Soil Care Is an Organic Imperative

8/10/2013 7:00 AM
By Philip Gruber Staff Writer

SPRING MILLS, Pa. — Listening to Gary Zimmer talk about soil is somewhat like listening to the announcer at a baseball game.

Instead of dropping a pitcher’s earned run average or strikeouts per nine innings, however, this energetic Wisconsin dairy farmer and president of Midwestern BioAg unleashes a nonstop stream of statistics about the cation exchange rate or the parts per million of boron in a pasture’s soil.

Zimmer imparted his knowledge to about 40 farmers at an organic dairy transition day at the Ben Stoltzfus farm east of State College on Aug. 2.

An intense speaker, Zimmer is a predictably intense soil manager. He irrigates with molasses and fish additives and spreads boron, trace minerals and green manure. He spends up to a few thousand dollars a year on soil testing for his farms.

Caring for the soil is a particular concern for organic producers because they have a limited number of fertilizers at their disposal compared to conventional farmers. Still, the organic zest for soil analytics is gaining popularity in mainstream agriculture, Zimmer said.

The problem is that “very few people do (soil management) well,” he said.

Balancing nitrogen, which builds protein, and carbon, which gives energy, is a tricky task that requires a little bit of science.

“You can’t violate the principles of the cow,” he said.

Zimmer distributed the results of several soil tests from around the eastern United States.

One sample from Virginia showed 16 percent protein in the feed, which he said is slightly high. If feed has too much protein and also too much sulfur, “it’s like feeding them urea,” he said.

Zimmer is a sulfur proponent, though. As air pollution has decreased, spreading sulfur has become necessary, he said.

The main organic source of sulfur is gypsum, which is calcium sulfate. Epsom salts, which are magnesium sulfate, are another source.

Increasing the potassium in the soil will decrease the amount of magnesium the feed crop can absorb. Magnesium deficiency makes cows nervous and tense, and the element is “terribly expensive to buy,” he said, so growers should be wary of overspreading potash.

Manganese is usually high when the soil is acidic, not a condition Zimmer particularly favors. He does favor soil alive with earthworms, a condition he does favor.

Strong sugar numbers are also a good sign. “That’s energy,” he said.

Sugars also show the grass is photosynthesizing.

Zimmer starts with several factors to analyze a soil test. Cation exchange capacity indicates the soil type. A number in the lower single digits suggests sandy soil, and a number in the mid- to upper teens bespeaks clay soil. Zimmer’s own farm rates a 10.4, which is sandy loam.

Zimmer also checks the pH. Lime can be spread to reduce the soil’s acidity. “Don’t overdo lime,” though, because the chunks can take a decade to break down, he said.

High levels of iron in cattle feed tend to coincide with acidity, but iron blocks phosphorus.

Chloride, the ionic form of chlorine, interferes with calcium intake. Humates in soil, however, make calcium available, he said.

Zimmer also values uniformity across soil samples.

“Every soil sample on every field needs to look exactly the same,” he said.

Zimmer, emcee Lee Rinehart of Pennsylvania Certified Organic and host farmer Stoltzfus then led a walk through one of Stoltzfus’ fields. The pasture was a mix of rye, clumpless orchardgrass and Barenbrug mix.

Zimmer said the grass was enviable, though he noted dead matter was accumulating in some places.

Ideally, cattle should graze a pasture where the grass is several inches high, but they should not be left to grow too high or thatch will build. Cows “won’t eat through that,” Zimmer said.

To eliminate thatch, machines can rip out the thatch and blow in more seeds, he said.

Rye is highly digestible, but its low resilience makes it less useful on Zimmer’s farm. Soft fescue and orchardgrass work for him.

Even in Pennsylvania, rye is best seen as a two-year crop, he said.

To preserve his pastures, he has a sacrifice area for when he must pasture in wet weather.

Zimmer’s approach does seem to be paying off. His 35-year-old son, who works on the family farm, has never seen a bloated cow.

Adam Seitz, a certification specialist with Pennsylvania Certified Organic who also spoke at the event, noted that monitoring fertility is a requirement of the organic certification process. Land must be organic three years before it can be certified, and a dairy herd can be transitioned in a minimum of one year, he said.

Organic dairy cows must be pastured at least 120 days a year, Seitz said, so having the proper nutrition available in the soil is an important way to keep a herd happy and healthy.

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