I agree that farm income is not a free market explanation. When you look at it on a global basis, it is an indication of why farmers around the world would increase their demand for fertilizer, creating competition for the available supplies. That's what, in equilibrium, delivers the prices.
To your question on natural gas, when the price of natural gas in North America has gone down, it has lowered the cost of production in manufacturing in North America. The cost of natural gas in North America is still dramatically higher than in other parts of the world, such as the Middle East. So you have to keep things in perspective. But if you were to look at the quarterly results published by publicly traded companies, such as Agrium and CF Industries, and the prices at which they are selling their products, you would find that in the last five months their prices have come down. That is a big part of the reason why, two days ago, Agrium announced a $60 million loss in their first quarter.