by Kristi Cox
No till, cover crops and wind breaks all play a role in mitigating wind soil erosion on The Prairies, but are they equally effective? Allowing soil to blow has negative effects, so it's important for producers to determine the best practices to ensure they are protecting this resource.
David Lobb, Professor in the Department of Soil Science at the University of Manitoba, explained that even small amounts of soil loss can cause big problems. Blowing soil and crop residue can: damage crops; reduce road visibility causing accidents; and cause respiratory problems.
Ultimately, even with careful measures to decrease wind erosion, it can't be eliminated completely.
"You should never have the expectation that wind erosion will be completely stopped," said Lobb. "We always need to produce food, and wind erosion occurs even in natural environments. But, when humans are involved, they need to make sure what they do doesn't make it dramatically worse."
How do we keep soil where it belongs?
"Use as little tillage as possible," said Lobb. "It reduces wind, water and tillage erosion problems."
No-till practices have a two-fold benefit when it comes to wind erosion. The plants themselves slow the speed of the wind at the soil surface, substantially decreasing soil loss. Tillage breaks the soil into individual, lighter particles, which are more easily lifted by the wind, so avoiding that practice holds soil in place as well.
Cover crops are used as an alternate source of fixed vegetation.
"If you keep your residue from the previous crop in the ground, the extra residue from the cover crop probably isn't going to make a significant dent in the wind erosion issues," explained Lobb. "They can add biomass, but they are not likely to have a huge impact on soil erosion. I would always argue that you shouldn't till in the first place if you can help it."
Cover crops can, however, be useful following low residue crops like pulses or potatoes.
"Soybean, for example, does not produce as much biomass, and what it does produce is very lush, so it breaks down rapidly. Its ability to provide cover is very limited, and short term," Lobb said.
The challenge is that soybeans tend to get harvested late in the fall, which makes it difficult to establish a cover crop. The same can be true for long season potatoes. In these cases, it is important to leave residue in place. Producers should consider rotation options. For example, barley can be planted early, reducing the duration of bare soil in the spring.
Another option people often look at is windbreaks. These can slow the speed of the wind across fields to varying degrees, depending on species used and spacing. However, they also take land out of production and may create shadowing effects.
"That doesn't mean there's not an argument to be made for windbreaks, but I would use no-till or cover crops first," said Lobb. "If there is still a problem, then consider a windbreak."
Emergency measures lack the long-term effectiveness
If the soil starts to blow, producers must mitigate it according to the Soil Conservation Act. However, emergency measures lack the long-term effectiveness of prevention.
"Typically, what's done in the prairies is to till the blowing field," said Lobb. "The tillage creates roughness, and it turns moist soil to the surface. Those two things stop wind erosion in its tracks."
However, this emergency solution is very short-term.
"There are long-term risks," Lobb continued. "What if you have wind two to four days from now? It's now disturbed, and it will be dry. It's potentially going to blow even worse."
If producers have a source of manure, spreading it can be another emergency solution. Adding moist material to the field will make it less likely to blow. As the manure dries, though, it becomes another source of material to blow in the next wind event.
"Unlike tillage, manure might help build up the organic matter level and provide long term stability," said Lobb. "It has a short-term benefit and a long-term benefit."
Prevention helps producers avoid reaching the point of choosing emergency measures. No till, cover crops and shelter belts are all tools available to keep soil where it belongs.
This is the last article in a series of 5 on soil blow
article 1 Yes, Blowing Soil Breaks a Law
article 2 Economics of Agricultural Blow-Dirt
article 3 Dollars Blowing in the Wind
article 4 Don't blow good neighbour relations