Soil compaction concerns add pressure to modern farm practices

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This article was published 19/10/2024 (366 days ago), so information in it may no longer be current.

You could call it one of crop farming’s most pressing issues.

As farm sizes have grown, so, too, has the size of equipment farmers use to manage their crops. All that weight moving across the fields is compacting soil unlike anything since the dinosaurs roamed the Earth.

European researchers published a 2022 paper that flagged the weighty connection between giant prehistoric herbivores and modern farming, theorizing by repeatedly walking over land that fed them, these creatures would have compromised its ability to do so.

“As the total weight of modern harvesters is now approaching that of the largest animals that walked (on) earth, the sauropods, a paradox emerges of potential prehistoric subsoil compaction,” researchers Thomas Keller and Dani Or wrote in the Proceedings of the National Academy of Sciences.

“We show here that while surface contact stresses remained nearly constant over the course of modern mechanization, subsoil stresses have propagated into deeper soil layers and now exceed safe mechanical limits for soil ecological functioning.”

Soil scientists have been pressuring farmers to take the issue seriously, and most do, but the problem is not easily solved. While farmers tend to focus on having enough traction to cross fields in all sorts of weather, compaction can cut into the soil’s ability to produce if they aren’t careful.

The topic surfaced this week as provincial extension specialists convened on their regular webinar to discuss learnings from this year’s growing season and answer farmers’ questions.

Manitoba Agriculture soil specialist Marla Riekman said dry soils are the least vulnerable to compaction, but as we know from the heavy rains that moved through the region during spring and harvest, working only when conditions are optimal is rarely an option.

She said the ragged ruts sometimes seen in fields aren’t the biggest concern. It’s when the field is travelled over when moist and the particles get squished, sometimes deep into the subsoil.

“The compaction is most severe when our soils are moist and when that soil can kind of crush down on itself, because the air pockets are there, but the soil is wet enough that the product particles can kind of slide on each other.”

Many farmers have moved to using equipment with tracks instead of wheels. While that spreads the weight over a longer space, it doesn’t change the amount of downward pressure.

“As long as your tires are run at the rated pressure, there’s very little difference in terms of the compaction impact between a tire versus a tracked machine,” Riekman said. “Axle load is the biggest problem, and the heavier the equipment, the farther that compaction drives deeper into the ground.”

In a 2020 review of existing research, northern U.S. researchers concluded yield losses due to soil compaction range from nine to 55 per cent. Compacted soils are less porous, so they can’t hold or move water as well. They are more prone to erosion, don’t absorb nutrients and plant roots can’t punch through them, which stunts a crop’s growth.

Tillage can’t reach far enough to loosen the deep-soil compaction. Besides, it further disrupts the soil structure, only adding to the damage.

Some are looking to what is known as “controlled traffic farming, in which equipment always runs on the same tracks. But barring that, the best defence is to minimize the trips across the field, which can add up quickly between field preparation, sowing, spraying and harvesting.

It seems logical to think the farmer might lighten the load by always choosing a different path across the field with fully loaded equipment. Wrong.

As much as 80 per cent of the total compaction occurs on the first pass, Riekman said. The best approach is to stick to established pathways. “What you’re doing, is creating that road bed to save a little bit of the rest of the field.”

In other words, farmers are advised to make like the sauropods, which the European researchers hypothesized must have adopted “ecological strategies,” such as following fixed foraging trails as a survival tactic.

Or maybe they didn’t.

Laura Rance is executive editor, production content lead for Glacier FarmMedia. She can be reached at lrance@farmmedia.com