regarding alibaba:

most listing are not manufacturers but trade companies with small amount of employees your talking about. They are the middlemen in the export market, helping find buyers and negotiating terms with companies. Generally, you really have to weed through many listings to get to manufacturer source. Over the years though, manufacturers have increased presence on the trade websites like alibaba etc. Due to manufacturing constraints depending on industry, large minimum orders are standard for manufacturing b2b trade.

lived in china 3 years sourcing and exporting ceramic to ME/North Africa market. For ceramic manufacturers, min orders are for 3 Heavy Duty Containers each carrying approx 25tons of cargo. This represents the cost/efficiency of producing a specific item/order on a production line where costs increase by stopping the line for each new product/order (changing the paint screens/compression, setup etc). Each tile design is 3container min im saying.

12500 tons of urea seems alot, but as others have pointed out bulk freight (open ships) are used for many commodities including lumber etc. Also you have to suspect urea production is all demand market; you need to secure purchase orders to sustain manufacturing. Or Urea manufacturers will resort to production of ammonia based products if market price is too low (according to this study http://marketrealist.com/2013/12/2-key-things-set-floor-ceiling-urea-prices/  )

my project is to contact a friend in china to connect with commodity traders for information and financing