Abstract
Over two-thirds of human water withdrawals are estimated to be used for agricultural production, which is expected to increase as demand for renewable liquid fuels from agricultural crops intensifies. Despite the potential implications of bioenergy crop production on water resources, few data are available on water use of perennial bioenergy grass crops. Therefore, the objective of this study was to compare dry matter yield, water use, and water-use efficiency (WUE) of elephantgrass, energycane, and giant reed, grown under field conditions for two growing seasons in North Central Florida. Using scaled sap flow sensor data, water use ranged from about 850 to 1150 mm during the growing season, and was generally greater for giant reed and less for elephantgrass. Despite similar or greater water use by giant reed, dry biomass yields of 35 to 40 Mg ha−1 were significantly greater for energycane and elephantgrass, resulting in greater WUE. Overall, water use by the bioenergy crops was greater than the rainfall received during the study, indicating that irrigation will be needed in the region to achieve optimal yields. Species differ in water use and WUE and species selection can play an important role with regard to potential consequences for water resources.
Highlights
Agroecosystems have been managed for years to provide food, fuel and fiber
In low input systems with little or no irrigation, our results indicated that elephantgrass or perhaps energycane would be better suited for bioenergy crop production compared to giant reed and presumably other C3 crop species
Daily water use by the bioenergy crops was similar to other crops, as was seasonal water use for crops with similar growing seasons
Summary
Agroecosystems have been managed for years to provide food, fuel and fiber. Demand for these services especially renewable liquid fuels has increased in recent years, as global production of ethanol exceeds 66 billion L per year [1]. In the USA, this renewable ethanol is currently produced almost exclusively from maize (Zea mays L.) grain produced in the Midwestern states This has led to an interest in producing energy from other more sustainable cropping systems like perennial grasses that do not directly compete with our food systems and are capable of higher fuel yields through lignocellulosic conversion processes [2]. While many perennial tall grass crops are very productive [3,4], bioenergy cropping systems have the potential to greatly diminish less visible ecosystem services [5], especially hydrological regulation at the expense of crop primary production [6,7].
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