Soybean School: To till or not to till

Photo: Dale Cowan

Tillage destroys soil structure, cuts organic matter and decreases soil water infiltration. If that’s the case, reducing tillage makes sense, right?

But the decision is not that simple, says Jodi DeJong-Hughes, University of Minnesota soil and tillage extension specialist.

In her presentation at the virtual Ontario Agricultural Conference, DeJong-Hughes notes that there’s no hard and fast rule to determine the right amount of tillage — it really does depend on the farmer and the farm. And when it comes to soybeans, research from Minnesota and the Dakotas shows the oilseed crop will deliver top yields in no-till more often than not.

DeJong-Hughes shares tillage insights on this episode of Soybean School. Based on her experience, she recommends growers try to be less aggressive with their tillage. When it comes to using a chisel plow, for example, she notes this system offers a range of shank options. Based on set-up, growers can leave between 20 and 40 per cent residue — it all depends on how aggressive you want to be, she notes.

When it comes to tillage implements, DeJong-Hughes prefers points and shanks rather than discs, which do much more damage to soil structure. She also touts the benefits of what she terms “true vertical tillage.” She defines this as straight or wavy coulters that run straight through the soil.

“If you bend those coulters you have a disc which moves soil much differently than a straight or wavy coulter. A gang of straight coulters pitched at 5 degrees or more can also create similar soil disturbance impact,” she adds. (Story continues after the video.)

DeJong-Hughes is also a fan of strip till. It’s the best of both worlds — a combination of no till and full tillage, she says. In the video, she shares 2019 Minnesota/Dakota research comparing the soil temperature and moisture at planting in strip till versus other systems. When it comes to soil temperature at planting, strip till temperature reached 51 degrees F followed by chisel plow (50), vertical tillage (47) and no-till (42).

A similar story played out when moisture levels were compared. In trials where 50 per cent moisture was considered saturated, strip till moisture levels measured 18 per cent; chisel plow, 19; vertical tillage, 25; and no-till, 32.

When it comes to strip till, trials show “it’s warm and dry when you are planting,” says DeJong-Hughes. She also notes that in strip till, the area under residue is much cooler and wetter at 29 per cent moisture: “that’s our reserve for later.”

However, in soybeans, those nice planting conditions don’t guarantee a yield benefit. Based on four site years of data, researchers have seen no statistical difference in no-till yields compared to strip till, chisel plow and vertical tillage. When it comes to no-till the key is to “make sure the stalks from the year before are standing tall so you don’t have a big residue mat,” adds DeJong-Hughes.

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