A recent policy discussion in the journal Science compared the nutrient balances of different agriculture systems.

VOA: special.2009.07.28

Iron is a vital nutrient, but too much iron can be harmful.

VOA: standard.2010.08.05

According to Ben Urbonas, president of the Urban Watersheds Research Institute, these nutrient contaminants tend to be more of a problem in closed water systems,like lakes, where concentrations can build up.

VOA: standard.2010.08.04