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MASTER GARDENERS: Soil is a 'dynamic entity'

The quotation "Man owes his existence to a six-inch layer of topsoil and the fact that it rains," is attributed to radio talk show host Paul Harvey in 1978. I, too, have great respect for topsoil.

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The quotation "Man owes his existence to a six-inch layer of topsoil and the fact that it rains," is attributed to radio talk show host Paul Harvey in 1978. I, too, have great respect for topsoil.

You can buy bags of topsoil at garden centers. These are good products and meet the needs of many gardening problems, but they are not really soil. They are almost 100% organic matter from sources like forest waste products, peat, coir, or coconut husks and compost.

Organic matter does a lot of good things in our flower and vegetable beds, but eventually, it decomposes into carbon dioxide and water. It is not, however, really soil.

The soil we find in a natural forest, grassland or farm field is composed of 50% air and water, or open spaces, depending on rainfall. It is 45% mineral matter which will be a mixture of different particle sizes of mineral matter from coarse sand to intermediate silt particles and fine particles, sticky clay with loam being a mixture of all particle sizes. These particle sizes will determine how well your soil holds water or if it is easy to cultivate. Only 5% of real soil is organic matter, but it is a very important 5%.

I learned in college that soil is a "dynamic entity" and I have spent years trying to find out what a dynamic entity is. Soil starts out as parent material, the original source of mineral matter which may be from glacial deposits or wind or water deposited minerals. It is affected by topography, the slope of the land and the direction the slope faces.


Climate is also a big factor. Soil development works at different rates depending on temperature and rainfall. Living organisms have a big effect on soil in adding and recycling organic matter. All of these factors are influenced by time. Time is continually improving soil unless it gets eroded away.

Real soil has capillary action which moves water and dissolved minerals from areas of high concentration to areas of low concentration. Gardeners of soil don’t have to water as often as raised bed gardeners. Our heavier clay soils are the best at capillary activity.

Real soil has an amazing population of 10 billion soil organisms per gram of soil. These organisms have adapted themselves over time to your particular soil, plants and climate to deliver everything that your plant population needs. It will take your bag of topsoil a long, long time to achieve this.

Having gardened the same plot for more than 30 years, I have seen the soil improve after years of cultivation and the addition of manure and other organic matter. Over time, the soil has been populated with microorganisms adapted to my climate and management practices.

My worm team is constantly mixing the organic and mineral matter between the layers of soil and making my topsoil even deeper. I occasionally pull up a carrot or parsnip root that is 30 inches long.

Soil is composed of topsoil, subsoil and the original parent material. If you remove the soil it becomes dirt, which is still a valuable commodity but it isn’t connected with the whole soil ecosystem.

Let us spend our winter days appreciating six inches of topsoil and hope that we get the amount of rain that we need.

These local garden articles will reach you each week throughout the gardening season, but gardening information can be found year-round by clicking on "Yard and Garden” at the University of Minnesota Extension website, , or by visiting our Facebook page at .


Local Master Gardeners will respond to questions via voicemail. Call (218) 444-7916 , and leave your name, number and question.

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