You’ve surely seen the headlines.

In recent years, the carbon footprint of livestock production has received a fair amount of criticism from environmentalists, journalists and even legislators. Some consumers have cited it as a reason for eliminating meat from their diets.

As the environmental implications of “cow flatulence” (as it is labeled in its most euphemistic form) are debated, contested and dismissed by consumers, it’s important for us to take a critical look at livestock and its position within the natural and renewable cycle of agriculture.

And the truth is, without livestock, the cyclical nature of the ag industry is not a closed loop.

Farmers are, by nature, stewards of the environment. For the sake of their land’s productivity, as well as the safety and livelihood of current and future generations, they must prioritize consumers and stewardship of the land, finding as many ways as possible to increase efficiency and minimize waste. And the best way to minimize waste? Find it a purpose.

Livestock manure not only provides key nutrients to growing crops, but it also builds up the organic matter in topsoil over time, lending it both structure and fertility.

Dr. Amy Schmidt is a livestock bioenvironmental engineer at the University of Nebraska-Lincoln. Her research, education and outreach appointments center around the environmental impact of livestock and – more specifically – manure management.

“My kids just call me a poopologist,” she joked. “Or a turd nerd.”

According to Dr. Schmidt, agricultural efficiencies have increased greatly over the past few decades. Farmers are producing the same amount of meat, milk and grains using less water, less energy and shorter amounts of time.

Livestock manure is a source of nitrogen and phosphorus, two nutrients essential for growing corn. It also adds carbon to the soil structure.

[From the Ground Up: Sustainable agriculture starts with soil]

Manure breaks down at a very slow rate. Instead of providing the plant with a lot of nutrients quickly, the way commercial fertilizers do, manure provides plants with smaller amounts of nitrogen and phosphorous, while continuously adding carbon to the soil over a period of up to three years.

This slow break-down process and added soil fertility are the real benefits to manure application, says Dr. Richard (Rick) Koelsch, a colleague of Dr. Schmidt’s in the University of Nebraska-Lincoln’s Department of Biological Systems Engineering.

“The carbon in manure is very beneficial for the health of the soil and the soil quality,” said Dr. Koelsch. “Applied at appropriate rates, it can actually reduce some of the water quality risks associated with adding fertility to soils.”

The rate of application is important. Applying too much of either at one time poses a risk to any nearby ground or surface water sources, should the soil begin to erode. Dr. Schmidt notes that, in terms of environmental impact, manure often gets a worse rap with the public than inorganic fertilizers do.

“It gets a worse image than inorganic fertilizer partly because people know when manure is being land applied,” she said.

The reason for that isn’t exactly rocket science.

“They smell it.”

By contrast, for many people, it doesn’t register when inorganic fertilizers are being applied.

“I don’t ever see manure completely replacing inorganic fertilizer, but the two together I think give the best fertility management plan for a system,” said Dr. Schmidt. “You’re building the soil, but you’re also meeting the needs of the crop at various points throughout the growing season.”

Dr. Schmidt and Dr. Koelsch both agree that rather than endangering the environment, proper manure management has a positive effect on the ozone layer.

Livestock manure sequesters carbon inside the soil system, in turn, reducing agriculture’s contribution to greenhouse gas emissions.

As the nutrients in manure improve the fertility of soil over time, the crops being grown in that soil system will benefit in the long run – and as healthier, heartier crops are produced each year, their roots will help build a stronger soil structure.

Protecting the cyclical relationship between livestock, crops, soil and the atmosphere is a big job – but it’s the key to sustaining agriculture and feeding the world’s growing population. That’s why farmers will continue to do it for generations to come.

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