If somebody asks you to buy half a ton of fertilizer on their behalf, I suggest you think twice about it. Why do they want you to buy it for them? Even if he's a farmer, with a rational use for that much fertilizer, why is he making such an unusual arrangement to receive fertilizer through his friend instead of buying it himself normally?

Who knows man, maybe feds caught him with some pot plants and now he's setting you up in some sort of bullshit anti-terror sting to cut a deal. Regardless of what kind of truck you have, casually buying half a ton of fertilizer for somebody else is an odd request that warrants some explaining.