Model-based evaluation of irrigation needs in Mediterranean vineyards

The irregular rainfall distribution causes interannual variation of water status in Mediterranean vineyards. A frequential analysis of irrigation needs was carried out from continuous simulation of the soil water balance during 39 years in south France. The off-season soil water refilling was often incomplete, with a higher frequency in soils with a high total transpirable soil water (TTSW) and/or susceptible to runoff and high evaporation. On soils with high TTSW (over 250 mm), the irrigation need was nil or small (except in situations of high runoff) and focused on the beginning of the crop cycle. On soils with lower TTSW, the irrigation need increased on average and was spread all along the grapevine cycle due to the limited buffering effect of the soil water reservoir. For 100 mm TTSW, the irrigation need was 40-60 mm for half of the years. The calculated irrigation needs were sensitive to the soil (TTSW, susceptibility to runoff and evaporation) and canopy (crop coefficient) properties. Therefore, soil and canopy management should be considered together with irrigation for an integrated approach of water management.