Organic Matter

Fall 2002
By Eric Sideman, Ph.D., MOFGA’s Director of Technical Services

It always amuses me to think back to when I was young and, like most, I understood very little of what my parents did. Now that I am an adult, most of their former actions make sense. Sometimes they had good reasons for their behavior and other times their actions simply must have seemed like the right thing to do. I regret not talking and listening more to my parents because it is too late to find out for sure which was which. Even some of my father’s gardening practices leave me asking myself: “How did he know that when he grew up in the slums of New York City?”

My father and mother moved us out to the suburbs of New York when I turned eight years old, and we started gardening that very week. We turned over a plot of sod and began planting seeds. I can remember looking at the color coded maps of climate zones on the backs of the seed packets and figuring out whether it was too early or not to plant the crops. I can still feel the pea seeds against the very tips of my fingers as I pushed them about an inch deep into the freshly raked soil.

But what I think about most these days is the way my father taught me to manage the organic matter in the soil. I will never know if he understood the importance of organic matter to the soil; or if he was thinking about recycling nutrients way before it was popular; or if he just had no place else to put the fall leaves; but he taught me a system that I still think ranks among the best for feeding the soil, which many say is the kingpin of organic growing.

In the fall we would rake all the leaves onto old blankets and carry them over our shoulders, then dump them on half of the garden. The leaves remained on that half of the garden all winter and through the following year, then were tilled in before vegetables were planted on that half of the garden. The other side of the garden got the leaves in alternating years, so we rotated our gardening back and forth year after year, with leaves composting into the soil.

The crops were great, and as the years went by I took over the garden and kept up the system. Now after 25 years of schooling and about 20 years working for MOFGA, I know why. We really were feeding the soil. Soil is really a system made up of inorganic matter (mineral material), about a thousand different kinds of living critters from worms and insects to bacteria and fungi, and recycling organic matter. A soil system that is working well can support great crop growth because nutrients are recycling round and round, and at any time a good amount are available to the crops. Great crop growth can also be supported by minerals bought in a bag, but organic growers recognize the detrimental aspects of this approach, from the excessive energy used to produce these fertilizers to the environmental pollution they can cause, to the destruction of the soil. Organic growers choose to maintain a healthy soil system.

The key to a healthy soil system is the organic matter that is recycling. We organic growers have been singing the praises of organic matter for half a century now: It recycles nutrients, holds water, builds soil structure and feeds the microbes. But like many of the practices of crop producers, recycling organic matter is a bit more complicated than it first appears, and understanding organic matter more can help improve your soil.

A phrase that Fred Magdoff from the University of Vermont uses in his new book, Building Soil for Better Crops, goes a long way to explain the complexities of organic matter management. He says there are three types of organic matter, the living, the dead and the very dead. He is referring to the plants and animals that are living in the soil, the recently dead material that is decomposing, and the mostly decomposed material that we call humus. In order to have a soil system that is cranking and recycling minerals through the generations, all three types of organic matter should be plentiful. Some of the living organic matter (mostly arthropods, bacteria and fungi) are doing the recycling by decomposing the dead organic matter. This process releases lots of minerals for reuse by the other living organisms, including crops. During this process, organic compounds are released that help build soil structure by cementing small particles together into aggregates. Decomposing organic matter passes through a phase that is very slow to degrade any further. This material is humus, and it is responsible for a great deal of the nutrient holding and water holding capacity of a soil.

When you are working in your garden, I suggest you slow down every once in a while and think about the importance of organic matter. Do you have freshly dead organic matter (green manures, fresh livestock manure, leaves as my father used, etc.) to feed the living part of the soil? Do you have enough very dead organic matter (humus or compost) in the soil to hold the nutrients and water? Fall is a great time of year to reflect back on the growing season and eye the plentiful harvest, but remember the memorable part is how you handled organic matter.

You can address your questions about organic farming and gardening to Eric at [email protected].

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