High-Intensity Rainfall Causing Significant Erosion

Soil erosion by water remains a significant threat to agricultural productivity and environmental quality across the USA and Pennsylvania. The last available National Resource Inventory (NRI) published by USDA reported that rill and sheet erosion on Pennsylvania cropland still averaged 4.5 T/A/yr on Highly Erodible Land (HEL) and 1.5 T/A/yr on non-HEL (in 2017). This was significant progress from 1987, when soil erosion on HEL was still 6.1 T/A/yr and 1.7 T/A/yr on non-HEL, but still excessive, causing degradation of cropland, reduced yields, and impaired water quality. Although we typically calculate and express soil erosion as average soil loss per acre per year, most water erosion is caused by high-intensity, isolated precipitation events. 

For example, we heard that this week in Mannheim, more than 4 inches fell in 24 hours on soil that was already wet. This type of event is likely to cause significant erosion if the soil is not protected and anchored. After such events, we often see rills and gullies. Gullies are not included in the above estimate. Whenever you see them, you can assume you have already far exceeded the tolerable soil loss level. The primary causes of soil erosion by water are tillage practices that loosen the soil, weaken soil structure, and reduce residue cover. Bare soil can also be the result of harvesting all the crop residue and not leaving any cover. It can also be the result of overgrazing on our pasturelands. Effective water erosion control relies on keeping soil covered and minimizing disturbance at all times to avoid soil exposure during that once-in-a-lifetime event. 

Recommended practices include:

• Conservation tillage: No-till and mulch-till systems that reduce soil disturbance and maintain residue cover.
• Cover crops: Cereals/grasses and broadleaves that protect soil during fallow periods and improve soil structure.
• Contour farming: Planting along the natural contours of the land slows runoff and reduces erosion.
• Vegetative barriers: Narrow strips of grass or shrubs across slopes trap sediment and slow water flow.
• Proper grazing management: Rotational grazing and maintaining adequate forage cover reduce erosion on pastures 

Soil erosion is a manageable threat. By adopting proven conservation practices, farmers can protect their land, improve productivity, and contribute to cleaner water. Technical and financial assistance is available through USDA's Natural Resources Conservation Service (NRCS) and your County Soil and Water Conservation District to help implement erosion control strategies tailored to each farm's needs.