Apricot tree response to withholding irrigation at different phenological periods (original) (raw)

Drip-irrigated Bu Âlida apricot trees (Prunus armeniaca L.) on Real Fino apricot rootstock were submitted, for 4 consecutive years, to water stress by withholding irrigation at different phenological periods: during the period of¯owering-fruit set which lasted around 1 month (T-1 treatment); during stages I II of fruit growth (including the initial exponential phase and the lag phase of the double-sigmoid curve), which lasted around 2 months (T-2 treatment); during stage III of fruit growth (second exponential phase) lasting around 1 month (T-3 treatment); immediately after harvest for one and a half months (T-4 treatment); and for 2 months during late postharvest, immediately following the T-4 treatment (T-5 treatment). These stress treatments were compared with a control treatment (T-0), irrigated throughout the year and receiving an amount of water equivalent to 100% of the crop evapotranspiration (ETc) demand. The greatest reduction in volumetric soil water content, leaf water potential and leaf conductance with respect to the control values was observed in plants from T-4 and T-5 treatments. A clear distinction could be made between the main periods of shoot and fruit growth in apricot trees, which may be considered an advantageous characteristic for the application of de®cit irrigation. Trunk circumference growth and canopy shaded area were unaffected by irrigation treatments. Stressed fruits from the T-2 treatment had a lower diameter during the water stress period, although they showed a compensatory growth rate after irrigation, reaching a similar size to fruits from the control treatment at harvest. Two critical periods for withholding irrigation were found. The ®rst corresponded to the second rapid fruit growth period (T-3 treatment), in which the water stress induced a reduction in yield due to a Scientia Horticulturae 85 (2000) 201±215 (M.C. Ruiz-Sa Ânchez) 0304-4238/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 -4 2 3 8 ( 9 9 ) 0 0 1 4 6 -6 smaller fruit size at harvest. In addition, fruits from this treatment ripened earlier. The second critical period was immediately postharvest (T-4 treatment), in which water stress induced a signi®cant decrease in fruit yield the following year, due to an increase in young fruit drop which lead to a lower ®nal fruit set. #