Studies on the presence of heavy metals in fertilizers conducted by Iowa State faculty are the subject of increased attention after a national report about the topic.

Contrary to previous findings, the wastes found in Iowa’s farmland are actually good for the soil, said Karen Bolluyt, agriculture informationalist.

Last week, the Environmental Working Group released a report detailing the problems of using industrial wastes in fertilizers.

Heavy metals are a concern because plants can intake them from the soil, and they could end up in human diets, according to a press release.

“In three studies we’ve conducted, we haven’t found levels in Iowa that are a concern,” said Ali Tabatabai, professor of agronomy. “Most Iowa soils, especially calcareous soils, provide protection because they tie up trace metals so they can’t move into plants.”

Tabatabai’s studies are just a few of the contributions he has made in a national effort to assess the trace metal problem.

He also is the Iowa representative of a regional project group that addresses issues such as plants’ susceptibility to heavy metals in wastes and chemistry of those metals. Tabatabai said the group works closely with the Environmental Protection Agency.

In 1992, Tabatabai analyzed 100 commercial fertilizer samples provided by the Iowa Department of Agriculture and Land Stewardship. He found that levels of heavy metals (cadmium, chromium, nickel, lead, copper and zinc) varied significantly among the fertilizers.

“But those levels are not of public health concern,” he said. “Most of the heavy metals were present at concentrations below those found naturally in agricultural soils.”

He noted that Iowa’s fertilizer law does not require testing fertilizers for the presence of trace metals.

Tabatabai said some national reports have masked important differences between the chemistry of heavy metals in waste materials and fertilizers.

“The chemical action of sewage sludge applied to land differs from the chemistry of fertilizers in soils,” he said. “Efforts to address public health concerns should take these differences into account.”