Drone or knapsack?

What the research shows.

Aerial photo of curved rice field plots in different shades of green — Photo: Ivan Bandura, Unsplash, Unsplash License

	Drone	Knapsack	Ground machine
Walking in mud	No	Yes	Can bog down
Time (MADA study)	About 24 hours	About 80 hours	Not measured
Workers (MADA study)	1	4	Not measured

The Rosedi and Shamsi (2022) study at Kampung Alor Gandak, Mukim Limbong, Alor Setar also reported field efficiency improving by 9.08% after drone spraying was adopted.

The limits

Small tank, frequent refills.
No flying in rain or strong wind.
Not every product is recommended for UAS use.

References

Rosedi & Shamsi (2022), Comparative Efficacy of Drone Application in Chemical Spraying at Paddy Field MADA Kedah, IOP Conf. Ser.: Earth Environ. Sci. 1059 012002