The effect of combined deficit irrigation and summer trunk girdling on theinternal fruit quality of 'Marisol' Clementines

The influence of girdling, deficit irrigation, and a combination of girdlin g and deficit irrigation on fruit quality of 'Marisol' Clementines was inve stigated over two seasons, 1998 and 1999, at two different sites in South A frica. Girdling increased the total soluble solids (TSS) by 2-10%, however, the effect was not always significant. There were no trends observed for e xternal fruit colour, fruit diameter, juice content (%), titratable acidity (TA) and TSS:TA ratios due to girdling. Deficit irrigation increased the T SS (by 2-17%) and the TA levels (by 9-13%) in both seasons and at both site s, increased the TSS:TA ratio at Citrusdal in 1998 (4-8%), and decreased th e 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 effe cts on external fruit colour and juice content in 1999, but decreased fruit diameter (by 10%) at Citrusdal. According to these results, deficit irriga tion, summer trunk girdling, or a combination of both, can be used as cultu ral practices to improve internal fruit quality. The combination of girdlin g and deficit irrigation increased the TSS more than when the practices are executed on their own. (C) 2001 Elsevier Science B.V. All rights reserved.