Soil Compaction

One of the most common and most overlooked issue affecting New Zealand farms.

Soil compaction is one of the most common—and most overlooked—issues affecting New Zealand farms. Whether you're running a dairy platform, cropping operation, or sheep and beef system, compacted soils can quietly limit productivity by restricting root growth, reducing water infiltration, and blocking air movement. In this blog, we’ll cover what causes soil compaction, how to identify it, and practical solutions to fix it—across all farming types.

What is Soil Compaction?

Soil compaction occurs when soil particles are pressed together, reducing pore space. This squeezes out air, limits root development, and slows water infiltration. It can happen on flat paddocks, hillsides, cropping fields, laneways, and anywhere machinery or livestock regularly travel.

Common Causes of Soil Compaction

Heavy machinery traffic, especially on moist or wet soils.
Repeated stock pressure in areas like gateways, troughs, laneways, and sacrifice paddocks.
Bare soil exposure, leading to surface sealing after rain.
Low organic matter makes soils more prone to compaction and less able to recover.

*Side-by-side comparison of compacted and healthy soil cross-sections.*

How to Identify Soil Compaction

Look for:

Stunted or uneven plant growth.
Ponding or runoff after rain.
Surface crusting or hard pans when digging.
Roots growing sideways rather than down.
Poor pasture regrowth or crop establishment despite adequate nutrients.

Simple test: Use a spade or soil probe after rain—if resistance is high and roots are shallow, you’re likely dealing with compaction.

Solutions to Fix Soil Compaction

1. Mechanical Aeration

Subsoiling or ripping: Breaks up hardpan layers, particularly in cropping or flat pasture paddocks.
Aerators or spiked rollers: Improve topsoil porosity and water movement.
Best applied when soils are moist but not saturated.

*Tractor using an aerator on a pasture.*

2. Biological Remediation

For all farming systems, encouraging deeper root systems is a sustainable way to fix compaction.

Use deep-rooted species like lucerne, chicory, plantain, tillage radish, or fodder beet.
Introduce multi-species mixes to build soil structure with a range of rooting depths.
Encourage earthworm activity and soil biology through reduced tillage and good organic matter.

3. Introducing Calcium-Based Products

Calcium plays a critical role in improving soil structure.
Products like lime, gypsum, and liquid calcium help loosen clay soils by flocculating particles.
Improved soil aggregation allows better water movement, root growth, and microbial life.
Best results occur when combined with organic matter and based on a soil test.

📌 Tip: Lime increases pH over time, while gypsum adds calcium without raising pH—ideal for already neutral or alkaline soils.

4. Improve Grazing & Traffic Management

Compaction is often caused by habits, not just events.

Avoid grazing during wet conditions, especially on heavy soils.
Use back-fencing and rotational grazing to reduce pressure on recovering paddocks.
Designate sacrifice paddocks or laneways to protect more valuable ground.
Limit machinery use during vulnerable times—and consider lighter gear or flotation tyres.

Long-Term Prevention Strategies

Once compaction is corrected, it’s important to maintain soil health:

Build organic matter with compost, manures, and diverse crops.
Keep ground covered to protect against raindrop impact and surface sealing.
Rotate crops and pastures to prevent repetitive stress on the same areas.
Monitor soil biology and structure as part of regular farm management.

Final Thoughts

Soil compaction is widespread but solvable across all farming types. Whether you're milking cows, growing grain, or running sheep, unlocking your soil’s structure can unlock serious performance gains.

By combining mechanical, biological, and chemical tools—and adopting smarter grazing and traffic practices—you can give your soil the air, water, and life it needs to support better growth year-round.

Fixing Soil Compaction: What Every Farmer Needs to Know