Earth Science News  





. New Study Confirms The Ecological Virtues Of Organic Farming

Organic in... nitrogen out...
by Staff Writers
Stanford CA (SPX) Mar 07, 2006
Organic farming has long been touted as an environmentally friendly alternative to conventional agriculture. A new study in the Proceedings of the National Academy of Sciences (PNAS) provides strong evidence to support that claim.

Writing in the March 6 online edition of PNAS, Stanford University graduate student Sasha B. Kramer and her colleagues found that fertilizing apple trees with synthetic chemicals produced more adverse environmental effects than feeding them with organic manure or alfalfa.

"The intensification of agricultural production over the past 60 years and the subsequent increase in global nitrogen inputs have resulted in substantial nitrogen pollution and ecological damage," Kramer and her colleagues write. "The primary source of nitrogen pollution comes from nitrogen-based agricultural fertilizers, whose use is forecasted to double or almost triple by 2050."

Nitrogen compounds from fertilizer can enter the atmosphere and contribute to global warming, adds Harold A. Mooney, the Paul S. Achilles Professor of Environmental Biology at Stanford and co-author of the study.

"Nitrogen compounds also enter our watersheds and have effects quite distant from the fields in which they are applied, as for example in contaminating water tables and causing biological dead zones at the mouths of major rivers," he says. "This study shows that the use of organic versus chemical fertilizers can play a role in reducing these adverse effects."

Nitrogen Treatments

The PNAS study was conducted in an established apple orchard on a 4-acre site in the Yakima Valley of central Washington, one of the premiere apple-growing regions in the United States. Some trees used in the experiment had been raised with conventional synthetic fertilizers. Others were grown organically without pesticides, herbicides or artificial fertilization. A third group was raised by a method called integrated farming, which combines organic and conventional agricultural techniques.

"Conventional agriculture has made tremendous improvements in crop yield but at large costs to the environment," the authors write. "In response to environmental concerns, organic agriculture has become an increasingly popular option."

During the yearlong experiment, organically grown trees were fed either composted chicken manure or alfalfa meal, while conventionally raised plants were given calcium nitrate, a synthetic fertilizer widely used by commercial apple growers. Trees raised using the integrated system were given a blend of equal parts chicken manure and calcium nitrate.

Each tree was fertilized twice, in October and May, and given the same amount of nitrogen at both feedings no matter what the source--alfalfa, chicken manure, calcium nitrate or the manure/calcium nitrate blend.

Groundwater Contamination

One goal of the PNAS experiment was to compare how much excess nitrogen leached into the soil using the four fertilizer treatments--one conventional, two organic (manure and alfalfa) and one integrated. When applied to the soil, nitrogen fertilizers release or break down into nitrates--chemical compounds that plants need to build proteins. However, excess nitrates can percolate through the soil and contaminate surface and groundwater supplies.

Besides having detrimental impacts on aquatic life, high nitrate levels in drinking water can cause serious illness in humans, particularly small children. According to the PNAS study, nearly one of 10 domestic wells in the United States sampled between 1993 and 2000 had nitrate concentrations that exceeded the EPA's drinking water standards.

To measure nitrate levels during the experiment, water was collected in resin bags buried about 40 inches below the trees and then analyzed in the laboratory. The results were dramatic. "We measured nitrate leaching over an entire year and found that it was 4.4 to 5.6 times higher in the conventional treatment than in the two organic treatments, with the integrated treatment in between," says John B. Reganold, Regents Professor of Soil Science at Washington State University and co-author of the study.

Nitrogen gas emissions

The research team also compared the amount of nitrogen gas that was released into the atmosphere by the four treatments. Air samples collected in the orchard after the fall and spring fertilizations revealed that organic and integrated soils emitted larger quantities of an environmentally benign gas called dinitrogen (N2), than soils treated with conventional synthetic fertilizer. One explanation for this disparity is that the organic and integrated soils contained active concentrations of denitrifying bacteria--naturally occurring microbes that convert excess nitrates in the soil into N2 gas. However, denitrifier microbial communities were much smaller and far less active and efficient in conventionally treated soils.

The research team also measured emissions of nitrous oxide (N2O)--a potent greenhouse gas that's 300 times more effective at heating the atmosphere than carbon dioxide gas, the leading cause of global warming. The results showed that nitrous oxide emissions were similar among the four treatments.

"We found that higher gas emissions from organic and integrated soils do not result in increased production of harmful nitrous oxide but rather enhanced emission of non-detrimental dinitrogen (N2)," Reganold says. "These results demonstrate that organic and integrated fertilization practices support more active and efficient denitrifier microbial communities, which may shift some of the potential nitrate leaching losses in the soil into harmless dinitrogen gas losses in the atmosphere."

Sustainable Agriculture

Washington State produces more than half of the nation's apples. In 2004, the state crop was worth about $963 million, with organically grown apples representing between 5 and 10 percent of the total value. But the results of the PNAS study may apply to other high-valued crops as well, according to the authors.

"This study is an important contribution to the debate surrounding the sustainability of organic agriculture, one of the most contentious topics in agricultural science worldwide," Reganold says. "Our findings not only score another beneficial point for organic agriculture but give credibility to the middle-ground approach of integrated farming, which uses both organic and conventional nitrogen fertilizers and other practices. It is this middle-ground approach that we may see more farmers adopting than even the rapidly growing organic approach."

Adds Mooney, "Organic farming cannot provide for all of our food needs, but it is certainly one important tool for use in our striving for sustainable agricultural systems. We need to explore and utilize all possible agricultural management techniques and technologies to reduce the very large global footprint of the needs to feed a population of over six billion people."

Other co-authors of the PNAS study are agroecologist Jerry D. Glover of The Land Institute in Salina, Ks., and Brendan J. M. Bohannan, associate professor of biological sciences at Stanford.

Related Links
Stanford University
USDA National Organic Program
The Land Institute

Japanese Researchers Extract Vanilla From Cow Dung
Tokyo (AFP) Mar 06, 2006
Japanese researchers have succeeded in making the sweet smell of vanilla come out of the last thing people could imagine -- cow dung. In a world-first recycling project, a one-hour heating and pressuring process allows cow feces to produce vanillin, the main component of the vanilla-bean extract, according to researcher Mayu Yamamoto.

.
Get Our Free Newsletters Via Email
  



  • Study Finds Californians Unmotivated To Prepare For Next Disaster
  • The Future Of Foreign Assistance
  • High Post-Hurricane Rents Push People Out Of New Orleans
  • White House Demands Whirlwind Changes To Hurricane Response

  • WFP Warns Of "Large Scale" Deaths In Kenyan Drought Crisis
  • IODP Scientists Acquire 'Treasure Trove' Of Climate Records Off Tahiti Coast
  • Massive Ancient Flood Linked To Climate Change
  • Fossil Wood Gives Vital Clues To Ancient Climates

  • Satellites Ensure Safe Passage Through Treacherous Waters In Ocean Race
  • ESA Satellite Program Monitors Dangerous Ocean Eddies
  • Envisat Marks Fours Year In ESA Mission To Planet Earth
  • Boeing To Process Radar Data From Endeavour

  • Researchers Find Ways Heat-Loving Microbes Release Energy
  • Progress In Hydrogen Fuel Quest
  • Advance Hastens Practicality Of Superconductivity
  • Critics Plan Court Case Against Russian Pipeline Across Asia

  • Crippling Indian Ocean Epidemic Detected in France
  • People of African Descent More Vulnerable to TB
  • Americans Downplay Widespread Outbreak Of Avian Flu In Next Year
  • Learning To Love Bacteria

  • Plants Eavesdrop For Their Own Protection
  • Smallest Triceratops Skull Described
  • Timing Helps Hummingbirds Know When They Are At Last Flower
  • Mass Migration Of Mormon Crickets Driven By Hunger, Fear

  • Pesticides In The Nation's Streams And Ground Water
  • Czechs, Slovaks Agree To Cooperate Against German Waste Dumping
  • Megacity Pollution Scrutinized During Mexico City Field Campaign
  • Suez Tanker Spill Damage At 12 Million Dollars

  • World's Oldest Ship Timbers Found In Egyptian Desert
  • Archaeologists To Establish True Value Of Roman Silver Coins
  • A New Awakening For Sleep Research
  • Evidence For Altruistic Behaviours In Human Infants And Chimpanzees

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement