Question

Which of the following helps to maintain the current level of nitrogen in earth's atmosphere ?

Answer 1

Human activities cause increased nitrogen deposition in a variety of ways, including

burning of both fossil fuels and forests, which releases nitrogen into the atmosphere
fertilizing crops with nitrogen-based fertilizers, which then enter the soil and water
ranching, during which livestock waste releases ammonia into the soil and water
allowing sewage and septic tanks to leach into streams, rivers, and groundwater