JDUtah
09-15-2008, 12:01 PM
Hey guys, it's an agg article, but I think might apply. My family pointed me to it. I think it is something to take into consideration, but not discourage us...
Part of the article...
"Scientists have known since the 1920s that organic fertilizers used by farmers to supplement conventional systems—composted animal manure, rock phosphates, fish emulsions, guano, wood ashes, etc.—further contaminate topsoil with varying concentrations of heavy metals. Organic advocates, who rely exclusively on these fertilizers, remain well aware of the problem today, although they rarely publicize the point.
No one is saying that organic soil has higher heavy-metal counts than conventional soil as a rule—scientists have not conducted enough research to make such a determination. Still, some evidence indicates that organic soil can, in some cases, be more contaminated. George Kuepper, an agriculture specialist with the National Center for Appropriate Technology, observed in a 2003 report that composting manure actually concentrates the fertilizer's metal content, which could lead to greater levels of the contaminants in organic soil.
Recent studies have lent Kuepper's concern tentative support. For example, in 2007, researchers conducted an analysis of wheat grown on various farms in Belgium; based on the results, they estimate that consumers of organically grown wheat take in more than twice as much lead, slightly more cadmium, and nearly equivalent levels of mercury as consumers of wheat grown on conventional farms.
Beyond the comparative impact of organic vs. conventional systems on the soil's heavy-metal concentration, there's the question of how easily these trace elements enter crops. Although the research here is also relatively thin, what has been done suggests that the problem of plant uptake is equally serious in both organic and conventional systems. For example, 14 percent to 28 percent of New Zealand's cattle (destined to be organic beef) were found to have kidney cadmium levels exceeding limits set by the New Zealand Department of Health because of a diet of plants grown in contaminated soil. Similarly, a 2007 study of Greek produce found that organic agriculture does not necessarily reduce the cadmium and lead levels in crops. As it turned out, "certified" organic cereals, leafy greens, pulses, and alcoholic beverages had slightly less heavy-metal contamination than conventional products, but "uncertified" organic products had "far larger concentrations" than conventional ones.
These findings might be preliminary and inconsistent, but pressure is mounting on the organic community to take action. Under rules set by the USDA's National Organic Program, responsibility has been left to the individual farmer to manage plants and animals in a way that does not contaminate crops with heavy metals. The question of how to monitor that responsibility, however, is complicated by the fact that there are as yet no federal limits on heavy-metal concentrations applicable to all fertilizers.
Organic farmers thus work with broad suggestions rather than concrete federal regulations. They're routinely forewarned by organic watchdog groups such as the Organic Trade Association about dangerous levels of copper and arsenic in poultry manure. They're reminded of proper "nutrient management planning" and encouraged to experiment with the relationship between soil pH levels and rates of heavy-metal contamination. They're advised to test soil regularly for heavy metals and to adjust fertilizer combinations and relative nitrogen, phosphorous, and potassium levels in the soil when metal concentrations rise. A handful of states—California, Oregon, Washington, and Texas among them—have established loose legal guidelines. But the fact remains: The decentralized sprawl of information about fertilizers and heavy metals fosters a far-flung approach to the problem.
...
Fortunately, complete despair may still be avoided. Consider this: Plant biologists are working to genetically modify a fern plant that, when ashed and dusted on soil, is capable of sucking up zinc. The dust can then be gathered so the recovered zinc may be recycled and put to better use. Of course, in order for bioremedial technologies such as this to move forward, the dichotomy between organic and conventional agriculture will have to be collapsed, a sober view of organic agriculture will have to be adopted, and we'll have to read the banana leaves with greater skepticism. "
http://www.slate.com/id/2198756
Part of the article...
"Scientists have known since the 1920s that organic fertilizers used by farmers to supplement conventional systems—composted animal manure, rock phosphates, fish emulsions, guano, wood ashes, etc.—further contaminate topsoil with varying concentrations of heavy metals. Organic advocates, who rely exclusively on these fertilizers, remain well aware of the problem today, although they rarely publicize the point.
No one is saying that organic soil has higher heavy-metal counts than conventional soil as a rule—scientists have not conducted enough research to make such a determination. Still, some evidence indicates that organic soil can, in some cases, be more contaminated. George Kuepper, an agriculture specialist with the National Center for Appropriate Technology, observed in a 2003 report that composting manure actually concentrates the fertilizer's metal content, which could lead to greater levels of the contaminants in organic soil.
Recent studies have lent Kuepper's concern tentative support. For example, in 2007, researchers conducted an analysis of wheat grown on various farms in Belgium; based on the results, they estimate that consumers of organically grown wheat take in more than twice as much lead, slightly more cadmium, and nearly equivalent levels of mercury as consumers of wheat grown on conventional farms.
Beyond the comparative impact of organic vs. conventional systems on the soil's heavy-metal concentration, there's the question of how easily these trace elements enter crops. Although the research here is also relatively thin, what has been done suggests that the problem of plant uptake is equally serious in both organic and conventional systems. For example, 14 percent to 28 percent of New Zealand's cattle (destined to be organic beef) were found to have kidney cadmium levels exceeding limits set by the New Zealand Department of Health because of a diet of plants grown in contaminated soil. Similarly, a 2007 study of Greek produce found that organic agriculture does not necessarily reduce the cadmium and lead levels in crops. As it turned out, "certified" organic cereals, leafy greens, pulses, and alcoholic beverages had slightly less heavy-metal contamination than conventional products, but "uncertified" organic products had "far larger concentrations" than conventional ones.
These findings might be preliminary and inconsistent, but pressure is mounting on the organic community to take action. Under rules set by the USDA's National Organic Program, responsibility has been left to the individual farmer to manage plants and animals in a way that does not contaminate crops with heavy metals. The question of how to monitor that responsibility, however, is complicated by the fact that there are as yet no federal limits on heavy-metal concentrations applicable to all fertilizers.
Organic farmers thus work with broad suggestions rather than concrete federal regulations. They're routinely forewarned by organic watchdog groups such as the Organic Trade Association about dangerous levels of copper and arsenic in poultry manure. They're reminded of proper "nutrient management planning" and encouraged to experiment with the relationship between soil pH levels and rates of heavy-metal contamination. They're advised to test soil regularly for heavy metals and to adjust fertilizer combinations and relative nitrogen, phosphorous, and potassium levels in the soil when metal concentrations rise. A handful of states—California, Oregon, Washington, and Texas among them—have established loose legal guidelines. But the fact remains: The decentralized sprawl of information about fertilizers and heavy metals fosters a far-flung approach to the problem.
...
Fortunately, complete despair may still be avoided. Consider this: Plant biologists are working to genetically modify a fern plant that, when ashed and dusted on soil, is capable of sucking up zinc. The dust can then be gathered so the recovered zinc may be recycled and put to better use. Of course, in order for bioremedial technologies such as this to move forward, the dichotomy between organic and conventional agriculture will have to be collapsed, a sober view of organic agriculture will have to be adopted, and we'll have to read the banana leaves with greater skepticism. "
http://www.slate.com/id/2198756