Effects of regulated deficit irrigation on growth and yield of young Japanese plum trees

Drought was applied to a 4 year-old, mid-season Japanese plum (Prunus salicina cv.'Black-Gold') orchard over 4 years in Valencia, Spain and the impact on tree water status, growth, yield and fruit size recorded. Water was restricted during phenological stages II and III of fruit growth, or after harvest, replacing 33% or 66% of tree evapotranspiration (ETc), or during both periods at 66% of ETc. Water deficit during fruit growth reduced average fruit weight, with a negative correlation between fruit size and integrated midday stem water potential. In contrast, drought after harvest did not affect flowering, fruit set, fruit growth or yield, in the short-term. However, in the last year of the experiment there was a 10% reduction in yield compared with control plots because the droughted trees were smaller. Thus, in young trees, post-harvest droughting may reduce productivity, in the long-term, as a consequence of the cumulative effects of water deficit on tree growth. Savings in water applications were similar with deficit irrigation applied after harvest, or before and after harvest. However, deficit irrigation applied during both periods not only reduced fruit growth, but also had a greater effect on tree growth. Post-harvest droughting, despite its moderate detrimental effect in the long-term, should be considered in commercial orchards not only in cases of water scarcity, but also as a tool to control vegetative growth.