Crop residues: rewards versus risks

John Berger marked the completion of his 57th harvest on his family farm near Nanton in southern Alberta this fall.

By most accounts, it was another productive year on Berger’s 5,000-acre grain farm. Still, something didn’t sit quite right with the long-time farmer. Whenever he toured the nearby countryside post-harvest, he noted many farm fields were bereft of any stubble or crop residue.

“I hope I never have to buy or rent that land because it comes with a yield deficit because of the nutrients being taken out,” Berger says.

“Some people think that baling straw is free money, but when I look at the nutrient removal it frustrates me. If we don’t replace those nutrients, it’s mining the soil.”

Much has changed on Berger’s farm since he started farming it with his dad back in the 1960s. Back then, summerfallow and tillage were common practices on most farms in the region as there was still an ample supply of organic matter in the soil.

That all changed in the 1970s, Berger says, when he and his dad quit summerfallowing and tillage and shifted to direct seeding, trying to keep as much crop residue on the surface as was practical.

The results appear to speak for themselves. Based on crop insurance records, yields on Berger’s farm are 1.3 to 1.4 times more than those of the area average for yields. Berger credits that in large part to the fact he and his son, who now handles most of the farm’s operations, have focused on leaving a sufficient amount of crop residue in the field.

Doing well

“We feel that what we’re doing is working pretty well,” he says. “We are getting yields that my father and father-in-law would not believe we are growing in such dry years with minimal rains.”

In addition to enriching nutrient levels in the soil, leaving crop residue behind has helped with snow retention and provides more moisture for the soil, he says.

Another benefit has been to alleviate the dry conditions caused by chinook winds from the Rocky Mountains that blow through the region. Those winds are “the world’s best grain dryer” but also rob the soil of valuable moisture.

“The standing stubble reduces the velocity of the wind at the soil surface and shades it so we have less evaporation due to a lower soil temperature and we’ve got the wind protection from the standing stubble,” Berger says.

That standing stubble also helps to fight weeds on his farm by acting as a barrier that makes it more difficult for weed seedlings to make their way to the surface and compete with his crops. Conversely, the stubble cover helps shelter seeds from wind and gives them a better fighting chance early in their life cycle, he adds.

Berger says leaving stubble or other crop residue behind on his farm also helps deliver more moisture directly to plants. The seeding openers used on his farm move the residue to the inter-row area between crop rows. As a result, rain will run off that “hump” and flow to the lower level where plants are.

“If you get a 10th of an inch of rain, it could double or triple that rain to our row where our plants are at and rob moisture from the area between the rows where the weeds might want to live,” he explains.

Pros and cons

Larry Durand is a certified agrologist and crop advisor at Humboldt, Sask., where he operates Field Good Agronomics. He’s also a member of the Saskatchewan Institute of Agrologists.

Durand says the question of whether to leave crop residue on a field comes up in conversation with some farm clients. His typical response is that there are both pros and cons to doing it — and whether it’s a practice farmers should follow depends on the specific farm operation.

“It’s not a one-size-fits-all kind of solution. It absolutely is not,” he says.

“I think there’s a lot of room for removal of crop residue to a point, but it would be unwise as a rule to remove your crop residue year after year after year. But I think there’s some important opportunities in doing so every once in a while, when opportunities or needs arise. I think farmers should be cognizant of that.”

So, how does a farmer know whether they should leave crop residue on their field or remove it?

Durand says some fields are more at-risk if crop residue is removed on a regular basis. Those include fields that are more prone to soil erosion because of coarse or sandy soil texture, or that are adjacent to landforms where there’s significant potential for water erosion and other risks.

“If you don’t have very good organic matter you might want to leave some of that crop residue to improve it on more of a long-term basis,” he says. “You want to keep working at improving that organic matter. It’s a very, very slow process.”

Conversely if a field has healthy soil with good organic matter and sound structural integrity, the risk of baling cereal straw to sell from time to time likely poses little short- or long-term risk, Durand says.

When discussing whether to leave crop residue on a field, Durand often tells clients many crops still leave behind significant nutrients, even after they have been baled.

“There’s still a lot of crop residue that gets left behind in the roots, stubble and chaff… because you’re not cutting it right to the soil surface. I think a lot of people overestimate what you’re actually removing with that straw,” he says.

Hairpinning

The upside to leaving crop residue behind on the surface of a field, Durand says, is that it can act as a protective blanket for the soil. As a result, it can help to maintain soil structure, prevent erosion and hold in moisture — something increasingly important in parts of Western Canada where there’s a soil moisture shortage.

The downside, he says, is that managing crop residue can sometimes become an issue, especially in the case of larger crops such as corn or cereals that produce a lot of plant material.

“Sometimes that crop residue just makes it difficult to get a good seed bed because there’s too much trash there and it causes hairpinning (straw is pinned in the seeding slot) when you’re trying to seed. In those cases, removing that crop residue is probably beneficial to help you with your farming operation,” he says.

Yield losses

Berger has some simple advice for growers when it comes to determining whether to leave post-harvest residue on a field: consider not only the short-term gain you can make, but also the long-term pain that might result.

“I talk to other older farmers who see these guys who are taking every kernel, every bit of straw and then their yields are nowhere near as high, but they don’t think their yields are that different. They don’t realize it. But just the moisture loss by hav- ing that soil exposed without the crop residue on it, it’s a big thing in dry years.”

– Jim Timlick is a reporter for Grainews magazine.