As stated above. A bit more saturation would do the trick on the pumpkins.
As for 3 / 4:
I like 3, however I feel the composition is out. There's too much sky. The Horizon should be a lot closer to the centre of the image, maybe even a touch over. I like the subject matter though. But same as pumpkins needs more colour and contrast.
4 , looks too much like a snapshot for me. Doesn't really look composed, and with the washed out colours, doesn't really hold my interest.
Perhaps, well, what I would have done was go down a bit to the wheat-looking-grass-stuff, and kneal down. Take a photo of the paddock with the grass stuff slightly in shot, however out of focus. Set's the scene, get's a nice vibe flowing.
I don't mean to sound harsh, but it looks like a random photo me or my wife take when we go driving down the south coast, when you point the camera out the window and take a shot. Because of the speed of the car, you can't really compose. Sometimes you get gems, but more often than not, you get photos like 4 where it looks more like a snapshot.
Sorry if that sounded, harsh, it wasn't my intention.