Optimal duration of irrigation withholding to promote early bloom and harvest in ‘Algerie’ loquat (Eriobotrya japonica Lindl.)

Postharvest deficit irrigation advances the following bloom and harvest in loquat (Eriobotrya japonica Lindl.), making the crop more profitable. This bloom advancement can be achieved by a combination of water shortages of different durations and intensities. Previous results have shown that completely suspending irrigation is more useful than deficit irrigation strategies in which watering is only partly restricted. In order to determine the optimal duration of irrigation withholding, ‘Algerie’ trees were subjected to different levels of water stress over two consecutive seasons, suspending watering for a short (3–5 weeks), medium (6–7 weeks), or long (8–9 weeks) period starting one month after harvest and ending when the trees reached prescribed midday stem water potentials (Ψs) of −1.4 MPa, −1.8 MPa, and −2.2 MPa, respectively. The results show that a severe water stress (Ψs ≈ −2.2 MPa) achieved by withholding watering for 8–9 weeks was more successful in advancing next bloom and harvest than milder stresses caused by the suspension of irrigation during shorter periods. The advancement of bloom was related to an earlier cease of new shoot growth, which led to earlier panicle development formed in the apical buds after summer rest release. Water use efficiency was improved the most by a moderate water stress (Ψs ≈ −1.8 MPa) achieved by suppressing watering for 6–7 weeks, although on average, loquat profitability was even greater under severe water stress, because the improvement in fruit earliness was higher when water withholding lasted 8–9 weeks. On the contrary, a slight water stress (Ψs ≈ −1.4 MPa) failed to substantially modify ‘Algerie’ loquat phenology. No detrimental effects on yield or fruit quality were attributable to regulated deficit irrigation.