They have been warned, threatened with prosecution and even offered inducements.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/crop-burning-habits-die-hard-punjab-haryana
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/business-standard-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/haryana
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/punjab
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/air-pollution
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/agriculture
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environmentalists
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/crops
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/farmers
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/state-pollution-control-board-spcb-0