What was it all about?

This project ran from 2015 to 2019 and investigated the effects of key environment and management factors on spur productivity in almond trees. The study was centered around Nonpareil and Carmel almond tree cultivars and was conducted on a commercial orchard at Lindsay Point in north west Victoria.

The project looked at three resource inputs - water irrigation, nitrogen levels and light interception and how the levels of these inputs affected spur productivity and yield formation.

Irrigation and nitrogen reductions increased yield

Water irrigation levels were decreased from 14 to 10 ML/ha/season equating to a 30 per cent reduction and nitrogen levels were reduced from 300 to 180 kg/ha/season equating to a 44 per cent reduction compared to the control group. The reduced volumes were still high enough to sustain the water requirements of the trees and did not have overall negative effects on the trees, yield, or spur productivity.

A reduction of water decreased the canopy density due to overall leaf fall allowing for more light to reach the lower spurs. The enhanced light exposure increased the fertility of buds in the internal and lower regions and was found to be a key factor in spur fertility and productivity. Lower water supply increased the total percentage of spurs that carried fruit by seven per cent on Nonpareil trees and five per cent on Carmel trees.

Meanwhile, applying less nitrogen increased the percentage of Carmel spurs that bore fruit by five per cent, but only had a minor effect on fruiting spur numbers in Nonpareil.

The effect of nitrogen supply on the number of floral-bearing spurs was not as strong as that seen for the effect of irrigation management. 

Light interception

Spurs need to be exposed to sufficient light to influence the likelihood of flower bud initiation and development and fruit retention. Spurs are generally more likely to be reproductive when located in the upper parts of the canopy due to the increase in light exposure in this zone. This highlights the importance of enhancing light exposure to the mid to lower tree areas – largely through reduced irrigation.

Consumer taste testing

Kernels from the harvest were tasted by around 300 consumers to see if the nuts from the Nonpareil trees in the trial were perceived as different from those from controls. Around a third of the tasters could detect differences, showing that irrigation and fertiliser supply treatments changed the properties of kernels somewhat, but the initial testing didn’t provide an indication what the basis of distinction might be, or whether there was preference for one lot of kernels over another. Further work is to come.

ACT NOW

The project produced the below resources for growers:

• Rootstock/fertiliser management systems for almonds (explaining the project’s research into the effect of variations in the ability of rootstocks to take up nitrogen)
• Spur survival: Difference between cultivars (the project’s first-year spur-survival data)
• Spurs: Driving productivity (showing the project’s non-destructive method used to estimate spur leaf area)
• Presentation: Factors that influence spur productivity in almonds
• Video: Introduction to almond research and spur dynamics video
• Video: Impact of Management and Climate on Spur Behavior
• An article on the management inputs and spur behavior
• Poster: Water - Almond productivity during deficit
• Poster: The effect of water and nitrogen on yield of almond trees
• Poster: The effect of water and nitrogen on almond production
• The Winter 2020 edition of the In A Nutshell magazine which introduces and reports progress from this project, see p26.

In case you missed it, project leader Michael Treeby also presented information on the research at the 2017 Australian Almond R&D Forum and Field Day, held in October. Access the video and presentation material here.