Tiling isn’t just for waterways and slopes
We’ve seen tremendous variation in weather over the past several growing seasons. First, there was a 100-year level drought. A couple years later we experienced a growing season that most would consider ideal. It was historic. It brought record yields. Regardless whether the extreme is wet or dry, tile drainage in agricultural fields has potential to increase yield. Given our variable weather and the high value of inputs, anything that mitigates extreme conditions in crops helps maintain yield potential and profitability.
University of Missouri Greenley Memorial Research Center in northeast Missouri by Dr. Kelly Nelson has focused on effects of tile drainage on corn and soybean yield. Dr. Nelson has collected 10 years of yield data showing a positive average yield response of 22 bushels per acre for tile drainage versus corn grown on non-tiled land.
Soils in northeast Missouri have an underlying claypan that restricts downward movement of water. The claypan layer can cause a “perched” water table—one that is shallow and potentially leads to high rates of nitrogen loss through denitrification and lateral leaching of nitrates. Both are major contributors to lost nitrogen from agricultural fields on claypan soils. Tile drainage can help reduce the severity of these nitrogen loss mechanisms, making more nitrogen available to the plants and resulting in higher yields.
Another potential use for drainage tile is subirrigation. A water resource such as farm lakes could supply water to be pumped into the field drainage tile during a dry period—essentially reversing the typical drainage in times of excess water. Results from a study by Dr. Nelson compared corn yield with no tile drainage only and drainage/subirrigation. Weather conditions ranged widely during the study, but overall results showed an average yield increase of 20 percent for drainage only versus no drainage. Results for drainage/subirrigation versus no drainage showed a yield increase of 58 percent.
Claypan soils and other slow-draining soils have a high potential for seasonal flooding. Frequent heavy rainfall events in the spring can cause water ponding and flood crops throughout the growing season.
Tile drainage helps alleviate long-term issues on flood-prone fields. Here again, as mentioned earlier, removing excess water in the soil profile increases soil aeration, which reduces potential denitrification and leaching of nitrates.
Proper soil drainage allows for better root penetration, and, over time, can lead to improved soil structure. Thus, even in dry years, well-drained soil can lead to higher yields through improved soil structure and better plant root development. Aside from benefits during plant growth, tiling can speed drainage of excess spring moisture, which helps fields dry quickly enough to be planted at the right time.
Draining soils with tile does not increase or decrease plant-available water in the soil. Rather, it improves rooting depth and overall plant-available water. Only excess water moves on. Water that is held by capillary action to the soil particles remains in the soil profile and is potentially plant-available.
Several factors should be considered if you are thinking about installing drainage tile on your fields. Soil type and grade are obviously important. Also, consider current yields attainable without tile and possible yield goals with tile. Do the math with current and historic prices on the yield difference. That gives you a better picture of whether installation is the right thing to do on a particular field. Your local MFA or precision expert can also help in determining the need for tile on your farm.
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