Checking for Soil Erosion

While soil conservation plans are great, they need to be complemented by field observations to determine if they are effective.

Several years ago, conservation professionals walked 15,000 acres on 60 Wisconsin farms from which we can learn. They reported that 40% of runoff and 80% of erosion occurred in April, May, and June, so it was especially important to protect fields from erosion during that time. 

While walking all these fields, they observed that most erosion came from 4 sources:

1. concentrated flow areas
2. waterway outlets
3. widespread in-field erosion
4. eroded stream banks

In talking to farmers, they developed a 'traffic light method' for walking fields. They took a printout of an aerial photo of the fields and marked it with 3 colors. Marked with red; areas that showed clear signs of erosion that needed attention. Marked with yellow; areas that showed moderate signs of erosion that might need work, and areas without erosion were marked 'green.' They also noted where conservation practices were effective in controlling erosion. The walkovers were meant to identify the source of runoff causing damage, during which times of the year the erosion occurred, determine what the fields looked like at that time and why that led to erosion, and then determine a plan with priorities to address the 'red' areas and if possible the 'yellow' areas.

Things to look for were smooth and sealed soil surfaces, numerous small channels in the field, crops that were washed out or buried, and corn stalks collecting in or around the field.

Signs of soil erosion were common on tilled fields with little cover, even when the slope was modest. If in-field erosion was observed, they started asking questions encouraging farmers to reduce or eliminate soil tillage and plant cover crops. If those were not options, other conservation practices such as contour planting, breaking up slopes by planting strips of different crops, leaving more crop residue, and buffer strips or terraces were explored.

If they noticed concentrated flow, they looked at whether grass was planted in the channel. However, many times, the grassed waterways were no longer functional. This could be due to excess soil inside or along the edge of the waterway, narrowing of the waterway due to tillage or herbicide applications, or gully formation at the outlet of the waterway. In those cases, action was recommended to repair (usually re-seed) the grassed waterway.

Another matter that was discovered in this project was the importance of neighbors working together. Water may enter or exit a field from a neighboring area. This may be a farm field, but it can also be something like a woodlot or a residential area. It will be important to work together to make sure concentrated flow from one property can be handled by the neighbor. 

Finally, stream bank erosion was also noted, but that was a whole lot more complicated to deal with and required assistance from conservation departments or other local organizations.

As the winter draws to a close, it is a good time for us in Pennsylvania also to check our fields for signs of erosion in the field as well as in concentrated flow areas. When we see areas of concern, let's make sure they get addressed before the start of the growing season. 

References:

Amber Radatz, Callie Herron, Kevan Klingberg and Todd Prill. 2016. Field Walkover Guide: A practical on-farm conservation tool. UW Discovery Farms.