Nitrogen Research

Nitrogen Dilemma - Synthetic Nitrogen Destroys Soil Health

Here is an excerpt from the paper, of the first few paragraphs:

For all of its ecological baggage, synthetic nitrogen does one good deed for the environment: it helps build carbon in soil. At least, that's what scientists have assumed for decades.

 

If that were true, it would count as a major environmental benefit of synthetic N use. At a time of climate chaos and ever-growing global greenhouse gas emissions, anything that helps vast swaths of farmland sponge up carbon would be a stabilizing force. Moreover, carbon-rich soils store nutrients and have the potential to remain fertile over time–a boon for future generations.

 

The case for synthetic N as a climate stabilizer goes like this. Dousing farm fields with synthetic nitrogen makes plants grow bigger and faster. As plants grow, they pull carbon dioxide from the air. Some of the plant is harvested as crop, but the rest–the residue–stays in the field and ultimately becomes soil. In this way, some of the carbon gobbled up by those N-enhanced plants stays in the ground and out of the atmosphere.

 

Well, that logic has come under fierce challenge from a team of University of Illinois researchers led by professors Richard Mulvaney, Saeed Khan, and Tim Ellsworth. In two recent papers (see here and here) the trio argues that the net effect of synthetic nitrogen use is to reduce soil's organic matter content. Why? Because, they posit, nitrogen fertilizer stimulates soil microbes, which feast on organic matter. Over time, the impact of this enhanced microbial appetite outweighs the benefits of more crop residues. And their analysis gets more alarming. Synthetic nitrogen use, they argue, creates a kind of treadmill effect. As organic matter dissipates, soil's ability to store organic nitrogen declines. . . .

Experimental fields where testing took place.

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