With an indistinct grey sky, indistinct green trees, and indistinct green field and focus on the yellow with a 100mm lens leaves me less than enthusiastic I'm afraid.
Are you talking about the first or the second group?
On the first I don't seem to be bothered by what you mentioned although you are right that DOF is not that good and the sky is far from interesting. I could try what stamper said and take it out entirely out of picture although I'm not sure what it would do to the scale.
On the second group the first 3 are more like showing the potential, they are not where I was hoping so I have no defending to do there.
The last color one doesn't fit your description anyway.