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MOF&G Cover Summer 1999


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New Research on the Benefits of Organic Soils
Compost, Mulch and Microbes May Protect Strawberries

New Research on the Benefits of Organic Soils

Organic farming may be an even bigger part of the solution to global warming. In a study reported in the November 19, 1998, issue of Nature, the Rodale Institute reported on its 14-year comparison of organic with conventional cropping systems, focusing on “carbon sequestration.” Carbon sequestration is the ability of different soils to retain carbon. The more carbon that is captured by plants and retained in soils, the less carbon is available to contribute to carbon dioxide levels in the atmosphere. The study compared corn/soybean rotations in two organic cropping systems – one using manure and the other composted legumes for fertilizer – and a conventional system using pesticides and chemical fertilizer. While the economic profitability of all three systems was comparable over the past 10 years, the study found significant increases in soil carbon levels over the 14 years in both organic systems, with no significant increase in the conventional system.

Extrapolating the measured differences to a larger scale, the report concluded that if the major corn/soybean growing region in the United States adopted either of the organic cropping systems, soil carbon sequestration would increase by 0.13 to 0.30 x 1014 grams per year, which would be “equal to 1 to 2% of the estimated annual carbon released into the atmosphere from fossil fuel combustion in the USA.” (L.E. Drinkwater, et.al, “Legume-based cropping systems have reduced carbon and nitrogen losses,” Nature, Vol. 396, Nov. 19, 1998.) In the distant future, if national policy makers work seriously to reduce greenhouse gas emissions, this could conceivably mean money in organic farmers’ pockets.

A recent article in the journal of the American Agricultural Economics Association argues that farmers may benefit from the development of a market for carbon emissions, structured like the market for sulfur emissions created by the 1990 Clean Air Act Amendments. Under this market, polluters who find it too costly to reduce their emissions can pay others who can reduce emissions more efficiently. The authors speculate: “If a market evolves for greenhouse gas emissions, those who are now contributing to carbon emissions may be willing to pay others to sequester carbon (remove it from the atmosphere) as a permanent offset to emissions, or as a means of buying time to invest in technologies needed to reduce emissions.” Apparently unaware of the research at the Rodale Institute, the article focuses simply on added carbon sequestering that could be accomplished by adoption of best management practices by conventional farmers. The authors estimate that by adopting best management practices, farmers could sequester an additional 200 million metric tons of carbon per year and could “sell” those tons to polluters on an emissions market for “$4 to $6 billion/year, or up to 10 % of typical net farm income.” (R. Sandor and J. Skees, “Creating a Market for Carbon Emissions: Opportunities for U.S. Farmers, Choices, First Quarter 1999.)


Compost, Mulch and Microbes May Protect Strawberries

A special compost, a plastic mulch and beneficial microorganisms may be ingredients for the perfect recipe to protect strawberry fields from weeds and soil-borne diseases, Deputy Agriculture Secretary Richard Rominger says. Scientists with USDA’s Agricultural Research Service in Salinas, Calif., are testing the strategy’s potential as a replacement for some uses of methyl bromide. This chemical fumigant is being phased out in the United States. because it is thought to deplete Earth’s protective ozone layer.

“The experiments in California are part of USDA’s nationwide search for reliable, affordable substitutes for methyl bromide,” said Rominger in remarks to an agriculture workshop on the Food Quality Protection Act. “Strawberry growers are major users of the chemical and have relied on it for decades to keep plants free of pathogens …” Strawberry growers fumigate their fields with a mixture of methyl bromide and chloropicrin before planting. That fumigation kills soil-dwelling pathogens, such as those that cause verticillium wilt in strawberries. It also kills weed seeds.

ARS plant pathologist Carolee T. Bull is leading tests of a compost that is enhanced with enzymes, organic acids and beneficial bacteria. The compost is combined with corn gluten meal and beneficial fungi. She is doing the work at commercial strawberry fields and research plots in central California.

“The enzymes,” said Bull, “should speed decomposition of the compost, making nutrients available to beneficial microbes that we have applied to the fields. The beneficial bacteria that we are investigating may stimulate the plants’ defenses against pathogens,” she continued. “The fungi – known as mycorrhizae – help plants take up water and phosphorus from the soil.” The experiments will also determine whether weeds are quelled by beneficial microbes and corn gluten meal, a corn processing byproduct. The tests are part of a cooperative research and development agreement between ARS and Soil Technology, Fallbrook, California.

The average American eats about five pounds of strawberries per year. Strawberries are fat-free, low in calories and a source of vitamin C, folic acid, potassium and fiber. The fruit also is high in antioxidants that may protect cells from damage. California is this country’s top strawberry producer. The nation’s 1998 strawberry crop of 869,350 tons was worth more than $1 billion to growers.

Other ARS efforts to find methyl bromide alternatives include: In Kearneysville, W.Va., testing natural plant extracts such as benzaldehyde as soil fumigants and postharvest fumigants on produce; In Weslaco, Texas, protecting grapefruit from Mexican fruit fly and green mold, Penicillium digitatum, with refrigerated storage in ultra-low oxygen chambers; and in Charleston, S.C., breeding bell peppers such as ‘Charleston Belle’ and ‘Carolina Wonder’ that naturally resist the southern root-knot nematode Meloidogyne incognita, reducing the need for methyl bromide as a soil fumigant.

USDA Agricultural Research News Service; scientific contact: Carolee T. Bull, ARS Crop Improvement and Protection Research Unit, Salinas, Calif., phone (831) 755-2889, fax (831) 755-2814, CTBull@aol.com.



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