The effect of combined deficit irrigation and summer trunk girdling on the internal fruit quality of ‘Marisol’ Clementines

Abstract

The influence of girdling, deficit irrigation, and a combination of girdling and deficit irrigation on fruit quality of ‘Marisol’ Clementines was investigated over two seasons, 1998 and 1999, at two different sites in South Africa. Girdling increased the total soluble solids (TSS) by 2–10%, however, the effect was not always significant. There were no trends observed for external fruit colour, fruit diameter, juice content (%), titratable acidity (TA) and TSS:TA ratios due to girdling. Deficit irrigation increased the TSS (by 2–17%) and the TA levels (by 9–13%) in both seasons and at both sites, increased the TSS:TA ratio at Citrusdal in 1998 (4–8%), and decreased the TSS:TA ratio (by 7%) in the second season (1999) at both sites due to the increased acidity levels (by 11–13%). Deficit irrigation had no major effects on external fruit colour and juice content in 1999, but decreased fruit diameter (by 10%) at Citrusdal. According to these results, deficit irrigation, summer trunk girdling, or a combination of both, can be used as cultural practices to improve internal fruit quality. The combination of girdling and deficit irrigation increased the TSS more than when the practices are executed on their own.