The problem of too much nitrogen

Penelope Whitney had a nice post at Civil Eats yesterday under the headline “Miracle Gro Gone Wild.” She writes,

Scientists have been leading a clarion call about the impacts of excess nitrogen for decades, but the issue remains little known, even though the impacts touch every part of our lives.

At the root of the problem is this: about half the chemical fertilizer applied to boost the growth of crops is not taken up by the plant– essentially adding unwanted, unneeded fertilizer to our natural systems with disastrous results. Think of it as a shape-shifting Miracle Gro monster run amok. Waste from livestock operations also creates nitrates that affect drinking water safety, and ammonia, which is disastrous for air quality.

She offers a number of reading suggestions to info-packed, high-quality publications from National Geographic, The Ecological Society of America, the EPA Science Advisory Board, and more. For the links, check out Whitney’s full post here.

As a teaser, here’s a brief excerpt of the EPA report (pp. 25-26):

While animal production has been increasing since World War II , this report emphasizes the period from 1970 to 2006. The production of chicken broilers increased more than four fold from 1970 to 2006 (Figure 10 [see below]) and milk production increased by nearly 60% in this time period…. Turkey production doubled and pork production increased about 25%, while meat from cattle (beef and dairy) remained constant (Figure 10)….

Another trend in animal agriculture has been the increased size and smaller number of animal operations, which results from the mechanization of agricultural practices and increased specialization. There were only 7% as many swine operations and 11% as many dairy operations in 2006 as there were in 1970 (Figure 13). There were half as many beef operations in 2006 as in 1970, but beef operations also expanded in size while smaller producers held jobs off the farm.

All of these trends show an increase in management and labor efficiency to produce a similar or greater amount of animal products. Also, because animal production is more concentrated on fewer farms with greater specialization, fewer crops are produced on those farms. As a result, it is increasingly common to have more manure nutrients produced on a livestock farm than can be used efficiently as fertilizer for crops on that farm. Therefore, unless the manure is applied over a larger crop area, the resulting over-application of manure on the livestock farm can reduce the subsequent efficiency of its utilization and result in greater nutrient losses.

That’s science-speak for “too many animals in one place make too much manure to be of use to farmers at or near where the animals are raised.”

From Reactive Nitrogen in the United States: An Analysis of Inputs, Flows, Consequences, and Management Options - A Report of the Science Advisory Board

From EPA report SAB-11-013, Reactive Nitrogen in the United States: An Analysis of Inputs, Flows, Consequences, and Management Options – A Report of the Science Advisory Board


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