Ok, so there are a few concepts here I wanted to expand upon. I will add some photos of my soil block set up as well as seedlings started in them in the coming days.
I was working yesterday and today with some soil of a slightly heavier type clay then what I have used in the past and I should point out that the ratio of sifted compost/worm castings and sand to soil along with lime will very depending on the type of soil you will be using as your base, so everyone will be a bit different.
For example, the soil I sterilized on Friday and used yesterday and today was quite heavy, a lot of organic matter, but quite a bit of clay base as well, in that case I used about 3:1 ration of castings to soil and quite a bit more sand as well, the sand is probably not necesary in the blocks but I use it basically as a way to amend the soil in the fields and loosen it some which it could certainly use.
I also failed to mention that when it is available I also make use of activated charcoal (bio-char/terra pretta concept) in the potting/blocking mix. I charge it using urine and break it into nearly dust sized particles and use it as about 3-5% of the base. As you all well know from my past research into terra pretta and your subsequent research this could most certainly have a great effect on the growth of the plant and longevity of the base NPK levels of the blocks which don't tend to need further fertilization until planting out (at which time I water seedlings in with worm casting tea)
Another concept I wanted to bring tot he forefront is the La Bonne Terre corn and high nitrogen crops fertilizer that I make use of.
I have access to literally a few hundred lbs of cofee grounds sans filters every year and thus it makes a great nitrogen base for corn and other high nitrogen crops. The concept is the same as before mostly, the cofee grounds become the base to which is added worm castings, lime, sand (for bulking and ease of spread) and sifted thermophilic poultry compost and wood ash for P. I should point out that for those with access to cofee grounds that used cofee grounds are almost always the exact same Nitrogen as composted chicken litter at 2.9-3.5 or so, if you keep them moist and don't let them dry down (1.5-2.0 for dry matter) they will actually be higher nitrogen than composted poultry litter and are usually free to the clever taker eager enough to aske a cofee house proprieter if they can have them! Of course to this I also add diatomacious earth. All of these fertilizers are either placed in the bottom of the planting hole for seedlings or seeds and covered with a quarter to half inch of soil (promoting root growth) or in the case of corn they are layed in the trench at a depth of 1-2 inches thick and covered with a quarter to half inch of soil and the seed is layed down on top of this and then covered. This keeps the tender seedlings from being burned by nitrogen in the high nitrogen version but also precludes insects from being attracted to rich organic layers atop the soil in spring to lay seed eating larvee. Oh, I should mention, sometimes I add bat guano too! I guess it's all about the baseline information and this info will give you an idea of where to go! Always soil test first, this will give you the baseline to make an informed decision in regards to your options. I will say, the more nitrogen you use, the more chance you are going to need woodash and calcium carbonate (lime).
Stay tuned, lots to come in the next few weeks, rabbit hutches, hatching turkeys, raising guinea keets, planting the raised bed greenhouse and so much more!