A 3 hectare load? That's a lot of loads on a 1200 hectare block 😜
Yes the technology is possible to have a high capacity aircraft flying autonomously, even spray. In real life it's just not going to happen. There are so many variables to try and allow for that it's an immensely complex task.
Drones are pushed as an answer where any person can do these involved and complicated jobs.
The drone operator will have a wide chemical knowledge, calibration skills, expertise with working gps and programming, weather insight with regard to chemical application and associated drift problems. That's just scratching the surface, obviously an intimate understanding on computer programming and drone aerodynamics would be a pre requisite. How much an hour do you think such a person would be paid? $50? $100? What do you think an agricultural pilot is paid?
The technology is here, there are capable machines available. The reality of drones replacing all flying industry tasks is a long way away.
Please post where broad acre spraying (commercially viable) is done by drones.