Desempenho da palma forrageira irrigada com déficit hídrico e baixa frequência de irrigação no semiárido brasileiro.

Abstract

The objective of this study was to evaluate the performance of the forage cactus cultivar Orelha de Elefante Mexicana (Opuntia Sctricta Haw), irrigated with water deficit and low irrigation frequency in the Brazilian semiarid region. For this, the climatological data in the experimental period, the morphometric variables, chemical composition, surface temperature of the soil and cladodes and the physiological variables, in the first cycle and in the regrowth, were analyzed, in addition to carrying out the agrometeorological modeling by the AquaCrop model, comparing the results estimated by the model with data obtained in the field. For this purpose, we used a randomized block design (DBC) with 2 treatments (I7 - irrigation frequency of 7 days and I28 - irrigation frequency of 28 days) and 4 replications (number of blocks), with each treatment being repeated 3 times within the block (triplicate) totaling 24 experimental plots, with the collected data being analyzed using SAS® (2002). The morphometry of the forage cactus Orelha de Elefante Mexicana is altered as a result of the frequency of irrigation, with greater number, height, width and thickness of cladodes under weekly irrigation, but even being irrigated at a frequency of 28 days, the cactus had weight of matter green of 187,58 ton ha-1 and dry matter yield of 14,32 ton ha-1 . With the exception of the ether extract, irrigation frequencies did not affect the forage bromatological components and the physiological variables respiratory rate and stomatal conductance. The surface temperatures of the cladodes were 4.5 to 8.8 ºC higher in the afternoon shift and the soil temperature decreased by 9 ºC after irrigation. Calibration and validation of the AquaCrop model for the cultivation of cactus forage, cultivar Orelha de Elefante Mexicana and specific climate of the mesoregion of the Agreste region of Paraíba showed satisfactory results in the first cycle of the forage, with simulated productivity, similar to those in the field for the frequencies of 7 and 28 days, making AquaCrop a great tool to aid agrometeorological forecasting in the field.