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Modern farming has helped to make food cheaper, seems simple enough and seems like a good thing. Turns out, though, it might be bad for the environment. Take the case of one simple, essential chemical element: phosphorus. When poultry and pork are produced on large scale, it concentrates phosphorus on nearby fields and pollutes streams and rivers.
If we fix this problem, it could end up making inexpensive food a little more expensive, as NPR's Dan Charles reports.
DAN CHARLES, BYLINE: Phosphorus is one of the nutrients that plants need to grow. And for most of human history, farmers have needed more of it.
KENNETH STAVER: There was this battle to have enough available phosphorus for optimum crop production.
CHARLES: That's Kenneth Staver, a scientist with the University of Maryland's Wye Research and Education Center, which sits between farm fields and the Chesapeake Bay. That's also the tension in this story: between agriculture and water quality.
Traditionally, farmers got phosphorus from animal manure. So, if you grew crops like corn or wheat, it was good to have poultry or hogs nearby. Your grain fed the animals, and their manure fed your crops. Everything worked together. Then came industrial fertilizer, big phosphorus mines, also factories for making the other important nutrient, nitrogen, and railroads or highways to carry that fertilizer to any farmer who needed it.
STAVER: With the development of the inorganic fertilizer industry, it's possible to grow grain without having any animals close by. So you can de-couple the animal agriculture from the grain agriculture.
CHARLES: And de-couple they did. Georgia, Arkansas and Alabama, for instance, now produce the most chickens - together, more than three billion birds every year. But they don't grow that much chicken feed. They haul in grain from far away. As that grain flows from fields to chicken houses or hog farms, so do the nutrients in it - the phosphorus and nitrogen. Some goes into meat that people eat, but a lot goes into animal waste - manure.
And here's where the problem starts: Farmers near those chicken houses or hog farms often take a lot of that manure and spread it on their fields. Their crops can often use the nitrogen, but nowhere near that much phosphorus.
STAVER: And this is happening everywhere. Where you have large concentrations of animal production you tend to have a buildup of nutrients. Primarily phosphorus is the one that accumulates in soils around concentrated animal-producing regions.
CHARLES: Wherever it accumulates, it washes into streams, lakes and estuaries, where it's a disaster. It drives the growth of algae.
STAVER: So it ends up clouding the water. You don't get the light penetration to support the rooted aquatic plants that were important in the food chain. You also get these big algae blooms, and then when they die, they draw oxygen from the water. You get dead zones.
CHARLES: In many places, environmental regulators are trying to stop this buildup of phosphorus. Until recently, it looked like Maryland was taking the lead. The state has a big poultry industry right beside the Chesapeake Bay, which has been choked with nutrient pollution. Last year, Maryland proposed new rules that would have stopped farmers from putting more phosphorus on any fields that already have too much of it. It required soil tests to determine a key phosphorus index number.
Farmer Lee Richardson was worried.
LEE RICHARDSON: The word we were getting was that if you were over 150, you weren't going to spread any manure.
CHARLES: And most of his fields are over that level, he says.
The manure ban would have hit him two different ways. First, he grows chickens. If he couldn't put their manure on his fields, he'd have to send it somewhere else.
RICHARDSON: Chances are growers were going to have to pay to get it hauled away and taken out of their chicken house.
CHARLES: And second, his corn fields still need nitrogen. If he couldn't get from manure, he'd have to buy the manufactured kind of fertilizer. Richardson and other farmers protested, arguing that the new rules would inflict huge economic harm to achieve uncertain environmental benefits.
Late last year, the State of Maryland backed down. It promised to study the issue some more. Kenneth Staver, from the University of Maryland, says it's not that hard to imagine a solution to the problem.
STAVER: The obvious one is find a way to redistribute the phosphorus from the animal production facilities, back to where the crop production is.
CHARLES: Back to fields that farmers are still fertilizing with fresh, mined phosphorus.
Hauling manure such distances would cost money. Staver says that's the price of cleaner, healthier water. If farmers have to pay it, growing chickens or hogs would get more expensive. And then we'd pay for it through more expensive meat.
Dan Charles, NPR News.