Efficiency of water use by Opuntia undulata Griffithis as a function of plant density and organic fertilization

In the Brazilian semiarid region, forage cactus is considered an important alternative for feeding herds in times of drought, among the varieties, Opuntia undulata stands out. This study aimed to evaluate the efficiency of water use by the African elephant ear variety (Opuntia undulata) subjected to different spacing and organic fertilization. The experiment was carried out under rainfed conditions at the Ignácio Salcedo Experimental Station, belonging to the Instituto Nacional do semiarid – INSA. Regarding the production of green matter, the highest efficiency in the use of water, occurred in the 1.0 x 1.0 m and 1.0 x 0.8 m spacing, with values of 165.86 and 140.87 kg MG ha-1/mm-1, respectively. The efficiency of water use in the production of dry mass, the values were inversely proportional to population density, ranging from 8.63 to 11.70 kg DM ha-1/mm-1. The increase in the number of plants per hectare generates a competition for water resources.