Organic matter: Build it up!

Increasing organic matter levels in your soils takes a lot longer than losing organic matter.

August 16, 2011 - Author: Emily Sneller, Michigan State University Extension

How do you build your organic matter levels? Very simply, you must add more organic matter in than is lost by decomposition and soil or water erosion each year. Reaching this balance combines multiple strategies, slowing decomposition rates, reducing organic matter losses and adding organic materials that breakdown and contribute to organic matter fractions.

A number of factors that influence decomposition rates are beyond our control such as soil texture, climate and landscape topography. However, tillage practices are not and can greatly influence these rates. Intensive tillage can speed up decomposition rates, burning up younger organic matter quicker and exposing older organic matter through breakdown of soil aggregates. Additionally, tillage affects the depth to which organic matter is distributed. Thus, reducing or minimizing tillage can have an effect on how much organic matter you keep, whether it is a change in management or a decrease in the number of tillage passes.

Establishing cover crops or incorporating green manure are other management practices which improve organic matter levels in multiple ways. Cover crops and green manures work to maintain organic matter levels and reduce organic matter losses by protecting topsoil, decreasing soil erosion, and reducing leached nutrients. In addition, they increase organic matter levels when residue from the cover crop or green manure is incorporated and starts to breakdown.

Another option that works not only to increase organic matter levels but to also supply nutrients to growing crops is the addition of manure or other waste products, or by-products, if you prefer, such as bio-solids, composts, and crop residues. These by-products contain a significant quantity of readily-available nutrients for plant growth as well as organic portions which not only release additional nutrients upon breakdown but also improve overall soil quality and health. Raw, un-composted manure or waste sources tend to offer larger concentrations of plant available nutrients and contribute more towards the active fraction of organic matter, the shorter-lived fraction. Composted or processed manures tend to offer lower concentrations of plant available nutrients and contribute more towards the stable fraction of organic matter, the longer lived fraction.

Regardless of your production system, there are management practice options which can fit on your farm and help maintain and increase your organic matter levels.

For more information on organic matter and the benefits of organic matter, see Building Soil Organic Matter with Organic Amendments from the University of Wisconsin-Madison or the Organic Matter Soil Management Series from the University of Minnesota Extension.

See related article, Organic matter: It matters!

Tags: field crops, msu extension, organic agriculture, vegetables

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