19. Which of the below is NOT a human intervention in the nitrogen cycle?
1. Nitrous oxide is added to the atmosphere through the action of bacteria on livestock waste
2. Large amounts of nitrogen are released into the atmosphere as forests are cleared
3.
Large amounts of nitrates are added to the Chesapeake Bay, causing a eutrophic dead
zone
4.
Specialized bacteria convert ammonia into nitrate and then into nitrogen gas, reducing
nitrogen available to plants
