Hi I want to flood some paddy land using an electric pump from a pond. The layout requires about 150m of buried 1.5-2" pipe/tube, 3 tees and 4 valves. Would the blue PVC pipe or black tube sold in big coils be better for this application? TIA

Black tubes are better , but i've seen both used many times.

The blue are standard pvc and are for inhouse use , they would deteriorate and fail faster then the black ones . Go to the local bigger shops and ask the options for then , since you have small to big lines in various materials upto te use ( flex hose , strong black as water company uses , etc etc ... ) .

Seconded, black tube.