Five‐year field trial of the biomass productivity and water input response of cactus pear (Opuntia spp.) as a bioenergy feedstock for arid lands

Abstract

AbstractClimate‐resilient and highly water‐use efficient crops are needed to meet the future food, feed, fiber, and fuel demands of a growing human population. Cactus pear (Opuntia spp.) are highly productive yet have crop water demands that are approximately 20% that of traditional crops due to their ability to perform crassulacean acid metabolism (CAM). In the first long‐term field trial of Opuntia for bioenergy in the United States, the aboveground biomass (cladode and fruit) productivity and response to different water inputs of O. cochenillifera, O. ficus‐indica, and O. streptacantha were evaluated at a planting density of 1418 plants ha−1 under three irrigation levels over a 5‐year period to investigate their response to different water inputs. Mean cladode fresh weight, cladode dry weight, cladode count, fruit fresh weight, and fruit dry weight increased linearly by 1.26‐, 1.88‐, 1.53‐, 1.89‐, and 2.13‐fold, respectively, with increasing irrigation from 300 to 716 mm year−1. Significant differences in irrigation response appeared in years 4 and 5 as the cactus trees grew larger. However, no significant differences were observed among the three Opuntia spp. for all parameters measured. Biomass productivity increased over 5 years by 140.8‐ and 132.5‐fold for cladode fresh and dry weight, respectively. Mean annual total aboveground biomass at 300, 407, and 716 mm year−1 water input resulted in 8.25, 11.16, and 15.52 Mg dry mass ha−1 year−1, respectively, at the sparse planting density used here to separate irrigation blocks, which could have been easily quadrupled. O. ficus‐indica performed better than O. cochenillifera and O. streptacantha in terms of cladode biomass and fruit count and quality. Biomass productivity was consistent with previous studies for Opuntia spp. demonstrating that cactus pear displays very high biomass and food/forage potential using substantially lower rates of supplemental irrigation than conventional crops grown in semi‐arid and arid regions.