There is a limited amount of farmland in the world. The amount of quality farmland is being slowly erroded by the forces of urban sprawl and climate change. With the supply of quality farmland in decline, we need to double grain production in the next 35 years.
Farmland in the US has appreciated an an average annual rate of 7% in the United States over the past 100 years.
Appreciation is driven by advanced in seed and farming technology, driving up production and revenue per acre.