During the depths of the economic crisis last year, the prices for many goods held steady or even dropped. But on American farms, the picture was far different, as farmers watched the price they paid for seeds skyrocket. Corn seed prices rose 32 percent; soybean seeds were up 24 percent.

Such price increases for seeds — the most important purchase a farmer makes each year — are part of an unprecedented climb that began more than a decade ago, stemming from the advent of genetically engineered crops and the rapid concentration in the seed industry that accompanied it.

The price increases have not only irritated many farmers, they have caught the attention of the Obama administration. The Justice Department began an antitrust investigation of the seed industry last year, with an apparent focus on Monsanto, which controls much of the market for the expensive bioengineered traits that make crops resistant to insect pests and herbicides.

The investigation is just one facet of a push by the Obama administration to take a closer look at competition — or the lack thereof — in agriculture, from the dairy industry to livestock to commodity crops, like corn and soybeans.