Ethanol and the Gulf of Mexico Dead Zone

I have seen several articles talking about the Dead Zone in the Gulf of Mexico and how ethanol production is going to make it worse. One article plainly stated in it's headline, As ethanol demand grows, so does 'Dead Zone' in Gulf of Mexico.

Now I will be the first to admit that I am no expert on what causes the Dead Zone in the Gulf of Mexico. But if ethanol production, and more specifically the growing of corn is to blame then there should a statistical correlation between the size of the yearly corn crop and the size of the Dead Zone. So I decided to pull together the numbers and see if a trend could be seen.

In the first column are numbers for the yearly size of the Gulf of Mexico Dead Zone. I pulled these together from news articles. If anyone knows of another site where the numbers can be found please let me know.

In the second column is the number of acres of corn planted in each year.

2007 - 7900 square miles      93,616,000 acres of corn planted
2006 - 6662 square miles      78,327,000 acres of corn planted
2005 - 4564 square miles      81,779,000 acres of corn planted
2004 - 5800 square miles      80,929,000 acres of corn planted
2003 - 3220 square miles      78,736,000 acres of corn planted
2002 - 8500 square miles      79,054,000 acres of corn planted
2001 - 8006 square miles      75,752,000 acres of corn planted

From looking at the numbers there doesn't seem to be any direct correlation. The two largest years for corn production (2007 and 2005) didn't result in the largest yearly dead zone. And the smallest corn crop (2001) corresponded to the second largest yearly dead zone. Clearly other factors besides corn production are involved.

From reading around from various sources I have found that the dead zone is caused in part by fertilizer use. And since corn production requires large amounts of fertilizer, it stands to reason that corn production has an effect on the size of the Dead Zone. But it isn't the only factor that contributes. Soil erosion and sewage spilled into waterways also has an effect. As does weather conditions.

But if you read the article I posted above no other possible cause is explored other than corn production for the ethanol industry. Clearly the numbers do not support such a claim.

Sources:

December 2007 Crop Summary
2003 Crop Production Summary
2006 Crop Production Summary
'Dead zone' in Gulf of Mexico among top 3 ever mapped
Gulf dead zone larger than expected
Gulf Dead Zone Likely to Be Smaller
Record Size Dead Zone Forecast in Gulf of Mexico
Shrimp Industry Finds Life in Gulf Coast 'Dead Zone'