“Sundial” experiment

Research aim: To quantify the relationship between light and spur fertility

The outcome sought from this experiment is an objective basis for orchard layout, particularly row spacings and directions.

There is strong awareness of the relationship between the amount of light intercepted by a tree canopy and that tree’s likely productivity, other limitations notwithstanding. Quantifying the amount of light a spur needs to intercept is a little more difficult. Knowing the quantity of light needed by a spur could, however, be an important orchard design parameter.

Two rows of trees will be planted perpendicular to each other with one orientated perpendicular to the path of the sun during the period of floral bud initiation. The trees will be trained to a 2D central leader, and lateral shoots will be trained horizontally on wires spaced approximately 50 cm apart and supported by posts four metres apart down the row (similar to modern high-density apple orchards). The tree row width will be maintained with careful pruning to minimise the canopy depth. The aim is to maximise the amount of light reaching spurs on either side of the trees in the row perpendicular to the path of the sun. The spurs on the trees in the row that will more-or-less be parallel to the sun’s path during the period of floral bud initiation will be predominately shaded during this period. In addition, by artificially shading parts of the canopy to varying degrees, the amount of light incident on individual spurs can be manipulated allowing the relationship between light and spur fertility to be quantified.

Video: Dr Micheal Treeby introduces research into light interception

Project Acknowledgement

This project (RnD4Profit-15-02-011 ‘Advanced production systems for temperate nut crops’) is supported by Horticulture Innovation Australia Limited, through funding from the Australian Government Department of Agriculture and Water Resources as part of its Rural R&D for Profit programme and the Department of Economic Development, Jobs, Transport and Resources (Victorian Government), the South Australian Research and Development Institute (SARDI), the Almond Board of Australia (ABA), and New South Wales Department of Primary Industries.