Ammonium nitrogen input increases the synthesis of anticarcinogenic compounds in broccoli
(PHYSorg.com Biology)

Plants need nitrogen to grow, and intensive agriculture requires the input of nitrogen compounds. However, classical, nitrate-based fertilization is responsible for considerable environmental problems, such as the contamination of surface and underground water due to nitrate leaching, and the emission of greenhouse gases, owing to the effect of the micro-organisms in the soil that use the nitrate and produce nitrous oxide, a significant greenhouse gas.