What was it all about?

This investment, which ran from 2014 until 2020, combined various studies on almond root systems, from commercial orchards to research greenhouses, to provide growers with information aimed at maximising production through the efficient use of inputs, such as irrigation and nutrition.

In collaboration with Hort Innovation project Identifying factors that influence spur productivity in almond (AL14005), work took place over four seasons within a 2.2 ha field trial at Lindsay Point in north east Victoria.

The team examined root system dynamics and tree water use in response to a 30 per cent reduction in irrigation, a 40 per cent reduction in nitrogen application, and a combination of the two.

Input reduction showed minimal impact on the root system, in line with the lack of any significant effect on yield reported by AL14005. This suggests that almond root systems can maintain adequate nutrition in a broad range of input scenarios, creating the potential for more efficient input use compared with current practices.

Detailed greenhouse studies were also conducted, using the stable isotope 15N as a label so that nitrogen uptake could be quantified and tracked very quickly (as little as a few hours). This work used six rootstocks and three scions in eight combinations, showing that:

• The fine root system swiftly reached maximum nitrogen uptake rate with little difference between rootstocks, meaning that shoot demand was likely the major driver of whole plant nitrogen uptake
• Despite having little effect on nitrogen uptake rate, rootstock genotype did appear to influence whole tree nitrogen allocation, meaning that if this effect is also present in mature trees it has implications for rootstock choice and tree management.

Finally, the team adapted a plant growth analysis method to create a rapid pre-screen for rootstock resilience to soil abiotic stress. The process was tested and simplified to ensure its reliable use by tree nurseries and importers of new genetic material to assess and categorise genotypes prior to selection for long-term field trials.

ACT NOW

• Read more in this comprehensive article Better tree performance and water use efficiency through root system resilience from page 26 of In A Nutshell magazine, Summer 2020/21 edition.
• Read the article Better tree performance through root system resilience - project update in the Autumn 2019 edition of Australian Nutgrower, pp15-17
• Information on the project was presented at the 2017 Australian Almond R&D Forum and Field Day – watch a recording of the presentation.