Does ducting help to stabilise heavy lift drones? I'm looking to build a UAV that is extremely stable. It doesn't have to be fast, it doesn't have to be agile, but it will have to carry up to 50lbs (agriculture focused UAV that has to operate for at least 8 hours at a time) over private land (where the drone is authorized to be, and with FAA registration) at an altitude of about 15 feet.

Is ducting the way to go here?

I'm looking to do a quadcopter with a very very low center of gravity right now because of it's inherent stability. Is ducting or more rotors the way to go here? And I have very few specifics because I'm still working on the basics of the platform. It will have to carry a lot of weight and potentially deal with being thrown off balance by a rover getting caught on plants.
There is too little information given to make a definite answer here, but things you should take into consideration are:


depending on the construction the bigger crosssection if keeping a similar rotorsize which will likely increase drag at higher windspeeds while on the other hand leading the airflow so with the right construction it might behave better then without ducting.
using at least 6 or better 8 rotors should enable you to increase lifting power and stability
putting the rotors in an angled position should increase stability while it might slightly reduce lifting power


additionally


the ducting will offer protection for the rotors/fans and people/things getting hit by the drone in case of a crash
as you want too operate it for such a long time the increase in weight which might increase the number of refuels/battery changes needed


Also we were talking about drones that produce the whole lift by rotors pushing air downwards. What about using a ballon or some kind of plane? This will make it more sensitive towards wind and sacrifice maneuverability but will allow extended flight time and potentially higher efficiency.