(Beyond Pesticides, December 1, 2011) Ongoing research at the U.S. Department of Agriculture’s (USDA) Sustainable Agricultural Systems Lab (SASL) finds that organic grain production reduces greenhouse gas emissions relative to chemical-intensive no-till and chisel-plow production systems. In fact, the research concludes that the organic system removes more greenhouse gases from the atmosphere than it contributes, while the other systems result in net increases. The results are based on data from comparable three-year crop rotations maintained for each production system at the Lab’s farm in Beltsville, MD under the direction of Michel Cavigelli, PhD. The rotations mirror typical commercial grain production operations in the mid-Atlantic region that begin with corn followed by a rye grass cover crop, rotate to soybeans and winter wheat in the second year, and conclude with a legume crop. Dr. Cavigelli’s team identified the substantial energy savings achieved in the organic system by using natural fertility sources, especially for nitrogen, as the critical factor in reducing its overall impact on climate change.
Previous research shows that carbon dioxide and nitrous oxide are the two most potent greenhouse gases that are produced and released as a consequence of crop production. It is also known that, due to its specific molecular properties, nitrous oxide is approximately three hundred times more powerful than an equivalent amount of carbon dioxide. The USDA research calculated how much carbon dioxide was gained or lost by measuring changes in soil organic matter and also measured the nitrogen added for crop consumption that instead escaped as nitrous oxide. Combining this data with standardized figures for the energy expended (and therefore carbon dioxide released through fuel consumption) to operate each system —the number of tractor passes, for example— provided a snapshot of their respective contributions to climate change.
Although the results find that organic systems are more management intensive than no-till systems and those additional tractor passes require excess and expensive energy, diesel fuel is only one component of the overall energy needed to operate the system. The energy expended to fix synthetic nitrogen actually far exceeds that used to operate machinery and accounts for an astonishing 30% of the total energy consumed by agriculture. Despite going back into the field multiple times to control weeds, resulting in nearly three times as much energy for machinery in organic corn than in no-till corn that incorporates two herbicide applications, the total energy costs in organic systems are less. While the no-till system which used herbicide-tolerant genetically modified seeds was twice as efficient with machinery energy as the chisel plow system, overall energy costs for the synthetic fertilizers applied in both the no-till and chisel till systems is greater than the total energy consumption of the organic system which utilizes poultry litter and cover crops.
Looking at what goes on within the soil itself, the research substantiated a tenet of conventional wisdom: organically managed soils are the best for adding organic matter. This is a vital process for mitigating climate change since it removes carbon dioxide from the atmosphere and stores it in stable organic compounds that enhance the soil’s agronomic productivity. The no-till system outperformed the organic system at increasing organic matter very near the surface but such increases can be quickly lost once the soil is disturbed. By contrast, the organic system generated greater increases in organic matter further below the surface and a significantly greater total accumulation. Use of the chisel plow results in even further degradation of soil organic matter, turning a potential sink of a greenhouse gas into a source. Beyond Pesticides maintains an extensive list of resources assessing organic agriculture’s potential to mitigate global climate change on our Environmental Benefits of Organic agriculture webpage.
Dr. Cavigelli points out that agricultural research like agricultural production is site-specific and that no single experiment can capture the variety and complexity of the farming systems used around the globe. However, his work provides compelling evidence that two key principles —increasing the organic matter content in soils and cutting the amount of fossil fuel used in agriculture— offer tremendous potential to protect future generations of life on Earth and even redress some of the damage that human beings have already inflicted. Recognizing that organic systems may yield less than their conventional counterparts (as was the case in Beltsville), Dr. Cavigelli weighted the results to reflect the respective productivity. The conclusion did not change: bushel for bushel for corn, soybean and wheat, the organic system was superior at reducing greenhouse gas emissions.
Video presentations of Dr. Cavigelli’s research on global climate change and other results from the long-term cropping systems trials conducted at Beltsville are available at the eXtension organic homepage. This site offers an extensive collection of video and print resources addressing organic crop and livestock production, certification requirements and marketing strategies and an events calendar. The site also provides expert responses to inquiries about organic agriculture and offers a monthly e-newsletter.
The U.N.’s Climate Change Conference currently underway in Durban, South Africa is the continuation of nearly two decades of negotiations by governments and private sector organizations from around the world to limit average global temperature increases and cope with the unavoidable impacts already underway. In its most recent findings from 2007, the U.N’s International Panel on Climate Change (IPCC) concluded that “It is virtually certain that increases in the frequency of warm daily temperature extremes and decreases in cold extremes will occur throughout the 21st century on a global scale.” The IPCC also concludes that, “It is very likely””90 per cent to 100 per cent probability””that heat waves will increase in length, frequency, and/or intensity over most land areas.” The 2007 report attributed 10 to 12% of the greenhouse gas emissions caused by human activity to agriculture and cautioned that increased utilization of synthetic nitrogen sources and destruction of biomass would lead to a future spikes in such emissions.
Beyond Pesticides actively supports conversion to organic production for the multiple environmental, human health and economic benefits it offers. In addition to its potential to mitigate and even reverse the effects of climate change, organic agriculture can conserve natural resources including soil, water and biodiversity while matching or exceeding the productivity of conventional production systems. To learn more, visit Beyond Pesticides’ page on organic food and agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.