I've been studying soil and the Nitrogen cycle, as a Master Gardener, so that I am better able to advocate for soil care and regeneration.
My education was not science, so it has been and is a challenge for me to understand the chemistry.
Here is a link to several webinars posted by the Organic Farming Research Foundation, narrated by Dr Mark Shonbeck:
https://eorganic.org/node/27448
Dr Shonbeck has a wonderful ability to take these complex concepts and present them in a way that I can understand (or at least begin to understand) them.
I recommend scrolling down the page to "Soil Biology for the Western Region: Organic Practices to Recruit and Nurture Beneficial Biota in the Soil" and to "Breeding New Cultivars for Soil-enhancing Organic Cropping Systems in the Western Region".
Here's my primitive understanding of the N cycle in the soil:
Atmosphere is 78% N in the form of Nitrogen gas, N2. This is a very stable form of nitrogen, not easily transformed. Only lightening, certain
nitrifying soil bacteria, and the Haber-Bosch process (which is very energy intensive, and polluting) can transform this form of N into plant available forms. Once in the soil, the N forms are more
labile, or dynamic, and get taken up and transformed by the soil organisms, and plant roots. Soil fauna hold N in their bodies
(immobilize) until their body is taken in by some other organism, which releases the N in its excretions to a plant available form (nitrate or ammonium). Anaerobic conditions are suitable for other bacteria to release it to the atmosphere as
nitrous oxide, a potent greenhouse gas, several hundred times more potent than
CO2. There are also aerobic
denitrifying bacteria that convert N back to the stable gas N2, and release it back into the atmosphere.
Excess nitrogen is either released back into the atmosphere or leached through the groundwater, which leads to dead zones in our waterways. About 50% of agriculturally applied N is wasted in the US, which means it becomes a pollutant. Synthetic N is bad news for soil biology and our atmosphere and hydrosphere. It tends to create acidic soil conditions, and what seems even worse to me, excess N in the soil causes the plant–microbe mutual relationship to diminish.
Plants overfed N (and other nutrients) loose the ability to partner with beneficial microbes (including fungi) in the soil.
In the webinar about breeding cultivars for organic production, Dr Shonbeck explains this.
Here's another article which is part 1 of 2 on explaining the N cycle, part 2 describes the human impact on disrupting the N cycle.
https://climateandcapitalism.com/2019/04/18/nitrogen-crisis-a-neglected-threat-earths-life-support-systems/