Agriculture's Nitrogen Fix

by Natasha Chart

categories: Livestock, Organic, Policy, Pollution, Soil

Published August 19, 2009 @ 01:43PM PT

Everybody involved in mainstream agriculture wants a piece of the glory for increased yields over the last half century, but the share of credit that's left over after irrigation and heterozygous, conventional hybrids goes mainly to a plant nutrient: nitrogen.

In 1918, Dr. Fritz Haber figured out a way to use natural gas and heat do something only bacteria had ever been able to manage, which was to turn inert atmospheric nitrogen into solid nitrogen compounds that are available to the terrestrial food chain. This process, whether performed in a lab or by a bacterium, is referred to as nitrogen fixation.

Atmospheric nitrogen, which exists mainly in the form of N₂, is an extremely stable compound, non-reactive in almost all cases. N₂ makes up around 70 percent of the atmosphere and acts as an effective fire retardant. If there were much more oxygen gas and much less nitrogen gas in the atmosphere, the entire atmosphere could ignite.

Terrestrial nitrogen, existing in many forms, is one of the most important nutrients available to living beings. It's the backbone of all RNA, DNA and protein. It's referred to in some cases as a limiting nutrient, one that puts a fixed limit to the growth potential of an ecosystem's biomass. It can also be referred to, in agriculture and horticulture as a macronutrient, something necessary in large amounts relative to other trace or micronutrients.

Nitrogen, phosphorus and potassium, and the greatest of these is nitrogen. As they might say.

Though one can have too much of any good thing. For example, the use of synthetic nitrogen fertilizer is likely the culprit in high levels of carcinogenic nitrates in conventionally grown food, as noted by Tom Philpott at Grist. As Philpott also points out, nitrates have also been linked to Alzheimer's, Parkinson's and Type II diabetes.

Type II diabetes, you might have noticed, is gleefully blamed on Americans' bad habits. Those with more knowledge of agricultural policy might tend to blame it on corn (syrup) subsidies. If one is acquainted with the usual bad outcomes of corporate city planning, it could be laid on the lack of decent grocery stores in many low-income areas, both urban and rural.

Though what if situational diabetes were also the fault of basic inputs to synthetic agriculture?

Nor would that be the only problem with the synthetic nitrogen we've become dependent on. As noted in this Scientific American article regarding the global warming impacts of corn-based biofuels, the nitrogen oxides put into the atmosphere by synthetic fertilizer have nearly 300 times the greenhouse effect of carbon dioxide. Though the same is true of any corn crop, which wastes much of its applied nitrates in leaching, and to a slightly lesser extent, any heavily fertilized industrial crop.

The nitrogen that isn't absorbed into a healthy soil food web and doesn't form planet-cooking gases then leaches into waterways, eventually to the sea. In freshwater and marine environments, this nutrient excess, or eutrophication, spurs outrageous growth of microorganisms that rapidly exhaust the oxygen dissolved in the water. Fish die, shellfish die, everything that can't swim away fast enough dies, as we have discussed before.

And while it's bad enough that the nitrogen we use to feed ourselves has unwanted side effects and is seriously harming the planet's ability to support life, there are a lot of other demands for the natural gas used to create it, even as that resource approaches its peak as surely as peak oil is coming. Some are predicting famine and scrambling for alternative nitrate sources, which doesn't really solve the environmental and health pollution problems.

Neither would merely replacing our currently imperiled nitrate supplies have the long-term benefits of manure fertilization, which last for many years, as opposed to sticking around for only the year of application as synthetic nitrates tend to do. And a fully organic agriculture with manure and leguminous cover crops as nitrogen sources not only produces high yields in multi-year trials, but they increase the soil's ability to retain nitrogen in the soil food web and boosts disease resistance in crop ecosystems.

(Also it'd be nice if the poultry litter that goes into cattle feed were instead repurposed as fertilizer. Doesn't that seem more reasonable, less disgusting?)

Better yet, organic agriculture offers a UN-verified yield boon to the world's poorest farmers, such as smallholders in Africa, who can't afford the necessary capital for synthetic agricultural practices and manufactured nitrates. Armed only with knowledge and livestock (speaking of which, The Heifer Foundation could use your help getting healthy livestock and veterinary support to farmers in need,) developing nations could use organic farming methods to feed themselves and make their land drought resistant. These benefits, also, will not accrue from either making synthetic nitrates more widely available or manufacturing them without the use of natural gas.

In short, there's a way out of this fix. A non-destructive, planet-healing way out, and no one has to starve for it.

(Photo credit: Image Editor on Flickr.)