OREGON STATE UNIVERSITY

SHOULD IT BE COWS PER ACRE OR ACRES PER COW?

08/09/1996

CORVALLIS - If you're a researcher studying it, you'll be the lonely person at dinner parties. If you're a dairy farmer, it's both a potential economic windfall and a knee-deep disposal problem.

Whatever your perspective on manure, it is piling up at alarming rates and it isn't going to go away.

Back when everyone had just a few cows, manure wasn't a problem, but with concentration of the dairy industry, it has become more of an issue.

In recent decades there has been a fundamental shift from acres per cow to cows per acre, explained John Hart, a soil scientist with the Oregon State University Extension Service.

"Maximum efficiency and production have tended to put more cows on fewer acres," Hart said. "But is this sustainable if you are producing more manure than you can properly dispose of? If one cow can fertilize 1.5 acres and you have five cows per acre, manure is going to start piling up pretty fast."

Two years ago Hart and several other OSU researchers started working with about 20 Oregon dairy farmers to assess the nitrogen fertilizer needs of their silage corn. "The plan was to save them money and to reduce the possibility of nitrogen leaching into the ground water," said Hart.

"We found that few of the sites we studied needed added fertilizer," he noted. "Our immediate advice was, 'If you are buying fertilizer, stop. If you are spreading manure, do so more carefully.'"

Spreading too much manure year after year can build residual nitrogen that can leach into the ground water. Excess nutrient may also affect the health of the dairy herd, explained Hart.

The good news, for many dairy farmers, is that Hart and his colleagues discovered that all the farmers' fertilization needs could be met by spreading the manure that was piling up in their barns and storage lagoons. Using manure to fertilize crops, instead of using commercially purchased fertilizer, now saves some of them as much as $10,000 a year, according to Hart.

This is how it works: A 1,400-pound cow producing 70 pounds of milk per day also produces about 160 pounds of manure. Even with today's low fertilizer prices (30 cent a pound for nitrogen and less for phosphorus and potassium), 100 lactating dairy cows can produce $10,000 worth of fertilizer in a year.

In many cases, this leaves farmers with manure they can sell to farmers growing other crops, or to other industries. But it took a while to convince dairy farmers that manure was a commodity and not just a waste product - that dairy cows aren't just milk producers, they are nutrient producers.

And creating markets for manure was a challenge, but there are success stories, Hart said.

Some dairy farmers have formed alliances with neighboring farmers. Also, some dairy cow manure is going to nurseries. There are some more exotic projects such as using manure in methane generators to create fuel.

For the average dairy, manure is still a disposal issue for the foreseeable future, according to Hart. But there is reason for hope.

"One of the things Oregon agriculture has going for it is diversity," said Ernie Marx, a graduate assistant who works with Hart. "There isn't a large concentration of dairies or any other single type of agriculture in one area. This may help dairy farmers find buyers or at least takers for their manure."

Ideally, Hart said, a farmer would like to cycle nutrients so that as much goes back into the land as comes out. Only about 15-25 percent of the nutrients in the feed dairy cows consume ends up leaving the farm in the milk. The rest is in manure.

"In the long run though, there is no easy way to just make it all go away. We may need to start re-evaluating what we consider success in the dairy industry," Hart said.

Oregon has about 90,000 dairy cows on 500 farms, according to Mike Gamroth, OSU Extension Service dairy specialist. They produce about $240 million a year in raw milk.

Major dairy areas include Tillamook, Klamath, Coos, Malheur, Marion, Polk, Clackamas, Benton, Yamhill, Washington, Linn and Lane counties.