Just getting started in grid sampling some fields. What's the usual grid size most folks are using. I have had some sampled by one company on a 1 hectare grid. Now I have hired a kubota off road truck type thing that has the gps and sampling probe on it. I was doing some today, pH on a 0.25 hectare grid and P and K on a 1 hectare grid. Obviously the smaller the grid the better the accuracy but where is the optimum point for grid size.

Any suggestions welcomed.

Also what do you guys test for "over there" generally here it's just pH,P,K (all tests also do Mg) and I test farms that I suspect have problems for Cu, although obviously not on a grid.