Research conducted in the Red River Valley of North Dakota by David Hopkins and Brandon Montgomery of North Dakota State University showed this decline in soil organic matter quite clearly. They visited the exact locations of several soils examined as part of soil surveys during the 1960s by the USDA. One particular soil in Walsh County had 34 inches of soil above the C horizon (the original material left behind in the area by glacial Lake Agassiz). The soil was examined again in 2014 and was found to have only 15 inches of soil above the C horizon; a loss of 19 inches of soil in roughly 50
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