Benefits of sward lifting for profit and environment

A decade of sward lifting on a Cornish farm has prevented run-off after heavy rainfall, shortened the winter housing period and is helping soils to sequester carbon.

A typical field at Trepoyle Farm in the Tamar valley, where Bill Harper farms with his wife, Suzanne, has some deep drainage installed in the 1960s or 1970s (some of which has silted up) and a system of old, shallow, clay pipes which are partially functioning.

Streams run through gulleys across the farm, and nearly all the fields have a wet spot in them.

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Sward lifting comes into its own on the more difficult pastureland, says Bill, who describes the farm’s cold, heavy clays (known as the Culm Measures) as “an absolute bombsite” of soil types – sometimes all in the same field.

There are two soil types that respond particularly well to sward lifting, he says.

“These are the alluvial flood plains, where we’ve got silt – some of which has gone peaty and is particularly heavy.

“The other land is gently sloping, mainly heavy loam over a shillet sub-base [small stones mixed with clay].”

Bill first saw an Opico sward lifter at a demonstration, bought one soon after and has been using it for the past 10 years.

Bill and Suzanne Harper © Emily Fleur

Water-holding capacity

Part of the Harpers’ Countryside Stewardship agreement is to hold water after heavy rainfall before it works its way into the River Tamar – a slow-moving, meandering river that does not clear easily, explains Bill.

“We need to try and get that water running into the base of the land rather than running off the surface. [To do that,] we need to work on our soil.

“If we didn’t, water would just course off the top of the soil and straight into the river.”

This is where the sward lifter comes in: it allows the water to dissipate slowly through the soil (see “How a sward lifter works”.)

© Bill Harper

Optimum timing

The season for sward lifting at Trepoyle is from August to October, when the land is past its best grass growth.

This ensures that the resulting drainage helps throughout winter, during which time plants can repair any damage caused by the slicing action of the tines.

“We start with the heaviest land – the river meadows – in August. In September, you do your medium ground, leaving your driest ground for October. We do each field every two or three years.”

As well as preventing run-off, the sward lifter is the Harpers’ key tool for preparing land for grazing:

“We have 50-60 inches [1,270-1,520mm] of rainfall on heavy land, so we’ll always have problems with poaching in April and October if we’re into a wet time,” says Bill.

“If a field is wet in April and the cattle trash it, we’ve got poor output for the whole of the summer.”

However, if the grazing period can be extended from the beginning of April to the end of October or early November, the result is a shorter winter for housing.

This saves a “massive amount” of silage if cattle can be turned out on 1 April, rather than the end of the month.

The machine is designed to close slits in the sward and has breakaway legs to avoid damage © Bill Harper

Grass growth

Grass growth on the farm is measured regularly using a plate meter.

A starter dressing of 75kg/ha of nitrogen is applied where allowed, followed by a dressing of fermented dung (bokashi) through the grazing season.

Suckler cows are stocked at three cows a hectare with calves. Grass production averages 12-15t dry matter/ha a year.

“This year, we’ve had the best output in terms of grass growth in many years,” says Bill.

“We’ve had to be pretty sharp to get crops harvested, but we’ve had grass growth all the way through and will achieve the best weaning rates we’ve ever had.

“We creep feed our calves to reach 350kg at weaning – you need to do that for early finishing, and it prepares the rumen for a silage and concentrate diet in the winter.”

Soil organic carbon

Bill and Suzanne are convinced sward lifting has also helped sequester carbon in the farm’s soils.

“We’ve got soil sampling data to show we’ve increased soil organic carbon by 1% a year over four years, from 7s and 8s to 11s and 12s,” says Bill. “We put that down to the sward lifter and the GS4 mixes we grow.

“We really believe getting oxygen to the grass roots and allowing them to breathe has increased our soil organic carbon, and we’re very keen to get that into practice as we’re so concerned [farmers are] being castigated for the methane we’re producing, but not being credited or rewarded for the amount of carbon we’re capturing.”