Yield and growth of mature pear trees under water deficit during slow fruit growth stages in sparse planting orchard

• Early water stress inhibits vegetative growth and improves fruit growth and yield.
• Early water stress span of mature pear trees should be shorter than young trees.
• Differences in pear fruit growth were obvious only in 40 days before harvest.

A field experiment was conducted in 2009 and 2010 in Korla, Xinjiang, China, which is in an oasis around Taklimakan desert, to investigate the effects of regulated deficit irrigation (RDI), applied during slow fruit growth stages, on yield and growth of mature pear trees. The experiment involved MRDI-1 and SRDI-1 treatments, which were irrigated with a 60% and 40% replacement of pan evaporation (Ep) respectively during the cell division stage, and MRDI-2 and SRDI-2 treatments, which were referred to 60% and 40% irrigation replacement of Ep respectively during fruit slowly enlargement stage, and an 80% replacement of Ep in other stages. The control treatment was watered with an 80% replacement of Ep in the whole growing season. All plots irrigated weekly. The results showed that water stress imposed in cell division stage effectively inhibited the vegetative growth, but had no remarkable impacts on fruit growth till six weeks before harvest. During the last 40 days of fruit enlargement stage, the fruit growth rate was higher in SRDI-1 and MRDI-2, and consequently higher fruit yield was observed in the two treatments. In addition, total soluble sugar content was significantly improved by MRDI-1 and SRDI-1. The growth pattern of vegetative growth of mature pear trees showed a significant distinction from young trees, and the appropriate span of water stress should be limited to early vigorous vegetative period and shorter than the young trees.