There are a few factors involved. The first is how many tires you have; remember that the load will be more or less evenly distributed among all of them. Another is what driving conditions will apply. Bouncing along at high speed over rough terrain is a lot different than creeping along a highway.
Your best bet is probably to contact various tire manufacturers, tell them what you need, and let them advise you.
Static load and dynamic load are different. If a tire is revolving at 1000 RPM, each segment of sidewall is flexing at the same rate. This flexing, due to static load, is heating the tire. High tire pressure minimizes flexing.
Suppose you wanted a tyre that could hold an operating pressure of 600 KPa (6 bar), and support 32 tonnes=32,000 Kg. Then the footprint area A of the tyre on the ground will be A = 32,000/600,000 = 0.053 square meters. The footprint probably should be about square, so about 0.23 meters by 0.23 meters. So with a tyre width of .23 meters. I'll guess that the tyre diameter is about 6 x the width or 1.38 meters.
I once got hold of the European way to calculate advice-pressures for car-tires.
Worked it out and learned myself Excell to make spreadsheets for it.
In my search I came by articles about it .
But the surface on the ground is for a radial tire almost rectangular ( sorry for eventual misspelling, native speech is Dutch).
You can look in the next map on my skydrive of hotmail adress, where I placed spreadsheet to calcuate the indentation of the tire for given maximum load and sises.This spreadsheet gave less indetation then it is in practice, and so I also made a picture with paint about how it to my opinion realy deformes the tire
This map I opened especially for discussion I have with maker of article about a new way of calculating in wich the indentation has to stay the same at lower load.
His article You can find navigating my complete public map with a link in my own first reaction there, Tire-pressure at reduced loads by J.C. Daws.
To make a long story short , mayby by studying my map and the article of mr Daws, you will get a good idea of what is important for the load of a tire.
If you cant open a spreadsheet in the browser, download it and open it in Excell or compatible programm, to work with it.
The browser cant handle sheetprotection and data-validation I used in most of them.
If , after reading, questions pup up , ask me here