You could get him a neato fuel caddy filled with gas or diesel, whichever his tractor runs on.
I bought one of these 14-gallon caddies on sale several years ago. I fill with gas and add Sta-Bil. I cycle it out in a vehicle and refill once per year.
I am definitely getting off of these.
DuraMax Flo n' Go LE Fluid Transfer Pump and 14-Gallon Rolling Gas Can https://www.amazon.com/dp/B000MT94QA/ref=cm_sw_r_cp_api_i_aztrFbQCTGPZV
I found it on Amazon. Not sure it's worth $100 though unless you live on a farm or something.
If you really do want to stockpile lots of gas use this: http://www.amazon.com/gp/product/B000MT94QA http://z2-ec2.images-amazon.com/images/P/B000MT94QA.01._SX187_SCLZZZZZZZ_V217191900_.jpg