STANFORD, California, March 8, 2006 (ENS) - Organic farming has been promoted as an environmentally friendly alternative to conventional agriculture, and new research provides evidence to support that claim. Writing in the March 6 online edition of the Proceedings of the National Academy of Sciences (PNAS) , Stanford University graduate student Sasha 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 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," Mooney says. "This study shows that the use of organic versus chemical fertilizers can play a role in reducing these adverse effects."
The PNAS study was conducted in an established apple orchard on a four 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 were 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.
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.
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
"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 Reganold, Regents Professor of Soil Science at Washington State University and co-author of the study.
"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."
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 five and 10 percent of the total value.
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