I wish you had made it a multiple choice question!

The guy on the trailer, styled in the T-shirt, jeans, gloves, and sunglasses (they may even be Rayans!) he has made it look like a stages picture to me, more in the current day. I know when I was a teenager stacking hay down here, the sweat kept any kind of sunglasses sliding down my nose, so I gave up wearing them. Others, well they make it work, but that's another thing that leads me to believe it may be a staged picture.

Plowboy picked up on the tractor tires being a recently newly developed and imported radial design. I'd would have never noticed that, but it makes sense.

Tractor driver is not wearing a wristwatch (at least on his left arm). It seems that more people used to wear wristwatches. Nowadays, everything has a digital clock in it, trucks, tractors, cell phones, so it's less important to carry your time with you.

I say that it's within the last five years. So, I'll make a guess: 2008.