But he says many parts of the world use too much nitrogen fertilizer, and that harms the environment.

VOA: special.2011.04.05

Scientists at the agroforestry center say the use of fertilizer trees can reduce the need for chemical nitrogen by up to three-fourths.

VOA: special.2009.09.01

Phosphorous from detergents often contaminates urban stormwater, while nitrogen comes primarily from fertilizer use in agricultural areas.

VOA: standard.2010.08.04