November 27, 2022
We like to pick and choose the best regenerative agricultural techniques available to us today. The single most important strategy on our farm has been cover cropping.
When soils are left bare, there are no roots to hold back the soil from wind and rain erosion. With no plant to absorb the water-soluble nitrogen, that element leaches out of the soil and into groundwater. On the land, it is fertilizer, but in the water it is a contaminant. With no plants in the ground, there is nothing to feed the microbes, the worms, the nitrogen-fixing bacteria, an all the critters that are essential to soil health. With no root in the ground, rain and snow melt simply wash away nutrients rather than providing life-giving sustenance. Cover-cropping is the practice of never letting these evils happen by always keeping a live root in the soil. It's not important that the plant be harvested, rather simply that it be allowed to grow.
During the winter, there are very few annual plants that we can grow that will yield a vegetable harvest. We do grow garlic and onions in a semi-dormant state during the winter, and you might find a little spinach in a high tunnel, but there is not much we can produce in the winter. Winter-hearty grains like wheat, rye, triticale, and barley will sprout in the fall, go dormant in the winter, then take off in the early spring, and be harvestable by early summer. The harvest may suprise you--it isn't the grain, but the carbon.
One acre of triticale will create 3-4 tons of dried biomass above ground. Put another way, if I spread 100 lbs of seeds in the ground in the Fall, I am rewarded with as much as 8,000 lbs of natural mulch in the Spring. There aren't a lot of things I can do that yield an 80 fold increase in my investment. The leafy biomass (not counting the seeds, the seed head, the stalk, or the root) will pull about 1400 lbs of carbon dioxide out of the air. Mother Nature will take her tax--the deer will browse the greenery through the winter and quail will hide from the coyotes near easy forage. Those tones of biomass above ground will supress weeds later in the year that threaten our main crop, and those tons of vegetation turn into soil. The roots will rot in place, adding more tilth to our soil.
During the summer, we plant buckwheat on our fallow fields. Buckwheat is a false grain--actually a cousin of rhubarb. Since it isn't a grain, it's gluten-free, but still can be used in cooking much like a grain. But our harvest isn't in grain. Buckwheat yields one of the most productive flowers for honey production. It grows quickly and supresses weeds. It forages nitrogen that might have gone to waste. But for us, the harvest is biomass, some 2 to 3 tons per acre of free mulch, free soil, free CO2 absorption.
Safflower is an interesting cover crop. It creates biomass for us just like triticale and buckwheat, but it also has a taproot. When that taproot dies, it decomposes in the ground, putting more carbon and soil nutrition exactly where we want it. It breaks through crusty layers in the soil that might otherwise be impervious to water or soil microbes. It leaves behind a hole to filled with the best detritus the wind and rain will bring.
Legumes like Austrian pea planted in the Fall or black-eyed peas planted in the summer have a symbiotic relationship with the soil biology, the net result of which is the fixaction of nitrogen. Every time you eat, you are using up nitrogen pulled from the soil. When you take home your big 25 lb watermelon, you took home 1/10 of one pound of nitrogen. That nitrogen has to come from somewhere, and we get it from those legumes. An acre of Austrian peas can create 200 lbs of nitrogen in an acre, or enough for 2000 big watermelons for the following crop.
I don't stress too much about weeds, particularly on a fallow bed. I think of weeds as a cover crop I didn't have to plant. They are busy storing carbon, creating soil tilth, increasing the water storage capacity of the soil, scavenging nitrogen and water soluble nutrients, providing forage for critters (even the microscopic ones), making channels in the soil for future little critters to follow, stopping erosion, absorbing water, and just doing a great deal of good. I daresay we don't have any weeds in the fields at all, just some scraggly out-of-place cover crops.
We're finished 3 years of cover cropping. The Extension office studied our soil and found that on average, we had increased the carbon content in the top 6 inches of our soil from 0.5% to 2.5%. That means we have put on the order of 300 tons of carbon into our soil. It doesn't affect our bottome line directly, but we're proud of that figure all the same.