Increasing planting density can increase kernel yield
By the SARDI Almond Research Team The Department of Primary Industries and Regions research division , South Australian Research and Development Institute ( SARDI )
EARLY results from the Almond Centre of Excellence ( ACE ) experimental orchard at Loxton in South Australia show that kernel yield can be improved if the planting density is increased on the full vigour rootstock Garnem . In Nonpareil , the cumulative kernel yield from 4th leaf plantings was 50 % higher ( 5.9t / ha compared to 3.8t / ha ) when the planting density was increased from 308 trees / ha ( 5m within row spacings ) to 615 trees / ha ( 2.5m within row spacings ) at 6.5m between row spacings ( Figure 1 ). These preliminary results are from one of the two planting density trials managed by SARDI with support from the ABA and funding through Hort Innovation and the Governments of Australia and South Australia ( Figure 2 ). The trial commenced in 2018 at the newly established ACE orchard with the aim of optimising the planting density in the range from the traditional orchard density ( Horizon One or H1 ) of approximately 300 trees / ha to a higher density ( Horizon Two or H2 ) orchard system . Six within row planting densities are being examined ( spacings from 2.5m to 5.0m in 0.5m steps ) in a fully replicated design at commercial scale to ensure that research findings and advice to almond producers are sufficiently robust to inform management practices . The 6.5m row widths allow traditional machinery and management practices to be maintained , thus making the potential benefits of higher density available to growers without significant change to existing production strategies or investment in non-standard equipment . The increase in kernel yields associated with higher planting densities was not seen in all varieties . While yield of Nonpareil was far greater in the higher density plantings in both 2021 ( 3rd leaf ) and 2022 ( 4th leaf ), Shasta ’ s yield was stable or increased by only a small amount . In contrast , kernel yield of Vela and Carina was higher at the higher density plantings in some years but not others . Crack-out did not change with
planting density but was different for each variety at roughly 30 % for Nonpareil and Vela , 25 % for Shasta and 20 % for Carina . A less attractive outcome was that kernels tended to be slightly smaller in the higher density plantings . The reduction in kernel size was on average less than 0.1g and the implication of this to the economics of production are yet to be explored . While early results show promise for increased production efficiencies for some varieties at closer plantings , results also point to questions of resource availability and biennial bearing . The longer-term implications of higher planting density upon kernel size and total marketable yields remaining unknown . It is because of these uncertainties that the trial will continue to be monitored for several more years and that greater emphasis will be placed on understanding the resource
demands of varieties at different densities . Together with concurrent assessments of canopy and root architectures , SARDI ’ s characterisation of resource demands will deliver almond irrigators optimised production efficiency information for multiple varieties planted at H1 through to H2 densities . Extending these investigations into the orchard ’ s most productive years will enable irrigators to make more informed planting and management decisions to maximise their marketable yields per ML of water . In the ABA ’ s next edition of ‘ In a Nutshell ’, SARDI will discuss the second of it ’ s planting density trials that examines the response of almonds to super-high ( Horizon Three or H3 ) planting densities . For more information , please contact the SARDI Almond Research Team at Loxton ( 08 8595 9149 ) or Adelaide ( 08 8429 2299 ).
34 In A Nutshell - Spring 2022 Vol 23 Issue 3