One (Soil) Test to Rule Them All

Nov 30, 2021

By Eric Hamilton

The soil is a vital foundation for most plant life. Our crops rely on this rich trove of nutrients and microbes to help turn sunlight into food. But we’ve learned over the last few decades that there can be too much of a good thing.

While synthetic fertilizers have greatly increased the yield of crops, they have downsides too. When plants can’t absorb all of the nutrients from fertilizers, rain can wash them away. Spilling into streams, lakes and oceans, too much nitrogen or phosphorus leads to dead zones. Dead zones are areas of low oxygen that come as a result of rotting algae. That algae growth was boosted by a big gulp of fresh nutrients once meant for our crops.

Agronomy researcher, Rishi Prasad (left), discussing results with a farmer engaged in a research field

Agronomy researcher, Rishi Prasad (left), discussing results with a farmer engaged in a research field.

If farmers know how many nutrients are in their soil, they can plan to add only what they need. The information can also tell them if their fields are at risk of losing nutrients to the water. That’s what soil tests are for. But just like how there is no unified power cord for all our tech devices, there are many different soil tests out there.

“The planet we live on has diverse groups of soils with different chemical and mineralogical properties,” says Rishi Prasad, a scientist at Auburn University’s Crop, Soil and Environmental Sciences Department. “Region-specific soil tests were developed in the past to meet the regional needs for agronomic fertilizer recommendation.”.

This research was recently published in Agrosystems, Geosciences and Environment Journal, a publication of the American Society of Agronomy and Crop Science Society of America.

Scientists collect cores of soil at various depths. Shown, a soil core of about two feet is measured and sectioned into respective depths for soil testing. Several chemical, physical and biological tests are better or worse for different kinds of soil

Prasad’s team recently tested if one “universal” soil test could perform better than these region-specific ones. One effective test would make it much easier to compare results between different areas. “It is easier to compare ‘apples to apples’ than ‘apples to oranges,’” says Prasad.

Those three tests are known as Mehlich 1, Mehlich 3 and Lancaster, named for the scientists who developed them. In Alabama, where Auburn is, scientists use Mehlich 1 for some soil types and Lancaster for others. Mehlich 3 was designed to work in most soil types, but had not been tested in Alabama to see if it was an effective testing method.

So, the lab collected soil samples from Alabama’s five different soil regions. Then they tested the soil samples using all three tests with regard to phosphorus levels in the samples.

They found that the Mehlich 3 test extracted about 1.5 times as much phosphorus as the Mehlich 1 test, and about the same as Lancaster. The results indicated Mehlich 3 could perform at least as well as the other tests.

The scientists also looked at how the tests measured water-soluble phosphorus. This form of phosphorus is readily available to plants. But it also is easily washed away or leached down by rainwater. They discovered that Mehlich 3 was better than the other two tests at accurately measuring this form of phosphorus.

Understanding water-soluble phosphorus is especially important in Alabama. That’s because the state’s large poultry industry produces a lot of manure. That manure, known as litter, is spread on farm fields as fertilizer. While it’s a good way to recycle nutrients, this spreading has tradeoffs. “Long-term application of poultry litter in excess of crop requirement leads to buildup of phosphorus in the soil,” says Prasad. “We needed to find a soil test extractant that can provide a better representation of the phosphorus loss risk from farmlands.”

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Video: The 15-Year Bet Behind Every New Variety!

Canada is trying to decide how much agricultural research capacity it can afford to lose. Brian Rossnagel believes the better question is whether the country can afford to rebuild it.

The longtime barley and oat breeder makes the case with a simple fact about his profession: the consequences of today’s decisions may not become visible for 10 or 15 years.

“Pick the right parents. That’s the biggest thing,” Rossnagel says. “If you pick the wrong parents, you’re not going to get anywhere—and you don’t know that until 10 years, 15 years later.”

That warning carries particular weight as Agriculture and Agri-Food Canada moves to reduce spending and streamline parts of its science operations. The department’s 2026–27 plan anticipates the loss of approximately 665 positions by 2028–29 and says some research will be reduced where capacity exists in academia or industry. AAFC says the changes will make its science operations more cost-effective over the long term.

For Canada’s seed industry, Rossnagel’s career illustrates what is at stake.

This fall, the retired University of Saskatchewan breeder will be inducted into the Canadian Agricultural Hall of Fame. During his 35-year career at the Crop Development Centre, he helped develop more than 100 barley and oat varieties, including CDC Austenson—one of Western Canada’s most widely grown feed barleys. His induction recognizes not only those varieties, but the collaboration and research system that made them possible.

Rossnagel is quick to emphasize that none of it was the work of one person.

“The first thing I thought about was all the other people who contributed to whatever success I and my program had over the years,” he says. “We know that it’s not an individual who does this. It’s a group—a team.”

That team extends well beyond the breeder whose name appears beside a variety. It includes technicians, pathologists, quality specialists, statisticians, regional testing sites, seed growers and industry partners. It also includes the breeders who came before and those who will carry the germplasm forward.

CDC Fraser barley, for example, moved through three breeding careers. Its parents came from Brian Harvey’s program. Rossnagel advanced the material after Harvey retired, and Aaron Beattie later guided it through registration and release.

That kind of handoff is normal in plant breeding. The person who makes the original cross may never see the resulting variety reach farmers.

It also explains why lost research capacity cannot simply be switched back on when budgets improve.

“If you shut it off, it’s very, very difficult—and particularly costly—to start it up again,” Rossnagel says. “If you have to start from scratch, it’s going to be at least 10 years before anybody notices whether you’re getting anything done or not.”

The concern is not simply how many experimental lines Canada can process. Modern equipment, statistical tools and genetic technologies allow today’s breeding programs to evaluate tens of thousands of lines—far more than Rossnagel could handle when he entered the field in the early 1970s.

But efficiency and automation do not generate every idea.

“If you pare back down, and instead of having six or seven individual scientists concentrating on wheat breeding, you go down and say three people could handle all this, well, that’s half the ideas gone,” he says. “Particularly if you happen to lose the three people who had the really neat and innovative ideas, boy, that’s a problem.”

It is a timely distinction for Canadian agriculture. Consolidating programs may preserve the volume of material moving through a system, at least initially. It may not preserve the diversity of thinking, regional knowledge or willingness to pursue unconventional crosses.

That regional knowledge matters because Canadian agriculture is not one uniform production environment. A variety suited to southern Alberta may face different disease, moisture and maturity pressures than one grown in Manitoba, Ontario or Atlantic Canada.

“Agriculture is applied biology,” Rossnagel says. “Biology, all around the Earth, moves from the poles to the equator. It does not move from Newfoundland to B.C. like politics do.”