Well, if we could fix even a fraction of the Nitrogen, we could support a lot more plant life, that’s for sure! Oxygen is very reactive, Nitrogen, not so much. I don’t think the lack of Nitrogen would be very noticeable even if it dropped by half.

If atmospheric nitrogen dropped by half, I'd imagine the effects would be pretty significant for aircraft, birds & internal combustion engines. Rocket launches would become more efficient (less drag), but reentry would be more challenging, w/ less overall drag & proportionally more oxidizing effect when aero-braking

Most engines would probably run hotter & weaker w/out as much nitrogen to use as a working fluid (maybe we'd compensate for this w/ water injection & get even better performance though?)

The speed of sound would decease slightly, while the speed needed to generate lift at a given altitude would increase. This would definitely affect airplanes, e.g. a plane that can cruise at 15k feet but not 30k feet might not be able to reach 15k feet anymore

Nitrogen is 77% of the atmosphere by weight.

For reference at 1 mile is Denver Colorado (which while researching is enough to cause altitude sickness) with 18% less atmosphere. Water boils at 200° F.

If half the nitrogen was gone (38.5% of atmosphere), sea level world be equivalent to ~15,000 feet today) water would now boil at ~194.3° F.

Mostly Nitrogen does not constrain growth in natural ecosystems. There are plenty of plants that fix nitrogen already, and nitrogen fixing plants would dominate an ecosystem if Nitrogen were a primary constraint on growth. There is plenty of Nitrogen available from the air - the main restriction is energy - the second restriction is that plants prefer to use most of their available energy on other things.

Nitrogen is important in fertilizer because our farming and agriculture is not a natural ecosystem.

> There are plenty of plants that fix nitrogen already, and nitrogen fixing plants would dominate an ecosystem if Nitrogen were a primary constraint on growth.

No plants can fix nitrogen. Hence this research?

You said this with such confidence I had to look this up, because I am quite familiar with the types of plants referred to as “nitrogen fixing plants” such as legumes. But here’s the answer for anyone else curious:

“Nitrogen fixing plants don't pull nitrogen from the air on their own. They actually need help from a common bacteria called Rhizobium. The bacteria infects legume plants such as peas and beans and uses the plant to help it draw nitrogen from the air. The bacteria converts this nitrogen gas and stores it in the roots of the plant.”

https://www.gardeningknowhow.com/garden-how-to/soil-fertiliz...

Thanks! Appreciate the reference. :)

> No plants can fix nitrogen

Plants fix nitrogen in common parlance but you are technically correct: I sincerely hope that your scientific pedantry works out better for you than it has for me (I won't delve into that topic further).

"Please respond to the strongest plausible interpretation of what someone says".

The research was specifically about introducing nitrogen-fixing organelles into plants because they have none. Precision is valuable since this was in direct contradiction to the original topic. Maybe common parlance is better-suited to a thread on vegetable gardening than microbiology.

What would replace it? I'd expect a thinner atmosphere.

I'd expect the lack of anything that it is made to react with.

There have been several PhD theses on trying to fix nitrogen to grow wheat in the dessert. To my knowledge none have been successful.