Learn about the different netting options and irrigation regimes that can combat heat stress and improve water efficiency, as shared with growers at Mauri and Ann Lyster’s property as part of an orchard walk in Manjimup, WA.
The orchard walk featured research conducted as part of a Horticulture Australia Limited and Australian Government-funded project to understand apple and pear production systems in a changing climate. Netting (hail netting or shade netting) has been identified as a potential climate change adaptation strategy due to reduced solar radiation under the netting and reducing sunburn damage on fruit.
The Department of Agriculture and Food Western Australia (DAFWA) has been measuring water use, air temperature, soil moisture, fruit surface temperatures and growth rates of ‘Cripps Pink’ apples grown under black net and white net compared to those grown without netting.
During the walk the growers saw the differences in fruit size and colour of apples grown under the two types of net compared to those grown without netting.
Daily maximum air temperature is always about 2 degrees lower under the nets. Solar radiation was highest, 31 megajoules, in the blocks with no netting. While under the white net it was 26 MJ and under the black net it was 23 MJ.
Every year fruit is lost due to sunburn. With the predicted rise in temperatures, netting orchards is one way to protect the fruit from sunburn damage.
Sunburn typically occurs when fruit surface temperatures go above 45°C. The highest fruit surface temperature recorded was 55oC on the 1st March when the maximum daily temperature was 38oC.
There were about twice as many days when fruit surface temperatures went above this threshold in the orchard without netting compared to fruit grown under the nets.
Apples under the black net were exposed to 10 days above this threshold while the white net had only 7 days. Fruit grown without netting recorded 17 days above 45oC.
An independent irrigation system within the trial block has been established as part of the More Dollars per Drop project. This system allows areas under each net and a control area to be run differently to growers’ standard practice. Irrigation decisions are made on the basis of weather conditions, evaporation and soil moisture.
The trial block received more water early in the season, but the season’s total water use was very similar between blocks. Mauri Lyster has already seen the impact of irrigation practices on the size of his fruit.
“We have noticed a greater size in the trial block and believe this is because of early season irrigation practice,” Mauri said.
“A 5mm increase in fruit diameter gives a 25% increase in fruit volume which increases the number of bins I pick. On the back of what I have seen I will certainly be changing my irrigation practice next year.”
The demonstration will be continuing for another two seasons.