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Digging into Healthy Soils – PIPS3 Program update

Research & Extension

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Article co-authored by Susie Green, Michele Buntain and Marguerite White.

Fruit Producers SA, in conjunction with Susie Green Consulting, is a partner of the Tasmanian Institute of Agriculture’s (TIA) PIPS3 Program project, Improved Australian apple and pear orchards soil health and plant nutrition project (AP19006). The organisation is hosting one of the soil health trial sites, located at Flavells Fruit Sales orchard in Forest Range, South Australia (SA).

The PIPS3 Program (Productivity, Irrigation, Pests and Soils)  is a co-operative of four projects that are working collaboratively to deliver research into new technologies, advanced management systems, and integrated biological and whole-of-orchard-system solutions to pest, disease and soil constraints for the apple and pear industry.

AP19006 is led by TIA Senior Research Fellows, Dr Nigel Swarts and Dr Sally Bound. In addition to the SA regional site, the project has two core research sites in Tasmania’s Huon Valley, and four other regional demonstration sites in Victoria’s Goulburn Valley (Agriculture Victoria’s Tatura SmartFarm Experimental Pear Orchard), New South Wales (Orange) and Western Australia (Manjimup).  The research trials are investigating how different plantings, both interrow and along the tree-lines, influence soil health, tree health and nutrition, fruit yield and quality, with consideration for regional climatic conditions and soil types.

This is the first season of the three-year program which aims to:

  • Identify the biological, structural and chemical indicators for soil health, including relationship to regional and soil type differences, and assessment methods.
  • Improve understanding of the interaction between management practices, soil health, nutrient availability, water availability, pest and disease control and fruit productivity/quality.
  • Measure the impact of sustainable orchard floor management on the presence and function of mycorrhizal fungi and the organic carbon content of the soil.
  • Conduct studies to understand relationships between soil health, tree health, growth and fruit yield, productivity and quality.
  • Understand and address grower perceived impediments to adoption including water requirements, herbicide and fungicide use, tractor movements and fire risk.
  • Coordinate local studies in response to local input; and
  • Develop an irrigation (soil water balance) and nutrient management decision support web App.

The SA trial has been established on a 5-year-old block of Kanzi on M9 rootstock covered in permanent netting.

Inter-row treatments include:

  • Planting of a meadow mix (beneficial insect mix) in the inter-row sward, containing a mixture of flowering annuals and perennials;
  • Planting of a native grasses mix, sourced from seeding natives; and
  • A control treatment of the inter-row sward of Lenswood Orchard Mix.

Under-tree treatments include:

  • Cultured compost (Supplied by Peats Soil & Garden Supplies), applied to a depth of 10 cm along the weed-spray strip;
  • A sown mix of legumes and grasses; and
  • A control treatment of grower’s practice- keeping the under-tree weed sprayed.

Multiple replicates have been set-up to allow for statistical analysis of the results.

The cultured compost was applied in early December 2020. The under-tree legume/grass mix was also sown in December 2020, however due to the very dry conditions, did not take well and was re-sown by hand in June 2021.

Cultured compost applied to the under-tree row.

Sowing time showing  to be very important. We initially planned to sow the inter-rows in spring 2020  but conditions were very wet and not ideal for the tractor access needed to spray the cultivated soils, particularly on the sloping terrain. Spraying was postponed until after harvest in early autumn 2021.  Once the first good opening rains were received, a repeat weed spray application knocked re-emergent weeds, and the ground was given a light harrow. The inter-row treatments were sown in June 2021, after significant opening rainfall.

The under-tree area was also lightly scarified prior to seeding. This was a very narrow window of opportunity for seeding, as the soils were beginning to become wet and slippery after the opening rainfall.

Inter-row strip weed sprayed ready for planting, with panel under-tree on the left-hand side scarified for under-tree planting.

The meadow mix and under-tree legume/grass mix were both sown by hand due to the relatively small plot sizes (10 trees per treatment replicate). Many of the native grass seeds are very fine so the decision was made to use a  specially adapted seeder, designed specifically for native grasses.

Planting of native seed.

The meadow mix emerged well and is now well established. The under-tree legume/grass mix is also emerging well. The native grasses mix is slower and contact weed spraying will occur shortly  to reduce competition from re-emerging seed from the previous inter-row sward. Competition is one of the greatest challenges to successful establishment of native grasses.

Flowering meadow mix in the inter-row. Note, tractor traffic in spring on wet soils when the meadow mix was only relatively newly germinated has led to poor establishment in the traffic strips. This is consistent across all treatments and this year was even problematic in the established inter-rows.

All regional sites of the project are being monitored using standard protocol, and this will continue over the next 2 growing seasons. The monitoring regime includes conducting floral bud counts, fruit counts, assessing the presence of beneficial organisms, pests and diseases, and fruit quality measurements at harvest. Soil samples are also collected to monitor a range of soil health and nutritional parameters that will assist to determine biological, chemical and physical (structural) soil health indicators for the industry.

Further updates will be provided as the trial progresses and an orchard walk will be planned to view the trial site when all treatments are well established.

The PIPS3 Program’s Improved Australian apple and pear orchards soil health and plant nutrition project (AP19006) project has been funded by Hort Innovation, using the apple and pear research and development levy, contributions from the Australian Government and co-investment from the Tasmanian Institute of Agriculture. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

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