What is benchmarking?

Benchmarking is used in many industries, from manufacturing to horticulture, and is a process of determining the best methods and practices for that particular industry to achieve optimal output, and efficiencies in time and economy. In a horticultural industry such as walnut growing, the processes are obviously quite different from those that would be identified in a financial or manufacturing business. Nevertheless, it is still possible, despite the complexities of soil, climate and tree variation, to determine those practices that have the most significant effect on tree growth and walnut production.

The Aims of this Project

In the simplest case, benchmarking is used to find best practice models that can be adopted in a walnut orchard. Working together and sharing information on a range of practices will enable us to learn from each other, ultimately for the benefit of the whole industry.

This walnut orchard benchmarking project aims to achieve:

• best practice models for the establishment and maintenance of orchards by providing a framework for growers to compare the growth and productivity of their trees with those of other orchards with similar characteristics.
• methods for assessing walnut tree performance and management inputs so that any orchard can contribute to future data and compare itself with best practice models and those best practice models can then be improved.
• a knowledge of factors contributing to walnut blight incidence and other issues.
• the ability to convert good luck, bad luck and doubtful decisions into decision making tools.

The Project

After considerable research into the most likely factors to affect tree growth, a wide range of inputs were identified, and an interview was designed to survey grower's orchard conditions and practices. We also identified a number of methods of measuring outputs - in terms of tree growth and nut production. (See Appendix 1 for the revised interview form. This interview can also be viewed on the WIG web pages, and may be completed online if you wish to participate in the project.)

Ten orchards were trialled initially, to enable us to determine the most significant conditions and practices, and best methods of measuring tree growth. From this we were able to refine the interview and simplify the measurements required so that it becomes a relatively easy process for orchardists to undertake. It is hoped that many other orchardists in Canterbury will join the project now the benchmarking process is streamlined. The larger the pool of information, the easier it will be to determine best practice.

General Description of Orchards Surveyed

There were no criteria for selecting orchards for the benchmarking project; in fact a range of orchards and management practices was desirable. Of the ten orchards surveyed one was organic, seven were producing and three were young orchards. Two were planted for hedgerow production. For comparison trees were selected of the same cultivar and year for at least two orchards. The trees were planted between 1989 and 2003. Measurements were recorded from trees planted between 1992 and 2002, giving us a range of ten years of growth.

The soil types varied from Lismores, which are quite stony soils, through Eyre stony and silt loams, to fertile Templetons and Selwyns. Most shelter belts were mature and porous although some were evergreen and dense, and some internal belts had yet to develop. The varieties of trees found in shelter belts were commonly Crows Nest Poplar, Alders, Matsodana Willows or Gums, with some Macrocarpa or Pinus Radiata on exterior belts. Internal belts could contain a variety of other species. Block sizes ranged from 60m x 60m through to 80m x 100m.

Most orchardists used a mini-sprinkler system for their walnuts and drippers for their shelter. Water was applied according to perceived need in most cases but only three orchards monitored soil moisture content.

Competition under the trees was usually managed by strip spraying, with the exception of two orchards that allowed understorey growth to the trunk. One orchard applied mulch. Most orchards applied fertilizer as they felt it was needed or in response to soil or leaf analysis results.

Spraying for blight in young orchards was normally done by the orchardist but in mature orchards a contractor was employed. All used Kocide to control blight and sprayed to runoff. Most orchardists sprayed at, or close to, budburst and at least once after this.

Pruning practices varied. Orchardists had varying opinions on the pruning of young trees with some advocating heading back in winter while others took a more minimalistic approach. Some also summer pruned side branches to shape trees. Overall, whatever the age of the orchard, the main aim of all was to produce a well shaped tree.

In each orchard, where possible, twenty-five trees of the same cultivar and year were selected. Trunk diameter at 600mm, tree height, canopy diameter and height, and shoot extension were recorded.

The Main Questions Posed by the Study are:

1. Is the trunk diameter a multi-purpose measurement of tree growth?
Is it related to height/canopy height/width/volume and tree vigour?

2. Does the canopy volume and shape differ between cultivars?

3. Do different cultivars require different management practices?

4. What is the effect of soil type on tree growth?

5. What is the effect of understorey management on tree growth?

6. Does shelter and/or block size have any significant effect on tree growth?

7. How does irrigation affect production?

8. What is the effect of fertilization on tree growth?

9. How significant are pruning practices on tree growth?

To read the full report with project results, open or download the PDF file.