Wisconsin and Minnesota Discovery Farms have collected tile drainage data from a wide variety of farming systems. Combining these datasets provides an enhanced assessment that neither state could accomplish individually. This more comprehensive dataset can help draw more conclusions and recommendations about how tile systems influence water quality.

TILE WATER FLOW DIFFERENCES: While surface runoff characteristics in Minnesota and Wisconsin were similar, the amount of tile flow was higher in Wisconsin compared to Minnesota, according to Discovery Farms’ projects in the two states. Twenty-three percent of precipitation moved through tile in Wisconsin compared to 9% in Minnesota since 2005. Reason? Wisconsin received more rain. (Photo courtesy of MAWRC)

Tile water quality information has been collected from 10 different farms and 14 fields, starting in 2005. In total, Discovery Farms has 47 site-years of data. The fields are very diverse, with slopes ranging from less than 1% to 5%. Soils range from fine sandy loams to clay loams, and there are both random and pattern tile lines in the dataset. Monitored fields include corn, soybean, alfalfa, sugarbeet, wheat and pasture. There are several clear lessons learned about soil and nutrient loss from tile systems, but the first piece to understand is tile flow quantity and timing.

More tile flow than surface runoff on an annual basis
Surface runoff and tile flow typically range from 1.3 to 4.2 and 1.8 to 6.5 inches, respectively. There are also differences between the timing and intensity of surface runoff and tile flow. Surface runoff is often inconsistent, but it generally occurs during snowmelt in the early spring and during the time from planting to crop canopy. On average, there are 10 days of surface runoff per year. On the other hand, tile drainage has many more days of flow and is much more consistent throughout the year.

Amount, timing of tile flow differs between Wisconsin and Minnesota
While surface runoff characteristics in Minnesota and Wisconsin were similar, the amount of tile flow was higher in Wisconsin compared to Minnesota. Twenty-three percent of precipitation moved through tile in Wisconsin compared to 9% in Minnesota. There were also many more days of flow per year in Wisconsin compared to Minnesota tile sites.

The flow time period in Wisconsin is typically from December through July, whereas in Minnesota it is typically from April through July. In Wisconsin, there was a significant portion of tile flow during the period when ground was frozen. The difference in the amount and timing of drainage is likely due to climate and landscape position. The Wisconsin sites usually have much more rainfall during the October through April time period. Three of the Wisconsin sites were located in low areas in the landscape that were influenced by shallow groundwater flow.

Precipitation differences between Minnesota and Wisconsin likely explain some of the differences in the amount of tile flow observed between the two states.

The amount of precipitation during the year has a large effect on the amount of tile flow. There is a strong correlation between annual precipitation and annual tile flow. There is an even stronger correlation between October through April precipitation and annual tile flow. Precipitation during this period has a significant impact on the amount of tile flow. Precipitation differences between Minnesota and Wisconsin likely explain the differences in the amount of flow observed between the two states. During the years monitored in Minnesota and Wisconsin, Wisconsin had more than 7 inches of additional precipitation during the October through April period. This is not unique to the years monitored. Looking at long-term, 30-year precipitation for the monitored sites, the Wisconsin sites have 3.8 inches more during the October through April time period.

More tile information, research at upcoming conference
The 2016 University of Wisconsin Discovery Farms Annual Conference Dec. 13 at Glacier Canyon Conference Center at the Wilderness, Wisconsin Dells, Wis., will feature a talk on tile. The presentation will continue to dive into the comprehensive dataset from Minnesota and Wisconsin Discovery Farms and offer three practical ways to avoid losing soil, nitrogen and phosphorus from tile drains. For details on the conference, visit uwdiscoveryfarms.org/store/products/winter-2016-conference-registration.

The Minnesota and Wisconsin Discovery Farms programs recently received a conservation innovation grant from the USDA Natural Resources Conservation Service. The grant will allow Discovery Farms programs in both states to continue efforts to identify the timing and mechanisms of soil and nutrient loss to tile drainage systems.

For more information about the project, visit agwaterexchange.com/2016/09/21/discovery-farms-awarded-conservation-innovation-grant.

Source: Minnesota Ag Water Resources Center