The 2012 drought devastated the crops of farms across the United States. Dane County in south-central Wisconsin was no different,  yet Gary Zimmer’s corn outperformed the county average by a wide margin.

“The county average that year was around 88 bushels per acre and we were about double that, getting between 160 to 176 bushels per acre on some fields,” Zimmer said. The farm averaged 116 bushels. What’s more, because he farms organically, his crops commanded a higher price.

Zimmer’s son and daughter work about 1,000 acres on Otter Creek Organic Farm outside Spring Green, Wisconsin. Zimmer’s son, Nicholas, farms the crops while Sadie oversees about 150 to 175 dairy cows. What makes the family’s style of farming different—and arguably more successful—is that for decades Zimmer has focused on what he calls “biological farming.”

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It Starts With The Soil

Early in his career, Zimmer was teaching at a technical college as a dairy nutritionist when he had a thought, “What would the ideal food for cows look like if we could make it?” It was while working as a consultant to dairy farms in Minnesota that he realized farmers knew what to give a cow to keep it healthy and producing milk, but they hadn’t given much thought about how to grow the plants (from the hay to the grass) that nourish their cows. He wanted to figure out the best way to produce high-yield, nutritionally packed crops with a minimal impact on the environment.

“I began thinking of the soil, the silo and the cow’s stomach as a complete system,” Zimmer said. A cow’s stomach and soil, according to Zimmer, are actually quite similar. “Both are fermentation vats that contain life and bugs and organisms,” Zimmer said. And in both cases, he said, you get out what you put in. “So I began talking about dairy nutrition from the soil up.”

In 1979 he moved to Wisconsin and started a small farm. “It seemed kind of silly if I couldn’t do it myself, and you had to read about it in books because I couldn’t demonstrate it.”

Otter Creek Organic Farms

Tailor-Made Plans

Zimmer is now president and co-founder of Midwestern BioAg, a consulting firm that, according to its website, shows “farmers how to create a tailored farm-management plan that builds the capacity of the soil to provide a wide range of economic and environmental benefits for the farm.” Zimmer said farmers who adopt these methods see increased yields, use fewer inputs and have a smaller negative impact on the environment.

“We’ve got such extremes today,” Zimmer said, noting that he read about one commercial farmer who wouldn’t eat his own farm’s potatoes because he knew what went into them. “At what point is it no longer even food?” Zimmer asked. On the other hand, he said, there are organic farmers who regularly sacrifice output and efficiency to meet strict guidelines.

“Organic is not about growing healthy crops. It’s about ‘I didn’t do this or I didn’t do that,’ but it could still be poor farming.” His hope is to change that. Otter Creek, his family farm, is proof that his methods work.

Zimmer finds it insulting when people expect him to produce fewer vegetables or lower-quality crops because he farms organically. He’s restricted on the use of pesticides and certain fertilizers, but said there are ways to prevent pests and disease without the use of pesticides, and sustainable ways to enrich soil while minimizing the impact on the environment.

“The secret to farming is manipulating biology,” Zimmer said. “Why would we let fertilizers be our limiting factor? Organic farmers can use any mineral any other farm does, it just needs a different source.” He regularly shows farmers his methods at Otter Creek. On the right are his six rules for biological farming.

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Balancing Act

There are about 13 minerals your soil needs. According to Zimmer, the mix of what inputs you will need is different for each soil, but you won’t know until you have your soil tested. A balanced soil includes a calcium/magnesium ratio of 70 to 75 percent calcium and 15 percent magnesium.

“When the soil is out of balance, the crop is too,” Zimmer wrote on the Otter Creek website. “If the crop isn’t in balance, the livestock feeding program is not balanced in minerals and other nutrients. Look for what you have excesses of as well as what you need. Your farm soil system has a certain ability to provide minerals. What is added can take your crop quality and production to a new level. You’ll likely need to use some fertilizer, regardless of how good your soil is, to replace what your crops use.” 

Dairy Cows
The cows going out to pasture after being milked. In the afternoon they are brought over to a different pasture.


“We use only natural-based fertilizer materials that are non-toxic and life-promoting. They contain not only nitrogen, phosphorus and potassium, but also calcium, magnesium, sulfur, zinc, manganese, iron, copper and boron,” he continued.

He recommends using naturally mined minerals, watching the pH levels (6.5 to 7.5 is the ideal range, but many fertilizers are higher) and providing a good mix of soluble and non-soluble nutrients. Slow-release nutrients help cover the course of the growing season and stabilize the soil to prevent runoff. By including cover crops, also known as “green manure,” that are grown to be fed back into the soil to increase micronutrients and macronutrients, you are feeding life back into your soil. On his farm, Zimmer said they will occasionally till a crop back into the soil before it’s harvested in order to increase and feed the variety of organisms living in the soil.

Maximize Diversity

By increasing the variety of crops and rotating those crops not only are you preventing the depletion of the soil’s nutrients—the same crop will drain the same nutrients each year—but are also helping prevent any one disease or insect population from taking over.

“Monoculture is more susceptible to disease and insects,” Zimmer said. In his book, Advancing Biological Farming, co-written with his daughter, Leilani Zimmer-Durand, he points out that potato farmers always rotate because soil-born pathogens are especially devastating to below-ground crops, but the same theory applies to above-ground crops, too.

Till With Purpose

“The sweet spot for soil is the ‘middle zone’ where roots develop,” Zimmer said, “so that’s where you want to build a rich biological life. Aggressive tillage allows too much air into the root zone, burning up carbon and damaging soil structure, but too little tilling and the soil becomes too tight, preventing air, residues and water from reaching the middle zone.”

Zimmer said to practice “thoughtful tilling” by keeping in mind what you want to achieve. On his own farm, he works the cover crops into the top 3 to 4 inches using a rotovator. With the residue from cover crops and compost on the field, he plants in furrows using a notched disc blade and row cleaner, which provides good soil-to-seed contact in a clean seedbed, and allows the residue to feed the soil.

Biological farming of corn
Gary Zimmer shows off feed corn which has 16 kernels around the diameter, indicating that the soil has a good supply of nutrients.


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“At any time we have about half our farm in production, so half of the soil is growing a crop and half is getting ready for production,” Zimmer said. According to Zimmer, when you’re starting out, preparing soil for planting and getting it certified organic can take two years, but in the end the results are worth it. Thinking of your farm holistically improves how it functions over the long term. And for Zimmer, that always begins from the ground up. For more information, visit

Two Great BioAg Books

If you want an easy-to-read, no-nonsense explanation of the scientific reasons why a biological approach to gardening or farming is better for the bottom line and better for the environment, read The Biological Farmer by Gary F. Zimmer and Advancing Biological Farming by Gary and his daughter, Leilani Zimmer-Durand, published by Acres, U.S.A. Both books are filled with suggestions for improving soil and production by working with nature, not against it.

This article originally published in THE NEW PIONEER® Spring 2015 issue. Print and Digital Subscriptions to THE NEW PIONEER magazine are available here.

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