Why did Murphy burn cornfields in Interstellar?

In the movie Interstellar, Murphy burned the cornfield to distract his brother.

Murphy's brother's son has a bad cough, which has always worried Murphy. His brother's family lives in a bad climate. Murphy wants his brother to take the little boy out of here, but he doesn't want to go. Murphy thought his brother didn't know why his father abandoned him and stayed. During the conversation, Murphy mentioned that his brother's first son died in a sandstorm, which completely angered his brother.

The sandstorm is getting worse and worse. Murphy's sister-in-law and nephew are both at risk of lung disease, but Murphy's brother refuses to move. As a last resort, Murphy burned the most precious fields and led his younger brother to put out the fire, trying to take his sister-in-law and nephew away in this gap. I didn't expect to find a clue from my father when I packed my things, which solved the problem of human survival.