By Liqi Han (University of Queensland) and Ian Goodwin and Mark O’Connell (Agriculture Victoria)

The Narrow Orchard Systems for Future Climates project is a partnership between state agriculture agencies in Victoria, SA, WA and NSW, the University of Queensland, and Plant and Food Research NZ. 

Laser scanning to create digital twins and measurements of light interception in stone and pome fruit canopies were collected to validate a light distribution simulator. They will be used for simulation-supported studies to investigate the effects of narrow orchard systems (NOS) on canopy light environment.

Ag Vic leads the project with experimental and demonstration sites at the Tatura SmartFarm, Loxton and Manjimup research stations, and in a commercial cherry orchard in the Adelaide Hills.

One of the components of the project is to determine the effects of orchard design (i.e. row spacing and orientation, canopy height and width) on the light environment within the tree canopy.

This is important because light has significant impacts on fruit colour development and bleaching, fruit sunburn damage, leaf photosynthesis, flower initiation and yield.

The project will harness an existing light simulator that uses the combination of solar position and a digital twin of an orchard (captured using a LiDAR scanner) to simulate light distribution in a tree canopy.

Planar canopies in apple, pear, nectarine, plum and cherry orchards in the Goulburn Valley have been scanned using LiDAR technology (see Figure 1) to create a digital twin (see Figure 2), which mirrors their physical counterpart with precise geometric and geographic details.

Digital twin data was subsequently incorporated into a high-performance light simulator where billions of explicit rays can be generated from the sky and traced throughout the orchard.

To validate the simulation outputs, corresponding measures of light interception were taken approximately every hour using a light trolley (Figure 3).

The span of the trolley was 1.5 m and light sensors were spaced at 125 mm.

The trolley was wheeled down the middle of the alleyway and one-second light measurements were stored in a datalogger.

Figure 4 shows the light interception (i.e. the fraction of the orchard floor that is shaded by the trees) in a narrow apple orchard with a 2.4m row spacing and a canopy width of approximately 0.3 m.

Light interception was highest in the morning and afternoon.

Minimum light interception occurred in the middle of the day when the sun was directly overhead.

The next step is to compare the computer-produced and field-measured results for validation.

Once we have confidence in the model from our measurements with the light trolley, we can explore “what if” scenarios.

For example, row spacing can be reduced and canopy height can be increased to see the effects on light distribution.

Later of course, when the NOS experimental orchards are established, the model outputs will be compared with observed data.