Agenda - Environmental Policy Board - 02/01/2010

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Attachment B Topsoil Ramsey is located on the Anoka Sand Plain. As the name implies, the majority of our soils are composed largely of granular sand. This layer of sand often extends downward to a depth of ten (10) feet or more. Sand has a very low water holding capacity, so when it rains, or more importantly, when yards are irrigated, much of the water percolates through the sand fairly quickly and ultimately moves down and out of the vegetative root zone. This is why it is such a struggle to keep many of our yards lush and green. The more we try to keep our yards green, the greater the demand on our drinking water supply. One tool that can help lessen the need for such frequent irrigation is topsoil. Generally speaking, topsoil is the upper (surface) portion of the soil, typically between two and eight inches (2-8" deep). Topsoil also contains varying levels of organic matter from decomposing plant material and microbes, which is critical for root development and nutrient and water retention. Topsoil, especially topsoil with a high level of organic matter and clay, has a much greater capacity to retain water, making it available to lawn grasses long after the rain stops or the sprinklers are shut off. In fact, according to the University of Minnesota publication Organic Matter Management (BU-07402), organic matter can hold up to six (6) times it weight in water. While high organic matter content is important, some sand is also necessary to provide proper drainage and soil structure. Sand also creates soil pore space, which is necessary for root growth. Healthy topsoil loaded with organic matter can provide numerous benefits, both to the yard and the environment as a whole. First and foremost, it improves nutrient and water retention, both critical for establishing and maintaining a healthy yard. This will result in the need for less watering and fewer applications of fertilizer and herbicides/pesticides. Furthermore, topsoil helps retain herbicides/pesticides and fertilizers, reducing potential contaminants from entering our waterways through runoff.