The data you need is too long. I probably found it for you and summarized it for you. However, you can't get the monthly price and output. The country is so big and there are many corn producing areas, so I have to copy the statistics of the Ministry of Agriculture to you. Hehehe.

Corn price in 2003: 900- 1000 per ton.

Corn price in 2004: per ton 1 100- 1250 or so.

Corn price in 2005: about 0/320-1400 per ton.

Corn price in 2006: about 0/550-1620 per ton.

Corn price in 2007: about 0/470-1560 per ton.

Corn price in 2008: about per ton 1630- 1720.

Corn price in 2009: per ton1650-1800 (released on June 2, 2009)

The above information is based on Shandong Science and Technology News and Hebei Agricultural Network. It's just a rough price. Go and have a look if you don't put it down.