I am trying to find a better way to budget liming cost.

I think it is correct that for every 1# of N we apply (and I don't think the source matters much) we will eventually have to apply the equivalent of 1.8# of CaCO₃ to neutralize it. So, if your lime's Effective Neutralizing Value (ENV) -- which I assume is the same as its Calcium Carbonate Equivalent, CCE -- is 90%, then for every pound on N applied, you can figure two pounds of lime.

So far, so good.

But what about soybeans? They fix their own N and, from what I gather, they only produce what they need. Even so, carbonates do leach so it seems like beans, which benefit from proper pH, should also reflect some of the lime cost. I'm sure it depends on texture, organic matter, and about ten other things, but is there a rule (or several rules) of thumb as to how much lime must be applied just to make up for leaching?

Aside from the chemical reaction with applied N and loss through carbonate leaching, are there other factors that lead to liming?