Food production leads to large disturbances of natural ecosystem by removing the diversity of plants and altering the soil. The soil nutrient cycles are interrupted by tilling and by the planting of an annual monoculture. Tilling exposes carbon deeper in soil to air, which allows it to be broken down by microbes, thus decreasing the carbon stores for the soil’s carbon cycle. Annuals also have shorter roots and are not able to deposit as much carbon or nitrogen deeper in the soil. This trait can also lead to a loss of carbon and nitrogen in the soil, which are needed for plant growth. If a perennial crop is used, the field does not need to be tilled as often. The perennial can grow deeper roots that can help sequester carbon and nitrogen deeper in the soil. The goal of our study was to determine the role of plant cultivation to affect soil carbon and soil nitrogen dynamics at shallower and deeper soil depths. We sampled at an ongoing field experiment that had three plant cultivation types (restored prairie, annual wheat, perennial intermediate wheatgrass) and collected soils at two depths (upper 0-15cm, lower 15-30cm) establishing a laboratory soil incubation experiment.
Results/Conclusions
We found that the cultivation type, not soil depth, strongly influenced soil carbon and nitrogen dynamics. The perennial cultivation type had greater CO2 evolution, soil organic matter, and nitrogen than the annual fields, especially in the upper layer (0-15cm) of the soil. Surprisingly, the restored prairie did not differ in carbon and nitrogen dynamics relative to the perennial or annual cultivation treatments. These results provide evidence that a perennial grain may be a better choice for soil nutrient cycling than annual wheat.