Here is the thing. When you make a batch of say1/3 peat, compost and whatever it is going to be a fairly low pH...it is going to be well short on base cations. For example you are going to need 7 lbs or so of Ca...so like 17.5 lbs of caco3.
When you chuck that in the soil it does not immediately break down into ions and exchange for H on the cec sites. You are going to have free lime in your mix until microbes break it down. And that takes interaction with the plant...it can take up to 3 grows in the case of caco3.
So if you chuck and measure you are not gonna get an accurate reading at all. You are fooling yourself. That is why it is better to get the soil test before amending...at least you know the starting point. Even worse with the paste test...until you get microbe activity you are always gonna measure low
Least that is how I see it
When you chuck that in the soil it does not immediately break down into ions and exchange for H on the cec sites. You are going to have free lime in your mix until microbes break it down. And that takes interaction with the plant...it can take up to 3 grows in the case of caco3.
So if you chuck and measure you are not gonna get an accurate reading at all. You are fooling yourself. That is why it is better to get the soil test before amending...at least you know the starting point. Even worse with the paste test...until you get microbe activity you are always gonna measure low
Least that is how I see it