Productivity and water use efficiency ofAgave americanain the first field trial as bioenergy feedstock on arid lands

Agavespecies are high‐yielding crassulacean acid metabolism (CAM) plants, some of which are grown commercially and recognized as potential bioenergy species for dry regions of the world. This study is the first field trial ofAgavespecies for bioenergy in the United States, and was established to compare the production ofAgave americanawith the production ofAgave tequilanaandAgave fourcroydes, which are produced commercially in Mexico for tequila and fiber. The field trial included four experimental irrigation levels to test the response of biomass production to water inputs. After 3 years, annual production of healthyA. americanaplants reached 9.3 Mg dry mass ha−1 yr−1(including pup mass) with 530 mm of annual water inputs, including both rainfall and irrigation. Yields in the most arid conditions tested (300 mm yr−1water input) were 2.0–4.0 Mg dry mass ha−1 yr−1.Agave tequilanaandAgave fourcroydeswere severely damaged by cold in the first winter, and produced maximum yields of only 0.04 Mg ha−1 yr−1and 0.26 Mg ha−1 yr−1, respectively. The agave snout weevil (Scyphophorus acupunctatus) emerged as an important challenge forA. americanacropping, killing a greater number of plants in the higher irrigation treatments. Physiological differences inA. americanaplants across irrigation treatments were most evident in the warmest season, with gas exchange beginning up to 3 h earlier and water use efficiency declining in treatments with the greatest water input (780 mm yr−1water input). Yields were lower than previous projections forAgavespecies, but results from this study suggest thatA. americanahas potential as a bioenergy crop and would have substantially reduced irrigation requirements relative to conventional crops in the southwesternUSA. Challenges for pest management and harvesting must still be addressed before an efficient production system that usesAgavecan be realized.