Opportunities in the Climate-Nitrogen-Food Connection

edavidson

President and Senior Scientist Dr. Eric A. Davidson

When you think of agriculture and climate change, you likely think of this summer’s crippling drought: dried corn stalks, thirsty cattle and rising food prices.

While the effects of climate on agriculture are clear, less well known is the great potential for agriculture to be a source for substantial climate solutions.

Agriculture is the nation’s largest source of nitrous oxide, a potent greenhouse gas. Each year, US farmers apply around 12 million metric tons of synthetic nitrogen fertilizer to crops. The problem is that only about half of the fertilizer that is applied is used by the crop, with the rest released to soil and water in the form of nitrate, and to the atmosphere in the forms of nitrous oxide and ammonia. This leads to harmful impacts, not just on our climate, but on air and water quality, human health and biodiversity.

What is the upside to this inefficient use of fertilizer? Real room for improvement. If current practices and technologies were applied, we could reduce nitrogen losses from farm and livestock operations by 30 to 50 percent. On October 23, leading soil and agricultural scientists shared their findings on solutions in a special session at the Soil Science Society of America’s conference in Cincinnati that I convened with Dr. Charles Rice, a soil scientist from Kansas State University. Among the highlights of the symposium, these experts noted that:

  • Managing fertilizer timing and optimizing fertilizer use is key to lowering nitrous oxide releases and reducing other forms of nitrogen pollution.
  • Planting cover crops in the winter between cash crops is a win-win for protecting water quality and the climate. As the climate warms, the regions where winter cover crops will be viable will expand. Cover crops also increase soil carbon.
  • Livestock management also offers solutions. For example, improved management of the amount of protein in animal feed will have the highest payback in terms of lowering nitrous oxide and ammonia emissions from manure. Livestock housing practices can also cut dairy barn ammonia emissions – which have an indirect effect on climate.

A largely unrecognized aspect of climate change and agriculture is how nitrogen pollution compounds climate change, and vice versa. This work draws from a new special report to the US National Climate Assessment published as a series of papers in the journal Biogeochemistry. WHRC Research Associate, Dr. Emma Suddick, and I coordinated this effort of over 30 scientists from many disciplines. Among its many findings, the report chapter by Dr. G. Phillip Robertson and colleagues demonstrates that the combination of climate change and nitrogen pollution can reduce agricultural productivity through higher ozone levels that decrease crop yields, causing billions of dollars of lost farm income. Floods, drought and heat will also make it harder to match crop needs with the right amount of fertilizer.

Most farmers want to avoid waste of expensive fertilizers and they want to be good stewards of their land, but more outreach and economic incentives are often needed for adoption of some of the most effective measures to increase the efficiency of fertilizer use and to avoid losses of nitrogen to the air and water. The technology exists – right now – to see substantial reductions of these losses. This would benefit farmers, and mean stronger, healthier food sources for us in our increasingly unpredictable growing seasons. The other benefits are substantial: safe drinking water, fewer algal blooms and fish kills in coastal waters, clean air, and slowing climate change.