Kaplan, S. and C.K. Harris, A.P. Rudy, B.J. Thomas, M.R. Worosz, and M.I. McCoy
Presented at the All Scientist Meeting (2003-09-12 )
Along with cattle, sheep and horses, swine have been one of the four main types of livestock in Michigan from 1854 to 1997. Although swine have never been the dominant component of livestock in southwestern Michigan, they have generally been the second most common. After 1954, the number of pigs grew sharply, then dropped dramatically between 1904 and 1940. This was likely due at least in part to the great Depression, and possibly was affected by the reform of the meat packing industry after 1904. After 1940, however, hogs have been growing steadily, and are now at about the same number that they were in 1884. Initially hogs were allowed to run freely in the wooded areas of the early farms, grazing on roots, nuts and mast in the forested areas of the farm. Permanent pig pens led to disease problems, and were replaced by movable pens. Contemporary facilities are entirely enclosed, have some degree of biosafety, and attempt to minimize the incidence of diseases. Over all these changes, the enduring constant has been the manure from the hogs. When the hogs ran freely, manure was also deposited wherever the animal happened to be. With the development of confinement systems, manure had to be transported from the pig pens to the fields for incorporation into the soil. Although manure from confinement operations is stored and composted, environmental threats from volatization and runoff still remain. At the same time, the pressure on rural land for residential purposes creates conditions where farms and even entire counties have more manure than can be spread safely on the available farmland. In these conditions, hog farmers have to make deals with other landowners to obtain access to additional land for manure disposal. This still leaves the possibility that the phosphorus in the manure will exceed the absorptive capacity of the land, and that the excess phosphorus will be carried in percolation and runoff to surface and ground waters.
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