containerized trade market in agricultural products

You're biggest companies, and therefore starting places for research, are ADM, Bunge, Cargill, Louis Dreyfus, and COFCO.

On the simplest level (this may differ slightly in the US, so take it with a pinch of salt), you originate the raw commodities from farmers/co-operatives, move them to somewhere they can be processed and then the products are sold on for further processing into whichever relevant final industry.

I would add Soya to the list of commodities you look at as it's quite interesting and I can give you a quick look into the supply chain. Soya is produced in most of the mid-west US, Brazil, Argentina, Paraguay (each country has relative quality differences in the crop), the reference market is CME Soybeans/Meal/Oil and shipped out of a variety of ports across NA/SA all over the world (think Europe, China).

In terms of trade rules/acceptance we use GAFTA and FOSFA rules when buying/selling commodities, their websites give insight into say the contract terms you have to meet in terms of quality etc.

Ags markets are made interesting by the elasticity of supply. Weather is a huge factor which effects the size of the crop and therefore supply into the market and would be worth commenting on.