Manure Happens

Before the advent of industrial agriculture, manure was a go-to fertilizer and soil amendment. Farmers who kept livestock had their own natural fertilizer factories. Today growers know that many organic materials — grass clippings, pine needles, leaves and other plant materials — can be beneficial, but manure is sometimes viewed as too unpleasant, at least when fresh, to keep pace with the fertility needs of large-scale farming.

This juxtaposition of old practices and a 21st century mentality requires a renewed appreciation of manure’s benefits. For eco-farmers striving to use the best inputs available, the quality of manure used to boost crop and soil health is a growing concern. One question is whether manure produced from pastured livestock is superior to manure from confined animals.

Retired University of Nebraska soil scientist and crop nutritionist Charles Shapiro cautions that “‘better’ is a vague term with no scientific information,” making notions of improvement or betterment difficult to evaluate because personal preferences come to the fore.

The progressive farmer knows that some people gravitate toward unsupported generalities and that any manure assessment depends on measurable

parameters. That is, farmers are as ready as scientists to embrace empiricism in judging manures.

HAPPY MEDIUM

Kentucky organic farmer and stockman Lisa Munniksma frames her position in terms of manure management options.

Her four-stage process stands at the junction between old and new — a recurrent theme, because she advocates that modern farming return to a time when livestock roamed the pasture dropping dung at intervals to deliver optimal nutrients to the soil, neither depriving nor supersaturating it with organic compounds. In Munniksma’s vision, simplicity defines the best approach to improving and maintaining soil health.

Too little organic matter degrades croplands, dismaying farmers and policymakers alike. Soil without organic materials is little more than pulverized rock. Geologists and paleobotanists have demonstrated that no land plants grew during Earth’s early epochs due to a lack of organic matter. Eons passed before enough bacteria, yeasts and other microbes had decayed to provide the organic compounds necessary to nourish plants. Scientists call these microbial aggregates stromatolites; their decay yielded the organics suitable for absorption by plant roots,

although the first terrestrial plants might have lacked roots.

Aspen Grove Gardens owner Robert Pavlis warns that too much organic matter is a problem as well. It can skew soil pH and imbalance nutrients. Pavlis pinpoints manure as the most potent and easily overused organic soil amendment, calculating that annual additions can endanger soils by distorting the nitrogen and phosphorus ratio, altering soil pH for crops that tolerate only modest variations.

Changes in soil pH especially hurt legumes, whose roots house nitrifying bacteria that perish when too many or too few acids impair microbial metabolism. These problems plague an entire species, Phaseolus vulgaris. Vulgaris is the root of the English word “vulgar,” which just means “common.” But nothing is ordinary about this species because it contains most New World beans — the lima bean being a notable exception. Without P. vulgaris, global nutrition would arguably collapse. Even in food surplus nations like the United States, Walmart shelves would look barren without cans and jars of kidney (both red and white), great northern, pinto, black, navy, flageolet, cranberry and wax beans.

Many texts preach what might be termed force-feeding, recommending the addition of as much manure as can be hauled in during a day’s exertions.

This difficulty reinforces Munniksma’s position that soils need only moderate doses of manure to be healthy, an aim achieved by allowing livestock to roam while they eat and excrete.

Wherever livestock are confined, manure is produced. This requires stockmen to discard it, notes food and agriculture writer Tove Danovich, leading to excessive algae and bacteria in water, which in turn can cause human illnesses via infections such as E. coli.

University of Nebraska biological systems engineer Richard Koelsch adopts the chemical and nutritional perspective that manure’s ability to promote soil health and fertility depends on what livestock eat and on how well they derive nutrients from it.

Urine and feces are nothing more than what exits an animal after it has derived what nutrients it can from what it eats.

Pastured livestock may yield more organic matter in their dung because grasses (excluding feed grains like corn) are difficult to digest and because inefficient digestion yields more organic matter than efficient digestion.

Because confined livestock are fed the most nutrient-dense and easily digested food, they produce less organic matter.

Yet Parvis implies that nutritional density means too much phosphorus in the diet, with the surplus excreted. Scientists have long advocated the benefits of phosphorus in jumpstarting plant growth, but this advantage disappears when the mineral is in excess because plant roots depend on microbes to create salts from these minerals.

For example, if a mineral ionizes into a cation, a microbe then combines that cation with an anion in a process that yields a salt; but these microbes evolved in soils that did not have excess nutrients as salts. Too many nutrients kill these microbes. Bereft of these microbes, plant roots cannot absorb nutrients, and they starve.

Unconfined and confined livestock produce different manures, but Koelsch emphasizes that differences often relate to stress. Confinement taxes the health of many animals, with experiments demonstrating, for example, that rats attack one another when they are overcrowded.

“There will be differences in the manure from similar ruminants fed in a pasture-based system versus a confinement system,” said Koelsch. “However, I would think it would be hard to suggest the manure from one group is better than the manure from another.”

Koelsch emphasizes the need for good livestock management: attentive managers do their best to protect animals from mistreatment and crowd diseases. Inattentiveness heightens stress and diseases in the same way that inadequate planning usually yields poor results.

ANTIBIOTICS IN MANURE

According to a pair of new studies led by Dr. Diana Aga, professor of chemistry at the University at Buffalo, two of the most elite on-farm waste treatment systems available today do not fully remove antibiotics from manure.

Advanced anaerobic digestion and reverse osmosis filtration leave behind concerning levels of antibiotic residues, which can include both the drugs themselves and molecules that the drugs break down into.

In addition, the study uncovered new findings about solid excrement, which is often filtered out from raw, wet manure before the treatment technologies are implemented.

Researchers found that this solid matter may contain higher concentrations of antibiotics than unprocessed manure, a discovery that is particularly disturbing because solids are often released into the environment as animal bedding or sold as fertilizer.

“We were hoping that these advanced treatment technologies could remove antibiotics. As it turns out,

they were not as effective as we thought they could be,” said Aga.

She does offer some hope, however: “On the positive side, I think that a multistep process that also includes composting at the end of the system could significantly reduce the levels of antibiotics. Our earlier studies on poultry litter demonstrated that up to 70 percent reduction in antibiotics called ionophores can be achieved after 150 days of composting. Testing this hypothesis on dairy farm manure is the next phase of our project, and we are seeing some positive results.”

SHARING THE LOAD

Manure sharing connects farmers who have too much of the stuff with growers who want to use it to enrich their soils. Each grower can absorb only a fraction of the excess, so manure sharing is likely to remain one of many solutions. Several agricultural extension offices throughout the United States are expanding these programs, but these efforts have not eliminated the flow of manure’s potent chemicals into waterways and groundwater.

Local efforts harness the internet to promote manure sharing, but no nationwide program exists. Large livestock operations and farms in particular have trouble coordinating efforts. The problem of distance magnifies this difficulty because many farmers do not have time to maintain close ties with livestock managers hundreds of miles away. And without easy access to manure, farmers often turn to synthetic fertilizers.

A shift in thinking may help. Consider Brazil, where sugarcane has been an important crop since the Portuguese, Dutch and English scrambled to establish plantations there in the 16th and 17th centuries. Once the juices are extracted from a sugarcane stem, it becomes little more than waste to burn for electricity. The United States and other livestockproducing nations could employ a similar strategy by burning dried dung — sometimes known as “buffalo chips,” to evoke the prehistoric Native American practice of burning dried buffalo excrement to stoke fires — to generate electricity, possibly sparing fossil fuels from further depletion and humans from global climate woes.

IN PRACTICE

Montana beekeeper and chicken raiser Amy Grisak focuses less on debates than on practicality. Knowing firsthand the value of chickens and their droppings, Grisak lets them into her garden. As they move about, her chickens deposit droppings wherever they go.

These relatively uniform scatterings are valuable on their own because they give soils moderate amounts of nutrients, avoiding Pavlis’ warning of microbial death from toxicity. Her chickens multiply this benefit by scratching the ground, tilling their dung into the soil.

Rodale Institute Compost Production Specialist Rick Carr composts manure in all weather conditions. Even when temperatures are frigid, manure piles stay around 130°F and cure in only a few months. The resulting compost is available for spring applications.

These examples demonstrate

that elaborate technologies are often unnecessary — farmers and gardeners can implement low-tech solutions without much cost or effort.

Simple steps and a moderate approach let manure work for farmers. Moderation, long the watchword of success, is an approach that honors the Greek philosopher Aristotle, who counseled readers to seek the golden mean between excess and deficit. Moderation benefits farmers, consumers, the food supply, livestock, soils and the planet.

RESOURCES

University of Illinois Extension Manure Share: web.extension. illinois.edu/manureshare

Maryland Manure Matching Service: bit.ly/2l4OTqE Lisa Munniksma: freelancefarmerchick.com