Better tree performance and water use efficiency through root system resilience (AL13009)
What’s it all about?
Established in 2014, this project is being conducted as part of a coordinated research program into boosting almond productivity and profitability. It aims to support more informed rootstock choice, more efficient irrigation strategies and more efficient use of nutrition.
Since the last report in November 2018, progress includes…
- Continuation of a soil amendment trial with Select Harvests—assessing the effect of ‘bunker waste’ (non-fruit material picked up at harvest, such as sticks, soil etc.) composted with wet ash applied to the soil surface around the drip irrigation lines. Soil nutrient content is being measured, as well as root mass.
- Glasshouse experiments to determine the role of the scion (grafted to the industry standard Nemaguard rootstock) in determining root nitrogen uptake and allocation within the tree by different root classes, are nearing completion, with all plant samples dried and assessment of nitrogen content underway. Root biomass data from these experiments shows variation in both scion and rootstock.
- The reduced nitrogen and reduced irrigation trial at CMV Farms Lindsay Point, has been maintained for a further season. Root imaging, root extraction and sapflow measures are continuing.
Read the article Better tree performance through root system resilience - project update in the Autumn 2019 edition of the Australian Nutgrower magazine.
Investigating nitrogen uptake
Plant material is entering a final season of pot experiments into root function and root/shoot interactions. Material is established for two sets of experiments, both of which are using a stable isotope of nitrogen as a tracer to look at uptake, assimilation and movement of nitrogen through trees. The first set of experiments is using a group of 30 trees (Nonpareil on Nemaguard rootstock) individually established in 200L pots in 2017, as described in the last project update. These trees are now well established. The aim of this work is to examine nitrogen uptake by various root size classes at different stages of tree development.
A second set of experiments has been prepared to investigate nitrogen uptake of Nonpareil scions on six rootstocks and three scions on Nemaguard rootstock (Nonpareil, Carina and Carmel), comparing uptake, transport and use of nitrogen. The study will begin in December 2018.
Optimising fertiliser application
The next phase of irrigation and management trials across multiple rootstock/scion combinations are also set to be established. This area of investigation is using a compost based on waste products from a processing plant, co-generation ash and bunker waste, applied to three scions (Nonpareil, Carmel and Monterey) on Nemaguard rootstock in an eight-year-old planting at flowering. This trial will be followed for two seasons to determine the impact on the trees and their productivity, with findings allowing growers to optimise fertiliser application.
Work has also started at Lake Powell, in collaboration with Select Harvests, investigating the role of a soil ameliorant in altering tree nutrient uptake and soil properties. Work has also continued at the DEDJTR managed site at CMV Farms at Lindsay Point, primarily collecting root images to see how well root systems have developed. Analysis of the root images is ongoing.
For the 2017/18 season, the project has two new experimental systems. For the first, young trees have been established in large, 200L pots, with season-long experiments to look at nitrogen uptake patterns in relation to natural root phenology. For the second, short-term glasshouse experiments will look at nitrogen uptake by roots of different classes and ages.
Work established earlier in the project will continue, including…
- Analysis/verification of data from 17 rootstocks that were earlier screened for resilience to soil-water deficit and high soil conductivity.
- Field experiments looking at root function under different irrigation and nutrition regimens, with the researchers studying root phenology, growth and turnover using regular photographic imaging.
- Field experiments using sap-flow sensors on some of the trees, to monitor whole tree water use. In combination with tree canopy and yield data, this has been allowing whole-tree water-use efficiency to be determined and linked with irrigation and nutrient treatments.
Information on the project was presented at the 2017 Australian Almond R&D Forum & Field Day back in October. If you missed it, a recording of the presentation can be found here and the presentation file is here.
- The project has screened 17 rootstocks for resilience to soil-water deficit and high soil conductivity. With the results expected to be made available to industry in the near future, the project is now moving to place emphasis on glasshouse and young-tree studies of root function.
- Field experiments continue to look at root function under different irrigation and nutrition regimens, with the researchers studying root phenology, growth and turnover using regular photographic imaging.
- Field experiments have also used sap-flow sensors on some of the trees, to monitor whole-season tree water use. In combination with tree canopy and yield data, this will allow whole-tree water-use efficiency to be determined and linked with irrigation and nutrient treatments.
- 12 rootstocks have been assessed for resilience to soil-water deficit and high soil conductivity (as described in previous editions of Hortlink).
- A further eight rootstocks are currently being assessed in glasshouse studies during the 2016/17 growing season.
- Root function is continuing to be assessed under different irrigation and nutrition regimens at the project’s field site. The use of ‘minirhizotron tubes’ for regular photographic imaging will allow the direct determination of root phenology, growth and turnover, and analysis over time will demonstrate the impact of the water and nitrogen regimens on these factors.
- As reported in the last edition of Hortlink, sap-flow sensors were installed in-field in 24 trial trees at the start of the 2016/17 season. These will allow whole-season tree water use to be monitored. In combination with canopy and yield data, the results will allow whole-tree water use efficiency to be determined and linked with irrigation and nutrient treatments, as well as root density and growth.
- The December 2016 issue of Australian Nutgrower featured articles on this project, including “Better tree performance through root system resilience”, which provided a general project overview.
The project started in the second half of 2014, with a trial rootstock screen for abiotic stress tested at the end of 2014 and rootstock screening beginning in mid 2015.
To date 12 rootstocks have been assessed for resilience to soil water deficit and to high soil conductivity, with additional supporting measurements to understand variations between genotypes also undertaken. All remaining genotypes available for grafting to almonds in Australia are expected to be assessed by the end of the 2016/17 growing season.
A field site, shared between three of the Almond Productivity Program projects, has been instrumented with minirhizotrons, with regular imaging underway since early in the 2015/16 season. Sapflow sensors were also installed in 24 trees at the site during mid-summer. In combination with canopy and yield data collected by Agriculture Victoria the results will allow whole tree water use efficiency to be determined and linked with irrigation/nutrient treatments and root density/growth.
This investment is a strategic levy investment in the Hort Innovation Almond Fund