Derek Peak
Derek Peak

What lies below

In a field in Niger, a woman carries a pail of fertilizer. She stops beside each millet stem poking out of the dusty soil and, using a bottle cap, sprinkles a bit of its precious contents beside each stem.

Half a world away, a tractor costing nearly a half-million dollars and pulling a massive air seeder is laying down canola and fertilizer in an 80-foot-wide strip. The goal is to place each tiny seed a half-inch into the ground and then band a mix of phosphorus and nitrogen fertilizer two inches to one side and two inches deeper than the seed.

The contrast seems so immense, but the two farmers have much in common. Both fret over the cost of their painstakingly applied fertilizer and hope Mother Nature provides sun, rain and the right temperatures at the right time.

And although our Saskatchewan farmer studied plant nutrition and soil chemistry in university, how those nutrients make their way through that soil is as mysterious to him as his West African counterpart. But it is a mystery Derek Peak and other soil scientists are beginning to unravel, thanks in part to new technology.

"There's no question that in soil chemistry we're able to measure and analyze in ways we were never able to before," said Peak, professor of environmental soil chemistry in the College of Agriculture and Bioresources.

"Even when I was a graduate student, we often couldn't look at a whole soil with the techniques we were using. We would have to ask, ‘What minerals do we think are important?' or ‘Is it organic matter that is important?' Then you would extract these different phases and do experiments.

"Now we look at whole intact soils all the time. The advent of synchrotron science has been a major advance for soil chemistry and fertility. The challenge is to disseminate those results."

Peak is part of a group of researchers (funded by Canada's International Development Research Centre) who have used the Canadian Light Source (CLS) synchrotron to study West African soils subjected to fertilizer micro-dosing. He is also part of a team examining how phosphorus applied in a band in Saskatchewan fields becomes available to plants.

It is research that is critical to dealing with the big challenge of our time.

"We're looking at the world having 10 billion people by 2050, so we need to intensify agriculture," said Peak. "That's going to take fertilizer, and just like fossil fuels, fertilizer is a finite resource.

"It's a really important area of science. We are starting to develop a clear picture of soils and how to make the right decisions so we can make agriculture sustainable."

Sustainability is critical for the semi-arid Sahel belt of West Africa, where the population is rapidly expanding but crop yields are not. The region should be ripe for micro-dosing, which can double yields with just a quarter of the usual amount of fertilizer.

But only five to 10 per cent of farmers are using the technique, said Peak.

"One of the concerns is that if you're only putting on a small amount of fertilizer and yields are doubling, you may be mining the soil, degrading the land, and creating an unsustainable system in the long term."

Sahel soils have very low levels of carbon—0.2 to 0.3 per cent—and there is no practical way to build them up. (Leave any stubble on your fields and your neighbours will graze their livestock or collect it as fuel.) Soil testing found micro-dosing was not depleting carbon levels, but the why was not known and so fears of soil mining remained.

But the synchrotron opens up a new window on what is happening below ground. Carbon comes in many forms—including carbohydrates, amino acids, carboxyls, phenols, and ketones—and the CLS can tell you precisely how much of each.

"So we can see how the types of carbon are changing because of agricultural practices," said Peak. "What we're really doing is taking a fingerprint of carbon in the soil."

The analysis conducted by Peak and his team showed micro-dosing was creating more readily bio-available carbon, which drove the yield increases.

"Micro-dosing isn't making things worse than normal agricultural practices in that area," said Peak. "Long term, we're not going to see major improvements unless we change those agricultural practices, but this could be a gateway, a stepping stone, to allow that to happen. If you can get a little bit of fertilizer into the ground at the right time and double yields, then you improve incomes and food security. Then farmers have the opportunity and means to employ more advanced agronomic practices."

Agronomic practices have been advancing by leaps and bounds in the West, but here, too, the CLS—and some plywood—are providing important new insights.

In this case, it is the phosphorus cycle in soil. Using the synchrotron to look at the "whole soil" would provide a wealth of knowledge. However, you can hardly take a device as big as a football field out to a farm.

So instead, Peak's research team, in collaboration with the soil fertility program of departmental colleague Jeff Schoenau, took shovels out to the field along with half-sheets of plywood, studded with nails.

"We used flags to mark where fertilizer was placed in the field and at different times of the growing season, we would dig a soil pit across the band, pound the plywood into the side of the soil pit, and then take the entire monolith of soil back to the lab."

Those clumps of soil clinging to the nails allowed the researchers to measure pH, adsorption, mineralization, soluble and fixed P, leaching potential, and other factors—and know what was happening where.

It is complex research, but with a clear bottom line. Banding fertilizer is the smart choice both environmentally and in terms of nutrient-use efficiency, but it also has to be the best economic choice for farmers, said Peak. The hope is whole soil research will lead to improvements in banding technology that promote both efficiency and profitability.

Peak is quick to note the magic of the synchrotron is only part of the equation. Technological advances in other areas are also allowing research that was impossible even a few years ago, he notes.

"Molecular biology and genomic techniques have given us an enormous wealth of information about the biota that make up the soil—the things that make soil alive. Modern techniques have really changed soil science."

For the farmers growing millet or canola, the focus is all on what happens above the ground. But Peak is hopeful modern soil science will give people a new appreciation of what happens below their feet.

"I just find soils so fascinating—I guess that's why I'm a soil scientist—but they really are the critical zone for how the Earth functions. They are the skin of the planet where all the important stuff happens that sustains life."

Glenn Cheater is the owner of High Bluff Media in Winnipeg and Edmonton.
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