You would think by now that those of us working in the conservation field would have a really good handle on the value of topsoil. Again, you would think. In the abstract, I think we would all say that we “value” topsoil. However, in the 80 years since we’ve identified soil erosion as an issue in the U. S., we have been unable to even begin to quantify the value of topsoil in real numbers; until recently. Thanks to the leadership of Iowa State University Professor, Rick Cruse, we’ve moved one step closer to identifying the value of one ton of topsoil. A huge breakthrough in the work of soil conservation!
According to his research, Cruse says that if you lose a ton of soil this year, it affects your yield for every year into the future, not just the next year. In other words, once you lose a ton of topsoil, that soil is gone forever. And as my mom says, “forever is a long, long time”.
Dr. Cruse explains that erosion of topsoil affects our land investment in two different ways. First, erosion causes a direct loss of crop nutrients. In today’s market, every ton of eroded topsoil has an average nutrient value of $2.10 (nitrogen and phosphorus alone). If a farmer is losing 5 tons/acre/year he is losing $10.50/acre annually in nutrient value. Secondly, erosion causes a decline in soil health, which can cause yield loss both now and into the future. Soil only regenerates at a rate 1/10 to 8/10 of a ton per acre per year, with an average rate closer to 1/4. When a farmer loses an amount greater than the level of regeneration, he is losing present & future yields. In general, soil erosion costs about $0.07/ton in productivity this year as well as every year in the future. Of course, if the price of corn doubles in value, then this loss also doubles.
What about the most erosive part of the field…
Since erosion is not distributed evenly across the field, the farmer may want to evaluate those areas of the field where erosion is the worst and costs the most money. Using the calculations above, the loss to the farmer would be 17.4 tons/acre/year on the most erosive 20% of the field. Erosion on as little as 20% of a field could cost the farmer $365.68/acre in nutrient value and $66.99 in lost productivity over this same 10 year period. This is a total loss of $432.67/acre. That adds up to $12,980 on 30 acres in (20% of 150 acres). With this financial information, the farmer might then choose to focus on the worst 20% of the field by installing site specific conservation practices like a terrace or grass strip.
By identifying the value of a ton of topsoil and understanding the distribution of soil erosion, a farmer can start making informed decisions on specific problem sites. Precision Conservation is applying conservation practices in the right place, at the right time, and at the right scale. With precision conservation we are taking another step toward being able to identify the value of a ton of topsoil, pinpointing where and how much erosion is occurring, and where farmers should target their efforts. Imagine a farmer targeting his conservation efforts to achieve the best return on investment and also solving the biggest environmental problem. I think that is what we refer to as a WIN/WIN!
Tom,
Great approach to visually show different soil erosion rates within a field and nutrients loss. And this doesn’t include tillage soil loss. Using a yield map and running the numbers to calculate the profit/loss numbers on the 20% portion of the field with the highest erosion rates could also help reinforce the need for converting this area to forages or wildlife. However, constructing terraces (with government cost-share) is not a sustainable option.
I am from a Kosovo and I am graduated on agriculture with my specialization on irrigation issues. Kosovo is grappling with soil erosion problems too. I read your article and it is quite interesting to me but I want to see something about best practices in the US on soil conservation issues.
regards!
Avdullah
Hi Avdullah,
Over the next few months, I hope to write more posts about the efficacy of different conservation practices. Unfortunately, my knowledge of irrigation is pretty slim.
Terraces or grass strips and water ways can be effective on reducing ephemeral erosion and average soil loss. They do not effectively reduce sheet and rill erosion off of the most erosive 20% of a field since the length of a steep slope is very short. Economic losses discussed will remain high on these areas.
Too often RUSLE type models are limited by a poor assumption that crop rotations and tillage practices and the K factor will remain fixed. To attack erosion more sustainably, one should strive to improve the intake rate of the water that is received as precipitation (or irrigation) and the water holding capacity of the soil.
The most effective and sustainable practices have clearly been by reducing tillage intensity to improving residue management (including no-till) and adjusting crop rotations to include cover crops designed to increase organic matter and infiltration rates and eventually water holding capacity. Cover crops can occasionally be planted between cash crops, and occasionally cash crops can be deferred and cover crops grazed with livestock to maximize the biological activity of micro-organisms in the soil. Soil aggregate stability will gradually increase, infiltration rate will increase, and soil erosion will decrease, even on the most erosive portions of the field.
Richard Sparks
Richard, I agree with you that waterways and terraces do little to protect sheet erosion. Certainly grass strips can be very effective if they are located on the critical part of the hillslope.
I think we need to consider that farmers apply conservation for different reasons. For instance, a farmer might want to do his part in a local water quality project that was designed to protect a stream or lake. In this case, the farmer may be more willing to install a grassed waterway instead of using a cover crop. Both practices may work to achieve his watershed objectives, but after the educational process, it really comes down to farmer’s decision.
This decision making process is the essence of NRCS’s 9 step planning process. Step #2 is to determine the farmer’s objectives. I am long past the belief that there is a silver bullet out there for conservation. If we expect that we can apply a one size fits all philosophy, then let’s just throw away the conservation planning process and get on with selling the one or two practices currently in vogue.
Throughout my 30 year career with soil and water conservation, the trail is littered with examples of conservation planners offering lip service to using all the tools in the toolbox. However, depending upon which program is popular and which way the political winds are blowing, a conservation planner may only promotes one or two practices in that toolbox. For example, in the 80’s, conservationists promoted structural practices because they were popular. In the 90’s it was buffer strips. And today, it seems like cover crops are the only thing that generates any buzz. I am all for cover crops, but not at the expense of giving farmers other choices. It seems the only practice that has stood the test of time is no-till. And even that has its future challenges with herbicide resistant weeds (more in my next posting.)