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1. Overview of agricultural drainage
Drainage refers to the process and practices used to remove excess water from the soil surface and from the soil profile. This bulletin briefly describes the history, need, types and extent of Michigan drainage as well as the pros and cons, and environmental impact related to drainage.
2. Drainage history
The U.S. Swamp Land Acts of 1849 and 1850 provided federal funding to encourage drainage to make the swamp areas in the Midwest more habitable, and thereby encourage economic development. Through this program, many miles of streams were deepened and channelized to create drainage outlets with the result that large parts of the Corn Belt were drained. Once drained, these areas became recognized as having among the most fertile soils in the world. Early medical professionals had suggested drainage in the Midwest as they found that it reduced malaria, although they did not know malaria was spread by mosquitos at that time (Huffman et al., 2013). With the increase in drainage in 1860, the human death toll due to malaria started to decline in the upper Mississippi River Valley.
3. Drainage need
Agriculture is one of Michigan’s leading industries with over 300 commodities. Corn and soybean are the state’s two leading crops with a combined planted area of 4.5 million acres, and a production value of $1.85 billion for grain corn and $1.46 billion for soybean in 2021 (USDA-NASS, 2022). Some of the most productive soils in Michigan require subsurface drainage for profitable crop production. Without drainage, crop production would not be able to meet the growing food demand because of poor crop yield due to excess water (Figure 1).
7. Michigan Drainage
In Michigan, lateral drain pipes are typically installed at a depth of 28 to 30 inches. Drain spacing ranges from 15 to 40 feet for a new installation with the lower range for fine-textured soils (clay, clay loam and loam) and the higher range for coarse-textured soils (sand and sandy loams. Overall, there has been a recent trend for narrower drain spacing, which allows for a quicker water removal from the field.
In Michigan’s Lower Peninsula, subsurface drainage is more concentrated in the southeast and the Thumb region where the dominant natural drainage classes are very poorly, poorly and somewhat poorly drained (Figure 7). Drainage class identifies the frequency and duration of wet periods under natural conditions.
It is difficult to know exactly how much land is subsurface drained in Michigan, but the 2017 Census of Agriculture estimated 3.0 million acres of subsurface-drained farms, which shows a 38% increase from the 2.5 million acres in 2012. This is because subsurface drainage pays well.