Best Soil and Water Management Practice for Bioenergy Sorghum Production in South Central US.

Bioenergy sorghum is a second generation biofuel crop with high biomass yield potential, nitrogen (N) and water use efficiencies, and genetic tractability. As a C4 crop originally from Africa, it has great potential to be successfully grown in the southern U.S. Texas is geographically located in the southcentral U.S. and leads the nation in several agricultural areas and associated commodity production. Grain sorghum is well-adapted to Texas, and its ability to yield consistently in harsh environments makes it popular with growers. However, inappropriate soil and water management practices may occur due to lack of information concerning production requirements and environmental effects of bioenergy sorghum, which may ultimately affect biomass production, soil fertility, and greenhouse gas (GHG) emissions in the long run. Texas has a wide diversity of climates and soils due to its large geographical area, making it difficult to achieve the same economic, agronomic, and environmental goals by adopting the same management practices in each county. Thus, our objective was to determine the optimum soil and water management practices including tillage, N fertilization, aboveground biomass residue return, and irrigation, for bioenergy sorghum production in each county in Texas, in order to maximize yield, sustain soil fertility, and minimize GHG emissions. Regional simulations of bioenergy sorghum production to the middle of this century were conducted for each Texas county under 45 residue return, N fertilization, and tillage management combinations at three different irrigation levels using the process-based biogeochemical model, DAYCENT. The model integrated representative GIS-based county-level weather, soil property and field operation schedules, and verified bioenergy sorghum growth information. Yield, soil organic carbon (SOC), and nitrous oxide (N₂O) emission were used as indices to determine best soil and water management practices for each county using life cycle analysis (LCA) of net GHG emissions.