It is well understood that soil productivity is closely tied to soil organic values and the nutrients contained within it. The economic loss of organic matter and reduced productivity far exceed the raw value of the nitrogen, phosphorus and potassium found in the soil because that organic matter also contains other macro and micro nutrients required for highly productive soil. To attempt an estimated value of nutrient loss, you must also consider the long-term impact on soil productivity.
To estimate the value of nutrients lost to erosion of organic matter, the market value organic fertilizer such as animal manure can be used as a proxy due to the similar composition.
Below is an example calculation for soil with 5% organic matter and an assumed animal manure value of $0.10/lb.
5% X 2,000lbs/1ton of soil = 100lbs of organic matter per ton of soil
100lbs/ton X $0.10 = $10.00/ton of soil lost
If we use the tolerable soil loss (T) value of 5 tons/acre, the nutrient value lost to erosion for Soil X is $50/ac.
The economic value of nutrients lost due to soil erosion is only a small indicator of the problem with far-reaching effects on soil productivity. The loss of soil productivity, both in the short and long run, stems from the degradation of the physical, biological and chemical properties of the soil and will impact crop production regardless of how much chemical fertilizer is applied. The loss of organic matter will lead to an increase in input cost of nutrients applied as chemical fertilizer to mitigate or manage the loss of soil productivity.
In addition to the direct cost of fertility loss from soil erosion to the producer and landowner, the long-term cost to society in terms water quality and other environmental risks can be significant. By implementing practices outlined in the Iowa Nutrient Reduction Strategy, soil and the nutrients found in the organic matter can stay in the field and out of the water.
The original article by Mahdi Al-Kaisi appeared in the March 6, 2015 Integrated Crop Management News and can be found here.
– Liz Juchems