I've done farming scenes before but when I saw a photo of a cropduster, well I had to make a painting. I don't particularly enjoy making landscapes (everybody does landscapes) so I hedged a bit and put in an airplane.
Still some work to do on the airplane itself then make the suggestion of spray coming from the sprayer doo-dads under the plane wings.
The unusual size (17x24) is a result of measuring three times and still getting it wrong at the saw. "Only" an inch off! I could have been more wrong - and have.
April 21, 2010 - update.
I gave the airplane a propeller - it isn't a jet after all! I also put a light cerulean blue glaze on the mountains and the far edge of the field..
April 24, 2010 - update
I put rows of crops in the field that the plane is dusting. It wasn't a lawn, for crying out loud! The rows are neatly done - Farmer Brown saved some money on the plowing so that she/he could have the field sprayed today. :-) Isn't art fun?