Solution for Nitrate Loss from Tile Drainage

When casting blame for excess nutrient loading in watersheds fingers often point to tile drainage. Farmers and other stakeholders are finding innovative ways in which they can mitigate nutrient loss from this practice and saturated buffers have proven effective, according to a recent study.

Saturated buffers might be new to you. They are a vegetated, riparian buffer where the water table is artificially raised by diverting water from subsurface drainage system along the buffer to denitrify surface water, according to USDA. With increased eyes on farmland runoff, this could be a method that reduces nitrates in the water and protects a farmer’s ability to operate.

In a study lead by the Agricultural Drainage Management Coalition (ADMC) and the National Laboratory for Agricultural and The Environment the group sought to actually quantify the efficacy of saturated buffers as they reduce nutrient loading from tile drainage. To do so they tested water pulled from ground enrolled in Conservation Reserve Programs to build on previous testing performed from 2012 to 2015.

In the study there were 30 million incoming gallons with 12 million (40%) gallons of flow diverted. Flow diversion helped reduce nitrate loading into nearby streams. Nine sites were tested for nitrates from tile drainage in Iowa, Illinois and Minnesota. Specifically, seven showed substantial nitrate concentration reduction on the main line of drainage systems. The average nitrate load reductions were from 22% to 96% removal with the average across all sites reaching 61%.