Spike:

   Unless you have fairly even soil types I would sample by soil type in grids. I wish I could copy over one of my soil sample maps. I have many soils often within the same field. Several fields I can change soil types 10+ times in the same round. I'm going to attempt to copy over one of my maps, but suffice to say, I take the different soil types then evenly divide them up into approx. 2.5 acre areas. Some areas may be 3.5acres, others 1.5. But everything is by soil type which I feel is much more accurate than grids(or should I say precise/ I always get them mixed up).