 "process paragraph : : Nitrogen-fixing bacteria convert atmospheric nitrogen to organic nitrogen. Plants absorb organic nitrogen from the soil through their roots. Animals eat the plants. Plants and animals die. Animals expel wastes. Fungi convert organic nitrogen to ammonium. Nitrifying bacteria convert ammonium to nitrate. Bacteria convert nitrate to nitrogen gas. Nitrogen gas escapes from soil into the atmosphere. ", "event : Plants absorb organic nitrogen from the soil through their roots.", "entity : atmospheric nitrogen" 
 not exist 