In part 1, I talked about how organic matter is the most important ingredient for many gardens, and how mulch and compost are two of my favorite ways of using it.
But there are two other ways of using organic matter. The first is in some ways the most powerful of all, and the second may play an important role in reversing climate change. Let’s get into them…
The third way to use organic matter is to plant a cover crop, often done in the fall to be grown until spring, or sometimes interplanted among food plants such as in an orchard.
A cover crop creates air in the soil when the roots grow and die, grow and die again. Sometimes a specific crop that’s especially good at breaking up hardpans is used, such as certain radishes, and more often grasses and legumes are used.
Cover crops hold onto water and nutrients that would otherwise leach down out of the topsoil if there were no plants there. They also provide food and habitat for soil microorganisms, many of which would die off or go dormant without plant cover.
And yes, when returned to the soil as a mulch, or used in the compost pile, they become food for the soil. Cover crop seed is relatively inexpensive to buy, and the many additional benefits a cover crop brings make it in some ways an even more powerful organic matter source than mulch and compost.
The fourth way to use organic matter is with biochar. The ‘char’ refers to ‘charcoal’, which is made when you burn carbon-rich material such as wood at a high temperature, generally without the presence of oxygen.
Biochar, then, is basically charcoal that’s been made in a biologically sustainable way – made with non-toxic (and hopefully non-gmo) materials, from plants that wouldn’t have been better left alive and growing, created in a sustainable way, and generally used as a soil amendment to increase the carbon in the soil.
We’re in the early stages of learning how to do this well. Biochar is in most ways not as beneficial for the soil as good compost. It doesn’t contain the wide array of nutrients, isn’t a source of beneficial microbes, and doesn’t moderate soil pH – it actually has a high pH that can cause soil nutrient imbalances even more than compost.
But it is an excellent habitat for soil microbes, holds water and nutrients, improves soil structure, and is comprised mostly of very stable carbon that can stay in the soil for a thousand years, which means biochar could end up playing a very important role in reversing climate change.
In summary, if I could only do one task in my garden, I would bring in some form (or hopefully multiple forms) of organic matter – as mulch, compost, cover crops and/or biochar – in order to give plants and soil organisms access to more air, water and food.
In a couple of days, I’ll talk more about where the 80-20 rule falls apart in the garden (update: here it is).
For today, which methods of organic matter make the most sense for your garden? Do you have any questions on what we’ve been talking about?
Let me know down below…
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