The Kenwood Press|
Everything you always wanted to know about carbon, but were afraid to ask
Last month we began to write about the issue and importance of carbon in our soils. Well, dear reader, get ready to dive deeper, as I find the science of carbon so fascinating and important.
Here’s that rant on carbon that I warned you about
Carbon is the building block of life. All living things contain carbon and it is the basic fuel that allows most organisms to live. To understand carbon, you need to understand the carbon cycle.
Almost all living things depend on the energy of the sun either directly, like plants who produce their own food through photosynthesis, or by eating a plant, a plant-eating animal, or decomposing plant material (see diagram above).
Carbon molecules (sugars) are produced by plants and metabolized by other living things to provide energy and the building blocks of many other complex organic molecules.
It is clear we need carbon. But carbon is getting a bad name because of the build-up of CO2 in our atmosphere. There is the same amount of carbon as there ever was … just too much of it is now in gas form – as opposed to liquid form (dissolved carbon sugars) or solid form.
If we want to be putting less carbon in our air in the form of CO2, methane, and other greenhouse gasses, do we want it in our soil? The answer is YES.
Healthy soil is a complex mixture of minerals (weathered rock), organic material, and living organisms. This matrix is the source of the nutrients necessary to grow plants. While there are some very important macronutrients, there are also many micronutrients necessary for healthy plants. And these micronutrients can be very difficult for plants to find and access without the help of the soil microorganisms.
Soil microbes live in the vicinity of healthy plant roots and, since they are not photosynthetic organisms themselves, depend on these roots for their carbon. Plant roots “leak” carbon in the form of dissolved sugars that are taken up by the soil organisms. Why would plants do this if it were not beneficial for them? Soil organisms, in turn, find and “fix” the micronutrients needed by plants into the compounds the plants can use.
When we go to the historical records and read about soils and plant communities that predate modern agriculture, we hear about soils that are thick and “spongy.” The spongy character of native soils was the result of high amounts of carbon stored in the form of humus – complex carbon molecules formed by soil microorganisms.
This humus has been largely mined out of our soils through modern farming techniques (heavy cropping, application of pesticides, use of synthetic fertilizers). The nutrients stored in humus have been replaced by synthetic fertilizers, which ironically, over time have created a barren soil devoid of the rich community of soil microbes necessary for a healthy soil complex. This results in a basic profile of nutrients being supplied to plants for growth and has reduced the nutritive value and flavor profiles of our foods. Think of trying to make chicken soup with salt as your only spice. It is possible, but sadly lacking in complexity.
How do we get more carbon into our soils?
Compost application is a good start, but is not enough. Soil management techniques require that there be a healthy, continuous network of living plant roots to sustain a healthy microbe community. Use of cover crops that encourage a healthy soil community not only improves soil health, but also improves the percolation of water. Studies show that farms with effective use of cover crops are actually more water efficient than those with barren, weed-less rows of crops.
In addition, foliar application (spraying) of nutrients and microbes known as “compost tea” can help reintroduce a diverse microbe population where the population has been reduced.
Here at MacLeod Family Vineyard we are constantly working to build healthy soils. From the annual application of compost, to use of cover crops between rows, reduced tilling (which disrupts microbe networks in the soil), and experimental plots without use of herbicides to control summer weeds. It’s all part of a more sustainable approach to farming, a topic we’ll revisit regularly in our Journey to Harvest.