Get Grounded: Dig into the Life of Soil
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Soil is teeming with life. With advances in technology, we, the ever-curious above-ground experimenters, are slowly unearthing how these various tiny creatures interact with each other and their environment. Learning how to manage this complex soil ecosystem can feel daunting, especially in the face of environmental extremes and changes, but many people are having success by focusing on soil health.
Different than previous soil management terms, soil health emphasizes soil biology (soil life) as well as maintaining soil functions long-term to sustain above-ground life. While at times, the term seems very new and technical (I mean, what is active carbon anyway?), many methods to improve soil health are oldies but goodies such as cover cropping, crop rotation, or prescribed grazing.
Over the next year, we’ll dive into varied aspects of soil health: ways to measure it, modern ideas, tried-and-true methods, and the long-term benefits. We hope that you’ll join us on this exploration of soil health and reach out to us with questions.
Our first topic is soil compaction, a physical change that can greatly affect the soil’s biology. Compaction occurs when soil particles are pressed tightly together, pore space is lost (particularly the bigger pores or macropores), and soil structure breaks down. Ultimately, the soil becomes denser. While roots have trouble growing through compacted soil, normal microbial functions can also change.
For example, microbes typically help convert organic nitrogen in the soil into forms that plants can more easily use (such as nitrate or ammonium), but when compaction decreases pores and available air, the new low/no oxygen environments limit these reactions.
SCD Farm planner Chase O’Neil holding healthy soil
In fact, these low/no oxygen environments actually increase other microbial processes that remove nitrogen from the soil. There is also evidence that soil compaction may decrease the number of mycorrhizal fungi, a species that lives harmoniously with plant roots. These fungi scavenge nutrients for plants and help build soil structure, and thus can be very useful in a healthy soil ecosystem.
For those of us in Western Washington, having wet conditions is like preheating the oven for a soil compaction recipe. When soils are wet, activities like livestock grazing, operating heavy machinery, and tillage can easily compact soils, which ultimately causes ponding, mud formation, soil erosion, and nutrient loss into waterways.
Sometimes it’s hard to avoid working in these conditions and other precautions can be taken (see sources below for more details on this), but in general, to avoid compaction, avoid working on wet soils. If you already have soil compaction, rebuilding soil health by adding compost or organic matter, planting deep-rooting cover crops (daikon radish, cereal rye, etc.), reducing tillage, or implementing crop rotations (with diverse root systems) can all help.
The following articles offer more details about soil compaction and methods to both prevent and mitigate it.
Washington State University - Soil Compaction: An inevitable part of modern agriculture or a symptom of poor soil health
National Center for Appropriate Technology:
University of Minnesota Extension: Soil compaction
This project (WQC-2022-SnohCD-00101 Nutrient Runoff Reduction From Agricultural Lands in Snohomish County) was made possible through a Centennial Clean Water Fund grant through the Department of Ecology.
