All information Copyright, Cranfield University © 2018

Citation: To use information from this web resource in your work, please cite this as follows:
Cranfield University 2018. The Soils Guide. Available: www.landis.org.uk. Cranfield University, UK. Last accessed 15/11/2018

0532a BLACKTOFT

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Soil and site characteristics

Deep stoneless permeable calcareous fine and coarse silty soils. Some calcareous clayey soils. Flat land. Groundwater controlled by ditches and pumps

Geology

Marine alluvium

Cropping and Land Use

Sugar beet, potatoes and cereals, some field vegetables and horticultural crops; dairying in Somerset.

Component soil series

Subgroup Series name Percentage WRB 2006 link
5.32 BLACKTOFT 75% Calcaric Fluvic Endogleyic Cambisols
5.32 ROMNEY 10% Calcaric Fluvic Endogleyic Cambisols
8.14 NEWCHURCH 10% Clayic Fluvic Calcaric Gleysols

Covers 190 km2 in England and Wales

Soilscapes Classification

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

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0532a BLACKTOFT

Detailed Description

The Blacktoft association is dominated by calcareous fine silty soils in marine alluvium. It is widespread by the Humber in Northern England and occurs also in Eastern England in the Fens near King's Lynn and, in the South West, beside the Severn estuary in Somerset and Avon.

Blacktoft soils which cover two thirds of the land, are fine silty, gleyic brown calcareous alluvial soils with faint to distinct subsoil mottling. They are stoneless, usually moderately well structured and often pass downwards into laminated silt loam or clay. In other places they overlie peat or clay at about 1.5 m depth. The Romney series, also gleyic brown calcareous alluvial soils, rarely forms more than one sixth of the association. It often has weak structure, is usually coarse silty throughout and becomes increasingly mottled and laminated downwards. There is a small but variable proportion of clayey soils, the most common being the slowly permeable strongly mottled calcareous Newchurch series, pelo-calcareous alluvial gley soils. Others include the similar, but non-calcareous Wallasea seriesand the better-drained non-calcareous Dymchurch series. Minor associates include the Walkerith series, where peat occurs within 80 cm depth and the wetter, fine silty Agney series.

Between the Nene and the Great Ouse near King's Lynn the alluvial silts and clays were mainly deposited in Romano-British times. The land to the north of the Sea Bank has been laid down more recently and enclosed and reclaimed within sea walls. The earliest reclamation, the Sea Bank itself, is medieval, the rest dating from the 17th century to the present day. To the south of the Sea Bank the alluvium overlies thin peaty beds, part of the Upper Peat, and below this at depths of a few metres is the Fen Clay. This slightly higher ground at 2 to 3 m O.D. was settled by the Anglo Saxons. Further inland a series of embankments was built between the eleventh and thirteenth centuries to reclaim the land from the fens to the south. In all embanked areas there is a network of old creek courses forming low ridges called rodhams. In the Blacktoft association which covers 151 km² on both sides of the Sea Bank, rodhams formed of fine silty material predominate and alternate with clayey hollows. The land ranges from between 0 and 3 m O.D., the lowest sites being furthest from the old creek courses.

Near Gloucester and Bridgwater the Blacktoft series, fine silty gleyic brown calcareous alluvial soils are the main soils, with Romney series, coarse silty gleyic brown calcareous alluvial soils, on the raised levees of the river banks. The clayey Newchurch series, pelo-calcareous alluvial gley soils, and fine silty Agney series are found further from the rivers where formerly tidal silts thin out.

The Humber estuary is flanked by two distinct tracts of the association, which covers 164 km². In the Goole district the soils were formed largely by 19th century warping, an artificial flooding and sedimentation process (Heathcote 1951). Near Sunk Island however, much land was reclaimed during the 18th and 19th centuries by means of a series of embankments, built in stages around naturally aggrading banks of tidal sediment. By this means Sunk Island was eventually joined to the mainland. The Blacktoft association contains what is known locally as heavy warp, the light warp being the soils of the Romney association. The ground is flat except for slight levees, with differences in level of 1 to 2 m along some field boundaries or ditches marking the limit of areas reclaimed or warped at different times. Altitude varies from 2 to 5 m O.D. along the whole 50 km length of the Humber estuary, the lowest ground often being furthest from the sea. Exposure is a limitation to agriculture on Sunk Island where gales sweep from the estuary across a treeless countryside.

The typical soil pattern is simple, with large expanses consisting only of the Blacktoft series, gleyic brown calcareous alluvial soils, and rare profiles of the Agney serie. The coarse silty Romney series, gleyic brown calcareous alluvial soils, is common only locally, as for instance around the mouths of the Trent and Ouse where the association adjoins the Romney association. The clayey Newchurch, pelo-calcareous alluvial gley soils, and Wallasea series are restricted mainly to the lower, wetter margins of warpland furthest from the river, particularly around Gilberdyke and Broomfleet. A few profiles of the Dymchurch series occur on better drained sites. The Wallasea series is also more common where the association passes into older natural marine alluvium at Walling Fen and the lower Hull and Ancholme valleys.

Soil Water Regime

In most places the groundwater level is kept low, even in winter, by a system of pumped dykes. Soils therefore have a drier regime than the subsoil mottling suggests, being well drained or only occasionally waterlogged (Wetness Classes I or II). Newchurch and Wallasea series are seasonally waterlogged (Wetness Class III). Soil compaction causes surface wetness in winter but otherwise the soils are permeable. The soils have a large silt content and are thus able to hold water at tensions which can be easily utilized by plants. Available water in the rooting zone may be augmented by a capillary rise from groundwater. In the Romney series available water is generally greater than the potential soil moisture deficit and droughtiness does not affect any crop except grass, for which these soils are slightly droughty. The more clayey Blacktoft soils hold less available water and are moderately droughty for grass and slightly droughty for potatoes in a normal year. The clayey Newchurch and Wallasea soils are more droughty still.

Cropping and Land Use

The Blacktoft association forms fertile land, most of it easy or moderately easy to work. More difficult clayey soils are restricted in extent, mainly on the lowest ground. Present cropping reflects the potential of the land which, although chiefly under cereals, grows potatoes, sugar beet and field vegetables. In most years there is ample opportunity for autumn tillage. Spring tillage is restricted in wet years on Newchurch and Wallasea soils. Cereals are best drilled in the autumn, leaving the suitable spring days free for sugar beet, potatoes and vegetables. Exposure is a limitation on the coast from sea winds sweeping across the treeless landscape. Weak topsoil structure is common because of the high silt and low organic matter contents, particularly in Romney soils where surface capping is likely after heavy rain if the seed bed is too fine. Subsurface compaction, causing surface wetness, is usual after sugar beet harvesting in wet conditions late in the year. This cannot be put right until the ground is fallow and dry enough for subsoiling, usually after harvest the next autumn. Direct drilling is not recommended because of the risk of compaction. The soils are well suited to large-scale vegetable growing, and there are vegetable processing plants nearby at King's Lynn. Drought is rarely a limitation and most crops except potatoes grow well without irrigation. Brussels sprouts and cabbage are grown, and need large applications of nitrogen fertilizer to yield well. Peas for freezing have increased in popularity in recent years. The soils are naturally fertile and as most are calcareous, lime is rarely necessary except on Wallasea soils. Fertility is easily maintained. Manganese deficiency in sugar beet is possible where the pH is very high.

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0532a BLACKTOFT

Typical Landscapes

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All information Copyright, Cranfield University © 2018

Citation: To use information from this web resource in your work, please cite this as follows:
Cranfield University 2018. The Soils Guide. Available: www.landis.org.uk. Cranfield University, UK. Last accessed 15/11/2018