New Research About The Productivity of Ancient Boreal Flood Plains May Offer Clues for Reducing Fertilizer in Modern Crop Production
What made floodplains fertile during the beginning of human agriculture in the Earth’s far north? A study published in the journal PLOS ONE in its November 6, 2013 issue argues it was not flooding that delivered nutrients, but rather cyanobacteria carrying out nitrogen fixation.
According to a University of Washington news story about the article:
Excerpt: Discovering that cyanobacteria in the floodplains were responsible for nitrogen fixation – that is taking it from the atmosphere and “fixing” it into a form plants can use – partially resolves the scientific debate of how humans harvested grasses there for hundreds of years without fertilizing…. It raises the question of whether farmers today might reduce fertilizer use by taking advantage of cyanobacteria that occur, not just in the floodplains studied, but in soils around the world…
The amount of nitrogen provided by the cyanobacteria to unharvested willows and sedges is perhaps a quarter of what U.S. farmers in the Midwest apply in industrial fertilizers to grain crops and as little as a sixth of what they apply to corn.
Human-made fertilizers can be fuel-intensive to produce and use, for example, it takes the energy of about a gallon of diesel to produce 4 pounds of nitrogen fertilizer. In developing countries in particular, nitrogen fertilization rates are spiraling upward, driving up fossil-fuel consumption… Meanwhile, cyanobacteria naturally occurring in farm soils aren’t fixing nitrogen at all in the presence of all that fertilizer, they just don’t expend the energy when nitrogen is so readily available…
Although modest in comparison to modern fertilization, the observation that cyanobacteria could drive the productivity of these boreal floodplain systems so effectively for so long makes one question whether cyanobacteria could be used to maintain the productivity of agricultural systems, without large synthetic nitrogen fertilizer inputs….
The findings of the PLOS ONE study might also lead to more accurate modeling of nitrogen in river systems.