It’s important to note that soil sampling and testing are excellent tools to assess nutrient levels in your fields. That information sets the stage for smarter fertilizer planning in the spring. It’s also relevant that fewer than 20 per cent of fields in Western Canada are sampled each year. To me, that’s a huge missed opportunity to understand your soil and build a solid fertilizer plan.

When to soil sample

Ideally, sampling in early spring gives the most accurate measurement of soil nutrient status for spring-seeded crops. However, springtime is often too short and rushed to allow proper analysis and developing your fertilizer plans. So, if soils are moist, late fall (after soil temperature has dropped to 5-7 C) is often the most practical time. If soils are very dry, sampling in early fall is fine.

Nitrogen, phosphorus and sulphur levels can fluctuate from fall to spring, especially in moist soils with warmer-than-normal winters. Variations in nutrient levels from fall to spring are more likely in the Chinook regions of the southern Prairies. I don’t recommend sampling frozen soils during the winter simply because of the difficulty in obtaining representative sampling depths.

Further, I encourage farmers to go out with the person doing the soil sampling on their farm. It allows you to develop a good sense of how soils vary across fields and to see where samples are taken to ensure representative sampling. When you are with the sampler, you know where and how the samples were taken.

What are the options for sampling?

Many fields across the Prairies have moderately rolling topography, resulting in soil variability across the landscape. This can pose a challenge in deciding how to take representative soil samples. Samples must be representative of the field or each soil/crop management zone of a field. Work with your fertilizer dealer or agronomist to help you decide how to sample each field.

Briefly, here are a few ways fields can be soil sampled:

Random sampling of a whole field: Works best in fields with relatively uniform soil and topography. It involves taking representative soil samples throughout the entire field, but make sure to avoid unusual areas.

Sampling soil/crop management zones: Works best in fields with variable soil and topography. Uniquely different zones are mapped based on soil characteristics, topography, and/or crop yield potential. Representative soil samples are taken within each management zone. This method works well in fields with variable soil. Each management zone can be randomly sampled or benchmark sampled (see point 3). Work with an experienced agronomist to map each soil/crop management zone carefully.

Benchmark soil sampling: Involves sampling a one-to-two-acre area that is representative of most of the field or soil/crop management zone. Each year, the same area is soil sampled. When a field is variable in soil or topography, three or more benchmark locations may be needed to account for that variability.

When selecting soil/crop management zones with your agronomist, make use of crop yield maps, aerial photos, topographic maps, soil salinity maps and/or satellite imagery information. Also, use your personal field knowledge and observations of crop growth differences (crop establishment, vigour, colour, and growth) and landscape/topography of each field to identify where different soil types occur.

Number of sampling sites

I suggest taking samples from a minimum of 20 sites for each field, soil/crop management zone or benchmark area. Les Henry used to suggest 30 sites, which is even better. The more sampling sites taken, the more representative your samples will be of the field.

A common mistake is only taking six or seven soil cores from a field or management zone, which is not enough and may result in unreliable information for your fields and the development of inaccurate fertilizer recommendations. Why? Typically, each soil sample sent to a soil testing lab weighs about two lbs. One acre of land, six inches deep, weighs about 2,000,000 lbs. If a 160-acre field is soil sampled to a six-inch depth, a two-lb. soil sample must represent about 320 million pounds of soil. The soil sample would represent less than one-millionth of the field. So, it is critically important that an adequate number of soil cores be taken!

Choosing depth increments

There are various recommendations for sampling depth. My preference is to separate each soil core into depth intervals of zero-to-six, six-to-12 and 12-to-24 inches (0-15, 15-30 and 30-60 cm) and place the three sampling depths into three clean plastic pails. Do not use metal pails! Do this at each site sampled. Many agronomists suggest zero-to-six- and six-to-24-inch (0-15 and 15-60 cm) depths, which is easier and faster but does not give as useful information on nutrient stratification.

Most research on nitrate and sulphur in Western Canada’s annual crops has been based on sampling to 24 inches. Sampling in three depth increments gives a clearer picture of how these nutrients are distributed through the soil profile.

Phosphorus and potassium are less mobile, so keep the zero- to six-inch depth sample separate.

After the 20-plus soil cores are taken, thoroughly mix each composite sample and lay out the soil samples to completely air dry to stop nutrient changes. If moist soil samples are sent directly to the lab in sealed bags, soil microbes can alter the levels of plant-available nitrogen, phosphorus and sulphur, causing incorrect estimates of soil nutrient levels. If samples are sent directly to the lab in a moist condition, they must be shipped in coolers and kept below 5 C and arrive at the lab the next day for drying.

Sample analysis

The key macronutrients to test for are nitrogen (N), phosphorus (P), potassium (K), and sulphur (S). Measure N, P, K, and S in the zero-to-six- and six-to-12-inch depths, and N and S in the 12-to-24-inch depth. For most soils in Western Canada, testing for calcium (Ca) or magnesium (Mg) isn’t usually necessary, since these nutrients are rarely deficient.

It is a wise idea every few years to check levels of soil micronutrients copper, iron, manganese and zinc. Testing for micronutrients every year is only necessary if one or more micronutrients are in the marginal or low range; otherwise, testing every few years is fine.

It is important to note the tests for boron and chloride are not reliable, so I do not recommend testing for them. The problem is with the soil test methodology and critical levels used, which often result in unnecessary fertilizer recommendations.

Checking organic matter, pH and soil salinity is worthwhile for keeping an eye on your soil. Other tests, like cation exchange capacity, base saturation, or base cation saturation ratios, generally aren’t useful for planning fertilizer. CEC doesn’t change much because it depends on clay content, and base saturation mainly flags soil problems such as sodic soils. Research shows that BCSR adds little value in Western Canada, so you can skip the cost.

Finally, make sure the soil testing lab that does your soil analysis uses the correct soil test methods. For Alberta farmers, all soil test P calibration has been with the Modified Kelowna method since 1990 by Alberta Agriculture. It is also the recommended P method by Saskatchewan Agriculture. Soil samples from Alberta and Saskatchewan should be sent to a lab that uses the modified Kelowna method for the best 4R interpretation and fertilizer recommendations.

For Manitoba farmers, all soil test P calibration has been with the Olsen method (also referred to as the bicarb method), so use a lab that uses the Olsen method. Other soil test P methods, such as the Bray method, have never been calibrated to Western Canada’s soils. I do not recommend methods that have not been calibrated for western Canadian soils.

Next, interpret your soil tests. Make sure you seek the advice of several agronomists when developing your fertilizer plans for next spring.

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This methodology was developed and first used commercially at Cornell in 2006, incorporating chemical, physical and biological properties to gauge soil health. Since then, this technique for measuring a comprehensive mix of indicators of soil health has been modified to fit locations around the world.

As the soil health lab manager at the Chinook Applied Research Association in Oyen, Alta., Zavala received the green light to modify Cornell’s technique for Alberta conditions, developing the Alberta Soil Health Benchmark.

“I learned from them everything I needed to put together here,” says Zavala.

Grading on the curve

The Comprehensive Assessment of Soil Health technique and the Alberta Soil Health Benchmark analysis provide test results with handy scores that assess soil using a familiar format — a score from 1 to 100. As well, colour codes make it easy to spot where an intervention or practice change might have the biggest effect.

Zavala and her research team developed scores for each measure based on data collected from 2018 to 2023. During that period, 11 of the 12 applied research and forage associations across Alberta collected soil samples for this project.

Using these results, they calculated the mean and standard deviation based on a standard normal distribution for each test result. Then a scoring curve was developed for each indicator. These scoring curves enable the lab to provide test results that show where your soil fits relative to other soil in Alberta. After analyzing the data, Zavala developed separate scoring curves for coarse, medium and fine soil across the province.

As an example, through these tests, the average soil respiration rate in Alberta was found to be 1.22 mg CO₂ per gram of dry-weight soil. If your soil’s test result is 1.22, your score will be 50 out of 100, right in the middle. If your score is above average, you’ll get a score above 50.

Using these curves, each test result has been converted to a score from one to 100, with 100 being the best. Then each test result is colour-coded for convenience. From worst to best, the scores and colours are:

• under 20: red, very low
• 20-40: orange, low
• 40-60: yellow, medium
• 60-80: green, high
• >80: blue, very high

With the colour-coding system, users can quickly see their biggest soil problems and consider potential solutions. Measurements shown in red are constraints, areas where improvement may increase soil health and ultimately yield. Measures in green and blue are areas where growers can sleep easy at night.

A curve for every test

For most soil health indicators, more is better. A higher test result means a healthier soil and a better score. In these cases, curves are generally shaped like the curve in Figure 1.

For some indicators, such as the amount of manganese or iron in the soil, a lower test result is better. As you can see in Figure 2, curves for indicators where smaller results are better are drawn in the opposite direction, so lower test results bring higher scores.

Sometimes the best test result is in the middle. These cases are shown in Figure 3 as an optimum curve. Soil pH is an example of a measurement in this category. Test results that are very high or very low would return a low score. A score in the middle of these extremes would be in the green zone (high, meaning “good”).

The Alberta scoring curves will change over time. As more soil tests are done, the new data will be built into the scoring curves so farmers can have more accurate results.

Meanwhile in Saskatchewan

To the east, a team led by Kate Congreves, a professor in the department of plant science at the University of Saskatchewan, is working on a Saskatchewan Soil Health Assessment Protocol that includes scoring functions similar to those developed for the Alberta Soil Health Benchmark.

There are subtle differences in this protocol. Rather than creating scores based on smaller regions of the province, the Saskatchewan protocol is developing scoring curves by soil type: brown, dark brown and black. Saskatchewan researchers noted that soil class generally influenced most soil characteristics.

For example, the Saskatchewan report mentions soil organic carbon. Generally, a soil organic carbon of three per cent would be a “good” score in Saskatchewan. But in Saskatchewan’s black soil zone, soil organic carbon levels tend to be higher. In the black soil zone, a soil organic carbon of three per cent would rate as “poor,” with a score between 20 and 40 on the scale of one to 100.

And the rest of the country?

In the spring of 2024, the Canadian Standing Senate Committee on Agriculture and Forestry released a report on soil, “Critical Ground: Why Soil is Essential to Canada’s Economic, Environmental, Human, and Social Health.”

This report includes 25 recommendations, the first of which is that soil be designated as a strategic national asset. Many other recommendations centre on encouraging soil stewardship, using tools like tax credits and carbon markets.

There are many ways to evaluate soil. This report recommends that the federal and provincial governments develop a consensus on how to measure, report and verify soil health.

Zavala would like to see comprehensive soil health testing in place across the country.

“If the government doesn’t see the importance of what we have done in Alberta and look in more detail at how beneficial this can be, we aren’t going to understand what’s happening in our soil,” she says.

“We need to see the soil in a different way.”

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“The first question I ask when I’m speaking to farmers is, ‘How many of you have done soil testing?’” says Yamily Zavala, soil health lab manager and soil health and crop management specialist at the Chinook Applied Research Association, Oyen, Alta.

Most farmers in the room raise their hands when she asks this, but when Zavala pushes them further, she finds that most have had an analysis of their soil’s chemical properties. These tests usually analyze micro- and macronutrients, pH, organic matter, electrical conductivity (to indicate salinity) and cation exchange capacity (to indicate the soil’s ability to hold nutrients).

This information is necessary to develop a fertility program, but, Zavala says, it’s far from the whole story.

“Soil is not just chemicals. Soil is not just minerals. Soil is holistic. It’s alive.”

The Chinook Applied Research Association’s Soil Health Lab has been testing soil from across Alberta using three categories of soil properties: chemical, physical and biological.

With more than 4,000 soil samples analyzed between 2018 and 2024, the association’s Alberta Soil Health Benchmark Report includes benchmarks and scoring systems that can provide Alberta growers with comprehensive reports on their soil health in an easy-to-use format.

What is “healthy”?

There isn’t one standard, simple definition of “healthy” soil. Most definitions mention the soil environment and how efficiently the soil cycles nutrients. Almost all definitions use “healthy soil” and “quality soil” interchangeably.

The concept of soil health goes beyond measuring the chemicals and nutrients in the soil and includes how the whole soil ecosystem is functioning.

One common indicator of soil health measures the amount of living microbes in soil. This is soil organic matter, the percentage of soil made up of plant and animal material. Soil organic matter is the basic building block of productive soils, holding the soil together and making soil’s biological functions possible.

We know that a higher percentage of soil organic matter is better. But how much is enough? What other components of soil affect soil organic matter?

What can we measure (besides soil organic matter) to get a good picture of trends, and analyze differences?

Three components of soil health

The theory behind the Alberta Soil Health Benchmark is that healthy soil has three general components. These are the chemical and fertility properties, the physical properties and the soil’s biological properties, such as soil organic matter.

The physical properties describe the inherent character of the soil. Indicators include soil texture, compaction, water infiltration, bulk density (an indicator of soil compaction) and soil wet aggregate stability.

Growers can change some of these physical properties over time through management changes. Other physical characteristics are permanent. Physical properties can constrain soil health and crop yield.

Improving the soil’s physical properties can also improve some of the chemical indicators, the soil organic matter, and other biological indicators. Zavala describes this as “building a really nice house for the biology.”

The third part of the Alberta Soil Health Benchmark evaluation is the biological component.

Zavala sees all three of these components as important and necessary for soil health, but she sees biology as “at the top.” Organic matter in the soil is what allows the soil to function as an ecosystem. The living organisms in the soil are dynamic, changing all the time.

When all three of these components are robust, Zavala says, “that’s what I call the healthy soil.”

Together, all three types of measures provide a snapshot of the health of the soil. With repeated, consistent tests, changes in these measurements will indicate where farm management is improving or depleting soil health.

Measuring biological health

Soil organic matter is a key indicator for measuring soil’s biological health. Soil organic matter is measured by drying the soil, weighing it and then heating it to a temperature that will burn off the organic matter. The remaining soil is re-weighed; the difference in weight is the organic matter. The measure is provided as a percentage of the total soil mass.

The soil organic matter includes many living organisms. Some of the smallest are bacteria and fungi. These produce their own secondary metabolites and digestive enzymes, they absorb pieces of plant residue, and they release nutrients that plants can use.

Among farmers and agronomists, nitrogen-fixing bacteria such as rhizobium are probably the most popular creatures in this category. Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia, a form of nitrogen that can be converted into plant-available nitrogen.

Protozoans in the soil are generally larger than bacteria and fungi and can move themselves through the thin film of water in the soil. They’re single-celled, but typically bigger than bacteria and fungi. They often consume bacteria, and sometimes fungi. This group of microbes (living organisms too small to see without a microscope) includes flagellates, amoeba and ciliates.

Nematodes are the largest microbes in our soil. They have multiple cells and can consume bacteria, fungi and protozoa. Most nematodes are beneficial to soil health, but some are agricultural pests that take nutrients from plants, such as cereal cyst nematodes. A diverse group of nematodes in the soil is thought to indicate a healthier soil.

Measuring soil organic matter measures the amount of life in the soil. Other tests examine what that life is actually doing under there.

Soil respiration is a measurement that captures a snapshot of the organisms’ metabolic activity. Soil respiration is measured by air-drying soil, rewetting it, putting it in an airtight container, and then measuring the amount of CO₂ produced by the rewetted soil. Results are provided as mg of CO₂ per gram of dry-weight soil.

When the microbes are more active, they release more CO₂. Some ways growers can increase soil respiration include adding more organic material to the soil, adding manure or cover crops, or diversifying crops. Too much tillage can lower the soil respiration rate.

Active carbon measures the share of soil organic matter that can serve as an immediate food source for living organisms — decomposed matter that plants can consume quickly. A high active carbon test result means the microbes have enough food and are producing matter useful to plants.

Active carbon is measured by adding purple potassium permanganate to the soil. Active carbon causes the purple solution to lose its colour. The amount of active carbon in the soil correlates to the amount of colour change. Active carbon is a useful early indicator of changes to soil health. This test will show the effects of a management change sooner than changes to soil organic matter measurements.

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One of the first steps to improving water-holding capacity is understanding what factors control it. Jeff Schoenau, a University of Saskatchewan soil scientist, said two key soil properties play the biggest roles.

The basics

“Water holding capacity of the soil is very much influenced by two things: the organic matter content and the texture, which is the percentage of sand, silt and clay,” said Schoenau. “If a soil has more organic matter and it has more clay, that’s going to increase the available water-holding capacity.”

Clay content, while important, can’t be changed, he explained. A foot of moist clay soil will hold two inches of available water, whereas if it’s a foot of moist sandy soil, it will only hold an inch, or even less if it has a very high sand content.

But water-holding capacity isn’t the whole story. Moisture conservation isn’t just about keeping water in the soil; it’s also about getting water into the soil, or infiltration.

“Things that influence infiltration, like having a surface residue, help promote water entry,” said Schoenau. “We also think about evaporative losses. If we don’t have standing stubble there, that increases the wind speed at the soil surface, and that increases the evaporation.”

He noted that Prairie farmers’ long-standing conservation practices have already helped, contributing to increased water holding capacity, improved infiltration and good soil structure.

“You have a good distribution of pores holding water and some that also hold air to make sure that the soil isn’t flooded or saturated,” he said.

Matching problems to products

While Schoenau focused on the fundamentals, Karthikeyan Narayanan, technical director with Cropland Analytics, zeroed in on how to identify problems and match them with solutions. Cropland Analytics didn’t have a booth at Ag in Motion this year, but we caught up with him at the Annelida Soil Solutions booth, one of the firms his company partners with.

Cropland Analytics operates a fully outfitted, professional lab in Tofield, Alta., testing the biological, physical and chemical aspects of soil.

“The idea behind the lab is to identify the properties of the soil and to understand what’s inhibiting any of those water-holding capacities of the soil as a whole,” said Narayanan. “We do have products, and we do have solutions, but until we identify what the soil needs, it’s going to be very hard to promote one product.”

The business model for Cropland Analytics is based on partnerships with soil amendment companies. His main partners are Annelida and Johnson’s Regenerative.

“They have the solutions that align with what we find in our labs,” said Narayanan. “Ultimately, the farmer needs a solution, and that’s why we align with companies who can provide that solution.”

The partnerships represent a three-way street between Cropland, their partners and the farmer. And Narayanan insists the farmers are the big winners.

“With every test we’ve done and every recommendation we provided, our response rate is over 98 per cent. And that’s on-farm,” he said.

But while Cropland Analytics mainly recommends the products of their partners, an arm of their company is also developing products. Cropland Solutions focuses on developing products while keeping the lab independent to avoid conflicts of interest. The team is actively researching calcium-based products, addressing a common issue with gypsum: limited availability.

Narayanan pointed to one product they’ve designed that he says can boost calcium availability by 400–500 per cent. The product is applied directly in the furrow, targeting only the row rather than trying to amend the entire field. This approach keeps costs low — under $50 per acre. The product aims to improve the rhizosphere while enhancing water infiltration, root growth, phosphorus availability and overall biological activity. He says farmers are seeing immediate benefits, almost as if nitrogen had been added.

Farmers come first

But Narayanan said the main goal is not to sell products. It’s to help farmers. It’s a consultative process more than anything, and if one of his partners doesn’t have a solution, he’ll recommend a third party.

“If I don’t have a solution, but a competitor does, it’s always good if it benefits the farmer,” he said. “As long as they’re doing certain parts of the Annelida, Johnson’s, or Cropland program, it’s fine.”

Narayanan said that many of the water-holding issues he’s called to address fall into the same broad categories identified by Schoenau: soil texture and infiltration.

He noted that sandy soils benefit from organic matter to help retain moisture, while clay soils may hold water but not release it readily to plants. Infiltration problems, he said, can be worsened when fine-textured soils disperse during rainfall, leading to surface sealing, clogged pores and increased runoff.

“So, you have more water runoff from the field than infiltration through the field,” he said.

High tillage or elevated sodium levels can make this worse, though calcium amendments can improve soil structure and help water move into the profile.

While too much tillage harms infiltration, the opposite extreme — continuous no-till — can create its own problem: compaction. Without tillage to break it up, compacted layers can persist and build over time, restricting root growth and water movement. Narayanan said lowering tire pressures by six or seven pounds per square inch can cut that compaction by as much as 15 to 20 per cent.

In his view, farmer awareness and management practices are just as important as any product he or his partners sell.

“There’s no way we can keep amending the soil if the farmer is using bad practices in the field,” he said. “If you want to get out of the hole, you have to stop digging first.”

Cover cropping debate

When asked about other methods for improving water holding capacity, like cover cropping, Narayanan said that while cover cropping will, over time, improve water holding capacity, farmers who are concerned about the water holding capacity of their soils are likely in dry areas — and adding extra mouths to feed when water is scarce isn’t the best idea.

“It’s not growing the cover crop as a problem. It’s about the water,” said Narayanan. “If your water rainfall is low, then what’s going to happen is your cover crop is going to pull that moisture out. So, the following crop won’t have that subsoil moisture.”

Not so fast, said Karlah Rudolph, president of SaskSoil, a farmer-led group promoting soil health and conservation in Saskatchewan.

“I’m in southwestern Saskatchewan, and I do not find that there is an issue with having a cover, even though we’ve been in five years of drought,” she said.

Rudolph farms with her family in Gravelbourg and south of Gull Lake, Sask., combining annual crops with forage and pasture. Her soil science background helped her see the role of cover crops and living roots in protecting soil structure and improving infiltration.

Because of those dry conditions, Rudolph has been closely examining whether cover cropping can work in southwestern Saskatchewan and she planted some crops on her farm to get some answers.

On one of her fields, she’s planted a monocrop system of red lentils.

“There wasn’t a thing growing on it in the spring. It’s as naked as can be,” she said. “I’m observing some visible wind erosion. I’m not very happy about that, but there’s absolutely no competition for the water.”

On another field, she had a hard red spring wheat crop that was underseeded with a low rate of Italian ryegrass and a low rate of sainfoin.

“Sainfoin is a perennial, and it came up in the spring. The Italian ryegrass overwintered, so I had roots at two depths. I had fibrous roots from the Italian ryegrass closer to the surface, and then I had this deep taproot from the sainfoin that was going down at depth.

On the red lentil field, she found that the moisture was closer to the surface, about two inches down. But when she dug where the Italian ryegrass had been planted, the ryegrass had used the water at the surface, and the moisture had moved further down the soil profile. But not by much, she said maybe an inch, and it was much wetter than the moisture level on lentils.

“The snow catch offered by high residue and a high infiltration rate far outweighs the issue of weed competition when it comes to moisture conservation,” she said.

Measuring the moisture

At their Ag in Motion booth, SaskSoil displayed a simple infiltration test kit consisting of a six-inch tube, a bottle of water, a roll of plastic wrap, a wooden block and a stopwatch — it’s exactly the kind of practical, low-cost, MacGyvered innovation you’d expect to see from a farmer-led, DIY group like SaskSoil.

However, just across the lane, Kyle Henderson, business manager for Crop Intelligence, offered a more high-tech option for understanding what’s going on beneath the surface — one perhaps more suitable for those gadget-loving farmers.

“This moisture probe goes one meter into the ground,” said Henderson.

Installed right after seeding, the probe reads initial soil moisture from 100 cm up to 10 cm depth. Combined with rainfall data from a weather station, the system calculates “water-driven yield potential” — how many bushels a crop can produce per inch of available water.

Farmers can also monitor infiltration in real time.

“If you get an inch of rain, does it actually equate to an inch of soil moisture?” Henderson said.

The tool’s data can help identify whether a soil’s holding capacity is limiting yields and guide management decisions throughout the season.

Shared success

From cover-cropping, conservation tillage and residue management to targeted amendments and soil monitoring, improving water-holding capacity is a multi-pronged effort. And for Narayanan, it’s also about the bigger picture.

“At the end of the day, as long as the farmer wins, the entire industry wins,” he said. “We can’t be shortsighted in our approach.”

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In this section we’re referring to wheat, barley, oats, rye and triticale. I have traveled from Quebec to the B.C. lowlands many, many times and in the event of violent wind storms, often during thunderstorms, especially accompanied by heavy rain, crop lodging at close to maturity is expected. You can see the bent or broken stems caused by the force of the wind and weight of the rain. Hail damage is another matter.

Losses in yield and quality from lodging can be high. This kind of weather damage is beyond our control and a good reason for crop insurance. Cereal crop lodging in a good, moist, calm growing season is the problem I will explain, in terms that can be understood. In moist growing seasons, cereal roots remain near the soil surface.

Minimum-till and zero tillage have, or seem to have, reduced the amount and number of cereal crops I used to see plainly and heavily lodged in early August, particularly across the Prairies, during good growing seasons. There is an explanation — and it is not shorter-stemmed cereal crops or growth regulators.

Why would we have lodging of seemingly well-growing crops during grain formation in good moist growing seasons, in the absence of significant winds, but little or no lodging in dry or drought conditions? Here is the most likely cause — and the only one that seems to elude soil and crop specialists. Soil microbes, or living soil biomass, are the primary culprit.

In good cereal cropland, with around two to five per cent organic levels, are teeming masses of living organisms, especially in mid-summer. In a gram of soil (there are about 28 grams to an ounce) there are 10 billion bacteria or more. These are made up of thousands of bacterial species, all living, multiplying and dying. This soil also includes algae, fungi, protozoa, insects, earthworms and many other microscopic organisms.

These soil organisms have a biomass that could range from 50 to 500 actual grams per square metre (or yard). Now, put this into context: let us say in an average No. 2 Prairie soil with a biomass of 250 grams per square metre or half a pound per square yard approximately, that half-pound per square yard (4,840 square yards an acre) gives you around 2,420 lbs. of bacteria. That is the weight of just about two cows an acre. This mass of two cows is just the bacteria portion. Now, if you add the fungi, insects, worms, nematodes et cetera, you have got another two cow equivalents. So, you now have in good cropland about four cows equivalent per acre chomping on the organic matter in a good healthy moist soil in mid-summer. This “four-cow” mass of soil microorganisms, bugs, fungi and worms wake up as soon as the Prairie soils thaw out and warm up in April of each year.

Now, if this soil is high in crop residue, and particularly if the grower has applied 10-20 tons of cattle manure and worked it into the cropland along with the crop residue, think — this grower has now provided a massive bonanza of organic carbohydrate in the form of crop residue and manure (hog, poultry or cattle) to soil macro and microorganisms. Now the grower sows a wheat crop and also applies the amounts of N, P, K and S needed for a 60-bushel crop of wheat. Then it depends on the crop growing season. Is the soil going to stay warm and moist, or is it going to stay relatively dry all summer?

If the top six to eight inches (15-20 cm) stay relatively dry, the wheat crop will pick up the required N, P, K and S and the roots may move two to four feet (90-120 cm) into the subsoil, the cropland delivers and the target yield of 60 bushels will be attained.

If, on the other hand, it’s a wet summer, the soil bacteria and other microflora and fauna in the top foot or so will just go “hog wild” with the added manure and crop residues. In the form of manure and crop residues, bacteria and associated organisms have all the carbohydrates (food) they need, but in many soils they may be short of nutrients, particularly micronutrients. These micronutrients, particularly copper and zinc, have been removed over 100 years or more in past crop growing seasons.

So, what happens? Were the soil micronutrients “tied up” in the organic residue? Not so — they were just picked up first by the microflora and microfauna, that is, the four cow equivalents or more per acre of soil. Those four cows’ worth of microflora grabbed up all of the already-low soil copper levels in the top eight inches of soil. No copper, no lignin formation, no stem strength — or no pollen formation, then ergots. The lack of copper causes the cereal crops to lodge, with wheat at its most susceptible.

Look up the YouTube video “Lodging Wheat Rescue with Dr. Copper.” There the maturing wheat is growing on roadside soil, low in organic matter and high in available copper. The lodged crop is growing on well-manured soil loaded with actively growing micro-organisms. These organisms have grabbed up the available copper levels that have been drawn down in over 100 years of micronutrient removal.

The wheat, starved of copper, cannot form lignin for stem strength or pollen in some instances for seed set and the wheat heads either have blanks, stray pollen pollination or ergot infection.

If you have any doubts about copper’s importance in organic soils, I will quote this information from Ontario’s Agronomy Guide for Field Crops, page 35: “When black highly organic soils are first brought into cultivation copper should be applied to the soil at 14 kg/ha (12.5 lbs./ac.); that’s 50 lbs. of copper sulphate at 25 per cent copper for each of the first three years.”

Why is it that horticultural specialists are so far ahead of agricultural crop specialists? Such levels of copper are applied to such high-organic matter soils — for example, Brandford Marsh, north of Toronto, or the organic soils of Michigan or Florida. Now, when you manure cropland on the Prairies, I am not suggesting such huge amounts of expensive copper. What I recommend is that if you have cropland prone to lodging, and low yields at the very least, treat a few acres with four to six pounds of actual copper (16-24 lbs. of copper sulphate) and check the results. That level of copper is good for 10-20 years or more. When you get positive results, plan your anti-lodging strategy for your cereal crops — especially wheat and barley — after you have soil-tested for copper levels in particular.

Peas

Peas do not grow on stems but vines, with tendrils that enable them to climb up and over other plants. In nature peas have huge advantages over most competing plants in that they, like other legumes, fix their own nitrogen. When I first grew peas, they were eight-foot climbing vines that grew on six-foot sticks or brushwood in the garden. Ontario in fact had a major industry 150 years ago growing thousands of acres of green peas on rows of canes for export to the U.K.

When I moved to Ontario in 1969, I grew peas in the trial plots and saw them grow six feet tall or more, then collapse on themselves and become heavily rotted. The variety I grew was “Trapper.” Back in 1962 when I visited the U.K. Cambridge Crop Research Station, I remember seeing its prize plots of leafless green peas, which it had obtained via California.

Not until I moved to Alberta in 1974 did I see my first leafless pea crops: all tendrils and few leaves. Pea vines need support, and as a field crop, that support to “stand up” comes from producing more tendrils than leaves, and a shorter stature. The answer to reduce or prevent lodging is following recommended row spacing and seeding heavy-tendril dwarf types that can stand up to windy or rainy weather. These peas may not be the best yielders, but they can be reliable for quality grain. Peas are excellent scavengers of soil-available copper and do not give any response to added copper on mineral soils — probably due to deeper rooting than cereals.

Canola

With the exception of windstorms, lodging in canola is related to seeding density, high fertility and sclerotinia infection. On heavily-manured fertile soils, at high seeding rates of six pounds per acre, and in humid summers, weather lodging can be severe. In soils that are fertilized for target yields in the 50- to 60-bushel range for the canola crop, seeding rates of four to six lbs. seem to be most effective.

Unfortunately, in very highly manured soils, where the soil nitrogen levels may exceed 200 lbs./ac., lighter seeding rates of three to four lbs. or less are recommended. High fertilizer rates (N, P, K, S), particularly of N, encourage very rapid dense canopies under good moisture conditions. These dense canopies at normal seeding rates favour sclerotinia infection in moist weather in July, causing weakened stems and crop lodging. At the higher fertility rates, it may be advisable to reduce seeding rates to three lbs. or even less per acre, to encourage better-standing multiple-branching canola plants less prone to sclerotinia infection and lodging. Canola, with its deeper rooting system of three to four feet, has shown little need for any micronutrient requirement — except perhaps for boron under dry weather conditions.

Flax

At seed set, flax always seems to be on the verge of lodging or sometimes lodged. Our research at Alberta Agriculture in the ’90s showed flax responds very well in many instances to additional zinc and copper micronutrients. Research at a few locations in Alberta on specific sandy-type soils showed significant yield increases when copper in particular was included in the fertilizer inputs. In one instance, upping the N, P, K and S at one central Alberta location, together with a few pounds per acre of both copper and zinc, took an expected flax yields of some 20 bushels to almost 40 bushels an acre. The copper amendment in particular reduces or prevents lodging in flax crops by greatly increasing straw strength.

My father’s opinion: ‘If you are not the lead horse, the scenery never changes.’

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Announced May 12, the initiative pairs ag-input platform AgList with soil microbiome analytics firm Biome Makers, to introduce a new “badge”-type system signalling when products have undergone independent, science-based testing.

AgList, a brand-new platform launched in January 2025, lets farmers and agronomists browse a curated database of biological inputs. Users can endorse products they’ve had success with, helping others make informed decisions based on shared experiences. The company describes itself as “Yelp for agriculture” — but without the negative reviews.

Biome Makers is a global ag-tech company specializing in soil biology founded in 2015 by biotech entrepreneurs Alberto Acedo and Adrián Ferrero. Its flagship platform, BeCrop, analyzes the functional potential of soil microbial communities in the lab. BeCrop Trials builds on that foundation by measuring how specific inputs affect the soil microbiome under real-world field conditions.

Biome Makers is the first company to contribute field trial data to AgList. Products tested through BeCrop Trials now feature a BeCrop badge on AgList, indicating they’ve undergone independent, science-based evaluation using DNA-based soil analysis.

Building trust

“This partnership is all about increasing transparency and building trust,” says Tyler Nuss, co-founder of AgList. “Our goal is to help the industry cut through the noise, and Biome Makers’ science-first approach gives credibility to the products that earn their badge.”

BeCrop Trials measure changes in the soil microbiome after a product is applied. While the badge doesn’t validate efficacy, it signals the product has been through third-party field trials. Trial results are also published on AgList to further transparency.

“When a user of the platform sees the BeCrop logo, it’s an indication the company has run field trials with BeCrop to understand how their product is impacting the soil microbiome,” says Sunny Kaercher, business development manager at Biome Makers. “It’s an invitation for the grower to review the results.”

The challenge for biologicals

The move comes at a time when biologicals — agricultural inputs derived from living organisms or natural materials — are under growing scrutiny. Interest is rising, but so are questions about how well these products work and how they work at all.

Biologicals face a unique challenge, according to Oleg Yakhin, lead author of a 2017 global review of biostimulants published in Frontiers in Plant Science. Unlike conventional inputs, they often lack a clearly defined mode of action, complicating regulation and product comparisons.

“There are few products for which a specific biochemical target site and known mode of action has been identified,” Yakhin notes.

He also points out that products can come from a wide range of sources — bacteria, fungi, seaweed and more — and that varied manufacturing processes add further complexity. That diversity makes it difficult to group products or predict performance.

Despite these hurdles, he argued that proof of safety and efficacy — regardless of whether the mechanism is fully understood — is essential for broader acceptance.

While Yakhin’s review focuses on biostimulants, the same issues apply across the biologicals category: unclear mechanisms, inconsistent results and limited standardization remain persistent challenges for researchers, companies and growers alike.

Addressing the challenge

Those are exactly the kinds of issues the BeCrop Trials aim to address.

Kaercher says Biome Makers’ lab capabilities allow them to map biological function in the soil — providing over 50 different biological metrics. Depending on trial design, data on yield, fertility, and even plant tissue can be layered in.

“What our technology really enables is an exploration of what a product is doing biologically and whether that’s tied to a measurable effect like yield gain,” she explains.

Biological products are often complex formulations involving multiple species and materials, and their effectiveness depends heavily on environmental conditions. Factors such as soil type, moisture, climate and crop all influence outcomes — but that nuance is often lost. As a result, stories about the failures of biologicals circulate widely among farmers.

“We hear from folks all the time, ‘Yeah, we’ve used biologicals. They didn’t do anything,’” Kaercher says, adding that this perception often stems from unrealistic expectations or a mismatch between the product and the field’s biological needs.

“It’s often a function of the law of diminishing returns,” she says. “If a soil is already sufficient in any given biological function — like nitrogen cycling — then adding a nitrogen-mobilizing bacteria isn’t going to deliver a return on investment.”

That’s why understanding baseline soil biology is essential. Kaercher says soil testing upfront can lead to smarter product recommendations — and, in some cases, show no input is needed at all. In those rare cases where it’s determined yield can’t be improved with a biological, that too should be viewed as a win for the farm.

Modern agriculture often judges the success of an input based on yield alone, and as a result, BeCrop spends a lot of energy focusing on products to increase yield. But yield is not always the most relevant metric.

“Farmers could also be focused on building soil health, sequestering carbon or increasing biodiversity. Those are all metrics we can measure and help predict in our recommendations,” Kaercher says.

Looking ahead

Yakhin’s review also highlights a lack of well-structured field trials and limited communication of results as key barriers to commercial development and grower confidence. The AgList/Biome Makers partnership may help close that gap, bringing third-party trial data directly to a platform farmers already use.

Looking ahead, Kaercher sees an expanding role for soil diagnostics in shaping not only input decisions but overall farm strategy. Properly deployed, biologicals could reduce irrigation needs, cut fungicide use or even enable the soil’s natural defences to manage pathogens.

Whether this partnership will be enough to shift industry skepticism remains to be seen. But as interest in biologicals continues to grow, Kaercher says the need for clearer data and smarter recommendations is more urgent than ever.

“We’re providing real data on what these products are doing,” she says. “The smarter we get as an industry about how to prescribe them, the more success we’ll see.”

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A field with adequate fertility doesn’t necessarily equate to adequate plant nutrition, SGS Crop Science manager and agronomist Jack Legg told Ontario Soil and Crop Improvement’s Microsmart Deep Dive presentation in Kingston.

Soil tests assess the potential availability of nutrients under optimal conditions. In contrast, tissue tests indicate the actual uptake under variable field conditions.

“Non-limiting in the soil is where you want to be, but it doesn’t necessarily mean that the crop is utilizing it efficiently,” Legg says. “Tissue samples tend to be reactionary. People see a deficiency; they want to confirm it. They send in the tissue.”

“We don’t really want to see deficiencies,” he says. “We want to test before things go deficient.”

Tissue tests are a proactive nutrient management tool that identifies “hidden hunger” before it escalates into a critical issue, he says.

Chris Roelands, president of Honeyland Ag Services, says soil sampling should follow the same schedule, ideally in the fall when soil moisture is sufficient, to provide comparable results on nutrient availability year over year.

“Soil testing is still the base of where everything starts, right?” he says, adding it’s the soil reserve baseline to inform needed inputs.

In general, soil testing in the fall provides ideal moisture levels for probing ease and nutrient accuracy.

Weather and soil moisture

Soil scientist Rigas Karamanos notes research from the Saskatchewan Soil Testing and Enviro-Test Laboratories indicates weather and soil moisture influence soil pH during the growing season. As the pH changes, which can be significant with soil moisture, the availability of nutrients also shifts. For example, potassium tends to bind to clay under drier conditions.

However, Roelands cautions, three aspects — genetics, environment and management (G.E.M.) — can affect how plants convert soil nutrients.

“Soil moisture, temperature, or whether it’s something related to management, can be what changes what we see in our plant tissue test versus what we’re seeing in our soil test,” Roelands says.

For example, manganese availability and uptake are more efficient in compacted, saturated and anaerobic conditions — but those are terrible for other nutrient uptake.

The soil and tissue tests of V10 corn at about six feet tall show that, on average, potassium levels in the soil and tissue concentration rose in unison. However, a closer look at individual field sites showed soil sites with a less-than-desirable 60 ppm level of K had plants with decent levels. Where plants tested poorly for potassium, the soil levels were decent.

This is where G.E.M. comes into play, to provide answers on why that’s happening, Roelands says.

Legg says tissue testing throughout the growing season provides unique insights into the plant’s current needs at the juvenile, mid-season and flowering or silking stages, to inform how to mitigate immediate issues and plan for the following season.

“The basic rule of thumb is to test as much, as frequently and as intensively as you’re willing to pay for obviously and willing to manage,” Legg suggests. “Starting with one or two tissues in a crop a year is a good starting point. Weekly is very interesting, but it’s a heck of a lot of data and a lot of work.”

Easy rules

There are a few easy rules to follow to ensure the best bang for your buck with tissue samples. The first is leaf quantity. Corn leaves are probably the easiest, but Legg suggests a third- to half-full paper lunch bag for other crops.

“When we dry that down, that only leaves us with a few grams of dried material,” he says. “One little soybean trifoliate is not enough to test.”

Due to nutrient mobility, the ideal sample is the most recent fully developed leaf, usually a few down from the top, wrapped in paper instead of plastic to avoid slimy samples.

Identifying the growth stage is important, he adds. “The critical values are usually tied to a physiological age, usually when the plant is under stress like flowering or silking. Make sure you label them appropriately.”

If selecting tissue samples for a v3 corn plant (which is rare), pull the entire plant cut at grade without roots, Legg says. Select the most recently collared leaf at the vegetative stage and the ear leaf at tasselling. Wheat follows a similar vein, with soybean requiring the most recently mature trifoliate throughout the season.

He encourages producers to provide a clean sample, cutting it as low as possible without soil contamination, which provides biased results.

“Folks think micronutrients are less important,” he says. “They’re essential nutrients required for that whole plant life cycle, but in much smaller quantities.”

We’ve managed without fertilizing micronutrients for decades, he says, but it’s becoming a soil management focal point.

He suggests farmers try check and zero strip trials with varying rates to test the payback on their farms, noting a pound of zinc and manganese costs about $4, while a pound of boron is slightly more expensive, at $7.25.

Fertilizers can increase manganese levels over time, he says, but application is crucial. Applying a foliar treatment to symptomatic soybeans, for example, is a quick fix, but fertilizing the leaves does not enhance soil fertility.

“The bottom line is, in general, if your (zinc and manganese) index value is greater than 15 ppm, you have enough nutrients,” Legg says. “(A boron level of) 0.5 p.p.m. is considered low, and 1.0 ppm is considered high.”

The post Taking the mystery out of soil and tissue tests appeared first on Grainews.

“The first question I ask when I’m speaking to farmers is, ‘How many of you have done soil testing?’” says Yamily Zavala, PhD, soil health lab manager and soil health and crop management specialist at the Chinook Applied Research Association, Oyen, Alta.

Most farmers in the room raise their hands when she asks this, but when Zavala pushes them further, she finds that most of the growers have actually had an analysis of the chemical properties of their soil. These tests usually analyze micro and macronutrients, pH, organic matter, electrical conductivity (to indicate salinity), and cation exchange capacity (to indicate the soil’s ability to hold nutrients).

This information is necessary to develop a fertility program, but, Zavala says, it’s far from the whole story. “Soil is not just chemicals. Soil is not just minerals. Soil is holistic. It’s alive.”

The Chinook Applied Research Association’s Soil Health Lab has been testing soil from across Alberta using three categories of soil properties: chemical properties, as well as physical and biological properties. With more than 4,000 soil samples analyzed between 2018 and 2024, the includes benchmarks and scoring systems that can provide Alberta growers with comprehensive reports on their soil health in an easy-to-use format.

What is “healthy”?

There isn’t one standard, simple definition of “healthy” soil. Most definitions mention the soil environment and how efficiently the soil cycles nutrients. Almost all definitions use “healthy soil” and “quality soil” interchangeably.

The concept of soil health goes beyond measuring the chemicals and nutrients in the soil and includes how the whole soil ecosystem is functioning.

One common indicator of soil health measures the amount of living microbes in soil. This is soil organic matter, the percentage of soil made up of plant and animal material. Soil organic matter is the basic building block of productive soils, holding the soil together and making soil’s biological functions possible.

We know that a higher percentage of soil organic matter is better. But how much is enough? What other components of soil affect soil organic matter?

Is there an optimum health level for soil? It’s unlikely that soil can be too healthy. Most of us just want to know if our soil health is trending in the right direction, and how the soil we’re managing compares to other soil in the area under different management.

What can we measure (besides soil organic matter) to get a good picture of trends, and analyze differences?

Three components of soil health

The theory behind the Alberta Soil Health Benchmark is that healthy soil has three general components. These are the chemical and fertility properties, the physical properties and the soil’s biological properties, such as soil organic matter.

The physical properties describe the inherent character of the soil. Indicators include soil texture, compaction, water infiltration, bulk density (an indicator of soil compaction) and soil wet aggregate stability.

Growers can change some of these physical properties over time through management changes. Other physical characteristics are permanent. Physical properties can constrain soil health and crop yield.

Improving the soil’s physical properties can also improve some of the chemical indicators, the soil organic matter, and other biological indicators. Zavala describes this as “building a really nice house for the biology.”

The third part of the Alberta Soil Health Benchmark evaluation is the biological component. “The creatures in the soil cycle nutrients,” Zavala says. “This cycle is what makes the soil alive.”

Zavala sees all three of these components as important and necessary for soil health, but sees biology as “at the top.” Organic matter in the soil is what allows the soil to function as an ecosystem. The living organisms in the soil are dynamic, changing all the time.

When all three of these components are robust, Zavala says, “that’s what I call the healthy soil.”

Together, all three of these types of measures provide a snapshot of the health of the soil. With repeated, consistent tests over time, changes in these measurements will indicate where farm management is improving or depleting soil health.

Measuring biological health

Of course, soil organic matter is a key indicator for measuring soil’s biological health. Soil organic matter is measured by drying the soil, weighing it and then heating it to a temperature that will burn off the organic matter. The remaining soil is re-weighed; the difference in weight is the organic matter. The measure is provided as a percentage of the total soil mass.

The soil organic matter includes many living organisms. Some of the smallest are bacteria and fungi. These produce their own secondary metabolites and digestive enzymes, they absorb pieces of plant residue, and they release nutrients that plants can use. Among farmers and agronomists, nitrogen-fixing bacteria such as rhizobium are probably the most popular creatures in this category. Nitrogen-fixing bacteria convert atmospheric nitrogen to ammonia, a form of nitrogen that can be converted into plant-available nitrogen.

Protozoans in the soil are generally larger than bacteria and fungi and can move themselves through the thin film of water in the soil. They’re single-celled, but typically bigger than bacteria and fungi. They often consume bacteria, and sometimes fungi. This group of microbes (living organisms too small to see without a microscope) includes flagellates, amoeba and ciliates.

Nematodes are the largest microbes in our soil. They have multiple cells and can consume bacteria, fungi and protozoa. Most nematodes are beneficial to soil health, but some are agricultural pests that take nutrients from plants, such as cereal cyst nematodes. A diverse group of nematodes in the soil is thought to indicate a healthier soil.

Measuring soil organic matter measures the amount of life in the soil. Other tests examine what that life is actually doing under there.

Soil respiration is a measurement that captures a snapshot of the organisms’ metabolic activity. Soil respiration is measured by air-drying soil, rewetting it, putting it in an air-tight container, and then measuring the amount of CO₂ produced by the rewetted soil. Results are provided as mg of CO₂ per gram of dry-weight soil.

When the microbes are more active, they release more CO₂. Some ways growers can increase soil respiration include adding more organic material to the soil, adding manure or cover crops, or diversifying crops. Too much tillage can lower the soil respiration rate.

Active carbon measures the share of soil organic matter that can serve as an immediate food source for living organisms — decomposed matter that plants can consume quickly. A high active carbon test result means the microbes have enough food and are producing matter useful to plants.

Active carbon is measured by adding purple potassium permanganate to the soil. Active carbon causes the purple solution to lose its colour. The amount of active carbon in the soil correlates to the amount of colour change. Active carbon is a useful early indicator of changes to soil health. This test will show the effects of a management change sooner than changes to soil organic matter measurements.

Adaptation

These tests and methodologies are not new or unique to Alberta. The comprehensive list of tests used by the Alberta Soil Health Benchmark study has been adapted from Cornell University’s Comprehensive Assessment of Soil Health. Cornell developed this method of incorporating chemical, physical and biological properties to gauge soil health. The Comprehensive Assessment of Soil Health was first used commercially at Cornell in 2006. Since then, Cornell has assessed more than 10,000 soil samples. And Cornell’s technique for measuring a comprehensive mix of indicators of soil health has been modified to fit locations around the world.

Conveniently, Zavala earned her PhD at Cornell University, where she learned about the Comprehensive Assessment of Soil Health techniques firsthand.

“I got the baseline,” she says. When Cornell gave her the green light to modify its technique, Zavala adapted the methodology for Alberta conditions. “I learned from them everything I needed to put together here,” Zavala says.

Grading on the curve

As anyone who’s looked at an elementary school report card in the past few years will understand, seeing a long list of unfamiliar indicators on one piece of paper can sometimes leave you more confused than informed. It can be difficult to know whether you need to make changes, and even harder to figure out where to start.

The Comprehensive Assessment of Soil Health technique and the Alberta Soil Health Benchmark analysis provide test results with handy scores that assess soil using a familiar format — a score from 1 to 100. As well, colour codes make it easy to spot where an intervention or practice change might have the biggest effect. In other words, deal with the red ones first.

Over time, soil-testers will see trend changes in their scores, as (hopefully) scores increase from year to year as land management practices evolve. But even in the short term, the scores can tell you how well your client’s soil is doing compared to other soils in Alberta and in their local area.

To make this work, Zavala and her research team developed scores for each measure based on data collected from 2018 to 2023. During that period, 11 of the 12 applied research and forage associations across Alberta collected soil samples for this project. Members from each of these associations were well-trained in soil sampling, to ensure consistent results across the province and across the years.

Using these results, they calculated the mean and standard deviation based on a standard normal distribution for each test result. Then a scoring curve was developed for each indicator. These scoring curves enable the lab to provide test results that show where your client’s soil fits relative to other soil in Alberta. After analyzing the data, Zavala developed separate scoring curves for coarse, medium and fine soil across the province.

Let’s look at an example. Through these tests, the average soil respiration rate in Alberta has been found to be 1.22 mg CO₂ per gram of dry-weight soil. If your soil’s test result is 1.22, your score will be 50 out of 100, right in the middle. If your score is above average, you’ll get a score above 50.

Using these curves, each test result has been converted to a score from one to 100, with 100 being the best. Then each test result is colour coded for convenience. From worst to best, the scores and colours are:

• under 20: red, very low

• 20-40: orange, low

• 40-60: yellow, medium

• 60-80: green, high

• 80: blue, very high

With the colour-coding system, users can quickly see their biggest soil problems and consider potential solutions. Measurements shown in red are constraints, areas where improvement may increase soil health and ultimately yield. Measures in green and blue are areas where growers can sleep easy at night.

A curve for every test

For most soil health indicators, more is better. A higher test result means a healthier soil and a better score. In these cases, curves are generally shaped like the curve in Figure 1.

For some indicators, such as the amount of manganese or iron in the soil, a lower test result is better. As you can see in Figure 2, curves for indicators where smaller results are better are drawn in the opposite direction, so lower test results bring higher scores.

And of course, sometimes the best test result is in the middle — not too high and not too low. These cases are shown in Figure 3 as an optimum curve. Soil pH is an example of a measurement in this category. Test results that are very high or very low would return a low score. A score in the middle of these extremes would be in the green zone (high, meaning “good”).

These curves have been designed using the same methods used by Cornell University. It was necessary to adapt the curves because Cornell’s benchmark data is based on data in the northeast U.S., where soil is very different from the soil in Alberta. This methodology has been adapted for locations around the world, by developing scoring curves based on local data.

The Alberta scoring curves will change over time. As more soil tests are done, the new data will be built into the scoring curves so farmers can have more accurate results.

The way it WAS

As an example of how these curves and colour-coding work, let’s look at results from wet aggregate stability tests in Alberta, known as WAS scores.

Aggregates in soil are the different-sized “crumbs” that form when soil particles bind together. In healthy soil, biological activity helps the aggregates stabilize and stay together. Too much tillage can break down these aggregates, increasing the risk of soil compaction or erosion. Farmers can build soil aggregates by adding animal manure or cover crops with fine roots to the soil and increasing the biological activity.

WAS measures how well soil aggregates hold together when the soil gets wet. In a lab, WAS is measured by simulating rainfall on soil placed on top of a sieve. Unstable aggregates will break apart and fall through the sieve holes. The share of the soil that stays on top of the sieve is the aggregate stability, provided as a percentage. Using the scoring curves, the Alberta Soil Health Benchmark study will convert that WAS percentage to a score from one to 100.

Because soil aggregates tend to be correlated with soil type, the Alberta WAS data has been analyzed separately for coarse, medium and fine soil.

For coarse soil, the average WAS test result was 48 per cent, meaning that when medium-texture soil is tested, almost half (48 per cent) of the sample stays on top of the sieve during a simulated rainfall.

The scoring curve converts that result into a score of 50, right in the middle of the yellow zone. The soil health report would call it “medium,” and this section of the report would be coloured yellow.

If your client’s WAS test result was 60 per cent, with 60 per cent of the soil left on top of the sieve, the benchmark score would be 70, and this section of the report would be coloured green, for “high.” It would take a test result below 19 per cent to have this section of the report coloured in red.

Comparing your client’s soil to a more local benchmark will give a different benchmark score for the same test result.

On average, soils in the Foothills Forage and Grazing Association area, in southwest Alberta, have much higher WAS test results. Here, a WAS test result of 48 per cent for coarse soil would give your client a benchmark score of only 25, in the orange (“low”) zone. These regional scoring curves allow you and your client to compare their soil to other soils in their area, soils that are probably similar to what you’re dealing with.

To get a score of 50 in the Foothills Forage and Grazing Association area, the WAS test result for coarse soil would need to be 65 per cent. Zavala and her colleagues attribute these higher regional WAS scores to land use patterns in the area. There is more pasture there, and less disturbed area.

In case you were wondering, in the northeast U.S., WAS results tend to be lower. A WAS result of 48 per cent would be in the blue, “very high” zone, and give you a local benchmark score of 80.

Sending in samples

Before sending a sample in, remember that any soil test is only as good as the protocol used to collect the soil samples. The Chinook Applied Research Association’s Soil Health Lab Protocol is available on the lab’s website. This protocol includes all the necessary information from field site selection, to tools, to how best to package your samples for mailing.

The current price for a benchmark assessment is $210 per sample for the biological and physical portion of the tests, plus an additional charge for chemical/fertility tests. This additional charge starts at $60 per sample, with prices depending on the exact list of chosen tests, and the chosen lab.

The forms note that this price is “still a good deal,” and that discounts may be available for special projects. This rate is not near the full cost of performing all these tests and sending you a handy list of results. Zavala explains that they aren’t charging the actual cost of the service now out of fear that “people aren’t going to do analysis because it’s going to be too expensive.”

Once the soil reaches the Soil Health Lab, a portion of the sample will be air-dried and sieved for biophysical tests. Another portion will be stored at 4 C for biological tests. For chemical testing, soil samples will be sent to the A&L Lab and the University of Alberta lab.

Once you get the results, you may see more than one indicator in the red zone, or maybe the orange zone. Sometimes, unfortunately, growers looking for areas to improve are spoiled for choice. And, of course, areas where test results are poor will be correlated. For example, a physical soil constraint makes it hard for microbes to thrive.

The colour-coding on a detailed soil health report identifies areas where management changes could have the most effect. But even with this easy-to-interpret result, not all growers will address every area of concern when they first see the results.

The Cornell manual not only suggests methods of addressing some of the indicators of poor soil health these tests identify, it also includes a discussion on the three main categories of factors that go into a soil management plan.

Soil health status is an important part of a soil management plan, but it’s not the only component. Grower goals and farm resources are also important considerations. A grower renting farmland may be more focused on maximizing short-term yields than on optimal long-term health scores. Or, after two years of drought, a grower may want to implement all of the recommended changes to improve soil health, but simply not have the financial resources to make the changes.

Meanwhile in Saskatchewan

To the east, a team led by Kate Congreves, a professor in the department of plant science at the University of Saskatchewan, is working on a Saskatchewan Soil Health Assessment Protocol that includes scoring functions similar to those developed by the Alberta Soil Health Benchmark project.

The project is very similar to the Alberta Soil Health Benchmarking project, but there are subtle differences. For example, rather than creating scores based on smaller regions of the province, the Saskatchewan protocol is developing scoring curves by soil type: brown, dark brown and black. Saskatchewan researchers noted that soil class generally influenced most soil characteristics.

As an example, the Saskatchewan report mentions soil organic carbon. Generally, a soil organic carbon of three per cent would be a “good” score in Saskatchewan. But in Saskatchewan’s black soil zone, soil organic carbon levels tend to be higher. In the black soil zone, a soil organic carbon of three per cent would rate as “poor,” with a score between 20 and 40 on the scale of one to 100.

And the rest of the country?

In the spring of 2024, the Canadian Standing Senate Committee on Agriculture and Forestry released a report on soil.

This report includes 25 recommendations, the first of which is that soil be designated as a strategic national asset. Many other recommendations centre on encouraging soil stewardship, using tools like tax credits and carbon markets.

There are many ways to evaluate soil. Many tools are not as comprehensive as the Alberta Soil Health Benchmark. Many are similar, but slightly different, like the difference in regional scoring between Alberta and Saskatchewan. This report recommends that the federal and provincial governments develop a consensus on how to measure, report and verify soil health.

Zavala would like to see comprehensive soil health testing in place across the country.

“If the government doesn’t see the importance of what we have done in Alberta and look in more detail at how beneficial this can be, we aren’t going to understand what’s happening in our soil. We need to see the soil in a different way.”

What’s going on down there?

Adding biological measures to soil tests has proven to be fascinating for researchers, including Yamily Zavala.

Using a microscope to visually examine the microbes living in the soil takes more time than the physical and chemical soil tests, but it’s also more rewarding. Soil is filled with a vital network of bacteria, fungi, protozoa and nematodes.

These microbes, along with other living things, such as earthworms and insects, are also called the “soil food web.” A healthy soil food web supports several functions, such as decomposing organic matter, helping plants access nutrients, stabilizing the soil structure, detoxifying the soil, and more.

Of all the microbes, Zavala is especially taken with the protozoa. “It’s so much fun to watch them,” she says. Protozoa are the single-celled organisms that consume bacteria. This class includes several types of organisms including flagellates, ciliates and amoeba.

Soil samples destined for biological analysis are stored in the fridge at 4 C. When it’s time to view the samples, the soil is placed in a plate with 24 wells (not completely unlike a tiny ice cube tray), and incubated for a few days in an agar broth, a solid growth medium that Zavala describes as a “nutrient soup.”

One indicator of soil health is the biomass of all living organisms in the soil. Another is the diversity of this underground ecosystem.

For now, there are no quantitative measures of microbe diversity. As a qualitative measure, Zavala classifies the organisms in the samples based on size, and also by colour, and makes careful notes about each sample.

A more diverse group has a wide mix of sizes and shapes, and a range of colours. These organisms tend to range from two to three micrometres to flagellates longer than 18 micrometres. In colour, these organisms tend to be clear, yellow, brown, black and sometimes burgundy.

It’s not an official part of the test, but Zavala’s favourite part of this assessment is watching the living creatures interact. One day she spotted a group of nematode-trapping fungi. These fungi are carnivorous, and release pheromones to sense and draw in their prey. While Zavala was watching, they formed a circle. “The nematode was swimming and passed inside the circle,” Zavala says. Then, the circle of fungi closed in and trapped the nematode while she watched.

In another sample, there were many bacteria inside an amoeba. “The amoeba started growing,” Zavala said. “Then it burst. The bacteria overcame the amoeba and took control.”

To take the CEU quiz for this article, CLICK HERE.

References

Agriculture and Agri-Food Canada, Resource management, indicators: Soil organic matter.

Chinook Applied Research Association Soil Health Lab Protocol for Soil Sampling.

Chinook Applied Research, soil health reports.

Cornell Soil Health Lab, Comprehensive Assessment of Soil Health, manual. (This manual includes a detailed explanation of data scoring, as well as detailed descriptions of each measure and suggestions for improving soil quality.)

Saskatchewan Soil Health Assessment Protocol, Phase II, Final Report.

Standing Senate Committee on Agriculture and Forestry. Critical Ground: Why Soil is Essential to Canada’s Economic, Environmental, Human and Social Health.

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“[The] pH is a measure of hydrogen ion activity in the soil,” Riekman said during a Manitoba Agriculture Crop Talk online seminar last month.

The pH scale is logarithmic, with each whole number indicating a tenfold shift in hydrogen ion activity. A neutral pH is seven, with values above that indicating less hydrogen ion activity, making the soil more alkaline. Values below seven indicate more hydrogen ion activity, making the soil more acidic.

A shift from pH five to six represents a tenfold decrease in hydrogen ion activity, and a shift from six to seven represents another tenfold decrease, Riekman says. This means moving from pH 5 to pH 7 results in a 100-fold decrease in hydrogen ion activity. Small changes in pH reflect significant shifts in acidity or alkalinity due to the exponential nature of the scale.

READ MORE: Liming and soil acidity

Soil pH in Manitoba tends to be on the higher end of the scale, with most soils testing in the neutral to alkaline range, Riekman says. Data Riekman shared from 2001 show fewer than 10 per cent of Manitoba soils had a pH of six or lower.

Sandy, well-leached soils, such as those found in the Assiniboine Delta and southeastern Manitoba, tend to be more acidic due to the loss of calcium and magnesium over time, Riekman says.

“Anywhere where you consider soils to be either sandier or more weathered — soils that have higher precipitation and have more leaching over time and weathering as they’ve developed — you tend to have a lower pH,” she says.

Over time, the more basic elements like calcium and magnesium leach through the profiles, leaving hydrogen behind.

Different crops thrive at different pH levels, Riekman says.

“Some plant species have very specific pH requirements. Some plants will be more tolerant of acidic conditions, or more tolerant of alkaline conditions, and that can help us to target certain plant species based on that.”

Acidic soils can reduce the availability of essential nutrients and inhibit nitrogen-fixing bacteria.

“When we’re talking about things like soil-applied herbicides, their performance can be decreased when you have more acidic soils,” Riekman says, adding that liming is a key strategy for managing acidic soils.

“It’s going to decrease those potential metal toxicities, or aluminum toxicity; it can improve the physical condition of the soil.”

However, lowering soil pH in high-pH soils is difficult, Riekman said. One study from North Dakota showed applying 8,000 pounds of elemental sulfur per acre in South Dakota lowered pH from 7.8 to 5.7 but significantly increased soil salinity.

It’s important to know soil pH when applying herbicides, says Kim Brown, a weed specialist with Manitoba Agriculture who also attended the Crop Talk.

“You do have to watch for some of our soil-applied herbicide. … There’s certain limitations on some of our herbicides,” she says.

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First, it’s important to remember that most soil testing labs report the phosphorus soil test as P, either in parts per million (p.p.m.) or in pounds per acre (lbs./ac.). Fertilizer recommendations are made using phosphate (P₂O₅) and recommendations are usually in lbs./ac. All phosphorus fertilizer is sold as phosphate: P₂O₅. To convert P to P₂O₅, multiply by 2.3. For example, to convert 20 lbs. of P per acre multiply by 2.3 to get 46 lbs. of P₂O₅ per acre. To make it a little more complicated, there is no P₂O₅ in P fertilizer. Our most common P fertilizer used is monoammonium phosphate with the chemical formula of NH₄H₂PO₄. The phosphorus form in the fertilizer is PO₄.

Next, it is important to have a good sense of how much phosphate is taken up by a crop and how much is exported from your fields each year. Table 1 shows the approximate amounts of phosphate (P₂O₅) uptake by various crops. To determine phosphate removal and export from your fields, use the Prairie Nutrient Removal Calculator, available online.

Soil test phosphorus

As mentioned in my previous article, Manitoba Agriculture recommends the Olsen method to determine soil P in that province. For Alberta and Saskatchewan, soil samples should be tested using the modified Kelowna method, as this is the method recommended by each province. Almost all soil test P calibration research in Alberta has been with the modified Kelowna since 1991.

Further, all soil test calibration work with phosphorus has been based on zero- to six-inch depth samples. So, always sure to sample the zero- to six-inch depth separately from deeper depth samples to accurately determine P fertilizer requirements.

If your agronomist is using other soil test P methods, such as the Bray method, it has not been calibrated to western Canadian soils and is not recommended for making P fertilizer recommendations in Western Canada. If the lab or agronomist you work with uses the Bray method or another uncalibrated method to make P recommendations for your farm, odds are the recommendations are from Ontario or the U.S., meaning you are probably not getting the best 4R phosphate fertilizer recommendations.

Phosphorus is either very low, low or medium-range in about 80 per cent of Prairie soils. In the past 10 to 15 years, many farmers have been applying P fertilizer at rates less than crop removal, resulting a slight decline in soil test P, which is a concern.

An important question farmers need to answer is how deficient is soil P in your fields? In Manitoba, using the Olsen method, if the soil test is 10 to 15 lbs. P acre, then P is low — and if higher than 40 lbs. P per acre, soil P is considered very high (Table 2). The modified Kelowna method has broader range; if the soil test is 20 to 40 lbs. P per acre, then P is low, and if higher than 80 lbs. P per acre, soil P is considered very high (Table 3).

Soil tests can give a good estimate of soil P levels but cannot predict with 100 per cent accuracy when crops will respond to added P fertilizer. The frequency of crop response is strongly influenced by environmental conditions, particularly soil temperature and moisture. For example, at research sites in Alberta, the observed response to P fertilizer, particularly with wheat, barley and canola, tended to be greater with wetter, cooler spring soil conditions versus warmer, drier conditions. Generally, farmers can expect greater crop response to P fertilizer in wetter or cooler spring conditions.

Soil pH effect on soil phosphorus

Some agronomists are concerned about the effect of soil pH on plant availability of soil P. Orthophosphate, the form of P taken up by plants, is highly reactive with certain soil elements. Generally, soil P is slightly more available to plants in a pH range of 6.0 to 7.8. At higher pH levels (>7.8), calcium (Ca) is more reactive with phosphate, creating forms that have slightly lower availability to plants. Magnesium (Mg) acts in the same manner, forming less-available magnesium phosphate compounds. In more acidic soils, aluminum (Al) and some other elements increase in solubility and will tie up soil P. This reaction limits the availability of inorganic P to plants when soil pH levels drop to less than 5.5. Generally, I am far more concerned about P tie-up at low soil pH than higher soil pH.

Phosphorus fertilizer recommendations

Phosphate fertilizer recommendations for various crops are provided on the web sites of Alberta, Saskatchewan and Manitoba departments of agriculture. In this article, I’ll refer to the Alberta Agriculture Agdex 542-3, titled “Phosphorus fertilizer application in crop production.”

Table 3, from the Alberta Agriculture Agdex, shows the example for phosphate fertilizer recommendations for wheat based on the modified Kelowna soil test P level by soil zone. Recommendations are adjusted for seed-bed soil moisture content. Table 4 provides an estimate of the probability of response of wheat to phosphate fertilizer, based on Alberta field research. To determine the recommended rate of phosphate, simply look at the soil test P level in Table 3 and match it with the soil zone of your farm.

For example, from Table 3, if you are growing wheat in the Thin Black soil zone and your soil test level is 35 lbs. P per acre, then the recommended phosphate rate would be 30, 35 or 40 lbs. P₂O₅ per acre, depending on if seedbed moisture conditions are drier, moist or wet, respectively. Normally, I would use the moist to wet values for the recommendation. Then, from Table 4, a farmer could expect a 90 per cent probability of at least a two-bushel-per-acre yield increase and expect a 70 per cent probability of a five-bushel-per-acre yield increase with wheat. This information is also available for barley and canola in the Alberta Agriculture Agdex.

Next, estimate your crop target yield and look up the expected crop P₂O₅ removal rate from the Prairie Nutrient Removal Calculator. If the removal rate of P₂O₅ is greater than the recommended fertilizer rate, consider applying the removal rate to maintain soil test P level in your fields.

Finally, for any fields that test very low or low for soil P, consider adding an additional 10 or 15 lbs. P₂O₅ per acre each year to help build soil P levels over the long term, keeping in mind your economic conditions.

Phosphate fertilizer considerations

Field research across the Prairies has shown placement of P fertilizer with, or banded near, the seed results in best yield response for most annual crops. Phosphate recommendations are typically based on P placement with or banded near the seed. Care is needed not to exceed the safe seed-placed rate for each crop grown. Table 6 shows general safe rates of seed-placed P using monoammonium phosphate (MAP) — for example, 11-51-0. Note that the recommended seed-placed safe rates vary slightly among provinces depending on field research over the years.

Some farmers purchase diammonium phosphate (DAP) — for example, 18-46-0 — in the U.S., due to proximity to the border and price. Phosphorus in DAP is less available on high-pH soils versus P in MAP. Alberta and Saskatchewan soils in the Brown and Dark Brown soil zones tend to have a higher pH, so MAP is a better fertilizer choice. Also, DAP has seed-placed P concerns, so not as much DAP can be safely placed with the seed.

Cereal crops grown on soils that are very low to medium in available P are most responsive to seed-placed phosphate at recommended rates. Crop response to seed-placed phosphate can be equal to or better than banding phosphate, except in drier spring conditions, when banded P can be better than seed-placed P.

For canola grown on soils very low to medium in available P, rates up to 15 to 25 lbs./ac. P₂0₅ can be seed-placed with a seedbed utilization of 10 per cent depending on seedbed moisture conditions. I prefer to use a more conservative rate of seed-placed phosphate to avoid germination injury. Higher P rates needed for canola should be split between seed-placed and side- or mid-row banding at the time of seeding or banding prior to seeding. Seed-placed or banded fertilizer P on soils high in soil test P, at rates up to 15 lbs./ac. of P₂0₅ may result in a small crop response 30 to 50 per cent of the time, depending on soil zone and environmental conditions.

Pulse crops tend to be less responsive to phosphate fertilizer, due to somewhat better efficiency to take up soil P. Alberta research suggests pea is most responsive to phosphate fertilizer when soil test P levels are less than 30 lbs. P per acre (modified Kelowna method). Above this level, there is a relatively low chance phosphate fertilizer will increase yield. When soil test P levels are medium to high, an annual maintenance application of phosphate fertilizer should be considered to meet crop requirements and replenish soil P that is removed.

Benefits of starter phosphate fertilizer

To get a crop off to a good start, having an adequate supply of P close to the seed during the first six weeks of growth is important. Most annual crops take up the majority of their P requirements in the first 40 days after emergence. Placement of P in or near the seed row has traditionally been the best method used for P fertilization across the Prairies, depending on seed safety concerns.

Effect of previous crop

Canola has a relatively high demand for soil P. It’s a non-mycorrhizal crop and uses different mechanisms to take up soil P, leaving plant-available soil P more depleted compared to cereal or pulse crops. As a result, cereal crops that follow canola tend to be more responsive to P fertilizer. I usually suggest adding an additional 10 lbs./ac. of phosphate over and above the phosphate fertilizer recommendation for cereals, when following a good-yielding canola crop.

To sum up: Prairie farmers spend over $1 billion annually on phosphate fertilizer. Hopefully, reviewing these three articles will assist with a better understanding of how soil P functions in soil, soil testing for P and then how to develop wise phosphate fertilizer recommendations.

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