The police could actually make post burning arrests too. Just drive around the countryside and wherever they see evidence of burning, it is not hard to see, inquire as to the land ownership and issue a warrant against the owner. Do that for a couple of years and they'll soon stop burning. Also, close down, or at least heavily fine, all sugar mills that accept burnt cane. If they stop accepting burnt cane, the farmers will stop burning. However, local authorities need to help out with supplying cane harvesters, as locals can't afford such machinery.