Corn Root and Shoot Biomass to Estimate C Returned Into Soil.

To calculate carbon sequestration potentials, accurate measurements of non-harvested carbon returned to soil are needed.  The objectives of this study were to determine the impact of corn hybrid and stress (water and N) on above and below ground biomass grown in four environments.   Root biomass was determined at silking, while grain and stover yields were determined at physiological maturity.  Yield loss due to water and nitrogen stress was determined using the ¹³C stable isotopic approach.    Corn growth and development was different for the different hybrids.  The findings showed that root-to-shoot ratios were influenced by hybrid and climate/soil/management. Within a site year, hybrid differences in root-to-shoot ratios were detected.  However when analyzed across site years consistent results were not observed.  Over the 4 site years, root-shoot ratios ranged from 0.4 to 0.78.  The amount of below ground biomass contained in the surface soil average 70% and the root-to-shoot ratios in 2 hybrids over for years was 0.52.  Root estimates included estimates of root exudates.    Additional findings suggest that: 1) water stress increased root development, and 2) corn growth and development are influenced by hybrid.