By: Cathy Mansfield at DPI Tatura
A research project conducted by irrigation researchers from DPI Tatura has revealed that removing fruit from trees under water stress may significantly reduce the stress on the tree and improve tree survival.
Andrew Mc Nab, an orchardist from Ardmona, volunteered the use of his Granny Smith apple block to assist with the research.
“We volunteered two patches (pears and apples) because they were earmarked for pushing out. The free blocks gave us a window of opportunity to see what would happen with various watering, crop load/pruning strategies” Andrew said. “We did this to test whether we could rest a block then bring it back into production the following year.”
Water is essential to optimal tree growth. If apple trees become water stressed growth will be inhibited and in severe cases plant tissues will die. As part of the demonstration, Researchers reduced the amount of water applied to the Granny Smith block, and in some cases took off the fruit from drought stressed trees. Trees were monitored to determine their health.
Water stress was measured by determining the pressure required to force water out of a covered apple leaf. This is called stem water potential. The more pressure it takes to force water out of the leaf, the more stressed the tree with less water available for plant health and growth.
Water was applied to the blocks at a range of different rates throughout the whole season. These included 0%, 10%, 20%, 40% 60 % and 100% of normal grower practice. At the beginning of the season, fruit was completely removed from some trees. Water stress in fruiting and de-fruited tress was monitored weekly.
Observations of stem water potential showed that those trees with fruit removed were under considerably less stress than those trees with fruit remaining on the tree the whole season.
Figure 1 (62kb JPG) shows that de-fruited apples trees were less stressed than fruited trees receiving either 100% or 0% water. Also interesting is that stem water potential in the defruited trees receiving 0% water was similar to the trees that received 100% water and had retained their fruit.
Image one is 0% of normal grower irrigation practice with fruit and image two is defruited apple trees 0% of normal grower irrigation practice
Andrew’s comments:
“If the drought continued we would change blocks the following year and not use the same treatments on the same blocks. We also tried a trial of our own where we irrigated with less water but only when we believed the tree needed it. Those trees will be brought back into production this year.”
An indication of the relative health of trees in different treatments can be seen in the images one and two (to the right) taken towards the end of last season. To see photos of fruited and defruited trees for each irrigation rate, click on the links to the right.
If you are interested in options for removing fruit to assist with tree survival please contact Cathy Mansfield at DPI Tatura on 58 33 5225
View The Other Images
|  | Image 1: 0% of normal grower irrigation practice with fruit
Image 2: Defruited apple trees 0% of normal grower irrigation practice |
