Sustainable farming isn’t a natural process, no matter how you slice it. Left to its own devices, our North Carolina Piedmont would sport nothing but hardwood forests, as it once did. For the most part, the soil here is rich with clay – good for holding moisture and nutrients — but low in pH, too low for most food crops to grow well. To change this, farmers add lime, manure and naturally occurring nutrients, grow cover crops, break up compacted soil with tractor implements, bring in irrigation systems, and many other things, to slowly build their land into the loamy, nutritious stuff that plants need to thrive. What they’re really doing, it turns out, is improving conditions for the vast army of life fungi, bacteria, worms, and even mammals that help food crops grow – what Alex Hitt of Peregrine Farms calls “The Beast”. Feed The Beast, he says, and the plants will take care of themselves.
But there is one other thing soil needs to support plant life well – heat. Just about the time we’re getting out our big jackets and crock pots to hunker down for winter, microbiological life is starting to do the same thing. As the days grow shorter and temperatures drop, soil life slows down, processing nutrients much more slowly, moving less, and generally providing less goodness for plants to use to grow. Today for instance, according to the NCSU CRONOS Network Map (http://nc-climate.ncsu.edu/map/) the soil temperature in this area is about 41°. Most crops won’t consistently germinate and grow until the soil is much warmer (which is why most seedlings this time of year are started in greenhouses). Green bean seeds, for instance, need soil temperatures of 77°-86° (2013 Johnny’s Seed catalog, p. 5) to germinate well.
So what can a farmer do to get a jump start on supplying vegetables for a March CSA or farmers market? Well, greenhouses and hoop houses are one way. Both can be seen on the student farm. They create sheltered warm places for air, and more importantly soil temperatures to be artificially elevated so biological activity can crank up and plants can grow quickly. Essentially, they are little areas of artificially created Spring. Farmers also do this on a smaller scale with row covers – the long white hooped tunnels you can see on the farm that enclose a single row of crops. By covering plants with even a single layer of fabric, they are sheltered from wind and frost. Additionally, moisture in the soil is retained, which retains heat in the soil, and the sun’s warmth is trapped to increase air and soil temperatures as well. Depending on the fabric used, the outside temperature and humidity, and whether the fabric is laid directly on small plants or arched over them using a hoop structure, a planting bed’s soil can be elevated five, ten or even twenty degrees. This can make a huge difference to the level of biological activity in the soil, and therefore how well and quickly plants grow.
So next time you pass by the farm and see a billowing row of cover over a bed of plants, know that a farmer is just working to create a little patch of Spring, free from frost and teeming with billions of happy microorganisms.