Soil compaction could be squeezing your yields

For years, soil compaction wasn’t something Jeff Hamblin gave a lot of thought to.

The Manitoba producer had heard about how the seasonal freeze-thaw cycle in the Red River Valley and elsewhere in the Prairies acted to naturally alleviate farmland soil compaction, but it wasn’t until he started investigating some problem areas in his fields that he realized compaction had become a yield-limiting factor.

Staying off the land is the best way to prevent soil compaction, of course. Hamblin, like any farmer, will tell you that’s not a realistic option, so he tried deep ripping with a five-shank subsoiler to break up compacted soil.

While Hamblin doesn’t view deep ripping as practical across a whole farm because of the expense, he did have some “limited success” with the technique on some high-traffic, headland areas.

“We found we could grow a crop there the next year after ripping, where we might not have been growing anything at all,” says Hamblin, who grows wheat, canola, soybeans, corn and flax on his farm near Morris, Man.

However, Hamblin also found that deep ripping had softened the soil in the headlands so much that there wasn’t much structure left, which slowed down farm equipment and created the same problem with compaction.

A better solution for Hamblin has been transitioning from tires to tracks on his farm, something he’s done over the past 15 years.

• Read more: Three common soil compaction mistakes

Hamblin’s tracked equipment includes John Deere two-track tractors and a grain cart, and he’s hoping to add combines to the list soon. For those vehicles without tracks, Hamblin tries to make sure they’re equipped with the best flotation tires available for reducing soil compaction.

“We bought the biggest floaters we thought we could get away with on our sprayers,” he says. “We do whatever we can to try to lower ground pressure.”

Controlled traffic farming

Adam Gurr, who grows wheat, canola, soybeans and dry beans near Brandon, Man., has a different approach for controlling soil compaction.

He’s a staunch proponent of controlled traffic farming (CTF) or tramline farming, a popular Australian practice where all field traffic is constrained to permanent paths to limit compaction. For a CTF system to work properly, every implement needs to have a particular tire or track width or a multiple of that span (40, 80 and 120 feet, for example).

Gurr says he first started thinking about CTF about a dozen years ago after a series of wet seasons caused spring seeding delays and other problems related to waterlogging. Like Hamblin, Gurr wondered if seasonal temperature fluctuations were doing enough to bring compacted soils on his farm back to where they should be.

“You could even see combine tracks from the previous fall, and that just got me thinking that maybe soil compaction is a bigger deal than it appears to be,” he says.

For Gurr, CTF just seemed to make a lot of sense. “We were set up with our (tramlines) already, so the initial investment really wasn’t there and I had equipment that was conducive to at least giving it a try.”

Gurr was able to incorporate his 80-foot drill and 120-foot sprayer into the CTF system he set up on his farm, later adding an 80-foot heavy harrow and 40-foot harvester headers to the equipment mix.

Gurr isn’t aware of any other Manitoba producers doing controlled traffic farming. He suspects some are, though, and he knows there are farmers in Saskatchewan and Alberta who’ve adopted the practice. “Every year I get a call from a producer who’s interested in doing it or is working towards it.”

Gurr acknowledges an obstacle to adoption is the high upfront cost associated with CTF if you don’t have the right equipment. For the practice to catch on in the Prairies, Gurr believes farmers need to see solid, local data that shows there’s enough economic value to make it a worthwhile investment.

Gurr acknowledges there has been a dearth of research like this in Western Canada, and that’s one reason why he decided to stage a CTF project on his own farm as part of his remote studies at Iowa State University, where he earned a master’s degree in agronomy in 2018.

While simulations from the study did show a slight yield benefit from CTF, Gurr says the real eye-opener for him was just how much improvement he saw in soil physical properties like water infiltration rate, which has important implications for nutrient-use efficiency and coping with drought.

Gurr says because conditions can change so much from one year to the next, he can’t provide a hard number on the yield improvement he’s seeing today with CTF. He estimates it’s somewhere around five per cent over time, although it’s obviously more in a soggy year when compaction is a bigger threat.

“There are other years where soil moisture is well distributed during the growing season and maybe you don’t see anything, but there are other benefits besides just the yield,” says Gurr.

Compaction: indirect effects

Marla Riekman is a soil management specialist with Manitoba Agriculture and Resource Development who frequently talks about soil compaction during extension presentations with producers. She maintains while there’s no question compaction affects crop growth, it can be hard to put a finger on precisely what the yield consequences are.

“We don’t have a great handle, let’s say, on what that true impact is on your year-to-year basis on yield,” says Riekman. “There is some impact on yield potentially that’s happening. We just don’t always know exactly what the number should be or is.”

She adds it’s important to note the indirect effects of soil compaction that can cause yield loss. An example is purpling in corn, which can be caused by a phosphorus deficiency. In some instances, it may not be a case of insufficient phosphorus in the soil, but rather the plant’s inability to access the nutrient due to compaction.

“It’s an indirect impact because the roots can’t grow well enough to explore the soil and take up phosphorus,” says Riekman, who urges farmers to try digging around with a shovel when they suspect compaction might be a problem.

Roots normally extend down and outwards in all directions as they grow, she says, so if you dig up a plant and the roots are growing sideways, there’s likely compaction going on.

Riekman has a penetrometer that can be used to measure soil compaction, but a shovel is her favourite tool when she’s out in the field. She often has farmers telling her they don’t have compaction problems, but when she hands them her shovel and asks them to dig a hole, they quickly realize just how tight the soil is because the digging is so hard.

“The nice thing about a shovel is, yes, you can feel that compaction as you’re trying to dig if you don’t have a nice, soft, mellow soil,” says Riekman. She adds breaking up the soil as you’re shovelling can also tell you if a plow layer has developed or some form of compression is happening.

“You can see different kinds of impacts where sometimes the soil, when it’s compressed down, gets almost a plate-like structure to it,” Riekman says. “You can see all of those things a penetrometer can’t show you because then you’re just pressing this little cone into the soil.”

She believes the best thing farmers can do to minimize the effects of compaction is to try to reduce equipment traffic whenever they can, especially in fields with wetter or moist soils, which pose the greatest risk.

Decreasing tillage as much as possible or moving to no till is also beneficial, Riekman says, “because you’re decreasing some of that disruption of soil structure and then alleviating existing compaction.”

She adds including a perennial crop in a rotation can be another helpful practice since it provides what’s essentially a rest period for the land. Riekman acknowledges a step like this may not be the most practical for every farmer, so she understands why some would see subsoiling as a possible solution. However, she believes any producer considering doing this should approach it with caution.

“Going through and breaking up the compaction with a deep ripper is something that can go well and can go sideways, depending on the situation,” Riekman says. She explains for a subsoiler to lift and shatter the soil properly, it has to go down below the depth of the compaction area and the soil has to be very dry. “And by dry, we mean near permanent wilting point.”

Riekman points out subsoiling is an expensive practice, which is why she thinks producers might be better off sticking to the headlands or other areas of the field where they know the soil is really compacted.

“Don’t do your entire field because it’s likely not going to pay. And then the other problem is, once you’ve done it, you have to do it again,” she says.

Reikman doesn’t consider subsoiling a one-and-done type of practice because once farmers start, they’re often subsoiling every four years or so. “That’s really what makes it not necessarily the most efficient or the most effective idea for alleviating the problem.”

– Mark Halsall is associate editor for Grainews. His article appeared in the Nov. 2, 2021 issue.