Modelling the effects of Niño and Niña events on water balance of grapevine (cv. Cabernet Sauvignon) in central valley of Chile

The tendency for more frequent events of El Niño!Southern Oscillation Event (ENSO) since the late 1970's has been questioned about how anticipate the water management strategies of the crops. Niño events are characterised by high rain and moderated temperatures, whereas Niña events produce the opposite effects. In this context, a research was carried out to evaluate the effects of both climatic phenomena on the water balance of a grapevine cv. Cabernet sauvignon in central valley of Chile. Water balance was simulated with STICS model which was combined with a climatic database of four periods of Niño and four Niña events on the soil type of Talca series. The irrigation scheduling was managed automatically by the model and then it varied between years. A descriptive climatic analysis for the normal grapevine growth cycle (between middle September and end of March) showed a climate water deficit (Precipitation - Potential evapotranspiration) significantly higher (average of +27%) in Niña events (-861 mm) compared to Niño events (-677 mm). However, simulation results showed that grapevine transpiration was only 4% higher in Niña events (196 mm) than in Niño events (189 mm). Also seasonal irrigation application calculated by the model was 170 mm in dry years compared to 154 mm in humid years. These results can be explained by: i) the grapevine phenology, with a total grapevine growth period (budbreak to harvest) 10 days longer in Niño than Niña years, and ii) the parameterised soil, which was thin (0.6 m). This last condition has a consequence that the higher rainfall in years "Niño" was not used by the vine, it was runned-off and deep percolated