Usually light weight small aircrafts were used to spray on big farms, the main problem with small aircraft spraying is that you need a very experienced pilot because you need to fly at very low height, so this requires money, skillful pilot, effort to find the pilot, multiple re-filling and is very risky approach.
Now with Agras MG-1S you have a reliable tool which solve a major spraying issue on big farms saving considerable time and money.