ATO RnD Grant Submission Structure

Improving Nitrogen Efficiency and Soil Function in WA Broad-Acre and Pasture Systems

A biology-first intervention for sandy soils

Executive framing for assessment:

Western Australian broad-acre grain and pasture systems operate predominantly on sandy to sandy-loam soils characterised by low clay content, low organic carbon, and poor nutrient retention. Nitrogen loss through leaching and volatilisation remains a primary constraint to productivity, profitability, and environmental performance.

This proposal reframes nitrogen inefficiency as a soil biological custody problem, rather than a fertiliser rate or timing problem, and evaluates whether re-establishing soil-borne microbial function can measurably improve nitrogen use efficiency (NUE), soil structure, and system resilience.

The problem: nitrogen leakage in WA systems:

In biologically depleted sandy soils:

• Nitrate nitrogen leaches rapidly below the root zone

• Nitrogen availability is limited to short uptake windows

• Organic carbon inputs oxidise rather than stabilise

• Root systems remain shallow and stress-prone

• Yield and pasture performance are volatile year-to-year

Despite increased fertiliser inputs, NUE continues to decline, increasing cost exposure and environmental risk.

Hypothesis

Re-establishing soil-borne, nitrifying and regulating microbial communities will:

1. Improve nitrogen retention within the biologically active root zone

2. Increase NUE without increasing nitrogen application rates

3. Improve soil aggregation and moisture retention

4. Enhance root depth and resilience under heat and dry stress

5. Stabilise crop and pasture performance across seasons

Intervention: biology, not chemistry substitution

The intervention introduces soil-adapted, living microbial consortia designed to:

• Attach to soil particles and root surfaces

• Convert nitrogen into plant-available forms in situ

• Temporarily immobilise nitrogen in microbial biomass

• Release nutrients gradually through predatory cycling

• Build micro-aggregation in low-clay soils

Importantly, this is not a fertiliser replacement trial, but a nitrogen efficiency and soil function trial layered onto existing nutrient programs.

Role of microbial regulation (critical mechanism):

Healthy soils include predatory (carnivorous) microorganisms that:

• Regulate microbial population dynamics

• Release nitrogen and minerals from microbial biomass

• Prevent nutrient lock-up and boom–bust cycles

• Maintain steady nutrient availability during crop and pasture demand

Their absence in degraded soils leads to stalled nutrient cycling and increased nitrogen losses.

Before / After system behaviour (expected):

Baseline (biologically thin paddocks):

• Rapid nitrogen loss after application

• Patchy crop or pasture response

• Shallow root systems

• Low soil aggregation

• High variability across paddocks

• Increasing reliance on rescue inputs

Post-intervention (season-by-season):

• Improved nitrogen retention and stretch

• Increased NUE at equal application rates

• Deeper, more resilient root systems

• Improved soil aggregation and moisture holding

• Reduced paddock variability

• Greater system stability under climatic stress

Applicability across systems:

Broad-acre grain (wheat, barley, canola):

• Focus on NUE, root depth, grain fill resilience

• Reduced nitrogen losses during rainfall events

• Improved performance in sandy zones within paddocks

Pasture systems (sheep and cattle):

• Improved nutrient cycling under grazing pressure

• Faster pasture recovery

• Improved ground cover and soil protection

• Better utilisation of dung-derived nitrogen

Biological systems adapt to stock class and management; chemical systems do not.

Measurement and evaluation (grant-relevant):

Primary indicators:

• Nitrogen use efficiency (NUE)

• Root depth and density

• Soil aggregation and stability

• Soil moisture persistence

• Paddock variability metrics

Secondary indicators:

• Crop or pasture resilience under heat stress

• Input efficiency over time

• Soil organic carbon trends (medium term)

Yield is treated as an outcome, not the sole metric.

Risk and realism:

• No claim of instant yield increases

• No reduction in fertiliser rates in year one unless supported by data

• Focus on system correction, not short-term stimulation

• Designed to integrate with existing farm practice

This reduces adoption risk and improves transferability.

Relevance to RDC priorities:

This work directly addresses:

• Nitrogen efficiency and cost pressures

• Soil health and resilience

• Environmental stewardship

• Climate variability adaptation

• Long-term productivity of WA farming systems

Summary for assessors:

WA sandy soils do not fail due to lack of inputs.
They fail due to lack of biological custody of nutrients.

This proposal tests whether restoring soil microbial function can reduce nitrogen leakage, stabilise production, and improve system resilience, delivering both economic and environmental benefits without increasing input dependency.

 

Bronwyn Holm

Founder, Earthfood™

Farmers' Friend • Gardeners' Guide • Soil Advocate • Growers’ Voice

Bronwyn Holm works alongside farmers, gardeners, land stewards and balcony pot legends to restore living soil through biology, not chemistry. Earthfood™ was built to return microbial intelligence to the ground quietly, effectively, and without dependence on industrial inputs.

© Bronwyn Holm 2026
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