Abstract
Regulated deficit irrigation (RDI) during stage 2 of fruit development and summer pruning (watersprout removal, WSR) can be used to control excessive vegetative growth in high-density peach orchards. The dynamics of tree-light interception after the application of RDI (no irrigation during stage 2) and WSR in summer were evaluated during two consecutive years. RDI and WSR treatments produced similar reductions in the percentage of light intercepted by the tree at the end of the 2-year experiment. However, it was not possible to produce the same seasonal dynamics in the percentage of light intercepted by the tree using the RDI and the WSR techniques; RDI trees showed a gradual reduction in the amount of light intercepted as the productive cycle progressed, while WSR trees showed an immediate reduction in the amount of light intercepted. Moreover, the mechanisms responsible for vegetative growth reduction were different in the RDI and the WSR techniques. The RDI technique was associated with reductions in tree water status and decreases in gravimetric soil water (theta g) and fruit growth capacity. RDI may have reduced theta g below the threshold required for optimum fruit growth, whereas WSR reduced water consumption, improved water status and therefore could have benefited fruit growth. Therefore, RDI and WSR greatly differ when the mechanisms responsible for vegetative growth reduction are taken into consideration.
Highlights
Water is becoming scarce in the Mediterranean area where agriculture accounts for the vast majority of consumptive water use
The differences in water supply between the full irrigation (FI) and regulated deficit irrigation (RDI) treatments reflected the different amounts of water delivered during stage II of fruit development: trees under RDI received no irrigation during stage II of fruit development
In 2003, the amount of vegetative fresh mass removed by summer pruning was 3.43 kg tree-1, 0.54 kg tree-1 (SD = 0.09), and 0.36 kg tree-1 (SD = 0.04) for the FI + watersprout removal (WSR), FI + commercial pruning (CP) and RDI + CP treatment combinations, respectively
Summary
Water is becoming scarce in the Mediterranean area where agriculture accounts for the vast majority of consumptive water use. It is necessary to develop and implement regulated deficit irrigation (RDI) techniques in order to optimize water use without affecting crop yields. Water stress has a negative effect on most agricultural crops, fruit trees seem to adapt well to deficit irrigation (Costa et al, 2007). Moderate water stress during stage II reduces tree crown development (Mitchell and Chalmers, 1982; Boland et al, 2000). This reduction in vegetative growth is desirable in high-density orchards. It would seem feasible to: impose moderate water stress during stage II of fruit development in high-density peach orchards, conserve existing water resources, reduce excessive vegetative growth, and avoid any negative effect on total crop yield
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