BIOFUELS AND WATER USE: COMPARISON OF MAIZE AND SWITCHGRASS AND GENERAL PERSPECTIVES

Two of the main plants currently being considered as potential biofuel feedstocks in the U.S. are switchgrass (Panicum virgatum L.) and maize (Zea mays L.). Recent expanded production of both has raised serious questions about natural resource utilization, notably, soil carbon, soil nutrients, and water. Water is often the limiting resource for crop and grass productivity. The objective of this study was to calculate and compare water use and water use efficiency of maize with current growth characteristics, switchgrass with current growth characteristics, and switchgrass with characteristics improved by normal plant breeding selection techniques. We used the calibrated and validated ALMANAC model for five sites representing the southern Great Plains (Stephenville, TX), the northern Great Plains (Mead, NE), and two locations in the Corn Belt (Ames, IA and Columbia, MO). Ten years of historical weather data were used. Mean values for water use and water use efficiency were calculated for maize, switchgrass with currently growth characteristics, and switchgrass with anticipated improved growth characteristics. These results show the relative impact of expanded maize production, expanded switchgrass production, and use of improved switchgrass varieties, on the water balance in these regions. The water use efficiency (WUE) of four switchgrass types showed means ranging from 3 to 5 mg g-1. Switchgrass WUE values were much greater than WUE of maize grain, but such was not always the case when