N2O rise linked to increased fertilizer use

Berkeley, Calif. — Scientists at University of California Berkeley are now saying that air samples from a Tasmania station show that increased fertilizer use over the past 50 years is responsible for a dramatic rise in nitrous oxide (N2O), which as a major greenhouse gas contributes to global warming. The new study, based on data from the Cape Grim Baseline Air Pollution Station located in remote northwestern Tasmania and reported in the April issue of the journal Nature Geoscience, uses nitrogen isotope data to identify what it called the unmistakable fingerprint of fertilizer use in archived air samples from Antarctica and Tasmania. The fertilizer industry responded that any such findings need to be balanced by the tremendous gains in efficiency, in which, for example, farmers in the U.S. are growing 87 percent more corn than in 1980 using four percent fewer nutrients. Through use of 4R nutrient stewardship similar efficiencies are being realized in developing agricultural systems around the world, according to The Fertilizer Institute (TFI). UC Berkley research principals insisted they are not trying to vilify fertilizer. “We can’t just stop using fertilizer,” stated study leader Kristie Boering, a professor of chemistry and earth and planetary science. “But we hope this study will contribute to changes in fertilizer use and agricultural practices that will help to mitigate the release of nitrous oxide into the atmosphere.” Boering explained that the study is the first to show empirically from the data at hand alone the nitrogen isotope ratio in the atmosphere and how it has changed over time, coinciding with increases in fertilizer use. The findings point to a rise of 20 percent in nitrous oxide levels since 1750, from below 270 parts per billion (ppb) to more than 320 ppb. The study identified a steep ramp-up in atmospheric nitrous oxide coinciding with the green revolution that increased dramatically in the 1960s, when inexpensive synthetic fertilizer and other developments boosted food production worldwide, feeding a burgeoning global population. In the meantime, TFI pointed out, N2O emissions in the U.S. have decreased since 1960, while global emissions since 1990 have increased slightly. On the positive side, many developing countries have lowered their N2O emissions in the period between 1990 and 2008.