Losing six inches of topsoil can result in financial losses exceeding $6,600 for farmers, according to a recent study conducted by researchers at North Dakota State University (NDSU). The analysis highlights the critical role of topsoil, the most fertile layer of soil, which contains essential nutrients and supports robust crop production. When topsoil erodes, the loss includes not only soil but also valuable organic matter.
Researchers at NDSU found that the combined cost of direct nutrient loss and the loss of nutrients tied to organic matter totals more than $1,100 for each inch of topsoil lost. Over six inches, this amounts to approximately $6,600. Naeem Kalwar, a soil health specialist at the Langdon Research Extension Center, emphasized the economic implications of soil erosion, stating, “Protecting topsoil from erosion is crucial. That layer is where farmers plant seed, and it is responsible for feeding the world.”
Soil erosion occurs through various processes, including wind, water, and tillage practices. In particular, tillage can exacerbate erosion by loosening the soil, leading to further loss. When topsoil washes into roadside ditches, it can contaminate drinking water supplies for both humans and livestock. As Kalwar points out, “Farmers, ranchers, and landowners will eventually have to pay to replace those nutrients.”
To quantify the economic impact of lost topsoil, Kalwar’s team collected a 6-inch sample of eroded topsoil from a roadside ditch adjacent to a field. This sample was sent to a soil testing laboratory for a comprehensive analysis. The results indicated substantial amounts of vital plant nutrients and a significant quantity of soil organic matter.
The researchers calculated that the cost to replace the nitrogen, phosphorus, potash, sulfate-sulfur, and iron in the eroded soil totals $2,541.22, or approximately $423.54 for each inch of lost topsoil. Additionally, replacing nutrients linked to the loss of organic matter adds another $4,141.73, equating to $690.28 per inch. The total replacement cost for six inches of topsoil, therefore, is approximately $6,682.95.
While fertilizers can restore lost nutrients, rebuilding soil organic matter can take decades, even with the best management practices. A study at the NDSU Carrington Research Extension Center revealed that soil organic matter increases by just 1% after 27 years of consistent livestock manure application. Based on this rate, replacing the 5.7% of organic matter lost from six inches of topsoil could take around 154 years, which is nearly two lifetimes.
Kalwar asserts, “Preventing erosion is far more cost-effective than trying to rebuild the soil.” He recommends practices such as reduced tillage and cover cropping to save farmers significant amounts of money over time.
The full findings of this research are detailed in the report available at ndsu.ag/erosion-cost. For further information on strategies to protect soil health and prevent erosion, visit ag.ndsu.edu/soilhealth.
