Ecological benefits of Crassulacean Acid Metabolism (CAM) in agricultural production
Increasing severity of drought conditions presents a major challenge for dryland agriculture. Plants that use Crassulacean Acid Metabolism (CAM) are adapted to survive in arid conditions and some are reported to be high-yielding. CAM species have gained attention recently as potential bioenergy feedstocks. Three Agave species were grown experimentally under four treatment levels of irrigation at the Maricopa Agricultural Center in Maricopa, Arizona. We used measurements over a four year period and models informed by these measurements to determine the optimal inputs for a viable CAM cropping system with minimal ecological impact.
Plant production was responsive to additional inputs in the first two years of growth, but differences among irrigation treatments declined over time. Significant differences in biomass were observed after two years of growth, but plant-insect interactions appeared to limit the maximum size of individual plants after three years of growth with the largest limitations to growth observed under the highest irrigation treatments. Thus, the benefit of additional irrigation for biomass comes at a cost. Plot-level biomass of Agave americana, an obligate CAM species, when cultivated in arid conditions without irrigation was lower than biomass yields previously estimated from individual plants. Despite this, biomass production of A. americana in arid degraded soils was similar to that of some C3 crops grown in areas of high rainfall and rich agricultural soils. Ecological benefits of CAM crops in arid conditions include conservation of water and, depending on the conditions, land resources.