Great subject for the obsolete theme. The sky is perfect. The shadows could be opened up a little to bring more detail to the subject. You might try playing with the Highlight/Midtone/shadow settings and getting a feel for how far you can lighten the midtones and shadows without hurting the sky. I hope this was helpful. The shot is pretty good over-all.
Fit to challenge criteria: 0/2 - It looks more usable than other tractors I have seen working fields.
Colors: 2/2 - good blue in the sky and organge works well
Photo Quality: 1/2 - a little to dark to see all the detail.
Composition: 1/2
My subjective affinity: 1.5/2
Score: 6