Had the United States signed the Kyoto Protocol, it could have met all of its greenhouse gas reduction commitments simply by shifting to organic agriculture.
That is one finding from a long-running agronomic experiment comparing organic and conventional cropping systems.
Researchers at Pennsylvania’s Rodale Institute said organic agriculture could be one of the most powerful tools in the fight against global warming.
A complete metamorphosis from conventional to organic farming would reduce annual carbon emissions by about seven percent from 1990 levels, which is the amount targeted for the United States under Kyoto.
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“Besides being a significant underutilized carbon sink, organic systems use about one-third less fossil fuel energy than that used in the conventional cropping systems,” said the executive summary of the recently released report.
Rodale is a research firm that promotes the benefits of organic agriculture. Since 1981 it has been comparing a conventional corn-soybean cropping system with a manure-based organic system and a legume-based organic system.
Research director Paul Hepperly said there is a significant carbon sequestration difference between the two methods of farming.
“It builds up more conclusively in the organic systems than in the conventional corn and soybean system.”
Between 1981 and 2002, the manure-based organic research plots increased soil carbon by an average of 1,019 pounds per acre foot of soil per year. The legume-based system returned 594 lb. per acre foot and the conventional system about half that amount.
The report stated the difference can be attributed to different decay rates of soil organic matter under the two management systems.
“In the conventional system, the application of soluble nitrogen fertilizers stimulates more rapid and complete decay of organic matter, sending carbon into the atmosphere instead of retaining it in the soil as the organic systems do.”
Organic agriculture also leaves more nitrogen in the soil. While conventional systems at the institute lost 1.9 lb. of soil nitrogen per acre foot, the legume-based system gained 43.8 lb. and the manure system twice that amount.
In addition to socking away more carbon and nitrogen, organic production methods require 37 percent fewer energy inputs than conventional corn-soybean production, which is the dominant crop rotation employed by American farmers.
About two-thirds of the energy used by the conventional system is in the form of nitrogen fertilizer input. Another 10 percent is attributed to herbicides.
While organic farmers use more energy seeding their crops, they more than make up for that with what they don’t do.
“Organic systems use neither synthetic ammoniated fertilizer for corn nor herbicides on corn or soybeans,” the report said.
