Under the Canterbury Air Regional Plan, if your property is less than 2 hectares, you can't burn outdoors (unless you're cooking). If your property is 2+ hectares, you can burn outdoors if conditions are met.
Call Environment Canterbury on 0800 324 636 or visit their website (external link)
Local by-laws may apply - check with your council.
Selwyn Fire and Emergency
0800 658 628