When I lived in the "country" (not Iowa, but Louisiana) we did not have trash pick-up. You had to haul your trash to the Parish (e.g County) dump and pay by the load. So, to reduce the volume of trash one has to haul to the dump, you burn everything that isn't metal. This way you could get it down to a monthly dump run with a few bags of empty tin cans. Once a year (or so) you buy a 55 gallon drum, knock some holes in it and you're good to go. No burn permit required in the pine filled Louisiana woods.
Also, my crazy next door neighbor (a disabled master welder who had done 20 years in Angola State Penatentary for murder - Which he ALWAYS referred to as his time in college) was always doing something on his 3 acres of land with a backhoe, and no one thought anything of it if he was out there digging another hole or a pond. The Parish did make him get rid of the acre of junked cars, over groundwater contamination issues; they went to the crusher (which is another way to dispose of a body if one is in a jam - pardon the pun).
We had a mutual friend who lost a bundle of money because of his investment in a race horse farm. The farm was legit, but the property manager was a serial killer who used the farm backhoe to bury his victims on the property. (LE spent a LONG time digging up the place.) That's how you get rid of dead horses, and every big operation has a backhoe parked in a shed somewhere. Most large farms will have a backhoe/skiploader combo on site, or a digger attachment that can be used with a tractor PTO.
In Iowa, a lot of farms have backhoes, and no one would think anything of a farmer digging a hole on his property, and filling it back in. Hey, you gotta have a place to dump the ash and burned cans from the burn barrel, right? If you need a reason for digging a hole, plant a tree. With the right fertilizer, it ought to grow good and strong. If you have the resources and knowledge of the lay of the land, Iowa can be a GREAT place to dispose of a body. I'm sure that my former neighbor, after his 20 years of "college" education would agree.