WATER BALANCE IN SOIL CULTIVATED WITH FORAGE CACTUS CLONES UNDER IRRIGATION

Forage cactus species may belong to different genera (such as Opuntia and Nopalea), which can result in different water dynamics at the biosphere-atmosphere interface. The objective of this study was to analyze the water balance in soil cultivated with forage cactus clones under different conditions of soil water availability in the Brazilian semi-arid. The experiment was conducted in the municipality of Serra Talhada, State of Pernambuco. The crop was subjected to nine treatments arranged in a randomized complete block design with three replications in a factorial arrangement of 3x3. The plots were composed of three water availability conditions, with the application of a water depth of 7.5 mm at intervals of 7, 14, and 28 days, and the subplots consisted of three forage cactus clones (IPA Sertânia, Miúda, and Orelha de Elefante Mexicana). The soil water balance (SWB) method was applied, and the ET/ETo ratio was estimated (ET is the actual crop evapotranspiration, and ETo is the reference evapotranspiration) at intervals of 14 days; the results were represented in nine periods of 28 days. There was a difference between SWB components along the cycle and between irrigation conditions (p < 0.05). Nevertheless, ET and rainfall were the most important components in SWB when irrigation was performed. There was no difference in water consumption between forage cactus clones belonging to different genera, resulting in an average of 1.50 mm day-1. The ET/ETo ratio had low magnitude (0.29 ± 0.12), indicating that the ET was more dependent on the water regime than on the atmospheric demand