytonia would definitely weather the coldest days and nights.
Beefing Up the Coldframe
In the absence of a greenhouse, I would beef up coldframe salad production to yield more and for more of the winter. I would, first of all, construct more coldframes because, with slow growth inside in winter, one harvest could decimate the crop, for a period at least, from just one coldframe.
Anything that helps the coldframe fend off cold and retain heat would also help increase the amount and duration of harvest. Insulating the sides helps, and said insulation need be nothing more than wood chips or straw piled up against the sides. Or make the box itself out of whole bales of straw!
Cover open, Sammy on guard
Heat rises and glass and plastic are poor insulators, so most of the heat is lost through the translucent or clear covering. The Exolite cover on my coldframe is actually 2 layers of polycarbonate plastic sandwiching polycarbonate ribs that hold the layers 1/4” apart, proving better insulating value than a single layer. On really cold nights, an insulating mat, even just a blanket could be thrown over the cover. In Europe a hundred years ago, cold frames were used extensively for commercial vegetable production, and mats of woven straw covered the glass to keep out the coldest weather.
A few feet down into the earth, temperatures remain constantly in the 50s. That earth is a source of heat, tapped into by sinking the floor of the coldframe a couple of feet deeper, which also allows head space for taller vegetables, such as Romaine lettuce. Too deep, of course, makes harvesting very inconvenient.
And finally, winter production can be beefed up by actually heating a coldframe, in which case it’s no longer a “coldframe” but what’s called a “hotbed.” The traditional heat source for a hotbed is horse manure, layered into the bottom of the bed after a foot or so of soil has been dug out. A certain art is involved in getting the right amount and moisture content of manure, packed in just right and then covered with soil for a steady even heat. I made my coldframe into a hot bed a couple of years ago, or, rather, tried to. I didn’t get it just right; will have to try again.
True, you can’t climb into a coldframe for a tropical junket, but the coldframe, with care, can become a hotbed of tasty, fresh, organic, very locally-grown vegetables from fall to spring.
To Every Thing There is a Season
Pruning is reduced to small steps, in time & process
So many branches, so little time. Or so it seems. Annual pruning is needed to get the best out of most trees, shrubs, and vines, of which there are many here on my farmden.
But wait. My brother once remarked — and the remark rang true — that a large part of feeling overburdened from so much to do comes from thinking about it, rather than doing it. And now that I think about it — if I may be allowed a bit more thought — many trees, shrubs, and vines do not need annual pruning except for size control, in which case a different plant or dwarfer variety could have been planted. My witch hazel shrub is in that hardly-ever-needs-pruning category, as is fothergilla, goumi (an attractive shrub with tasty fruits), mountain laurel, and rhododendron.
Witch hazel is a shrub needing little or no pruning
Most ornamental trees do not need annual pruning, and the same can be said for ornamental vines, except when they threaten to take down an arbor, fence, or trellis that is lending them support.
Mostly, what needs annual pruning are flowering shrubs, and trees, shrubs, and vines that bear tasty (to us humans) fruit. But exceptions exist even among those edibles. Fruit plants that hardly ever needing pruning include such delicacies as pawpaw, persimmon, huckleberry, juneberry, Nanking cherry, elderberry, and lingonberry.
All shrubs are pruned the same, sort of
I already feel like pruning is under control, without even lifting a finger. And usually I don’t lift a finger to prune until, as is commonly recommended to avoid winter cold damage, after early February, when the coldest part of winter has passed. The last couple of years, though, I decided to go ahead and get a jump on pruning my rather extensive collection of gooseberries and currants. These plants are very cold-hardy so would be expected to laugh off winter cold, even following a December pruning, and they have.
Pruning currants and gooseberries captures the essence of pruning any flowering or fruiting shrub. Shrubs are shrubs because they are shrubby (duh!). That is, their stems are not long-lived but new stems, called suckers, are always popping up through the ground to replace old, decrepit ones. So these shrubs are “renewal pruned.” Old stems are cut away and the number of new stems, if too many, are reduced so that they don’t become crowded as they age.
Gooseberry bush, before & after pruning
The questions then become, “How old is too old for a stem, and how many new stems is too many?” The questions are related because shrubs whose old stems perform well in terms of fruit or flowers also tend to make fewer suckers, and vice versa. The easiest way to approach shrub pruning (and the way it’s detailed in my book The Pruning Book) is to group shrubs into one of four categories. At one end of the spectrum are shrubs that flower or fruit well on very old wood and make few suckers — and, hence, are in the aforementioned hardly-ever-needs-pruning category. At the other end of the spectrum are shrubs that flower or fruit only on new stems, such as butterfly bush, so can have every one of their stems lopped to ground level every year.
A now I do it, prune currants & gooseberries
The other day I stopped thinking about pruning my gooseberry shrubs and, instead, approached them with lopper and hand shears and a new-found sense of having all the time in the world. Gooseberries fruit best on stems that are 2 and 3 years old. Pruning is straightforward. Merely lop to the ground any stems more than 3-years-old (they were 3-years-old last season and bore fruit) and reduce the number of new stems to about a half-dozen of the sturdiest, most upright ones. The ideal, pruned gooseberry shrub, then has about a half-dozen each of 1, 2, and 3-year old stems. A shrub never becomes a tangle of stems nor has old, decrepit, unproductive ones.
Black currant, before pruning
Red, white, and pink currants get pruned exactly the same as gooseberries; black currants, though, are a whole ‘nother animal. They bear best on 1-year-old stems and, to a lesser degree, 2-year old stems. So for the black currants, I lopped back to the ground any stems more than 2-years-old as well as some 2 year olds and thinned out new, 1-year old stems, again to the best half-dozen.
How do I know the age of any shrub’s stem? I could count back the age of the various side branches starting at their tips. That would be tedious. The thickness of the base of a stem and the appearance of the bark are just as telling. Old bark is darker and, often, peeling.
After pruning any shrub I go over the plant to remove or shorten stems that will droop so low as to set their fruits on the ground. Especially with strictly ornamental shrubs, I also lop back any stems shooting gawkily skyward or otherwise looking out of place. And then, for any shrub, ornamental or fruiting, I step back to evaluate and admire my handiwork.
Black currant, after pruning
The why, how, and details of pruning any plant
For more about how to prune everything from houseplants to delphiniums to maples to raspberries, check out my book, The Pruning Book.
Live, On Stage Now!!!
I’ll be giving a number of lectures at various venues over the next few weeks. For a listing of what and where, see Lectures.
