Tragedy of the Commons in the Field.

The Tragedy of the Commons model of root allocation and competition has received little attention in applied fields compared to the debate seen in basic plant biology. It predicts that plants that share soil space will over-allocate roots to the space (compared to what would be predicted based on resource availability alone) in an attempt to minimize loses to competition. The tragedy is introduced when all plants use this strategy, which removes any benefit while maintaining the costs of producing the extra root. The result has generally been a 20-30% reduction in seed yield for crops such as soybeans and peas. As the theory gains acceptance, it is important for agricultural scientists and crop breeders to be aware of the ramifications of the theory in the field. The green revolution dramatically increased yield in part because of the development of semi-dwarf varieties that minimized the Tragedy of the Commons that resulted in taller plants. A similar revolution may be on the horizon if plant breeders can create varieties that do not engage in the belowground Tragedy of the Commons. To support this idea, I present data from a small field experiment where soybeans were separated by water impermeable barriers. Yield increased as the number of plants per isolated compartment decreased. This suggests that breeding or possibly even changes in cultivation practices could dramatically increase yield per acre without increases the use of fertilizers, herbicides or pesticides.