SOIL CARBON AND CLIMATE CHANGE NEWS
From Kansas State University's:
Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS)
Charles W. Rice, K-State Department of Agronomy, National CASMGS Director
(785) 532-7217 firstname.lastname@example.org
Scott Staggenborg, K-State Department of Agronomy (785) 532-7214 email@example.com
Steve Watson, CASMGS Communications (785) 532-7105 firstname.lastname@example.org
July 2, 2010
* Enhanced-efficiency fertilizers as mitigation options for N2O and NO emissions from agriculture
* High-yield agriculture slows pace of global warming
* Climate change complicates plant diseases of the future
Enhanced-efficiency fertilizers as mitigation options
for N2O and NO emissions from agriculturE
Agricultural fields are an important anthropogenic source of atmospheric nitrous oxide (N2O) and nitric oxide (NO). Although many field studies have tested the effectiveness of possible mitigation options on N2O and NO emissions, the effectiveness of each option varies across sites due to environmental factors and field management. In a recent article in the journal Global Change Biology, Hiroko Akiyama, of the National Institute for Agro-Environmental Sciences in Japan, and co-authors combined these results and evaluated the overall effectiveness of enhanced-efficiency fertilizers (nitrification inhibitors, polymer-coated fertilizers, and urease inhibitors) on N2O and NO emissions. They performed a meta-analysis using field experiment data (113 datasets from 35 studies) published in peer-reviewed journals through 2008.
The results indicated that nitrification inhibitors significantly reduced N2O emissions compared with those of conventional fertilizers. Polymer-coated fertilizers also significantly reduced N2O emissions, whereas urease inhibitors were not effective in reducing N2O. Nitrification inhibitors and polymer-coated fertilizers also significantly reduced NO.
The effectiveness of nitrification inhibitors was relatively consistent across the various types of inhibitors and land uses. However, the effect of polymer-coated fertilizers showed contrasting results across soil and land-use type. They were significantly effective for imperfectly drained Gleysol grassland, but were ineffective for well-drained Andosol upland fields. Because available data for polymer-coated fertilizers were dominated by certain regions and soil types, additional data are needed to evaluate their effectiveness more reliably.
Nitrification inhibitors were effective in reducing N2O emission from both chemical and organic fertilizers. Moreover, the consistent effect of nitrification inhibitors indicates that they are potent mitigation options for N2O and NO emissions.
-- Steve Watson, CASMGS Communications
Slows Pace of Global Warming
Investment in agricultural research is rarely mentioned as a greenhouse gas (GHG) mitigation strategy. In a study published in a recent edition of The Proceedings of the National Academy of Sciences, Jennifer A. Burney and co-authors estimate the net effect on GHG emissions of historical agricultural intensification between 1961 and 2005.
“We find that while emissions from factors such as fertilizer production and application have increased, the net effect of higher yields has avoided emissions of up to 161 gigatons of carbon (GtC) (590 GtCO2e) since 1961. We estimate that each dollar invested in agricultural yields has resulted in 68 fewer kgC (249 kgCO2e) emissions relative to 1961 technology ($14.74/tC, or ∼$4/tCO2e), avoiding 3.6 GtC (13.1 GtCO2e) per year. Our analysis indicates that investment in yield improvements compares favorably with other commonly proposed mitigation strategies. Further yield improvements should therefore be prominent among efforts to reduce future GHG emissions.”
The researchers estimate that if not for increased yields, additional greenhouse gas emissions from clearing land for farming would have been equal to as much as a third of the world's total output of greenhouse gases since the dawn of the Industrial Revolution in 1850.
The researchers also calculated that for every dollar spent on agricultural research and development since 1961, emissions of the three principal greenhouse gases -- methane, nitrous oxide and carbon dioxide -- were reduced by the equivalent of about a quarter of a ton of carbon dioxide -- a high rate of financial return compared to other approaches to reducing the gases.
"Our results dispel the notion that modern intensive agriculture is inherently worse for the environment than a more 'old-fashioned' way of doing things," said Burney.
-- Proceedings of the National Academy of Sciences, June 29, 2010
Climate Change Complicates
Plant Diseases of the Future
Human-driven changes in the Earth's atmospheric composition are likely to alter plant disease in the future, according to a recent article in the journal Global Change Biology by Darin Eastburn, University of Illinois. Eastburn and his co-authors evaluated the effects of elevated carbon dioxide (CO2) and ozone (O3) on three economically important soybean diseases (downy mildew, Septoria brown spot and sudden death syndrome) under natural field conditions at the soybean free air concentration enrichment (SoyFACE) facility at the University of Illinois.
Disease incidence and/or severity were quantified from 2005 to 2007 using visual surveys and digital image analysis.
Elevated carbon dioxide levels are more likely to have a direct effect on plant diseases through changes to the plant hosts rather than the plant pathogens.
"Plants growing in a high carbon dioxide environment tend to grow faster and larger, and they have denser canopies," Eastburn said. "These dense plant canopies favor the development of some diseases because the low light levels and reduced air circulation allow higher relative humidity levels to develop, and this promotes the growth and sporulation of many plant pathogens."
At the same time, plants grown in high carbon dioxide environments also close their stomata, pores in the leaves that allow the plant to take in carbon dioxide and release oxygen, more often. Because plant pathogens often enter the plant through the stomata, the more frequent closing of the stomata may help prevent some pathogens from getting into the plant.
In elevated ozone, plant growth is inhibited and results in shorter plants with less dense canopies. This can slow the growth and reproduction of certain pathogens. However, ozone also damages plant tissues that can help pathogens infect the plant more easily.
"Elevated levels of carbon dioxide and ozone can make a plant more susceptible to some diseases, but less susceptible to others," Eastburn said. "This is exactly what we've observed in our climate change experiments."
He believes rising temperatures and changes in rainfall patterns will also affect development of plant disease epidemics.
"In some cases, changes of only a few degrees have allowed plant diseases to become established earlier in the season, resulting in more severe disease epidemics," Eastburn said. "The ranges of some diseases are expanding as rising temperatures are allowing pathogens to overwinter in regions that were previously too cold for them."
For example, warmer winters may allow kudzu to expand its range northward. Because kudzu is an alternate host for the soybean rust pathogen, one result of rising temperatures may be that soybean rust arrives in Illinois earlier in the soybean growing season, Eastburn said.
"Information derived from climate change studies will help us prepare for the changes ahead by knowing which diseases are most likely to become more problematic," he said. "Now is the time for plant pathologists, plant breeders, agronomists and horticulturalists to adapt disease management strategies to the changing environment."
-- ScienceDaily, June 26, 2010
MEETINGS OF INTEREST
August 29-September 3, 2010
The 9th International NCCR Climate Summer School
Adaptation and Mitigation: Responses to Climate Change
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