Erosion: Treat the Problem, Not the Symptoms
Beauty and the beast. A tale as old as time. This story has nothing to do with love. It’s all about erosion and what can be done to transform overworked, abused soil into healthy, productive soil teeming with life.
The situation is grim across the Midwest. Soil is eroding around a rate of 5 tons per acre per year, with severe cases losing closer to 100 tons per acre, says Jerry Hatfield, director of the USDA-ARS National Laboratory for Agriculture and the Environment located in Ames, Iowa. These numbers are above the rates of soil restoration, so soil will continue to be lost.
“Erosion rates are dependent upon the year,” says Hatfield. “It’s all rainfall driven.”
Intense weather events in the spring are becoming the norm across the Midwest. There is more precipitation in the spring – a time of year with little or no crop to use that water, says Hatfield.
Since there’s no vegetation to use the water or break up the raindrop energy, it leads to increased runoff and erosion, causing concern over how much erosion rates will increase across the Midwest. You battle this beast yearly. As of January 2017, 23.5 million acres were reportedly enrolled in the CRP across the U.S. Voluntary participation has helped to improve water quality and reduce soil erosion.
But is it enough?
“You protect land from erosion and reduce the amount of sediment you put into streams with these practices,” says Chad Watts, executive director of the Conservation Technology Information Center in West Lafayette, Indiana.
The bottom line: You need less soil disturbance and more residue and cover crops.
“Your soil is more than just the medium in which you grow plants,” says Watts. “The downfall of many civilizations was when they degraded their soil to the point that it was no longer productive. When soil degrades to the point of no return, that’s when civilizations begin to fail. It behooves you to protect your soil.”
The practice of tillage has conservationists exasperated.
“There is no agronomic or economic reason for tillage to be justifiable anymore,” says Doug Peterson, NRCS Iowa and Missouri regional soil health specialist. “It destroys everything that restores soil function.
“The practice of tillage is more ingrained in most people than their religion,” he says.
After all, passed down from generation to generation was the thought that tillage was required to make soil function, but that is not the case. Instead, tillage causes a loss in aggregate stability, explains Peterson. Root exudates in the soil act like glue and hold together soil particles. Erosion occurs when one piece of soil breaks loose from another aggregate.
Sediment loss, nutrient loss, and water availability are the main conservation concerns for Hatfield. “We’ve induced more and more field variability over time,” he says.
“If you have good root exudates coming from year-round plant roots and a healthy biology, you have a better aggregated soil,” says Peterson.
The slake test is a good visual demonstration of what is happening in the field. The slake test consists of two clear containers full of water. A clod of soil from a tilled field is placed in one container, while a clod from a no-till field is placed in the other.
“The tilled soil dissolves rapidly,” says Peterson. “In the presence of rain, without the glues or exudates, the soil particles in the aggregates break loose, and they are very susceptible to erosion.”
That’s not the case for the no-till field, which remains intact. A field with poor soil health doesn’t allow for as much water infiltration as a healthy soil. Maintaining soil structure is important to help with infiltration, explains Hatfield.
“It’s not how much rain you get in the rain gauge that matters; it’s how much you get in the soil. Your job should be determining ways you can capture rain and store it better,” says Hatfield.
It’s not just a problem with water – there’s an issue with oxygen, as well.
“Those roots growing in the soil are really oxygen-dependent,” says Hatfield.
Having nonfunctioning soil biology is akin to having COPD. The soil needs to have an oxygen exchange – that’s limited in soil without a healthy biology.
It’s a Beast
You see these areas with washes get filled in by tillage. The answer to this type of erosion is to manage water better, explains Watts.
The ideal system is a continual no-till with cover crops, which builds soil aggregates and allows more air and water movement through the soil.
The following three steps will help you manage your soil for the future.
1. Adjust your strategy. Leave residue. Material left on the soil surface is an impediment to water movement. Cover crops or a grass waterway help deflect that water, resulting in more infiltration and less runoff.
Gully erosion, a concentrated flow of water that cuts deep channels, is different from other types of erosion because you notice it right away. Other types don’t appear to be a significant problem – yet, looks can be deceiving. Sheet erosion (the uniform removal of soil in thin layers by raindrops and overland flow) and rill erosion (the removal of soil by concentrated water through small channels) are the types that cause the most soil loss.
“If you lose .10 inch of soil a year, you don’t notice it,” says Watts. “You’re losing more than you think. A tenth of an inch over 40 acres adds up – it’s just less noticeable.”
Don’t think this is affecting you? Losing the thickness of one sheet of paper across an acre is equivalent to losing 5 tons of soil, says Peterson. If you have perfectly clear water in your field after a rain event, then you didn’t have much sheet erosion, he explains.
2. Fix it right. Available programs with cost sharing have made it easier to fix issues, says Watts. Over the years, farmers have done a pretty good job addressing the critical areas with waterways. “For example, if you get a gully, you don’t get a lot growing. You’re money ahead to fix it and fix it right rather than try to farm with it,” he says.
Growers are certainly headed in the right direction. “Even more than 10 years ago, protecting your soil is part of the conversation. As you talk about being sustainable, soil has to be part of that conversation,” Watts says.
When considering conservation practices, it’s key to think of the context of how it fits into your production system.
There’s a direct tie between conservation and your production system. There are enough options within conservation that you can protect soil while being productive and profitable, says Watts.
3. Treat the problem, not the symptoms. An emphasis has been placed on buffers in past years, but they should be considered the last line of defense.
“If you have water, it’s going to move some soil,” says Watts. “Some movement is inevitable.”
In-field management should be the answer instead of relying on capturing soil, nutrients, and water leaving the field.
“Edge-of-field practices (such as buffers) slow down water movement and stop those sediment and nutrient runoffs before they get too far,” says Watts. While valuable practices, they only treat symptoms – not the problem – and should only be half of the system.
“When you get to the point where you have a big gully, you need to pinpoint why you can’t fill it in with tillage,” explains Watts. “Look up the hill to see what’s happening.”
In-field management gives you an opportunity to address the problem. “The beauty is that there is an opportunity to tie conservation practices to production,” says Watts. “Cover crops build organic matter, and there are production benefits that go along with building organic matter.”
The Beauty of Transformation
The conversation needs to move from no-till to never-till. “Any time you make a tillage pass, you begin to break down aggregates,” says Peterson.
Water infiltrates the pore spaces in the aggregates, and tillage passes destroy those spaces in the aggregates. Ultimately, this destroys the ability of the water to infiltrate the soil. That’s not all it harms. It also slashes the earthworm habitat.
“The more active the biology, the more you’re going to get out of the system,” says Peterson.
Take nutrient cycling, for example. In a tilled environment, only about 30% to 50% of nutrients make it into the plant, says Peterson. However, with no-till, 70% to 90% of nutrients will be accessed by the plant. This may improve yield, and it lowers the risk of nutrient loss.
Producers have installed a lot of practices without understanding that they’re treating only symptoms of the problem instead of the root cause, says Peterson.
The goal of a bioreactor is to trap nitrates that leave the field and prevent them from going into a river or stream. Even if it’s just $10 to $30 per acre in nitrates leaving the field, that’s a $10 to $30 investment going unutilized because the soil couldn’t hold the nutrients. It’s an investment you can’t get back, he says.
“Historically, the problem hasn’t been understood. The soil wasn’t functioning properly. Those edge-of-field practices may function really well, but it’s still costing you,” he says.
Cover crops combined with no-till could be the answer. Cover crops add organic matter to the soil, while no-till builds aggregate stability, he says. “Neither practice is as effective by itself.”
Together, the combination can help build healthier soil, resulting in less need for conservation practices that merely treat the symptoms.
Watts believes having organic matter and healthy soils will result in a reduction in the amount of tillage.
That’s why cover crops are gaining ground. “A lot of people are realizing they can make them work in their system,” Hatfield says. “More and more producers are beginning to see the value of that, but they need to figure out how to work it into their systems.”
This age-old tale may just have a new, sustainable ending.