Economists, environmentalists, and farmers may all give different answers to the question posed in the title. However, a recent 17-year study by Pioneer suggests that, for corn grown in rotation with soybeans, the answer may be a "a lot less than we thought".
The NPK with a soil “test” method is so incredibly corporate, agrabusiness sales driven.
Do you have a PhD in maintaining the dominant planet killing toxic paradigm. You certainly don’t know anything about agriculture if you are lending this antiquated industrial reliant model legitimacy.