why did national farm workers association leaders cesar chavez and dolores huerta organize a nationwide boycott of grapes?

Answer

They organized the boycott to protest the poor working conditions and low wages of grape farm workers, and to pressure growers to recognize the union and negotiate better contracts.

Q: Who were Cesar Chavez and Dolores Huerta? A: Cesar Chavez and Dolores Huerta were leaders of the National Farm Workers Association, a union fighting for the rights of farm workers in the United States.
Q: Why did they organize a nationwide boycott of grapes? A: They organized the boycott to protest the poor working conditions and low wages of grape farm workers, and to pressure growers to recognize the union and negotiate better contracts.