India, Oct. 30 -- A day after two cloud-seeding operations over Delhi short of delivering rain, another round of seeding, planned for Wednesday, had to be called off due to "insufficient moisture" in the clouds, the Indian Institute of Technology (IIT) Kanpur said on Wednesday.

The trial, meant to test whether artificial rain could help cleanse Delhi's notoriously toxic air, also became the subject of political sparring and scientific scepticism.

While the Delhi government hailed it as a "science-led intervention" that showed encouraging results despite the dry weather, opposition parties dismissed the exercise as a "waste of taxpayer money." Environmental scientists, meanwhile, cautioned that cloud seeding is not a viable or lasting so...