A good topic for a speech about agriculture is seed patents. For certain patented crops, farmers can only use their purchased seeds for one planting season. They can't use the seeds that are produced from the harvest.
The patenting of seeds started with the passing of the Plant Patent Act of 1930. With this law, plant breeders receive incentives that can supply them with the resources to further develop and improve plant varieties. This creates a conflict with farmers who typically use seeds from the current harvest to plant the same crops in the next planting season, which saves money. Patent holders defend their side by saying that farmers can also save money from the reduced water and pesticide needs of the patented seeds. The Center for Food Safety, however, believes that the world's food supply should not move to corporate ownership.