Yield and fruit quality of avocado trees under different regimes of water supply in the subtropical coast of Spain

The subtropical Mediterranean climate of southeastern Andalusian coast allows Spain to be the largest European producer of subtropical fruit, with the avocado as the main representative. In this region, precipitations are scarce and erratic and limit water availability for irrigation. Under this climatic uncertainty, appropriate water use is required for assuring crop environmental sustainability and increasing water productivity (WP) of avocado orchards. For this purpose, it is necessary to evaluate if current water endowments in the region match crop water requirements and to what extent water use can be improved. In this study, water productivity was assessed in a mature avocado (cv. 'Hass') orchard along six consecutive seasons. The physiological and agronomical responses of avocado trees to five water treatments (T1-T5) were also evaluated during two consecutive seasons. Water amounts supplied by irrigation were compared with FAO's estimations. For the six seasons, averaged FAO irrigation needs were 7916 +/- 395 m(3)ha(-1) season(-1) but averaged water supplied was 6503 +/- 328 m(3) ha(-1) season(-1) ((-)18% below FAO's) with yields 11 +/- 2 t ha(-1), meaning a WP of 1.7 kg m(-3). FAO's recommendations matched T2 and irrigation over or below T2 affected avocado yield, fruit quality (i.e. size) and WP. Water supplies 15% above FAO's (T3) did not involve better yields but decreased WP. Conventional irrigation for mature orchards (Ti) was (similar to)20% lower than FAO's and entailed yield decreases ((similar to)16%) but similar fruit sizes and WP. Water supplies 40% and 60% below FAO's (T4 and T5, respectively) caused significant water stress and decreased yields and fruit quality of avocado trees but increased WP. These effects were more noticeable during the productive season, in which T5 trees showed weakening symptoms and marked fruit drop. Results are discussed in the context of viability of avocado cropping in the Mediterranean region under low water resource scenarios.