The dirt on organic farming: it can harm the environment

Organic farming that uses only animal waste to fertilize can contaminate the soil with heavy metals such as cadmium, copper and lead, according to the studies

February 12, 1999
Web posted at: 11:30 AM EST

Organic farming may not be as good for the environment as it seems, according to the Netherlands Organization for Scientific Research.

Agricultural studies have found that some systems of ecological farming, which use only animal manure and compost as fertilizer, contaminate the soil with heavy metals such as cadmium, copper and lead.

Cadmium can be extremely dangerous if ingested or inhaled by humans.

Scientists from Wageningen Agricultural University have found that the levels of these metals are twice as high in ecologically farmed soil when compared with soil that is fertilized using a combination of manure and artificial fertilizer.

During the study, a scientific team calculated contamination levels by examining the difference between the soil makeup before and after precipitation, fertilization, leaching and uptake in crops. Certain indicators showed scientists when levels of metal exceeded the quality norms for soil, crops or groundwater. By looking at the input and output levels, the scientists are able to predict the future quality of the soil.

For example, they predict that conventional arable farming in the Netherlands will exceed the accepted norm for cadmium contamination within 70 years, while ecological arable farming -- crops fertilized only with compost and animal waste -- will exceed it in 145 years and integrating the two forms of farming will push it out 300 years.

Therefore, the scientists assert the most environmentally friendly farming technique is to use a combination of organic and artificial fertilizers on arable crops, but then allow the soil to rest between use -- such as integrating wheat fields with dairy farming. This will ultimately lead to less heavy metal contamination and a more sustainable system.

For more information, contact Dr. Simon Moolenaar, email: SWM@rotterdam.iwaco.nl.

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