Regulated deficit irrigation techniques enhances sweetness

Dr Tahir Khurshid from the NSW DPI leads a project team which is working on improving citrus fruit quality. The Horticulture Innovation Australia funded research is using a range of regulated deficit irrigation treatments at different phenological stages during summer and autumn to make citrus sweeter.

A grower reference group meets annually to review the results and refine the treatments based on past results. Data is collected on fruit quality (total soluble solids (0brix, BrimA, acid, sugar:acid and fruit size) and tree productivity (fruit yield and fruit size distribution). The trial is monitored with soil moisture monitoring equipment during the entire season (Figure 1).

The research is looking at early-maturing (M7), mid-maturing (Houghton) and late-maturing (Lanes Late) navel oranges growing on Poncirus trifoliata Tri22 and Troyer citrange rootstocks.

In Afourer mandarins, two deficit irrigation demonstrations are also underway in Sunraysia and the Riverina. These are still in the early stages and it is too soon to publish concise recommendations yet; however, preliminary results indicate that deficit irrigation has enhanced the sugar levels in oranges and mandarins. Growers are urged to wait for the final recommendations after the conclusion of this project.

Dr Tahir Khurshid is looking at the flowmetre