My Kubota tractor battery keep's getting to low to start the machine?

I recently bought a Kubota grey market 24 hp diesel 4wd tractor with a front loader and rear blade for road work/maintenance. The battery seems to loose it's charge more regularly than I would have expected. This is my first diesel engine as well as my first tractor. It is often a couple of weeks between uses, and I usually use it for 2-4 hours each time...though it is stopped and started several times during this period.

Is this just a typical characteristic of diesel tractors?

Does the starting process drain the battery to a high degree?

Do I need to get some sort of device to continually charge the battery between uses (it starts easily when battery is fully charged)?

If I need to get some sort of continuous charging device, what is recomended?