Well, it's not exactly crop-spraying, but the technology is very similar. Oil Spill Response describes itself as:
... the largest international industry-funded cooperative which exists to respond to oil spills wherever in the world they may occur, by providing preparedness, response and intervention services. We are wholly owned by most of the environmentally responsible oil and gas companies, and our membership represents the majority of global oil production. We currently employ 300 people across 9 locations around the world.
It seems the company has bought a former FedEx Boeing 727 airliner (the last ever produced, built in 1984) and converted it to spray dispersant chemicals over oil spills (presumably at sea). Flight Global reports:
The 727’s usual oil-spill spraying flight profile involves passes at an altitude of 150ft (45m) and a speed of approximately 150kt (278km/h) with flaps at 15°. At Farnborough, the demonstration flyby is undertaken at around 300ft, followed by a steep climb-away.
Here's a video clip of its flight at the Farnborough air show in England this week, including a spraying demonstration. Watch it in full-screen mode for best results.
That's pretty amazing, when you think about it - handling an airliner designed for high-altitude, high-speed point-to-point flight as if it were a low-flying, low-speed, turn-on-a-dime crop-sprayer! It must take some very precise flying, particularly when the weather's stormy. I suppose it's not dissimilar to the conversion of jet aircraft for use as water-bombers to fight fires, such as the well-known (and much larger) DC-10 Air Tanker.