When setting out to establish an orchard, the difference between a great-performing orchard and a poor one can come down to the site selection. Growing avocados on a marginal site can be a costly battle. To ensure the best site, a number of points should be considered.
Avocado trees performing exceptionally well under high density planting and optimal management regime.
Soil: Avocados require well-drained soils with good organic matter content due to their susceptibility to Phytophthora cinnamomi, a root rot disease. In the Bay of Plenty, where there are rainfalls of 1000-1500mm per year, a minimum depth of 1.5m well-drained soil is required.
It is essential to take soil samples for testing and dig holes to assess the soil profile, drainage, and water table during times of high rainfall. Avocados have shallow, surface-feeder roots and therefore a good topsoil is vital. If the land has previously been heavily contoured and the top soil removed, problems will be experienced.
Temperature: Avocados are cold-sensitive due to their origins in a subtropical climate. Heavy frosts and consistent low winter temperatures can result in leaf and flower burn, poor fruit set as well as internal fruit damage.
Slope and aspect: The ideal site has a four to eight per cent slope. It may be difficult to operate machinery onslopes of more than 10 per cent and erosion can become a problem. North-facing slopes are warmer and have the best light conditions as opposed to the more shaded, colder south facing slopes.
Water availability: Consistent water availability is both important for establishing young trees as well as during fruit set and development of older productive trees. Without adequate rainfall during these critical periods, significant economic loss can occur and irrigation should be considered.
Wind: Exposed sites with strong winds can cause both structural damage to the trees as well as wind-rub scarring on the fruit. This, combined with excessive fruit drop in these windy conditions, result in reduced pack-outs and returns.
Spacing and planting density: An optimum orchard design should favour maximum yields without compromising the management of the orchard, e.g. access for spraying and harvesting. If you space the trees so that no thinning is necessary in the orchard’s lifespan, you will utilise only slightly more than 50 per cent of the land. This is uneconomical use of space and takes many years before the orchard achieves a profit.On a cumulative yield basis and thus profitability of returns, more densely spaced orchards outperform widely spaced ones, especially for the first 10 years.
Rather, consider planting the trees closer together initially and then you have the option to thin them out systematically and selectively at a later stage, or alternatively manage them as hedgerows.
An orchard is expensive to establish and the decisions made from the outset will affect the performance of your orchard over its lifetime. Choose your site wisely, manage your young trees well and remember that money and time spent wisely now on establishing the site and the trees ensures quicker returns and is money saved later when trying to remedy poorly performing trees.