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U. S. OE PARTMENT OF AGRICULTURE NATURAL RESOURCES CONSERVATION SERVICE PHYSICAL PROPERTIES OF SOILS Endnote -- PHYSICAL PROPERTIES OF SOILS--Continued PAGE 7 OF 9 OB/17/00 ORGANIC MATTER is the plant and animal residue in the soil at various stages of decomposition. In report J, the esc rmaced content of organic matter is expressetl as a percentage, by weight, of the soil material that is lees Chan 2 millime cers in diameter. The content of organic matter in a soil can be maintained or increased by returning crop residue to the soil. Organic matter affects the available water capacity, infiltration rate, and filch. I[ ie a source of nitrogen antl other nutrients for crops. EROSION FACTOR K indicates the susceptibility of [he whole soil (including rocks and rock fragments) to sheet and rill erosion by water. Factor K is one of six fat to ra used in the Universal Soil Lose Equation (USLE1 to predict the average annual rate of soil loss by sheet and rill eroa ion in tons per acre per year. The estimates are based primarily on percentage of sil c, sand, and organic matter (up to 9 percent) and on soil structure and permeability. Values of K range from 0.05 to 0.69. The higher the value, Che more suscep Cible the soil ie to sheet and rill erosion by water. EROSION FACTOR Kf ie like EROSION FACTOR K but it is for the fine-earth fraction of the soil. Rocks dnd rock fragments are not considered. EROSION FACTOR T is an estimate of the maximum average annual rate of soil erosion by wind or water that can occur wi thou[ affecting crop productivity over a sustained period. The rate is in tons per acre per year. WIND ERODI BI LITY GROUPS are made up of soils [hat have similar properties affecting their resistance to wind e on in cultivated areas. The groups indicate the eusceptihility of soil [o wind erosion. Sails are grouped according to the following distinctions: 1. Coa rae sands, sands, fine sands, and very fine sands. These soils are generally not suitable for crops. They are extremely erodible, and vegetation ie difficult to establish. Z. Loamy coarse sands, loamy sands, loamy fine sands, loamy very fine sands, and sapric soil material. These soils are very highly erodible. Crops can be grown if intensive measures to control wind eroa ion are used. 3. Coarse sandy loans, sandy loans, Eine sandy loans, and very fine Bandy loamy. These soils are highly erodible. Crops can be grown if intensive measures to control wind erosion are uaetl. aL. Cal careoua loans, silt loans, clay loans, and silty Clay loans. These sails are erodible. Crops can be grown iE intensive measures [o control wind erosion are used. 9. C1 aye, silty clays, noncalcareoue clay loans, and eil ty clay loans Chat are more Chan 35 percent clay. These soils are moderately erodible. Crops can be grown if measures to control wind eroai on are used.