True Value of Carbon in Agricultural Soils

True Value of Carbon in Agricultural Soils
Hatfield, J.L. 2007. True Value of Carbon in Agricultural Soils [CD-ROM]. South Dakota No Till Association Annual Conference.
Technical Abstract:
Carbon (CO2) in the soil plays a critical role in the development of a stable soil aggregate and contributes to the formation of soil particles that are resistant to the destructive forces from wind and water. The dynamics of carbon in the soil are complex because the amount of carbon is affected by the cycling of CO2 from the atmosphere into carbohydrates and ultimately into plant components of leaves, grain, stalks, and roots. Over the course of a year the constant exchange of CO2 between the soil and atmosphere is dependent upon the dynamics of the cropping system. There is a linkage between the CO2 uptake and water vapor release by the crop through the transpiration process. Carbon that is extracted from the atmosphere and incorporated into plant components is released through respiration. Crop growth is dependent upon the soil water availability during the growing season and in the Midwest there is a direct correlation between available water during the grain-filling period and grain yield. Crop residue on the surface mediates the water vapor and energy exchanges between the soil and atmosphere and provides an immediate impact on crop water use rates through a reduction in soil water evaporation. In the longer term, the increase in soil organic matter content leads to an increase in soil water availability and increases the aggregate stability that allows for more effective gas and water exchange between the soil and the atmosphere. The value of carbon in the soil has a positive effect on plant growth and yield through the effect on water availability, short¿term water stress, and more effective gas exchange that benefits the root and biological systems in the soil volume.