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
Video transcript: Introduction to light interception experiment. Dr Micheal Treeby, Irymple. September 2018
There's a fourth trial which we are establishing where we're looking at trying to quantify exactly how much light is needed by fruit, by buds in order to promote what we call floral primordia. So that's the initiation of a couple of cells in a bud, in the case of almonds, a spur that will end up being flowers. Know we know that on the top of almond trees that the spurs are generally highly productive. There's lots of flowers, and as we move down the profile, we move down through the tree, the amount of light that gets to the bottom is greatly reduced. It's a very shaded environment, and those birds are less productive. So, we know that there's a relationship there. We want to take that relationship. We want to quantify that relationship and when we can when we can quantify that relationship, so that these things need so many hours whatever it might be, we can then make informed judgements of how the orchard of the future might need to look in order to maximize that light, right down the profile of the tree. The layout of the orchard is the bit we don't know and the light experiment, if you like, trial is trying to provide the design specifications in one of another term.
Video: Almond Research 2019 - Introduction and update on the almond light interception experiment with Dr Michael Treeby
Dr Michael Treeby, Senior Research Scientist from Agriculture Victoria, updates us on the research experiment focused on almond tree light interception, December 2019, at the Nut research orchard in Irymple, Victoria.
Transcript: Introduction to almond light interception experiment with Michael Treeby
This particular trial is concerned with light. The aim is to try and establish what the relationship is between the amount of light that spurs receive during a critical period in late January, early February, when floral or bud primordia are formed.
So, what we have here is two rows, one row perpendicular to the other. When one row will be more or less in shade, most of the time during that particular period. So, the buds on those trees, the spurs and those trees will be shaded most of the time during the critical phase in late January, early February. The other row that we have behind us, going left to right, they will be exposed. The spurs on those trees will be exposed most of the time during that period. So, when the sun comes up, its path will be perpendicular to that row orientation behind us, but be more or less in parallel with the row on my right hand side.
Now, what we hope to do is, as I said, establish a relationship between the amount of light that those spurs receive and what their subsequent reproductive behaviour is. Do they actually bare a flower in the future, in this subsequent season? Because of the design of the row and the way we could be training them and so forth, we'll be able to actually shade particular spurs so we know that they don't receive light, or they'll be shaded directly from direct light, or we will be able to exclude particular wavelengths to try and quantify what the relationship is between light quantity, and light quality. Ultimately, when we have that relationship established, we will be able then to maximize the likelihood of spurs being reproductive, bearing a flower. They will need to receive this much light during this period of time. That then dictates, gives us another parameter in the orchard design thing. i.e. How close can we plant those rows together? And what orientation might, they need to be for light to be reaching the whole part of the canopy, at some point during that day, and of sufficient quantity and quality to maximize the likelihood of them forming a flower?
It stems from an ongoing concern, we've all had, that we know that light is involved somehow, but quantifying what that relationship is, that's been the difficult bit. With an experiment like this, we can manipulate the amount of light they get. We can manipulate it from the maximum possible. They're not shaded at all, most of the day, to all the way through. They're shaded most of the day. And then we can manipulate those other scenarios and then, as I said, shade particular spurs and exclude particular wavelengths thing so we can modify quantity and quality.
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.