Net Greenhouse Gas Emissions in Major Crops in Texas.

County level simulations will be carried out for the state of Texas to examine C dynamics and GHG emissions in selected conventional crops in the period of 1982 - 2012. The focus of regional simulations for all Texas counties and the state as a whole during this period will include: (1) yields of major crops (grain corn, upland cotton, winter wheat, grain sorghum, and hay) under conventional field management practices , (2) SOC levels in respective cropping systems, and (3) net GHG budget for each cropping system, including crop/soil system CO₂ flux, direct and indirect N₂O emissions, CH₄ uptake, and the fuel CO₂ costs of farm machinery operation and production of N fertilizer input.