Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 22, 1998
Publication Date: N/A
Technical Abstract: Cattle grazing systems, where cattle grazed bermudagrass pastures in a four-year experiment, caused an increase in soil organic carbon when compared to systems where bermudagrass was harvested as hay or left unharvested. The GRAZE beef-forage simulation model was used to identify major carbon-flow pathways involved in this process. Simulations were planned to compare grazing systems with hay-only and unharvested treatments using actual fertilizing, weather, harvesting, and initial animal and forage data. Because GRAZE did not explicitly model carbon pathways, we used literature values to estimate root mass, rates of carbon fixation and mineralization, and rates of decomposition of feces, dead plants, and roots. GRAZE predicted forage and steer growth. Ruminal carbon losses were estimated by difference by estimating forage intake to contain 42% carbon, feces 50% carbon, and by estimating the carbon content of steer gain. Simulations suggest GRAZE may be adapted to estimate the carbon balance in grazing systems.