Water takes the path of least resistance, which in row-crop fields means the loss of soils from fields. Soil erosion is costly and was most recently estimated to cost farmers in Iowa 1 billion dollars annually. Erosion occurs on steep slopes where water is allowed to gain momentum unchecked as it travels downhill. Grassed waterways with perennial vegetation helps slow the rate at which water runs off fields and have been shown to be extremely efficient at decreasing sediment runoff. However, waterways are frequently implemented in lower parts of the field to catch soils before they run off the field. In contrast to waterways, contour waterways are placed on the steepest slopes, which are frequently the hardest to farm, to prevent soils from eroding rather than trying to stop transport. Once soil has started to erode it is nearly impossible to stop erosion from continuing. Functionally, contour and traditional waterways act in harmony to prevent soils from beginning to erode while then catching the small amount of sediment that is mobilized.
Whiterock Conservancy partnered with the Iowa Soybean Association (ISA) to seed contour grass waterways and monitor the changes in soil erosion. Water quality runoff from storm events was monitored over 3 years in micro-watersheds (<30 acres) between a traditional field and a field contour waterways. The Iowa Soybean Association monitored the amount of runoff and the amount of sediment, nitrate, and phosphorus over many different size storm events. Stay tuned as the ISA wraps up monitoring.