Relationships between canopy size, light interception and productivity in conventional avocado planting systems

Avocado (Persea americana Mill.) is a relatively under-developed tree crop, grown commercially in climates ranging from tropical to temperate. Orchard productivity across a broad range of tree crops has been demonstrated to be related to total light interception. However, little information is currently available for avocado. Here we document the relationships between canopy volume per hectare, total orchard light interception and yield per ha for avocados of cultivar 'Hass' grown in low density planting systems. Total orchard light interception increased with canopy volume, with increases in light interception per unit canopy volume becoming smaller at the higher levels of canopy volume/ha. Yield/ha increased with light interception and canopy volume up to approximately 80-84% total light interception and 30,000-35,000 m(3) canopy volume/ha. It is unclear whether the trend in yield/ ha at the very highest measured levels of orchard light interception and canopy volume should be described as plateauing or declining. Mean fruit weight decreased as light interception increased, although the relationship varied between seasons. For these conventional planting systems there is no yield benefit from increasing canopy light interception above 80-84%, and there may be yield decline at higher levels of orchard light interception.