Farmers burn their fields to remove plants that are already growing and to help the plants that are about to come up. These burns are often called "prescribed burns" because they are used to improve the health of the field.

What tools do farmers need for a burn?

To keep the fire contained, farmers need to clear away burnable matter around the edges of the field, which usually requires a lawn mower or larger machinery. The burn itself can be managed with some simple, specific tools.

Flames are usually spread with a drip torch, which drips a mixture of diesel fuel and gasoline. Small flames can be smothered with a flapper, which looks like a mud flap with a long rake handle attached. Running a drip torch requires some experience – the flapper, not so much.

What are the right conditions for a burn?

A farmer wants to burn in Goldilocks conditions – everything needs to be juuust right. If it's too windy, the fire can escape easily. If there's no wind, the fire can be unpredictable. If the field is too dry it may burn out of control, but if the field is too wet it may not burn at all.

The plants in the field have to be at the right stage of growth or the fire won't do them any good. Wind direction can make the burn easier or harder, and temperature and soil moisture also play a role. There may only be a few hours out of the whole year when conditions are right for a burn.

Why doesn't it doesn't get out of control?

An essential first step is checking the weather – if conditions are wrong, the fire can easily get out of control. A burn boss should have the training and experience to know when a burn would be unsafe.

Even if conditions are right, the edges of the field are still mowed short, watered down, or plowed up before the burn to leave a strip of ground that won't burn easily: a fireline. On the inside of this strip, the burn crew will carefully burn the edges of the field to expand the unburnable area. The firelines need to be wide enough and clear enough that the flames on the inside aren't able to burn their way across. In the end, fires can't really be controlled – only contained.