A concept that could help cut down on the number one pollutant in water – soil particles loosened by soil erosion, and an important nutrient, nitrate – is still in the demonstration phase in Indiana. It's called the two-stage ditch. A few have been installed on f arms, but more have been installed as part of demonstrations so people in a community can watch how they are built and how they work compared to regular drainage systems.
The concept is simple: provide an extra bench or settling out point for sediment and nutrients before the water carrying it reaches a ditch or stream that empties into a larger tributary. They can be installed in conjunction with bioreactors or alone. The bioreactor is an artificially-created box of natural material that filters tile water to remove nutrients, particularly nitrogen, before the water exits on into the tile drainage system and flows to an outlet.
Both were installed at the Purdue University Throckmorton Farm near Romney last week. The Indiana Land Improvement Contractors did the work, and turned it into a field day so anyone interested in the installation process could watch.
The two-stage ditch in this case will be studied by Purdue specialists to see if it in fact does reduce nitrate load heading into streams. The process involves creating a lower-than-ground-level area next to the regular ditch or stream channel. Once grass is established, water should accumulate there first, allowing particles to filter out. On most farms today, especially without a filter strip, the nutrients go directly into the stream or man-made ditch and are lost to the farm, but picked up by waterways. Environmental groups are very sensitive, especially this year, to nitrates that will be leaving fields and winding up in important bodies of water, such as the Gulf of Mexico.