Soil Associations

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Soil and site characteristics

Deep stoneless calcareous clayey and fine silty soils. Groundwater levels controlled by ditches and pumps. Flat land with low ridges giving a complex soil pattern.

Geology

Marine alluvium

Cropping and Land Use

Permanent grassland and some cereals, some potatoes on Romney Marsh.

Component soil series

Subgroup	Series name	Percentage	WRB 2006 link
8.14	NEWCHURCH	30%	Clayic Fluvic Calcaric Gleysols
5.32	BLACKTOFT	20%	Calcaric Fluvic Endogleyic Cambisols
8.12	AGNEY	18%	Fluvic Calcaric Gleysols
8.12	STOCKWITH	11%	Fluvic Calcaric Gleysols

Covers 148 km² in England and Wales

Soilscapes Classification

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

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Detailed Description

This association is mapped on marshland along the south coast between Romney Marsh and Havant in Hampshire, where clayey and silty soils form complex patterns in marine alluvium in recently silted estuaries. Romney Marsh and the West Sussex Coastal Plain were mapped in detail, although the soils have since been reclassified and some renamed.

All the main soils are calcareous, although, locally, upper horizons are decalcified. Clayey Newchurch, pelo-calcareous alluvial gley soils, are dominant overall, with frequent subsidiary fine silty Blacktoft series, gleyic brown calcareous alluvial soils, the similar Agney series and silty over clayey Stockwith series, both calcareous alluvial gley soils. There are occasional browner, less mottled, clayey Brenzett soils, some clayey over coarse loamy Guldeford soils and some non-calcareous clayey Wallasea soils.

Most of the land is below or only slightly above the level of the highest tides but is protected from sea flooding and further silting by natural shingle spits or bars, and by sea walls or artificial river embankments. The association is confined to the most recently reclaimed, "New", marshland on Romney Marsh. Here, low swampy relics of creeks or old river courses at 1-1.5 m O.D. are typically fringed by high silty levee-like ridges up to 3 m high and 100 m or more wide beyond which are finer-textured soils, in so-called pools, about 1 m lower. Agney or Blacktoft soils occur on the ridges, and Newchurch or Stockwith soils are typical of creek beds and pool areas. Guldeford soils occur on the youngest enclosures where clay overlies sands at shallow depth. To the west, Pett, Brede, Tillingham and Rother Levels and Shirley Moor have a similar soil pattern but there are fewer creeks and less relief.

In West Sussex, clayey and silty soils occur in a complex pattern showing little relation to landform. Here, the association was mapped as the Arundel complex along various streams north of Selsey and Bognor Regis, and on enclosed marshes bordering Hayling and Thorney Islands. Alluvium in the Adur valley is generally more silty, but that in the main Arun valley is uniformly clayey. Fine silty Agney or Stockwith soils dominate the lower Cuckmere and Ouse valleys, but there are more non-calcareous Wallasea soils upstream, where the alluvium is clayey.

Soil Water Regime

The water regimes depend mainly on arterial drainage systems controlling the groundwater level. Newchurch and Stockwith soils in pumped catchments remain seasonally waterlogged (Wetness Class III) after pipe drains have been installed. Without adequate arterial control of the groundwater, as in parts of the Arun, Adur, Ouse and Cuckmere valleys, these soils are waterlogged for long periods in winter (Wetness Class IV). The clayey subsoils are variably permeable and waterlogging is mainly the result of high groundwater levels. However, compaction of surface and subsurface horizons is common under arable farming systems and leads to surface ponding. Agney and Blacktoft, intrinsically more permeable than Newchurch soils, are only occasionally waterlogged after drainage (Wetness Class II), and, on slightly elevated ground on Romney Marsh, may be well drained (Wetness Class I), contrasting markedly with the wetter adjacent land.

They are slightly droughty for cereals, moderately droughty for potatoes, and moderately or very droughty for grass, unless groundwater within rooting depth supplements soil reserves. Crops growing on Agney and Blacktoft soils are less subject to drought. No soils are droughty for winter oilseed rape.

Cropping and Land Use

Arable cropping, chiefly winter cereals and oilseed rape with potatoes and some beans and peas for processing, is the chief land use. The clayey topsoils of Newchurch soils retain large amounts of water at field capacity, which restricts the period when they can be satisfactorily worked without compaction or causing damage to soil structure. On Romney Marsh there are long periods in autumn when the soils can be cultivated, but in other parts of the association further west the onset of field capacity is earlier, and there are fewer autumn machinery work days. Spring opportunities for landwork are very limited in all districts. Stockwith, Agney and Blacktoft are easier to work than Newchurch soils, and on Romney Marsh can be worked without damage over a longer period, but because of the intricate soil pattern, the condition of the heavy Newchurch soils commonly controls the timing of cultivations.

Grassland, most of it permanent but with some leys, covers a third of the land. It is mainly confined to areas without underdrainage. In Kent and East Sussex, summer growth is restricted by droughtiness. However, from Brighton westwards, with a longer growing season, growth continues well into the autumn. On Romney Marsh the quality of pastures is closely related to soil type. Here, traditional breeding pastures are mainly on fine-textured Newchurch and Stockwith soils which carry a moderate poaching risk, and better fields with fine swards used for fattening are on Blacktoft and Agney soils where risk of poaching is negligible. Sheep rearing and fattening is characteristic of Romney Marsh, but in wetter districts to the west the pastures are mainly grazed in summer by beef cattle. Liming is not normally needed. The soils contain little available phosphorus, but potassium and magnesium reserves are large in fine-textured Newchurch and Stockwith soils and lower in Agney and Blacktoft soils. Fertilizer requirements may differ widely in fields with complex patterns of these contrasting soils.

Wildfowl and other wetland birds winter on the traditional grassland with its drainage network of dykes and fleets. Unimproved pastures support a wide range of plants, and many areas are valued for their nature conservation interest.

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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

Typical Landscapes

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 20/04/2024