THE project trial at Ladycroft Orchard in Manjimup, situated in a Lady in Red block, was planted in 2018 on 2D trellis with drip irrigation. The first season of the project commenced in 2024, with six under-tree treatments established and assessed:

1. Control: bare herbicide strip (current practice)

2. Living legume mulch (cover crop), comprising peas, faba beans and oats

3. Mushroom compost

4. Living legume mulch (cover crop), cut in spring and covered by compost

5. Native Australian ground covers (Kennedia prostrata and Myoporum spp)

6. ‘Mow and throw’ multi-species pollinator mix, cut and mulched in spring

Treatments were established in autumn, with fruit harvested and assessed a year later.

Impact on fruit quality

In year one there were no significant differences in fruit size or yield. Differences were observed in fruiting efficiency (Figure 1), firmness (Figure 2) and red colour coverage (Figure 3). As these are initial results within a multi-year trial it is too early to delve too deeply into detailed analysis, therefore the following is a high-level overview.

The pollinator treatment (dark green) had the lowest fruiting efficiency. It is likely that the treatment species outcompeted the apples in attraction, both flowering at similar times causing the bees to select the treatment over the apple canopy

FIGURE 1. Fruiting efficiency in spring of 2024. Efficiency is determined by the ratio of cluster count to fruit set per branch.

FIGURE 2. Firmness measures in kg across all treatments in 2025 harvest.

FIGURE 3. Blush coverage across fruit (% score) in the 2025 harvest.

FIGURE 4. Pest damage evident in the field and the laboratory, competing flower species in October 2024.

flowers on offer. Firmness was higher in the legume (light green), legume + compost (red) and pollinator treatments than in the control (orange). Future seasons will confirm whether this trend holds. The compost (pink) treatment had the lowest red colour coverage, potentially caused by increased soil nitrogen as the compost was breaking down. However, this relationship was not seen in the legume + compost treatment. All other treatments improved colour relative to the control.

Given changes in soil parameters can be slow to show effect, further data collection and analysis until 2028 is crucial to give confidence in the longer-term effects of the treatments.

Pest pressure

Pest damage was substantial in the trial plot, impacting between 16–23% of the fruit sampled. Damage was primarily caused by looper and weevils, other pests were present to a lower extent. Fewer passes of spring mowing (to let living mulches flower and set seed) allowed tall species such as oats and mustard to form a ‘ladder’ into the canopy during flowering and early fruit growth.

Changes were made in the 2025–26 season in response to learnings from first year results. Mowing has been undertaken more frequently to keep ground covers lower, and treatment species have been selected to avoid flowering competition with the apple crop. Additionally, insect monitoring showed certain treatment species had been more attractive to pests in the first season, and these species were therefore excluded from the 2025–26 reseeding mix.

Impacts on soil

Soil carbon and nutrients were baseline-tested and are being monitored annually. Microbial activity was assessed in spring 2024 using 6 week buried cotton assays. The results are shown in Figure 5, with higher percentage weight loss implying more microbial activity. All treatments showed higher activity than the control, however, cotton assays can demonstrate variation based upon their location, hence additional microbial testing will be conducted by an external laboratory.

Straight from the orchard: what worked so far (and what didn’t)

• Avoid tall species (e.g: oats, mustard) in seed mixes—spring growth can quickly become unmanageable.

• Brassicas (e.g: mustard, forage rape) can draw flying pests and aphids into the orchard during flowering. Later in spring they may also compete for water under drip irrigation, even though they produce strong ‘mow-andthrow’ biomass.

• Chicory and linseed self-seeded well and did not appear to harbour pests.

• Clover provided reliable ground cover for beneficial insects, and legumes in the cover-crop treatments did not appear to reduce fruit colour.

• Multi-species mixes without brassicas have since been adopted as inter-row plantings elsewhere in the orchard, with no observed adverse effects.

• Native species persisted well over two seasons and tolerated traffic and fertiliser. Their flowering appeared to be counter-seasonal to apples, reducing competition for pollinators.

• In 2025–26, the orchardist kept undergrowth low and away from the canopy (prioritising canopy access over seed set) and avoided heavy flowering during the apple bloom window. After removing the ground-to-canopy ‘ladder’, pest damage in 2026 was substantially reduced.

At time of writing, fruit quality data from the 2026 harvest was being collected and the two seasons will soon be compared.

Acknowledgements

The PIPS 4 Profit Program’s Building Sustainable Soils Project (AP22003) has been funded by Hort Innovation, using the apple and pear research and development levies, contributions from the Australian Government and co-investment from the Tasmanian Institute of Agriculture. It is supported regionally by Pomewest, Fruit Producers SA, NSW Department of Primary Industries and Regional Development and APAL. Hort Innovation is the grower-owned, not-for-profit research and Development corporation for Australian Horticulture.

FIGURE 5. Approximation of microbial activity from weight loss of cotton assays buried over spring 2024.