TRJ How does compost relate to soil health? What does putting compost into your soil do? LF Compost is a soil amendment. It is very biologically rich. It does help to activate the biology in your soil, although you need good soil structure in order to keep that biology — so you typically need more than just compost to really build soil back from a degraded place. But there are nutrients in the compost. Compost is typically pretty high in phosphorus; food scraps contribute a lot of potassium, and you also see an abundance of other nutrients, like calcium and magnesium and all those other micronutrients. You go through this metabolic process with the microbes that release micronutrients, beneficial compounds, antioxidants, disease- suppressive properties, and more. All of these things help the soil build structure, which helps it retain more water, sequester more carbon, and — if the microbial community is very good — it can also help suppress diseases, like root rot. Compost can also help break down pollutants like pesticides. A lot of microbes will break down petroleum and hydrocarbons, and they can help sequester heavy metals. That’s not to say that compost is a complete solution for contaminants, but it does help and provide support.
TRJ How do plants and microbes interact in soil? LF Plants release sugars through their roots. That is directly feeding bacteria, which then attract protozoa and nematodes. And, in addition to releasing nitrogen, these guys are releasing plant-growth-promoting hormones. In a way, the plant is releasing these sugars to cultivate the microbial community around itself that it needs to survive. Plants also make connections with mycorrhizae. These fungi connect to the plant root directly, where the plant exchanges sugars for other nutrients. Like, maybe the plant needs more phosphorus. The fungi can bring that nutrient in from somewhere else in the soil, where it’s more abundant, and exchange that nutrient with the plant. It can be other nutrients, too. It could be water, as well. Different types of plants can cultivate different types of microbial communities in the soil. Trees cultivate more fungal relationships, which helps to create more fungal dominance in the soil overall.
TRJ How does this relate to the challenges we now face with conventional agriculture? LF You should think of soil structure as the home — the habitat — for microbes. If you had a giant tractor tilling up your neighborhood every week, you’d really struggle to rebuild in between and live your life. You don’t have enough time. So, conventional agriculture generally engages in a lot of disruptive practices for microbes, like tillage, synthetic fertilizers, pesticides, and monocropping. The soil biology then has to expend more energy rebuilding, rather than building on top of what was already there. People like tilling because it makes the soil soft, it’s easier to germinate things, and it releases a temporary flush of nutrients. So it seems like a good method. But over time, your soil texture and quality will not be able to maintain itself. The biology is not able to sustain, either. And then you end up with compaction. The use of fertilizers is also a problem. Generally, they’re used to provide an abundance of nutrients to get plants going.
The plants can’t use all those nutrients, though. Excess leeches away, which causes all kinds of downstream pollution. It also bypasses the microbiology you need for healthy soil. If nutrients are abundant, the plants don’t develop mycorrhizal relationships. You end up with less mycorrhizae in the soil overall. Pesticides, of course, are going to kill off your soil biology. So you have all these forces suppressing the ability of your soil to establish itself, and you have to artificially create it instead — which is a lot of work for us to be doing when we could just be helping the soil biology, and then the microbes are doing all the work to create soil structure and nutrient fertility.
Visit LACOMPOST.ORG and SOILWISE.EARTH to learn more.
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ISSUE 02
THE MICROSCOPIC LIFE OF COMPOST
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