Losing ground is never a good situation.
Soil erosion had been declining since the late 1970s, but latest statistics show “we’re headed back up,” said Rick Cruse, professor of agronomy at Iowa State University in Ames.
But conservation practices could help reverse the trend and actually rebuild soil, some experts say.
“There will always be some movement of soil," said Matt Russell, food policy project coordinator at Drake Agricultural Law Center in Des Moines, Iowa. "However, we need to get much more serious about setting our goals for the least amount of soil loss possible. We need to keep innovating and challenging ourselves as farmers to strive towards zero soil loss even if it may not be technically possible. We should be able to rebuild soils, so a net gain in soil over a longer period is possible,” Russell said.
Cruse and Russell were both part of recently completed studies by the Leopold Center for Sustainable Agriculture. The center is a research and education center at Iowa State University created to identify and reduce negative farming impacts and to develop new ways to farm profitably while conserving natural resources.
Cruse led the study on the economic impact of soil erosion in Iowa. It measured topsoil depth on seven Iowa farms in a corn to soybean rotation to determine the impact on yield. The researchers found that the cumulative effect of soil loss is significant and can contribute to a large loss of revenue for the farming community.
Estimates put corn yield loss at $4.3 million the first year, and soybean yield loss at $2.75 million, for a $7 million total loss. Over 10 years, the loss could be $315 million, the study found.
“Relationships between topsoil depth and yield varied among fields and with summer rainfall amounts. Across all sites the average drop in corn yield per inch of topsoil lost was 1.49 bushels of corn per acre. If sites for which manure was not part of the cropping history were considered exclusively, yield loss per inch of topsoil lost was 2.19 bushels per acre. Soybean yield loss was 0.79 bushels per acre per inch of topsoil thinning,” the study found.
The results of the study did not surprise Cruse, who said he believes they could be extrapolated to other lands.
“If the topsoil is already thin, the impact is much greater,” he said.
Farmers can tolerate the loss of soil and income, particularly in the short term. But erosion has a cumulative effect that compounds the loss.
“Topsoil thinning is closely linked to loss of crop production potential. Typical statewide average erosion rates have only a minor impact on crop yields in the subsequent year,” the study reported.
“However, cumulative effects are far more significant and contribute to a loss of state revenue that becomes much more important as time progresses. Short-term minor yield impacts on a per acre basis create little incentive for investing in short-term soil conservation strategies available for many farmland renters. However, as the cumulative effect compounds the economic effect over time, landowners that have longer term planning horizons are much better positioned to recover their financial investments in soil conservation practices.”
“Conservation costs,” Cruse said. Farmers who plan to pass the land down to the next generation might be more willing to spend money because someone in their family will see the returns.
But he cautions people not to paint farmers and landowners with a broad brush. Some farmers do the right thing because they believe in stewardship. It’s a bell curve, he said, and “a few on the other end care less.”
If consumers were educated and engaged and asked questions about farming techniques, that could help change tactics, he said.
In conversations with farmers, they tell him that when state subsidies for cover crops end, it will also mean an end to the cover crops. One of the challenges is that if competing states don’t have the same practices, Iowa farmers can be at a disadvantage.
Less intensive rainfall, less row crops and reduced tillage would help decrease erosion, Cruse said. So would adding perennials, like alfalfa. That would mean having livestock and pasture on more farms, instead of concentrated in fewer large livestock operations. But he cautions that how the hay is tilled under makes the difference. Grass waterways also need to be protected.
Industrialization, with its economies of scale, worked well for most industries, he said. But most industries don’t raise living animals or plants.
Russell was a co-investigator on a study called “Protecting Iowa’s Land Legacy: Soil and Water Conservation, Past, Present and Future.”
One of the study’s suggestions was to focus work at the watershed level.
“A watershed provides a physical place where farms are connected,” Russell said. “It also provides a measurable outcome to show progress. Finally, there are increasing examples of people in watersheds organizing as a community. In some ways, watersheds make more sense than county or other jurisdictional boundaries.”
Increasing cover crops would help, the study said, and they work well with keeping livestock.
“Cover crops are just starting to take off. There is going to be a tremendous increase in research and innovation in the coming years. I think we'll see a wider variety of approaches as farmers tailor particular mixes and plantings to their specific needs on a field by field basis,” Russell said. “There are state and federal subsidies for cover crops, but they are limited. There is talk of expansion, and I would not be surprised if we see a real expansion of support for cover crops in the next farm bill.
"Cover crops are typically terminated on an annual basis or right before the growing season. I think the challenge is to keep farmers using cover crops even after a subsidy or incentive program is finished.”
The study said there is no acceptable soil loss.
“Ditch the idea of tolerable soil loss and focus on soil health. We need to change our thinking about... the idea there is an acceptable level of soil erosion. The goal should be no soil erosion. And we need to shift our attention to soil health so we take a more comprehensive view of our soil,” the study said.
“I think we need to look at the whole farm as a unit. This would encourage a greater number of crops, longer rotations, and the integration of livestock on more Iowa farms,” Russell said.
And there should be shared stewardship.
“We don't all farm but we all participate in agriculture. Thus, we all have a stake in supporting better conservation. I think the agriculture community needs to continue to reach out beyond ourselves to invite others into helping us become the best stewards possible,” Russell said.
“We're all in this together. There is so much room for greater dialogue, new leadership, and the development of new practices and products to promote sustainability,” he said. “Climate change is going to drive a lot of innovation all along the supply chains and that includes farmers and the crops they grow. While it's mostly about the carbon footprint and climate change right now with retailers and manufacturers, Iowa farmers need to integrate water quality and soil health into the discussion so we can get the most bang for the buck in terms of sustainability.”
The Leopold Center for Sustainable Agriculture was established in 1987 through the Iowa Groundwater Protection Act. The Center is named for Aldo Leopold, a native of Burlington, Iowa, known internationally as a conservationist, ecologist, and educator. He saw the need for development of a land ethic, outlined in his 1949 book of essays, “A Sand County Almanac.” Leopold was a professor at the University of Wisconsin-Madison.