Soil Associations

0813f WALLASEA 1

Soil and site characteristics

Deep stoneless non-calcareous and calcareous clayey soils. Soils locally have humose or peaty surface horizons. Groundwater controlled by ditches and pumps. Flat land. Slight risk of flooding.

Geology

Marine alluvium

Cropping and Land Use

Winter cereals and some grassland.

Component soil series

Subgroup	Series name	Percentage	WRB 2006 link
8.13	WALLASEA	60%	Clayic Fluvic Eutric Gleysols
8.14	NEWCHURCH	20%	Clayic Fluvic Calcaric Gleysols

Covers 846 km² in England and Wales

Soilscapes Classification

21	Loamy and clayey soils of coastal flats with naturally high groundwater

0813f WALLASEA 1

Detailed Description

This is the main association on the marine alluvium of the coastal marshes of north Kent, Essex and Suffolk. It occurs in the Humber estuary, and there are small areas in north Norfolk, Devon, Wales and along the Hampshire coast. Sea walls, river embankments and other works protect the land from daily flooding as much is below high tide level. On the east coast the sea defences are designed to withstand tidal surges in the North Sea that may reach heights of 4-5 m O.D. Occasional breaches have occurred, sometimes with serious consequences. Drainage is by open ditches leading to tidal sluices or pumps. There is little microrelief partly a result of recent levelling. The soil pattern is simple with non-calcareous clayey Wallasea pelo-alluvial gley soils, and clayey Newchurch pelo-calcareous alluvial gley soils (Fordham and Green 1980) occupying almost all the land. There are inextensive inclusions of fine loamy Paglesham, fine silty over clayey Pepperthorpe, fine silty Agney and clayey Dymchurch soils. Humose-topped non-calcareous clayey soils of the Downholland series are frequent in Humberside, but rare elsewhere.

The association covers 30 km² in Wales at the mouth of the Vale of Clwyd and in the lower Usk valley. From Abergele and Prestatyn inland almost to Bodelwyddan, Wallasea and Newchurch soils, formerly described as Rhyl and Rhuddlan series by Ball (1960), are present in roughly equal amounts. Occasional Pepperthorpe and Stockwith soils occur in fine silty over clayey alluvium. In south Wales the small area along the Usk has frequent Downholland soils.

The association covers 196 km² along the deeply indented coastlines of Essex and Suffolk south of the river Alde, with small areas at Blakeney and Brancaster on the north Norfolk coast and on the River Ancholme in north Lincolnshire. It is almost entirely composed of Wallasea soils with calcareous Newchurch soils randomly distributed. On Bradwell marshes in Essex which have been reclaimed relatively recently, the proportion of Newchurch soils is larger and this soil is dominant locally in Suffolk where there are also a few sulphuric soils mainly of the Normoor series. Peat soils and soils with humose or peaty topsoils are rare components, confined to narrow fringes at the landward edges of the marshes. In Suffolk, Appledore, Dowels and peaty Adventurers' soils, and on Little Thurrock marshes Downholland and Walkerith soils, occur in such positions. Goldhanger and Old Hall marshes to the north of the Blackwater and other small areas elsewhere are crossed by deep creeks, and remain under rough grazing or permanent grassland. Elsewhere the land is level without creek beds or ridges. Roman and medieval salt and pottery works are marked by a series of low mounds at the landward edge of many marshes, although most have now been ploughed flat leaving patches of reddened earth.

This association, extensive on Humberside and coastal marshes in South East England is found on marine alluvium around the coast of Devon and in west Somerset. It occurs in the estuary of the Exe and at the mouths of the Axe and Teign in the south, and in Porlock Bay and the Taw estuary in the north. Sea walls, river embankments and other works protect the land from daily flooding as much is below high tide. The soil pattern is simple with non-calcareous clayey Wallasea pelo-alluvial gley soils occupying almost all the land. In the Exe estuary, the soils were mapped as the former Exminster series, and soils belonging to Downholland, Dowels and Pepperthorpe series have also been identified.

The association occurs along the middle reaches of the river Hull and in the lower and middle Ancholme valley. Large areas are composed almost entirely of Wallasea soils; associated soils rarely cover more than a quarter of the land. Calcareous Newchurch soils are most common near to the Humber and humose Downholland soils become more frequent towards the landward end of the valleys. The land is flat and lacks creek ridges and the associated silty soils that are characteristic of Wallasea 2 association.

The association occurs principally in north Kent along the Thames and Medway estuaries, on the Isles of Grain and Sheppey, and south of the Swale. Wallasea soils are dominant and there are small areas of calcareous Newchurch soils on Luddenham and Graveney marshes near streams flowing from the chalk upland. There are also occasional less-mottled Dymchurch soils. Wallasea soils with thin black humose surface horizons are common on old permanent grassland. These were formerly classified as Downholland series in an earlier survey of Kent. Where such grassland is ploughed up for arable cropping the distinct organic surface layer disappears. Large mounds 4-5 m high mark the sites of Roman or Medieval salt works near the landward edge of many marshes.

In Hampshire, Keyhaven, Pennington and Beaulieu marshes are dominated by Wallasea and Pepperthorpe soils and, unlike elsewhere, there are no soils with humose surface horizons, and no calcareous soils. Farlington Marshes in Langstone Harbour, managed as a nature reserve, have common inclusions of Paglesham and Stockwith soils, the latter over chalky drift at shallow depth.

Soil Water Regime

High groundwater levels cause severe waterlogging (Wetness Class V). Some drainage improvement can be achieved by a close network of ditches as subsoils are relatively permeable but, since most land is in grass, water levels are kept high to contain stock. With pipe drainage the soils may be only seasonally waterlogged (Wetness Class IV). The soils have moderate available water capacity so with water from groundwater sources and small summer soil moisture deficits, grass does not suffer from drought.

In Eastern England the water regimes depend mainly on arterial drainage systems. Without adequate control of groundwater Wallasea and Newchurch soils are waterlogged for long periods in winter (Wetness Class IV). Subsoils are relatively permeable and waterlogging is mainly caused by groundwater. After pipe drains have been installed, pumped catchments or areas with efficient tidal sluices are occasionally or seasonally waterlogged (Wetness Classes II or III). Compaction of surface and subsurface horizons is common under intensive arable farming, leading to surface ponding. The soils have moderate available water capacity and are slightly droughty for cereal crops and winter oilseed rape, and very droughty for grass especially in dry years.

Pumped catchments or areas with efficient tidal sluices in the low rainfall zone along the north Kent coast remain occasionally or seasonally waterlogged (Wetness Classes II or III) after pipe drains have been installed but the soils have a slightly wetter regime along the south coast.

Cropping and Land Use

In the Midlands most of the land is in productive permanent grass, although infestation by rushes in hollows reduces the herbage value on the wettest land and grazing by cattle is restricted to the summer months when poaching risk is least. Grazing ceases towards the end of October as soils return to field capacity and the risk of poaching increases although the grass continues to grow for about a further six weeks. Slurry spreading is also confined to dry periods between late spring and early autumn; at other times trafficability is poor and permeability slow, leading to surface run-off and pollution of watercourses. In some places, for example near Rhuddlan where Newchurch soils are most extensive, better drainage and workability permit occasional winter cereal crops often as a break before reseeding grassland.

In Eastern England the land is mainly in arable production, the chief crops being winter cereals with oilseed rape, peas and lucerne as breakcrops. Grassland varies from rough grazing on unlevelled marshes to reseeded long leys. Although the winter rainfall is small, the clayey topsoils retain large amounts of water at field capacity, which restrict the period over which the land can be worked satisfactorily and increase the risk of damage to soil structure during the late harvesting of root crops. Opportunities for spring cultivations are more limited than in autumn, so autumn sowing is favoured. The soils are susceptible to compaction and if sequentially direct drilled the soils benefit from being loosened periodically. Shallow cultivations and minimum tillage techniques are commonplace. Some land is affected by salinity which, followed by leaching, has led to clay deflocculation, and the stopping of drains by dispersed clay, eventually causing patchy waterlogging and crop failure on arable land. Grassland productivity is limited by summer drought but, because of the poaching risk, grazing by cattle is restricted to the summer months. Occasional liming is needed, but manganese deficiency can occur if the soils are over-limed. The soils contain large reserves of potassium and magnesium.

This land has traditionally been in permanent grass but, especially in north Kent, over half has been brought into arable use in recent years. Winter cereals with oilseed rape are the chief crops. High standards of arterial and field drainage are essential for arable cropping. Some arable land in north Kent is affected by salt and consequent dispersion of clay particles leads to structural collapse, blocked drains and wet patches in fields. The damage occurs some years after the change from grassland to arable and is difficult to put right.

Some of the land provides feeding grounds for waders and wildfowl from adjacent saltmarshes. Neutral bent-fescue grassland is usual where the sward has been improved but on Farlington Marshes and elsewhere brackish and freshwater marshland is included and here the swards are more varied. Similar marshland occurs in the Test, Beaulieu and Lymington estuaries, in the Brading Marshes, along the Thames estuary including the High Halstow and Higham Marshes and on the Isle of Sheppey.

0813f WALLASEA 1

Distribution Map

Note that the yellow shading represents a buffer to highlight the location of very small areas of the association.

Keys to component soil series

South Eastern Region

Wales

Eastern Region

Northern Region

Typical Landscapes

Wales

Eastern Region

Eastern Region

Eastern Region

Northern Region

South Eastern Region

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Citation: To use information from this web resource in your work, please cite this as follows:
Cranfield University 2024. The Soils Guide. Available: www.landis.org.uk. Cranfield University, UK. Last accessed 19/04/2024