It has been my experience that it is very difficult to visually show yield variations of <10-12 bu./acre on a yield map when comparing side-by-side and even replicated trial plots -- especially when the field average is >150 bu./acre.

My question is, can it be done? If so, what is the best method for doing so?

As an example, I ran a replicated trial last year comparing 3 products. The yields within the trial varied from 176.5 bu./acre on the low end to 188.4 bu./acre on the high side, with the average across the plot at 182.4 bu./acre. The standard deviation was 3.7 bu.

Below is the plot layout:

 Here's the plot with the yield overlay:

Here's the plot showing the yield map only. Without knowing where the plot is located, it is almost impossible to pick out from the rest of the field:

Here's the same plot using a different mapping program. Again, it's difficult to see the plot location:

I've played with the legend by increasing and decreasing the range and I can get no improvement from the above pictures. I've also tried defining the ranges by standard deviation and by defining my own splits. I can get no improvement. Any ideas?