Tommy tells Gus to rotate his crops because peas eat up nitrogen. In fact, peas are nitrogen-fixing plants and contribute nitrogen to the soil.
Tommy "Big Man" Jepperd says that peas eat up all the nitrogen in the soil. The opposite is true: Peas (like many legumes) are known for their ability to fix nitrogen from the air and thus enrich the soil with nitrogen.
Big Man tells Gus that he should plant other vegetables as peas remove nitrogen from the soil. In fact, it's the opposite: peas (and other legumes) add nitrogen to the soil.