Crop and feed analysis can tell a soil health story

U.S. farmer puts focus on tissue testing

Long-time organic agriculture advocate Gary Zimmer believes he can come up with the perfect recipe for his Otter Creek Farm’s soil health.

Gary Zimmer. photo: Supplied

They look at plant tissue and feed tests. Feed tests should include a full mineral analysis, plus feed digestibility, said the founder of the Wisconsin-based Midwestern Bio-Ag crop and livestock input supplier at the recent Guelph Organic Conference. “I think you can learn a lot about your soils from looking at that.”

Why it matters: Organic farmers have fewer options when tackling pest or disease threats, so they must strive to prevent rather than react to outbreaks.

Zimmer added that soil tests are also important, but don’t necessarily need to be done annually. They should be done when a decision is made to improve a particular aspect or a particular field. But the recommendation coming out of the soil test “is your project. The feed test is your report card.”

Zimmer, who holds a Master’s degree in Dairy Nutrition, told conference attendees that his farm’s work over 40 years in balancing soil chemistry has led to them never needing to reach for crop protection or pesticides.

“We do some pretty radical things on our farm.” They used to milk 300 cows and crop 1,500 acres. With the next generation now actively involved in managing the farm, they milk 80 cows that are fed exclusively forages and pasture, and grow crops on 3,000 acres. 

His presentation, which was followed by an engaging, live question-and-answer session, outlined numerous forays into soil-health strategies: cover crops, intercropping, mob grazing of cropland, and innovative tillage. Recently, he has been involved in three trials into adding elemental sulphur to compost – as a way of softening the harshness of the product when applied to soil.

Their main method of monitoring soil health is through feed analysis. They’re happy with about double the potassium, magnesium and manganese that might be the target in conventional feed. And this is because of the health of the farm’s soil biology.

Although Zimmer approves of the more recently popular term “regenerative,” he has resisted tying his company’s or farm’s names to “organic” or “no-till.” Neither, he argues, defines a farming system. Instead, the word he likes most to describe his farm’s approach is “biological” – a word that plays prominently in Midwestern BioAg’s promotional campaigns.

For this farming system, biological diversity – of crops and in the soil – is key. “You organic guys are in a better position because you’ve got a lot of weeds, so you’ve got diversity – whether you like it or not,” he said.

Soil health, Zimmer said, is “the capacity of the soil to function without intervention.” Water must infiltrate. You need plant diversity. There must be living roots. Nutrients must be cycling. And there must be no crust – something calcium and sulphur go a long way towards preventing.

If you’re testing for soil biology, he cautioned, you’re just getting a moment in time. Things could change very quickly. The same test won’t show the same results the next day under different weather conditions.

Soil chemistry, by contrast, tells a longer-term tale. When converting conventional cropland to organic, Zimmer said, he has learned to get the soil chemistry right first and then grow cover crops to build up soil biology. After that, if problems arise, adjustments in micronutrients are often all that’s needed.

About the author


Stew Slater

Stew Slater operates a small dairy farm on 150 acres near St. Marys, Ont., and has been writing about rural and agricultural issues since 1999.



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