The nice weather we have had for the last couple of days in Denver sent me out into the pumpkin patch to get some soil samples for soil testing. You don't ever know when the soil will be nice and dry again before spring.
To have great soil to grow a giant pumpkin you need to know what is in your soil. A soil test from a trusted lab is the only way to go. Putting on fertilizer and compost without knowing what is in the soil is like shooting in the dark. I am sometimes suprised with the results that I get back in the soil tests because there can be a lot of things that can make NPK to high or to low and without a balanced soil it can be hard to grow a big pumpkin.
I learned from Thad Starr that you have to be kind of careful in how you collect your sample. Take soil samples from multiple spots and use a clean spoon without any rust on it or your test results can be thrown off. A drop of sweat on the soil can change what should have been a normal sodium level in the soil to high sodium levels so you have to be careful what you soil comes in contact with. Take samples from about 6-8 inches down where your roots are going to be so that you know what is going to be available to your pumpkin plant.
Most labs can help you interpet what your soil needs but most labs don't know a lot about giant pumpkins need so ask a grower or post your results on bigpumpkins.com to get advice from other experienced growers.
I like where my soil is at right now. It has a sweet smell and you can see the last remanants of the shredded leaves that I put into the soil last fall. Depending on what my soil test shows I plan on adding three yards of well composted cow manure, humic acid and alfalfa in the next 6 weeks.