Dr. Paul's Research Perspectives
Maintaining the big "O"
Recent research demonstrates how organic farming systems build organic matter and soil fertility over the long haul

By Paul Hepperly

Editors' note:
As New Farm Research and Training Manager at The Rodale Institute, Dr. Paul Hepperly has been a regular contributor to NewFarm.org for some time, providing research updates, op-ed pieces, and white papers on topics like carbon sequestration in organic farming systems.

None of those venues do full justice to the range of Paul's experience, however. Paul grew up on a family farm in Illinois and holds a Ph.D. in plant pathology, an M.S. in agronomy and a B.S. in psychology from the University of Illinois at Champaign-Urbana. He has worked for the USDA Agricultural Research Service, in academia, and for a number of private seed companies, including Asgrow, Pioneer, and DeKalb. He has overseen research in Hawaii, Iowa, Puerto Rico, and Chile, and investigated such diverse crops as soybeans, corn, sorghum, sunflowers, ginger, and papaya. He has witnessed the move toward biotech among the traditional plant breeding community and the move toward organics among new wave of upcoming young farmers. Beford coming to the Rodale Institute Paul worked with hill farmers in India to help them overcome problems with ginger root rot in collaboration with Winrock International.

Now we've decided to give Paul his own column, in which he can report on agricultural research from around the world and reflect on its relevance to The Rodale Institute's research program and to the progress of sustainable agriculture more generally in light of his own broad perspective. Enjoy.

November 19, 2004: The Organic Farming Research Foundation in Santa Cruz, California, has been supporting organic farming by funding grants for research and education projects since 1994. In their most recent Information Bulletin (Fall 2004, no. 14), they feature an article entitled "Long-term Organic Farming Impacts on Soil Fertility," by Professor Jessica Davis of Colorado State University. This OFRF-funded project took a look at Grant Family Farms, the largest organic mixed-crop farm in Colorado. The researchers focused on the transformation of soil fertility under organic farming management, following 12 fields in 3, five-year periods from 1985 to 2000.

To assess the impact of transitioning to organic in these fields, soil acidity, electroconductivity, organic matter, phosphorus, potassium, zinc, iron, manganese, copper and nitrates were measured. Under organic management, fields received cover crop green manure as well as periodic dairy manure applications. With the exception of this study, there are few long-term studies of organic farming in the semi-arid climates of eastern Colorado and the Great Plains.

Conventional and organic practices were contrasted in one case in the same field under conventional management from 1972 to 1979 and after transition to organic from 1985 to 2000. Under conventional production, soil pH increased from 8.1 to 8.3, while organic matter fell from 2.6 to 1.5 percent. Phosphorus was at very low levels (1 lb/ac or less) and potassium shrank from 226 to 154 lbs/acre. Zinc, manganese and copper were also low and diminishing from 1972 to 1979.

Under organic management from 1985 to 2000, however, soil pH fell from 8.2 to 7.9 while organic matter rose from 2.3 to 3.0 percent. These changes were associated with large increases in phosphorus, potassium, zinc, iron, manganese, and copper. At the same time, nitrate nitrogen did not increase in organic production in this or any of the test fields.

Increasing soil organic matter is crucially important to improving the chemistry of the soils. Jessica Davis and her co-workers had hypothesized that equilibrium would occur and soil fertility improvements would stagnate. However, her experimental evidence did not support this contention, for 30 years of soil building under organic agriculture did not show any evidence of decreasing soil fertility improvement.

Because organic farming locks carbon in the soil, it is a vital tool in moderating runaway greenhouse gases. The doubling of soil organic matter from 1.5 to 3.0 percent in this carefully monitored before and after case study underscores the magnitude of this potential.

Despite persistent voices suggesting that soil improvement and organic management has limited scope for moderating environmental conditions, hard data like these point to a different conclusion.

With this in mind, we prefer to view soil building not as a limited process and soil as a limited resource, but rather as a dynamic and resilient entity with the ability to grow and expand under appropriate biological action, management, and genesis.

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