140 percent yield bump on knolls

BRANDON — Moving soil from lowlands up to eroded knolls is the single most profitable soil management action you can take — more profitable than precision farming, drainage or irrigation.

In Manitoba field trials, moving soil to the tops of knolls created yield increases of 40 to 140 percent in the first years after the project.

“Take a piece of ground that has no top soil and grows little or no crop, then add topsoil and now you get a crop,” said David Lobb, who conducted the studies.

“It’s easy to get yield increase for 40 to 140 percent because you’re starting at almost zero yield.”

Lobb has been delving into the question of how to best manage farmland since he joined the University of Manitoba’s soil science department in 1999. In the last 19 years, he has initiated knoll renovation research in Manitoba and participated in similar projects across North America.

“Knoll renovation is the most profitable land improvement practice we have, more profitable than drainage and more profitable than irrigation,” he said.

“Knoll renovation will pay for itself with increased yields within 3.6 years to 5.2 years.”

There’s an obvious visual difference between soil from an eroded knoll in the right hand and soil from a knoll that has been renovated. Lobb ac the payback can come as quickly as 3.6 to 5.2 years. | David Lobb photo

In the studies he has conducted around the province, the economic analysis was based on full economic costing. The payback of 3.6 to 5.2 years was based on using the full custom rate for the tractor, scraper and driver. It was costed out as if an outside custom operator did the entire project. Of course, full economic costing is far more expensive than if the farmer did the work himself at his own convenience with his own equipment.

Lobb said farmers he has worked with in the past 19 years realize that the obvious answer to fixing eroded knolls is to move some of the extra lowland soil up to where it can contribute to the overall yield in the field. However, farmers have been largely hesitant to do that. Only a small number have followed their instincts and put the scraper blade into that rich soil at the bottom of the slopes.

The procedure itself is not complicated. Using the scraper and tractor a farmer already owns, it’s a matter of skimming the top few inches of high quality soil from the productive lowland and spreading it on nuisance knolls. Farmers have realized since the 1930s that they obtained their good quality lower slope soil at the expense of knoll erosion.

Lobb and his grad students used plots 10 feet by 10 feet, where they moved material from the deep soil area at the bottom of a slope and brought it to the test area. At each trial location, two renovation plots are seeded with conventional till and two renovation plots are zero-till.

“After a few years, you could see the soil we hauled up was starting to spread thin. Even with what we call zero till, we experience high disturbance seeding. The equipment started scraping away that soil, so your benefits start to diminish,” he said.

“With the information we gather about the soil, we did some economic modelling. We assume that there will be a modest level of tillage erosion, even in no till, because after all seeding is a form of tillage. We think you’d have to repeat the renovation every 20 to 30 years, but there’s no long-term study in place to find that answer.

“Unfortunately, the nature of agricultural research today is there’s no longer funding for long-term evaluation. We cobbled together whatever monies we could find to track the project’s performance for three or four years, then the money ran out. In all the trials, there’s an immediate positive response and it lasted for the duration of our tracking.”

Lobb said he’s frustrated with the lack of funding for follow-up studies, especially because the cost-benefit ratio on knoll rehab is so favorable. He submitted another request for federal-provincial research funding in January, and that was turned down along with all previous submissions. He said the farming community as a whole is missing out on a good thing by not delving into knoll rehabilitation.

“We just got turned down again to do some more work on this,” he said.

“This is one of the hardest projects for getting funding. One: nobody believes farmers will take the time to do this. Two: nobody believes it makes any economic sense. But it’s simple. It’s not rocket science. There is a high payback.”

Lobb said he is now focusing on the moisture management and climate change aspect of knoll renovation. Climatologists are looking at the extremes of drought versus too much water.

“We’ve suggested to them that the best way to deal with climate change and extreme moisture is to restore the land on the Prairies. We suggested this should be explored strictly from a moisture management standpoint, but we got turned down. They clearly don’t understand,” he said.

“Many people still believe that erosion is caused by wind or water, and the soil is lost forever. That is simply not the case. The majority of erosion is caused by tillage. So most of that topsoil isn’t lost. It just gets pushed down the slope by our machines. You’ll often find 100 centimetres at the bottom of the hill. So that’s a tremendous under-utilized resource just sitting there. You don’t need soil that deep to grow a good crop. You need 25 cm.

“We’re sure that the yield benefit on renovated knolls relates to moisture and nitrogen, but we need to do more work to prove it. That’s what we wanted to study with this latest proposal. If we understand that better, we can give farmers better advice on how to make this work.”

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