Dear Sir, 
About 3 years before I had approached you about  using a tractor mounted power sprayer  by keeping the tractor in a remote corner of the garden and using a long distance higher diameter delivery hose. Now that system is working well since last three years.  Further now we are using electric motors to energize the sprayer instead of tractor, using the IP set power. This system is  being used for supplying nutrients  by foliar spray to the pepper vines .which are trained to areca trees. (foligation).
I think this system can also be used  for taking up spraying operation and also for foligation  in the  bigger fields with row crops  such as sugarcane without the  human entrance inside field .. We may have to use sensors and an (electrically  operated) self propelled bicycle using solar energy for charging. 
 I think this may revolutionize spraying and nutrition supply system  . If you are interested I would like to discuss further in this regard. You may also visit my farm to see our present working system. 
Thank you. 