Why, even though I'm all for free markets, I believe that farm subsidies are necessary

 Here's the rub. Farm productivity has risen so dramatically over the past century that we, as humans, are capable of producing orders of magnitude more food than we need. Two things collide in the economy of farming that create a perfect storm of problems. First, there is the fact that farms take at least six months from planning to production. Second is that supply and demand fluctuations encourage immediate action. In order for supply to meet demand, there must be space for that supply to fluctuate as it gets used to knowing what kind of product the market will absorb. Sometimes, there will be surpluses. Sometimes, there will be shortages. 

However, unlike with computer chips, a true shortage of food is unacceptable. If too many farmers plant wheat this year, and the price of wheat drops so low that no one plants for next year, then next year we will have either very high food prices or no food at all. When you are making smartphones, you can adjust your production numbers fairly quickly, and no one is going to die from a smartphone shortage. However, food shortages are a bad deal. 

Subsidies artificially increase supply of a commodity. This creates a "base level" of food production that, no matter market conditions, can be reliably drawn upon. 

To a farmer, having the security of knowing that your grain will sell for a guaranteed baseline price motivates you to plant that crop anyways. And while I don't advocate this method of production for any other business, when it comes to food, security is more important than efficiency. A government must supply its citizens with bread and circuses. This has never changed and probably won't ever change. While I think direct price controls would be counterproductive, I believe that paying someone to not grow corn and promising to buy the corn that is produced regardless of market conditions will give a ground level of food that is always being produced, even if it must be destroyed most of the time. Because food production is such an investment in the future, and because the effects of a shortage would be so severe, I believe that this one industry should be allowed government interference through subsidy.