Fertilizer runoff causes toxic algal blooms. This one covered a third of Lake Erie in 2011. © Peter Essick/National Geographic hide caption toggle caption © Peter Essick/National Geographic The Salt Fertilizer Shows Its Deadly Side April 19, 2013 This week's explosion at the West Fertilizer Co. plant in Texas reminds us of the "cursed" side of the nitrogen that powers most of agriculture around the world. Through habit or necessity, we've come to depend on it. But there are costs.