Buy something else with less mass per ratio of weight, like gold or silver. That would be easier to hide away, maybe. Those are also less likely to degrade if you continue to bury it in the ground...
I'm wondering why the op is trying to hide money in the first place lol.
You are more then welcome to hide some on my land if you'd like or I can put it in my safe. I'm just a nice guy like that and willing to store money for people
With cash, inflation will devalue it so it's a poor choice to bury. Buy gold and/or silver and bury that instead. I wouldn't put it in the bank either because if you die and don't have a will, they will lock out your family and the court will take a large chunk of it in taxes. Obama also wants to raise the "death tax" back up near 50% for wealthy people so make sure the government can't get at it......
several small gold purchases, spread out over a large area. dont go to the local place every week. travel around a bit. anitques are good to, you could blow 40g's on a Tiffany lamp or a Dahm vase really easily.
You could buy bit coins with it but that fluctuates a bit and you could end up loosing money, then again if the price goes up you could get rich, i suppose if you have so much money you need to hide it you can afford a bit of risk. http://en.wikipedia.org/wiki/Bitcoin