Which of the following would be one way a farmer could increase the amount of available nitrogen in his fields without adding a synthetic fertilizer?

One way a farmer could increase the amount of available nitrogen in his fields without adding synthetic fertilizer would be to grow a legume crop to support the development of root nodules.  

The soviet union beat the us to the first successful launch, with the october 4, 1957, orbiting of sputnik 1, and later beat the us to have the first human in earth orbit, yuri gagarin, on april 12, 1961. the "race" peaked with the july 20, 1969, us landing of the first humans on the moon with apollo 11

Iwould say overuse ( but not 100% sure ) in the u.s. we tend to overuse water by leaving it running, throwing it away, taking long showers, etc.