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What’s good about soil?

Soil health indicators often relate to properties that you can’t see

We’re planting more cover crops, we’ve got a heightened focus on soil organic matter levels, and now we’re adopting what’s thought to be a relatively new term: soil health indicators. They’re each part of a wave that’s been building, reflecting a renewed interest in the soil as the basis for all crop production.

“It’s been building for a long time,” says Anne Verhallen, soil management specialist for horticulture with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). “People talk about soil health as though it’s wonderful and new, yet calling up my Diagnostic Day files, I know that in 1999, soil compaction was the (tour) stop I was doing. In 2000, it was ‘Soil Life: the Good, the Bad and the Just Plain Ugly.’”

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Drs. John Lauzon and Kari Dunfield at the University of Guelph, Dr. Lori Phillips with Agriculture and Agri-Food Canada (AAFC), Dr. Jill Clapperton and Odette Minard — the “Earthworm Lady” — have all been driving the messaging about the value of healthy soils for years.

Earthworms are the simplest, most visual indicator for soil health but Verhallen notes that soil organic matter (OM) is the other default metric in the science, although it’s also the property that requires the most investment.

“While we’re still going to be looking at organic matter as a decent indicator, there’s a lot of interest in looking at the different parts of organic matter — the different fractions,” says Verhallen. “Those start getting to be very expensive as a test. The other challenge is that the methodology used to measure soil organic matter doesn’t show rapid changes.”

She still likes using OM as a basic soil health test, whether growers rely on Cornell, Haney or the Solvita test. Everyone who gets their soil tested should be asking for the organic matter component because it’s not part of the accredited test, yet Verhallen believes it’s worthwhile to track it over time.

“When we’re looking at soil health, we’re looking at other things that organic matter influences, and one is nutrient cycling, and it really influences structure and water infiltration,” she explains. “We do see that with some of the other measurements we conduct.”

Valuable resources

Two documents have become valuable tools in Verhallen’s efforts to provide worthwhile information and resources on soil health. One is the section in the current Agronomy Guide for Field Crops (Publication 811), containing 24 pages devoted to “Managing for Healthy Soils.” It covers the foundations of soil science and the research findings of the past few decades — why healthy soils are productive soils, the value of soil organic matter, and the benefits of cover crops and the different types of tillage. It also provides a soil health check so growers can look at their own soils and determine the structure, the colour, the texture, drainage, plant and root growth, and water-holding capacity.

The other resource is one that Verhallen is quick to promote, and that’s “New Horizons: Ontario’s Agricultural Soil Health and Conservation Strategy,” a 68-page reference guide published by OMAFRA. It’s an extensive look at soil health and why a strategy is needed, as well as sections on soil data and mapping, evaluation and monitoring, knowledge and innovation, and implementing the strategy.

Verhallen is concerned that so much went into the creation of the strategy yet in talking about soil organic matter or incorporating cover crops, the goals and fundamentals of the strategy might be forgotten. She doesn’t want it to be “another project that gathers dust on a shelf.”

How many traits?

Dr. Laura Van Eerd is another soil scientist who believes earthworms and soil organic matter levels are simple and good indicators of soil health. She’s been studying the effects of soil health since 2009 and maintains that it’s a “total package” effort, although she does connect the effect to yield benefits. In a drought year such as 2012, healthy soil might have been the difference between having a crop to harvest while others didn’t.

“It’s yield, but it’s yield stability or yield resiliency that we’re talking about,” says Van Eerd, associate professor of sustainable soil management with the University of Guelph’s Ridgetown Campus and a joint-director of soils at Guelph. “You can only grow so many bushels of corn in a stressed year, and that number depends largely on your soil.”

Where most people can name three or four — maybe five — soil health indicators, Van Eerd’s list has more than 30 different measurable traits. Is it useful, she asks? She’s not sure but it is something that Ontario is working towards with the Soil Health and Conservation Strategy. It’s a slow process but it’s one that has long-term benefits.

“But it’s not easy and the first step is to get people thinking about it,” says Van Eerd. “Seeing soil eroding into the ditch should get them thinking whether something could or should be done. More than five years ago, a farmer asked if cover crops were a trend or a fad: I responded, ‘In the late 1980s, was no till a trend or a fad?’”

Is agriculture at that same stage with soil health? Van Eerd doesn’t think so, but it becomes a question of can everyone get to that next step. One of the more evident signs that we’re not “there” yet is that roughly 25 to 30 per cent growers soil test once every three years (according to CCAs, agronomists and other industry stakeholders). Too often it’s dismissed as “a cost” when soil testing should be viewed as “an investment.”

“There are those who are the early adopters or ‘soil health investors’ and are willing to incur some costs,” says Van Eerd, perhaps being an example to others. “Come back in five or 10 years and see what’s changed.”

Grassroots movement

Ontario agriculture is very fortunate to have the kinds of grassroots organizations that invest serious time and effort in education and promoting soil health.

The Ecological Farmers Association of Ontario (EFAO) is another farmer-led research program, which began in 2016 and has garnered funding from the Ontario Trillium Foundation, George Weston Ltd. and Loblaw Companies Limited. In 2016, the program began with nine different farmers receiving funding for 14 trials. In 2017, 14 farmers were funded for 19 trials and in 2018, 23 farmers received funding for 19 trials.

With many of these organizations, cost is always a consideration and a potential barrier, yet according to Dr. Sarah Hargreaves, growers are increasingly motivated to track and improve soil health.

“They want to know that the cost is worth it,” says Hargreaves, research director for the EFAO, based in Guelph, Ont. “Because of this, one of the first farmer-led research questions brought to the EFAO’s program was, ‘What soil health tests are best — reliable and sensitive?’”

That was in 2016 and it involved three growers taking replicated soil samples from different fields and sending them to Ward Labs for testing using the Haney Soil Health Test and to the Cornell Soil Health Lab for additional indicators. Each grower wanted results for reflecting different production settings. They took cores from areas of high productivity and low productivity, and from a fence row as a reference. One grower wanted to track soil health in his grazed pastures, another wanted analysis on his hay fields and the third wanted to measure soil health in vegetable fields.

The results indicated active carbon and soil organic matter as the most prominent and reliable metrics. Other measurements told a different story with each replication, making the results less reliable or sensitive.

“To my knowledge, this is the first study to look at soil indicators in this way,” says Hargreaves. “Lack of knowledge about the sensitivity and reliability of different soil tests is a detriment to growers everywhere. As for the indicators and their meaning, yes, you can’t ‘see’ these indicators but they are very sensitive. Visual indicators like earthworms are also informative and important. In terms of soil health, it’s important to document the changes in soil carbon and soil organic matter.”

The cost-effective power of grower-led research is undeniable, yet it’s also underappreciated. Hargreaves maintains that growers from all sectors and scales are interested in soil health and establishing best management practices that promote its continued advance. She sees a lot of curiosity from grazers who want to improve their pastures or restore degraded land. For cash croppers and horticulture producers, yield may be the primary metric, but there’s the growing realization that healthy soils are better at buffering conditions during stressful years.

If there’s one thing she cautions in farmer-led research, it’s the need to emphasize the value of replicates. Soil sampling’s status quo doesn’t require replicates: there may be 10 cores taken but once they’re consolidated in a bag and sent to the lab, that constitutes only one replicate.

“With no replicates or information on how many replicates a specific measure needs, you can’t make conclusions,” says Hargreaves. “This is especially true with soil — we all know how variable soil is. So I caution growers about trusting results they hear from suppliers or others unless they know the data are rigorous with a proper number of replicates.”

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