Soil fertility is more than just health; it also encompasses yield, climate regulation, water filtration and biodiversity
Soil health is not a scientific term. It conjures imagery of human wellness but the term is imprecise and ambiguous.
So says Henry Janzen, well-known Agriculture Canada research scientist in the fields of carbon, nitrogen and sulfur cycling, greenhouse gas emissions and soil carbon sequestration.
Soil health is context dependent, he told those participating in a Feb. 20 webinar organized by the Beef Cattle Research Council.
“You cannot assess the health of a soil divorced from its setting without thinking about where it came from,” said Janzen. “The criteria for soil health will vary from place to place and from time to time.”
For farmers in particular, soil fertility is often equated with soil health but Janzen said the criteria has expanded over the years to encompass more of soil’s functions including crop yield, climate regulation, water filtration and biodiversity.
Janzen took a philosophical approach to his introduction but the topic at hand was forages and soil health.
Given that all function is driven by sunlight and that carbon is the pre-eminent indicator of soil health, Janzen said forages can enhance soil in three primary ways:
- Enhanced energy capture. Forages extend the duration of photosynthesis in the growing season.
- Investment in ecosystem. Cereals put most of their energy into seed heads. Forages generate seed too but return a larger share of energy to the ecosystem by storing more carbon.
- Enhanced recycling. Annual crops are linear, but forage crops provide opportunities for grazing and thus livestock production, manure generation and recycling. Their use creates a loop in which the same nitrogen can be used for multiples cycles of carbon flow.
“Forages form the foundation of what I would call here sun-powered lands,” said Janzen.
Many questions remain about soil health, he added. It’s underlying mechanisms and processes are not well understood. As well, it is difficult to study an entire system and its interactions from a research perspective.
“Soil health emerges best when we see the entire system and manage our lands accordingly. That is still a challenge.”
An additional challenge is to measure soil and its benefits to entire ecosystems, such as biodiversity or aesthetics. For example, “what is the value of the sound of a meadowlark on a bright, crisp June morning?”
Sustainability, another commonly used term, is only measurable in hindsight, Janzen added. It can take years or decades to see the effects of a management change on soil health.
Janzen suggested a human dimension be added to discussions and assessments of soil health, and that should include farmers, consumers and policy makers.
More people are using the land and fewer are thinking about it than ever before, he said.
“I think many producers, most producers, all producers, I would say, are still very much connected to the land and recognize the beauty and the value and the functional benefit of land.
“But increasingly, I think what we need to do is tell some of these good news stories to audiences outside of our farming circles, to tell all these narratives and show the important ways that good management can enhance stewardship.”