How do I learn about grain trading?

I work for an agricultural lender. It would help me advance in my position if I knew the ins and outs of grain trading. The department I work in does a lot of business with grain elevators. I know very little on how elevators make money, trade, margin calls and what not. What are some good sources of information for a beginner to learn about this process so I can understand what my co-workers are talking about.