Lockout happens at low pH. Plants don't take up carbon through the root system of course, thats through the stomata in the leaves they get CO2. The carbon in the root system is only for consumption by microbes which work to mineralize the nitrogen into plant available forms.
I would check out Purdue Agronomy for more information. The carbon is more important when considering soil amendments and how they will break down not soil as a whole.
I would check out Purdue Agronomy for more information. The carbon is more important when considering soil amendments and how they will break down not soil as a whole.