Digging deeper: Strategic Farm unearths drainage solutions

Ellie Dearlove provides an update from our drainage trial at Strategic Cereal Farm North.

A spade isn’t always enough to reveal what’s going on under your feet, sometimes you need to dig deeper to see the full picture.

This is clear at Strategic Cereal Farm North, which is hosted at David Blacker’s farm in North Yorkshire.

On David’s largely heavy clay land, we are investigating how drainage upgrades affect soil health, weed pressure, crop health and yields.

Recently (in midsummer), David fired up the digger and carved out soil pits (as deep as 60 cm) across the treatment field.

The treatments include:

• New drains (at varying spacings)
• Mole drains
• Old drains (not touched since the end of grant aid in the mid-1980s)
• Undrained ground
• New drains in lighter, sandy soils

The field is currently fallow (stubble), mainly due to poor crop establishment in autumn 2025.

With support from ADAS, Anne Bhogal (a principal soil scientist) and David Motley (a field research scientist), we found significant variation beneath the soil surface.

What we saw was encouraging and sometimes puzzling, but always useful.

On paper, the heavy clay soil is perfect for mole drains, but only two years after their installation, water movement had slowed.

The top 5 cm were dry and cracked, with roots (of naturally established plants) pushing deep, which is exactly what we wanted to see.

With some smearing in the drainage trench, we were braced for smeared moles and collapsed channels.

Instead, we found intact mole drains that were clearly improving lateral water movement.

Although we saw some unexpected organic matter inside the channels, this indicates usage by earthworms, which will promote water movement.

It appears that the sluggish performance is mainly because the mole channels have shrunk (from 10 cm to 5–6 cm).

It was potentially too wet when they were installed (October 2024), which stopped the mole drains from fully curing.

We plan to disc and subsoil this area, then re-establish the moles, before drilling winter wheat later this year.

The old-drain and no-drain areas were equally ineffective at shifting water.

Although both had decent angular soil structure, there were hardly any roots in the topsoil. This is because crops failed to establish during prolonged spells of waterlogging, with the impact clearest in the most poorly drained field areas.

There was clear orange staining near the top of the soil (top 20 cm), with purple-grey patches lower down and mottling throughout. These are clear signs of anaerobic activity.

The low porosity, minimal cracking and dense, compacted subsoil we saw are also telltale signs of persistent saturation.

Earthworm burrows also petered out at just 20 cm (in good conditions, deep-burrowing worms can get a metre down).

Visual evaluation of soil structure (VESS) scores were also poor (5 in the lower profile and only slightly better in the middle).

Initially, we were baffled at the lighter, sandy field section.

With freer-textured soil and 10 m drain spacing, it should perform well, but it always consistently underperforms.

Although water was moving above the pipes, almost no water was moving horizontally through the surrounding soil.

Despite sitting about 1 m from a drainage pipe, it featured the wettest soil of any pit.

The soil profile was grey and anaerobic, with orange staining, which suggests fluctuating wet and dry spells.

We also recorded few earthworms and a poor VESS score (around 5 below the surface).

Although there was no plough pan or obvious compaction layer, roots hit a tightly packed sandy clay layer at 20 cm and stopped dead.

But subsoiling won’t help (and could cause smearing).

Mole drains won’t hold in this texture, either.

Interestingly, there’s a pond at the top of the field that never fully dries, with a willow tree sitting 100 m off in the hedgerow. This is indicative of a high water table.

We’re now investigating whether water is coming in from outside the field. If it is, then some form of water interception or diversion might be better than more drainage interventions.

• Full profile pits show much more than spade-sized holes
• The new drains promote lateral water movement
• The mole drains work (despite their shrinkage)
• The old drainage system is spent
• Soil texture and hydrology cause the issues in the sandy patch (not compaction)

We’ll keep monitoring all areas to understand which investments deliver the greatest improvements and how long it takes to recoup the cost.

Finally, another key message is to keep living roots in the ground to feed soil biology, build structure and increase resilience.