Soil health measurement project seeks standard set of indicators

The North American Project to Evaluate Soil Health Measurements hopes to recommend scientifically sound indicators

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Glacier FarmMedia – Soil health measurements can vary widely depending on management practices, show early results from a North American study.

Paul Tracy, who manages the non-profit Soil Health Institute’s project to assess 31 indicators of soil health in all three countries, said agricultural and environmental interests are promoting lots of measurement systems and indicators.

But he told the Indian Head Agricultural Research Foundation soil and crop management seminar that preliminary data from the North American Project to Evaluate Soil Health Measurements found some unexpected results, leading him to suggest that different measurements will be required, depending on intrinsic soil qualities and management.

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The project goal is to recommend scientifically sound indicators that can be widely applied and therefore encourage practices that contribute to healthy soil.

“We’ve done a tonne of work on soil health,” he said. “We need some standardization and some uniformity because there are too many groups out there promoting soil health and not knowing what the heck they’re talking about and certainly not having a set of indicators that are going to predict the soil health at your location.

“Often the intrinsic soil properties trump management and so we’re going to have to measure management within smaller geographies to make any sense out of it.”

The project involved soil scientists from across North America and was designed to find indicators that would be most useful across wide geographies, Tracy said. Tests were taken at 124 long-term agricultural research sites, including 18 in Canada and 16 in Mexico.

Tracy used water infiltration as one example of an important consideration for soil health. Typically, water is expected to move faster into no-till soils than conventionally farmed soils, he said.

But at four test sites in Illinois, Missouri and Kentucky, that didn’t happen.

In Mexico, where residue is usually removed through burning, soils under no-till didn’t move water well either.

“Even with no-till you crash the ability to infiltrate water” when residue is removed, Tracy said.

In Canada, Tracy said water movement at a Swift Current site wasn’t different between a pulse-wheat rotation farmed conventionally or no-till. Nor was it different in a wheat-fallow system.

“Water movement into this site was really not tied to the rotation and the tillage,” he said.

The study also compared different soil indexes. Tracy said these indexes are “being pushed big time” but so far the study hasn’t found that they are interchangeable or necessarily accurate.

Tracy said measuring soils against a reference state is an idea gaining ground in the United States.

“A lot of folks in the soil health community want you to get your soils in line with what that reference soil may be, regardless of whether it’s unhealthier compared to what you’re doing,” he said.

If a prairie grass of some type is considered the reference state for the Canadian Prairies, then he said the NAPESHM study should have been able to measure water infiltration on crested wheat grass at Swift Current.

“That’s your reference soil,” he observed, pointing to a graph showing little to no infiltration. “For whatever reason, we couldn’t get water to go into that crested wheat grass. A purist in the soil health arena would say we want crested wheat grass, a perennial, living roots year-round, and look what it did to your water infiltration.”

There are newer measurements on the horizon, such as DNA sequencing of microbial populations in soils to determine health. There is more emphasis on biological soil indicators.

“Understanding the soil micro biome has become a big thing,” Tracy added.

He said he is concerned about the disconnect between those in the soil health community and those in farming and agri-business.

“I believe very strongly that before we can figure out what we’re going to be promoting in terms of soil health, those two groups have to get together,” he said.

This article was originally published at The Western Producer.

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