AgronomyKeeping Soil Where It Belongs

Keeping Soil Where It Belongs


[deck]New research is helping shed light on what’s working and what isn’t in the battle to combat soil erosion in potato fields.[/deck]

Ongoing research being conducted in New Brunswick promises to give potato farmers valuable insight into the effectiveness of the best management practices in use to combat soil erosion.

The study, being carried out near Fredericton, N.B., by staff at Agriculture and Agri-Food Canada’s Potato Research Centre, is examining how the movement of water off farm fields in New Brunswick’s Black Brook watershed produces channels and gullies, accelerating soil erosion and nutrient losses on agricultural land.

Sheng Li, a research scientist heading up the project, says the eventual results will give potato growers valuable data showing how they can best combat soil erosion to help reduce revenue losses.

“We want to give them a better idea of how to manage the potato production system as a whole,” he says. “We are on the right track to give the farmers a better idea of all the different practices they are using in terms of exactly how good they are [and] to convert that even to money value, which is our end goal.”

It’s research like Li’s that will be of great value to potato growers, says Matt Hemphill, executive director of Potatoes New Brunswick.

“We’ve had extreme weather the last few years, and according to the meteorologists, these sporadic weather patterns are going to continue. We received well over three feet of rain in New Brunswick this past growing season,” says Hemphill. “It’s just way too much water. When you get three- or four-inch rainstorms, the water has to go somewhere, and it takes the soil with it.”

Li is using an unusually long test plot — 80 metres instead of the typical 20 — to study how gullies develop in potato fields and how they evolve over time. It’s an erosion phenomenon that has not been well quantified, says Li. It’s quantifying those processes that will ultimately be of value to potato growers routinely affected by erosion.

Value of Long-term Data

“The long-term data will really be valuable. You don’t know in the long run what kinds of problems will come up. Long-term monitoring becomes very valuable when you’re trying to answer very complicated questions,” says Li. “Some of [those questions] we probably don’t even know at this point.”

Research scientist Sheng Li of Agriculture and Agri-Food Canada’s Potato Research Centre is studying how channels and gullies develop in potato fields and how they evolve over time.

“The adoption of that practice is much higher [in New Brunswick] than the other areas [of Canada]. Part of our success is just getting the message out,” says Li. “A lot of farmers have their own way of doing business — unless they can really see the good things, they won’t necessarily adopt the practice. We’re just doing our best to show the data to the farmers and demonstrate how it works.”Research done over the years in New Brunswick and in other areas of Canada has led to countless revelations about soil erosion and how to combat it, notes Li. He points to diversion terraces — a Best Management Practice that break up a long, sloping field into a series of fields with shorter slopes in order to divert runoff and encourage infiltration — as something that’s taken off after researchers quantified how effective they really are.

New BMPs for combating soil erosion in potato fields have been widespread in recent years, many of those practices being borrowed from American potato growers. Potatoes New Brunswick has also been studying their effectiveness, and is in the final year of a two-year soil health project. They’re not only looking at erosion, but soil compaction and precision agriculture, to see what parts of certain fields might need special care to prevent erosion and compaction.

“If a field is more compacted in other areas or more prone to erosion than other areas, how can we mitigate that by either putting in more terraces, waterways, drain tile, those kind of preventative measures?” says Hemphill. “We also just entered into a five-year project with McCain Foods and some local universities studying erosion and soil health. We’re flying the fields with drone technology with 3D imagery and are looking at the ground before planting and after planting. We’re really getting a better feel for exactly where the water is going. A picture is worth a thousand words. Farm sizes have changed, fields are larger, there’s more water running and possibly more soil erosion.”

Li is using 3D technology, too, making use of photogrammetry to take special photos and create 3D models of erosion channel development during his three-year study that runs until 2016.

Evaluating Efficacy

According to Hemphill, one question the research is trying to answer is if diversion terrace technology is as relevant today as it was a decade ago. Li says the unintended consequences of BMPs designed to reduce soil erosion — like nutrient loading to groundwater — are a major focus of his work. But thanks to modern testing methods, finding out how widespread those effects are is now possible.

“There are monitoring stations in the stream to monitor the flow rate, how much water is flowing through all the time, and then what’s in the water. We take samples and analyze the sediments, nutrients and other chemicals in it. That’s been going on almost 20 years on some sites. We also have weather stations to monitor weather and deep wells to monitor ground water in the watershed. We are putting more things in to complete the water monitoring systems, including a set of monitoring stations right at the edge of the field,” Li says.

Researchers can now analyze sediment in runoff and identify where it comes from. Li says certain kinds of substances found in runoff tell researchers whether or not that sediment is coming from a cultivated field or from the stream bank.

More Research Needed

Glen Shaw, executive director of the Soil Conservation Council of Canada, says studies like this will benefit not just potato growers in New Brunswick, but in other areas of Canada as well. “It’s a real challenge for all potato growers, no matter where they are, to control their erosion to a tolerable level,” he says. “It costs a lot to terrace a field and have diversion structures so water runs off slowly and doesn’t cause erosion. It’s a challenge.”

Any soil erosion research, Shaw says, is welcome — for the simple reason that not enough of it is being done. “We continually lobby for more soil-related research. With the federal cutbacks, it appears there’s less research than was done, say, 10 years ago,” Shaw says. “We’ve seen a reduction in the amount of research in Western Canada, that’s for sure.”

Hemphill agrees. “The research is long overdue. We need to start implementing some strategies to keep the soil where it belongs.”


Looking At Wind Erosion

Potato producers on the Prairies face many of the same challenges as their counterparts in the east, Soil Conservation Council of Canada Executive Director Glen Shaw says, even though the Prairie landscape tends to be significantly flatter than in New Brunswick. In the Portage la Prairie region of Manitoba, he notes, water erosion is a problem, although the land is flatter and growers in the region don’t experience as much runoff.

Shaw says in Manitoba’s Carberry region, wind erosion is an issue — something Potato Research Centre scientist Sheng Li adds is a controversial subject. Recent attempts to quantify total soil loss from many cultivated sites in Western Canada have found that tillage erosion is actually a significantly more serious problem.

“Although adverse effects such as crop damages due to wind-carried sediments may be serious sometimes, our data so far show that wind erosion in Western Canada, even in the most vulnerable locations, is negligible in terms of loss of soil. The major form of erosion in cultivated fields is tillage erosion. When you till a field, you move soil. In people’s mind, people think that soil is moved uniformly across the field. That is not true. Actually, the movement of soil by tillage equipment varies by speed, topography, a lot of things,” says Li.

“The major pattern of soil erosion you see in the Prairies — eroded hilltops are caused by tillage erosion. We are trying to do more work on wind erosion. In terms of the process, wind erosion is the one that’s the most complicated and least understood.”


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