Soil Compaction I Where, how bad, a problem

Soil compaction is a more common problem now than it was 15 years ago, regardless of the tillage system used. Producers now use heavier tractors, larger implements, bigger combines, earlier spring tillage, reduced tillage, and no-till planting systems. While all of these have a potential to increase compaction, the major cause of the problem is conducting field operations when the soil is too wet. Most think about tilling wet soils in the spring as being the major problem, but harvesting a too-wet field in the fall can cause just as much compaction. Large combines and auger wagons can have loads exceeding 20 tons per axle. Continuous no-till has also created concerns regarding soil compaction and potential yield decreases. A study in Minnesota that compared no-till and other tillage systems used for 10 years on a clay loam soil showed the greatest soil density for the no-tilled soil. A study in Illinois indicated more compaction with no-till and other reduced tillage systems than with moldboard plow or chisel systems. Generally speaking, no-till is undesirable on a fine textured soil which has poor internal drainage or on a soil that has marginal tilth at the outset. On top of the soils themselves, the residue cover with no-till conserves moisture and slows soil drying, which can further complicate the problems of compaction when no-till is used on poorly drained soils. Soils with good structure, high organic matter, and good internal drainage are less likely to have compaction problems. Also, in low-rainfall areas, such as the Great Plains, compaction is less likely to be a problem than it is in areas of more moisture. The biggest single cause of compaction is the degree of wetness in a field when work is performed in or on that field. Defining compaction Compaction can be defined as the moving of soil particles closer together by external forces exerted by humans, animals, equipment, and/or the impact of water droplets. Packing the soil particles together results in the loss of pore space within the soil. This, in turn, leads to poorer internal drainage and aeration. Under many soil conditions compaction leads to slower water infiltration, which results in greater runoff and soil loss from both rainfall and irrigation. Compaction effects on the crop include reduced plant growth, especially root development, decreased crop yield , and delayed maturity