Effect of Different Irrigation Programs on Structural Characteristics, Productivity and Water Use Efficiency of Opuntia and Nopalea Forage Cactus Clones

The objective of this study was to evaluate the structural characteristics, yield and water use efficiency of forage cactus under daytime and nighttime irrigation in a Brazilian semiarid region. The experiment followed a completely randomized design in a 3 × 2 factorial scheme, with ten replications: three clones of forage cactus (“IPA Sertânia”—IPA, “Miúda”—MIU, “Orelha de Elefante Mexicana”—OEM) and two irrigation schedules (daytime and nighttime). Irrigation was applied once a week using a graduated cylinder. The structural characteristics (i.e., plant height and width, total number of cladode—TNC; cladode number per emergence order—CN1, CN2 and CN3; cladode area—CA; cladode area index—CAI), productive characteristics (fresh mass production per plant—FM and dry mass—DM) and water use efficiency (WUEFM and WUEDM) were obtained from the plant harvests. Our results showed that the irrigation schedules did not lead to significant differences in most of the response variables (p > 0.05), except for the TNC (13.2 und), CN2 (7.4 und) and CAI (1.58 m2 m−2) of MIU. It was observed that OEM presented the highest yield, WUEFM and WUEDM (p < 0.05). Adopting the OEM clone, regardless of the irrigation schedule, is the strategy that achieves the best production.