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Forages and grasses for marginal land

Permanent cover crops can increase fertility in "problem soils" over time

Jeff Schoenau has a word for agricultural areas currently in annual production that fail to deliver a return on expensive inputs: “heartache land.”

It’s better known as “marginal” land, and it can be defined as land with soil that has limitations including poor water-holding capacity and water availability to roots due to sandy texture or structural issues. The latter can include, in solonetzic soils of the Prairies, a “hardpan B horizon” that restricts the rooting volume.

Other problems include restricted drainage that result in a high water table, which is frequently associated with salinity.

Schoenau, a professor in the Department of Soil Science at the University of Saskatchewan and Ministry of Agriculture Strategic Research Chair, says that much of this land is in permanent cover, such as forage production. But some is still planted to annual crops each year, creating headaches for growers hoping to maximize productivity.

In the 1960s, 1970s and early 1980s, 2.5 million square kilometres of Canada’s rural land was mapped and soils were rated under the Canada Land Inventory (CLI) classification scheme. Seven classes were used to distinguish between soils’ agricultural capability, with one indicating the highest and seven indicating the lowest capability.

Ratings of four or five indicate severe or very severe limitations of the land, meaning it is not very suitable for annual crop production. Though the information is old, Schoenau says much of it is still relevant.

Revitalization with forages

In some cases, Schoenau says, modern cropping methods such as direct seeding, maintenance of crop residues and continuous cropping have allowed farmers to crop marginal lands fairly sustainably.

Schoenau recommends farmers analyze what is planted in steep, sandy or saline areas and assess how returns relate to inputs.

“When it comes to steeply sloping land, if you were to till that land and cultivate it and have a bare fallow period like in the old days, you have the potential for a lot of erosion to take place,” he says.

Saline areas can be planted to deep-rooting, salt-tolerant forages or annual crops that can lower the water table and reduce migration of salts to the soil surface.

David Lobb, professor in the Department of Soil Science at the University of Manitoba, says perhaps 10 per cent of Manitoba’s agricultural land is considered marginal — but some land is marginal because it’s been degraded through poor management practices.

“If it’s degraded marginal land, you have to ask why it’s degraded,” says Lobb. “Some land is heavily degraded by erosion, and in those cases you might want to potentially restore it by changing cropping and tillage practices or moving topsoil from areas where eroded soil has accumulated to areas where soil has been lost.

“If it’s natural land that’s not very productive due to issues like stoniness or steepness, you can put crops in, but not if they’re crops that are impacted by stoniness or steepness.”

Forages are farmers’ best friend in these scenarios, says Schoenau. “That land might be better put into forage for a period of time to improve that soil by increasing organic matter inputs from roots and, if the forage stand contains a legume, increasing fertility by adding fixed nitrogen from the air,” he says. “You need to understand what the limitations are on that land and take a look at what kinds of crops that would do better than others. Select crops that can do best under the particular limitations of that land, like droughtiness or salinity.”

Forages aren’t the only option for maintaining groundcover in problem areas; some annual crops can help mitigate problems. For example, barley and canola can tolerate soil salinity better than some other crops. Camellina can be efficiently and productively grown on marginal land.

Schoenau recommends soil testing to hone in on each fields’ particular strengths and weaknesses.

In soils where annual cropping has become impossible, Schoenau says planting forages or perennial grasses is the best option for slowly improving the quality of the land. “If you can get something to grow on these marginal lands, the establishment of permanent cover is effective in building up the organic matter of those soils, and that’s a key component in building fertility and productivity,” he says.

He’s also been involved in research work on planting short-rotation willow for the bio-energy sector in marginal lands, examining the salt tolerance of different willow clones.

“There are opportunities there for new crops on marginal lands, and this is something for people to look at. What’s the market? How will you harvest it? There are things to work out, but looking ahead there is potential opportunity,” he says.

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Julienne Isaacs is a Winnipeg-based freelance writer and editor. Contact her at [email protected]

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