Horticultural Plant Nutrition at Northfield

Plant and soil analysis were techniques sparingly used in horticulture until the 1960s. Fertiliser application decisions were usually made by rule of thumb. Research on plant nutrition was to a large extent limited by the finite analytical capacity of the Department of Chemistry and the consequent slow turnaround times which often exceeded a whole growing season.

The establishment of the Northfield laboratories, where Max Till and later Ben Robinson were based alongside young and enthusiastic crop and pasture agronomists (who as we have seen had a brief to develop soil and plant tests as an aid to decision making by farmers) coincided with the development of the “Mill Laboratory” in the lab of a disused flour mill at Loxton. Suddenly it was possible to ask a question and get an answer prior to the next growing season. At Northfield Michael McCarthy and Norbert Maier and at Loxton Phil Cole, Keith Watson, John McCarthy, Philip Nicholas and Trevor Glenn all became involved in work aimed at understanding soil water and plant relationships in horticultural crops.

There was leaf analysis survey work in citrus, stone- and pome-fruit, almonds, and grapes to validate plant tests developed in North America and Europe. These standards even though they have limitations served SA horticulture well for 40 years. The Mill Lab provided the soil and plant analysis for these surveys.

Ben Robinson, by sampling the soil from long term fertiliser trial sites in citrus near Renmark was able to show that in orchards on mallee soils, P fertiliser was better applied in a heavy corrective band than in small annual dressings. Bill Harris and Reg French had come to the same conclusion after sampling a long term grape experiment at Nuriootpa.

Michael McCarthy’s study of grapevine responses to irrigation with nutrient and salt rich sewage effluent was pioneering in its use of multiple drip lines to allow a properly laid out experiment in a commercial vineyard. He went on to use this approach in a major study in the Riverland later.

At Northfield, Norbert Maier calibrated soil and plant tests for major nutrients in potatoes, and the team which included Louise Chvyl and Kerry Potocky addressed a range of nutritional problems in green-house tomatoes, apples, Brussels Sprouts, Sturt Desert pea (with Gail Barth), and celery, as well hydroponic culture of cut flowers and green house crops.

Rapid analytical turnaround and the cooperative involvement of the soils laboratory were integral to this work.

Late in the life of the Northfield group, Ben Robinson followed up a report of serious acidification in drip irrigated Goulburn Valley orchards by sampling soils in older sprinkler irrigated citrus orchards on light soils at Waikerie and from beneath drippers in a range of districts. In some cases acidification was serious.

Corrective recommendations were developed and trialled with inputs from CSIRO’s Richard Merry and Alan Richards. This work has been followed up in a new study by Richard Merry and Ben Thomas (SRHS) who have developed calculator that can be used as a risk management tool.

Ben Robinson was Co-Editor with Doug Reuter of Plant Analysis: A Manual published in 1986, which has since been produced in a second edition with much revision.

Looking back on the work done by Northfield group and its associates around the state, its achievements have been:

• Understanding the nutrient status of a wide range of fruits, nuts, grapes and vegetables across the state.
• Understanding the soils we use for horticulture, the risks of nutrient shortage on these soils and how best to deal with them.
• Assessing the suitability of a range of empirical plant analysis tests as guides to the use of fertilisers for orchards, vegetable growing, and in intensive horticulture (eg greenhouses).
• Developing calibrated soil and plant tests for potatoes, Brussels sprouts, celery and other crops. Adapting and adopting such tests for other crops from the literature where none has been developed locally.
• Understanding of the risks of soil acidification in intensive horticulture.
• Communicating this knowledge to growers, and their advisers.
• Contributing to the preparation of the Plant Analysis Manual which has been influential Australia wide in the adoption of sensible criteria for fertiliser use.
• Training a new generation of scientists who have continued to try to understand how best to use fertilisers and help growers make good decisions.

The work of the nutrition group was very solidly underpinned by close relationships with the extension staff (Brenton Baker on the Adelaide Plains, John Steed in the Adelaide Hills, John Jennings, Bill Baskett, Ross Wishart, Tom Simes and Greg Botting in the Riverland, Trevor Twigden at Murray Bridge, and David Moss in the South East).

(Source: Ben Robinson)