Soil science can often take back seat to philosophy

More unproven soil science theories seem to propagate each growing season. Science and philosophy have become so intertwined that it’s hard to know where one stops and the other takes over.

If you have enough grey hair you’ll remember a time when summerfallow was commonly believed to be good for the soil. It was important for the soil to have a break every second year and if you didn’t summerfallow, you were going to wear out your land.

Those were the days when cultivators and rodweeders ruled. You tilled three, four or more times through the season to control weeds. Soil scientists claiming that summerfallow was bad for the soil didn’t know what they were talking about.

As air seeding technology advanced, direct seeding with minimum soil disturbance became the gold standard. As the price of glyphosate came down, chem fallow replaced tillage. Fallow acres dropped precipitously in favour of continuous cropping. Many farmers came to believe that tillage was evil and should be avoided at all cost.

In recent years, tillage has staged a comeback. In many cases, it’s deemed necessary for residue management. If you call it vertical tillage, it’s somehow high tech and doesn’t hurt soil structure.

Some believe they need to deep till to solve soil compaction.

An even bigger debate occurs over fertility. Send soil samples to different labs and you’ll get different results due to different testing regimes. Show the results to a half dozen different agronomists and you’ll get just about as many fertilizer recommendations.

Fertilizer stewardship is supposed to be guided by the four Rs — the Right source at the Right rate at the Right time in the Right place — but that’s obviously open to a lot of interpretation. That’s why we see an increase in broadcasting nitrogen in the fall onto frozen ground or onto snow even though it breaks pretty much all the guidelines.

Beyond fertilizer, there’s a growing awareness of the micro-organisms in the soil biome that make nutrients available for plants. This is an important area of study, but some people seem to believe healthy soil micro-organisms can solve every fertility issue.

Everyone, of course, knows that rhizobium bacteria work in conjunction with the roots of legumes to produce nitrogen from the atmosphere. While other micro-organisms make nutrients more available to plants, it’s important to remember that they don’t create nutrients out of thin air.

Poly cropping and cover crops have gained quite a following. Crop diversity and maintaining a plant cover throughout the growing season is viewed as a benefit to soil health and this would seem to have merit. Unfortunately, a cropping practice that works in one geographic region may not be viable elsewhere.

Ask any farmer if their soil is healthier than 10 or 20 years ago and you’ll usually get an affirmative answer. We like to believe that we’re improving the soil resource for the next generation even if we don’t have empirical evidence.

And we like it when someone tells us that we’re sequestering carbon and that we’re part of the climate change solution and not the problem. Sadly, the farming practices that sequester carbon are complicated to quantify and verify. On top of that, farmers are unlikely to be rewarded for “business as usual.”

The term sustainable is overused with many different definitions. A newer buzzword term is regenerative agriculture.

When soil health and fertility beliefs are guided by philosophy, science takes a back seat.

Kevin Hursh is an agricultural journalist, consultant and farmer. He can be reached by e-mail at kevin@hursh.ca.

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