Optimising almond production systems (AL21001)

Over the past six months, the key focus for the project team has been a ten-week harvest of SARDI’s field experiments at the Almond Centre of Excellence (ACE).  As with many South Australian horticultural crops, the 2022/23 almond season was delayed by two weeks due to prevailing La Niña climate conditions.  Whilst poor drying conditions complicated the harvest and storage procedures for the ACE orchard, SARDI’s experimental harvest operations were not adversely affected thanks to the use of large drying ovens at the Loxton Research Centre.  These facilities enabled timely postharvest assessments of crop moisture contents, crack-out percentages and conversion of bulk yields to accurate kernel weights for each of 580 experimental plots across five individual field experiments.  Postharvest assessments of kernel quality metrics remain ongoing and will complement yield data by answering questions of marketability as influenced by genotype, density, training system and soil amendments.  

In general, the health status of ACE field experiments remained strong despite the season’s wet conditions.  However, there were some combinations within SARDI’s rootstock compatibility trials that expressed Verticillium like symptoms.  Trees grew out of the symptoms as conditions warmed but may have their future productivity compromised.  Links between genotype and susceptibility to disease symptoms were identified and will form part of SARDI’s ongoing monitoring and communication programs.  

Measures of canopy water status were collected prior to the 2023 harvest and suggested an interaction between plant water status and cultivar.  Future measures need to include additional growth stages and the measurement of other physiological variables to better understand the principal drivers behind differences in water use and the relative impacts of cultivar, density and crop load.  These additional measures are scheduled for seasons 2024 and 2025.  Early observations suggest the heavy cropping Vela cultivar was significantly more stressed than Nonpareil across densities ranging from 308 to 615 trees/ha, with average midday stem water potentials being 20% more negative than the industry standard variety. Complementary measures of plant nutrients, soil water content and rootzone solute dynamics demonstrated that the site’s irrigation and nutrient schedules were meeting plant demands and there was no significant loss of nutrient beyond the rootzone.  The only suggestion of nutrient deficiencies at the ACE site were in SARDI’s rootstock compatibility trials where trends in leaf nutrient concentrations followed a largely predictable patterns as influenced by novel rootstock and/or scion cultivars.

Alongside the ongoing collection and collation of field datasets, SARDI has maintained a program of industry communications through hosting field walks, publishing grower articles and presenting at national and international forums. 

The last six months, the project’s activities focused on the characterisation of canopy development metrics and the analysis of 2021/22 datasets. This included:

• Installation of Water Use Efficiency (WUE) monitoring sensors; more than 36 experimental plots were fitted with continuously logging soil moisture probes to supplement field measures of stem water potential, leaf gas exchange and the various canopy development metrics gathered through fixed and mobile ground-based and aerial-based sensing platforms.
• Preliminary analysis of 2021/22 data; treatment yield response from multiple trials is described herein, with some genotype by density combinations suggesting that this fourth leaf season was a recovery year following the very high yields of 2020/21, clearly demonstrating the value of longer-term projects for perennial cropping systems. Integrating plant water use metrics with yield performance will be an important output for growers seeking to better understand the yield potential and water use efficiency of alternate varieties and planting systems.
• Extension activities; more than 200 individual industry members visited SARDI’s trials through the MS103 reporting period. Further to this, the project team presented to multiple conference and workshop presentations, including the 2022 Australian Almond Conference.  SARDI scientists also contributed three conference papers to the Irrigation Australia Conference and Exhibition plus one industry article to the Spring edition of ‘In a Nutshell’.