Effects of post-harvest deficit irrigation in ‘Red Beaut’ Japanese plum: Tree water status, vegetative growth, fruit yield, quality and economic return

In early maturing fruit crops, post-harvest is usually the preferred period to apply regulated deficit irrigation (RDI) because it offers the opportunity of reducing vegetative growth and saving water without interfering with fruit growth. There are few studies of RDI on Japanese plum, in comparison with the number available for other fruit crops. We examined the effect of RDI over the post-harvest seasons of 2009–2013 on tree water status, vegetative growth, yield, fruit quality and economic return in an adult orchard of early maturing ‘Red Beaut’ Japanese plum. All treatments received the same pre-harvest irrigation of 100% of crop evapotranspiration (ETc) and post-harvest irrigation treatments were: irrigated at 100% of ETc (Control); applying 60% of water in Control (RDI-60); and applying 30% of water in Control (RDI-30). The average annual irrigation water applied to Control was 639mm. Maximum annual water savings with respect to Control were 39% for RDI-60 and 70% for RDI-30. Intercepted photosynthetically active radiation at solar noon displayed a similar pattern throughout the years with no significant differences between irrigation treatments in any year. However, the RDI treatments were suitable for reducing total pruning weight. Fruit yield in RDI-30 was similar to Control for each of the five years following deficit irrigation. In the long-term (five seasons), the effect of post-harvest RDI had no negative cumulative effect on tree productivity. Therefore, for early maturing Japanese plum it can be concluded that allowing a progressive post-harvest water stress that limits the decline in Ψstem to values of −1.65MPa in early August, with a maximum decrease of 0.014MPaday−1, corresponding in this study to RDI-30, appears not only to be an effective way of saving water, but also acts as a useful tool to control vegetative growth (considered as total pruning), maintain fruit yield and quality and increase grower's final return.