RESEARCH UPDATE
Progressing ultra-high-density orchards
Figure 1 . SARDI ultra-high-density demonstration trial , June 2020 .
Figure 2 . SARDI ultra-high-density demonstration trial , October 2022 .
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SARDI Almond Production Research Team The Department of Primary Industries and Regions research division , South Australian Research and Development Institute ( SARDI )
SARDI manages two density optimisation trials at the Almond Centre of Excellence ( ACE ). The first tests the response of multiple varieties to densities ranging from 308 to 615 trees / ha ( early results summarised in the Spring edition of In a Nutshell ). The second density trial , described in this article , is a more ambitious investigation of a planar growing system using size controlling rootstocks and new self-fertile varieties . This ultra-high-density trial ( 635 to 1481 trees / ha ) contributes to SARDI ’ s collaboration with Plant and Food Research ( PFR ) and is part of a multi-crop , orchard intensification project ( AS18000 ) that is supported through Hort Innovation and the Hort Frontiers Advanced Production Systems Fund .
In A Nutshell - Summer 2022 Vol 23 Issue 4
Trial objectives and design SARDI ’ s ultra-high-density trial was planted at the beginning of the 2019 / 20 irrigation season and was designed to test the response of two self-fertile varieties ( Shasta and Vela ) grafted to three size controlling rootstocks ( Controller-6 , Controller-7 and Rootpac-40 ) planted across three densities ( 635 , 889 and 1481 trees / ha ). Trees in large , replicated plots have been trained as modified central leaders to fill trellised rows that are 4.5 m apart ( Figure 1 and Figure 2 ). Whilst this orchard design is not currently practical for commercial application , SARDI expects the trial to test and demonstrate some of the almond industry ’ s longer-term goals . These include increased early yields , improved water and nutrient efficiencies , single pass shake and catch harvesting , alternate mid-row management strategies and improved hygiene for both kernel and trees .
Canopy development To date , the trial ’ s orchard operations have been dominated by canopy development activities including the
Figure 3 . Light hedging operation in late spring to contain canopy width and guide canopy fill down the row .
early training of leaders and the guiding of major scaffold branches down the row including regular hedging of lateral growing tips ( Figure 3 ). Unlike traditional orchards , this experimental block was established using a re-usable trellis structure ( Eco Trellis ) with bamboo stakes to support the developing canopy . The trellis helped protect trees from wind damage and assisted in some of the training operations . Now that the orchard is self-