UGA Scientists find heavy metals may be locked out of crops with organic compounds

ATHENS, Ga. — Large quantities of copper are used in farming, horticulture and animal industries as ingredients in fungicides and as a growth promoter in pig and poultry farming. Some soils are enriched with compounds containing copper. Vineyards and citrus orchards use copper-containing fungicides, as do those interested in organic farming. The use of copper in these ways is effective, but may result in high levels of copper in the soil. This can be toxic to plants and microbial communities and can present a hazard to grazing animals.

Inactivating the copper in the soil — without removing the soil itself — has been the topic of study for scientists from the University of Georgia’s Savannah River Ecology Laboratory and others. In a paper published recently by Environmental Toxicology and Chemistry, scientists Nanthi Bolan, Domy Adriano, Senniappan Mani and Afiqur Khan tested the effect of biosolids on copper in soil.

In the research, five different manure composts were applied to greenhouse-grown mustard plants. The plants were then harvested, dried and tested for copper uptake. The results indicated that such applications were helpful in reducing plant toxicity, especially in plants growing in soils with heavier loads of copper.

Unlike organic contaminants, most heavy metals do not undergo biological or chemical degradation and may remain in the soil for a long time after their introduction. However, the movement of heavy metals in the soil and their availability for plant uptake can be minimized by such technologies as biological immobilization. The results from this study show that organic manures that are low in metal content acted as a sink to sequester the copper in the soil, which kept the copper out of the plants.

Binding copper and other heavy metals to organic composts can lead to more diverse land use in many parts of the world struggling with contaminated fields. In addition, this technology may be helpful in cleaning up environmental waste sites.