Henry Whipple (Dennis Quaid) did recycle seeds for next years crop, for which he is being investigated. The people that he got their land from in the beginning of the film, were the ones that told Liberty Insurance.
Dean (Zac Efron) accidently kills Brad Johnson (Ben Marten), the son of a local rival in the farming industry, for he thought his dad was the one that called Liberty. Henry helps Dean dispose of the body. Henry tells his wife Irene (Kim Dickens) that he killed Brad, and not Dean.
Dean eventually starts to help his father out on the farm. Whether it's the result of blackmail by his father, or the lack of a failed nascar career, is not certain.
Thanks Michael R!