All information Copyright, Cranfield University © 2017

Citation: To use information from this web resource in your work, please cite this as follows:
Cranfield University 2017. The Soils Guide. Available: www.landis.org.uk. Cranfield University, UK. Last accessed 19/10/2017

0712b DENCHWORTH

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Soil and site characteristics

Slowly permeable seasonally waterlogged clayey soils with similar fine loamy over clayey soils. Some fine loamy over clayey soils with only slight seasonal waterlogging and some slowly permeable calcareous clayey soils. Landslips and associated irregular terrain locally.

Geology

Jurassic and Cretaceous clay

Cropping and Land Use

Winter cereals and short term grassland in drier lowlands; dairying on permanent grassland in moist districts.

Component soil series

Subgroup Series name Percentage WRB 2006 link
7.12 DENCHWORTH 38% Eutric Vertic Stagnosols
7.11 WICKHAM 19% Eutric Luvic Planosols
7.12 LAWFORD 15% Clayic Ruptic Eutric Stagnosols
4.11 EVESHAM 14% Calcaric Stagnic Vertic Cambisols
5.72 OXPASTURE 14% Endostagnic Luvisols

Covers 3469 km2 in England and Wales

Soilscapes Classification

18
Slowly permeable seasonally wet slightly acid but base-rich loamy and clayey soils

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0712b DENCHWORTH

Detailed Description

The Denchworth association is extensive on Jurassic and Cretaceous clays and clay shales in the Midlands, South West and South East England. It consists mainly of wet clayey soils belonging to Denchworth and Lawford series, both pelo-stagnogley soils, with calcareous pelosols of the Evesham series. Wickham and Oxpasture series are found where thin clay loam drift overlies the clays. Denchworth soils are stoneless, strongly mottled and waterlogged for long periods in winter. The similar Lawford soils, though also clayey throughout, are formed in a slightly stony drift which is commonly separated from the underlying clay shales by a thin gravelly seam. The other associate soils also have clayey subsoils but have drier water regimes, being waterlogged in winter for short periods only. Oxpasture soils have clay loam upper horizons similar to those of Wickham soils, but Evesham soils have stoneless calcareous clayey topsoils. There are also a few soils of the Hornton, Fladbury, Holdenby and Dale series.

This association covers 656 km² in a discontinuous strip at the foot of the Jurassic escarpment from near Bredon Hill in Hereford and Worcester to the Vale of Belvoir. Dale soils are more common than elsewhere when the association is mapped on the Upper Lias which has a high silt content, but their proportion is difficult to estimate. Along the Oxfordshire-Warwickshire border and in east Leicestershire, there are inclusions of Banbury and Irondown soils on small knolls of ironstone or small patches of drift derived from ironstone. East of Rugby, on low-lying gently sloping and level land, thin drift deposits give frequent Wickham soils. Some Beccles, Ragdale, Lawford and Holdenby soils occur on the footslopes of higher ground capped by till. Evesham soils are found mainly in south Warwickshire on moderately steep eroded slopes and on small knolls. Some Evesham soils are slowly permeable and mottled above 40 cm but the extent of these gleyed profiles is uncertain, though in some places they cover up to a tenth of the association. Strips of alluvium along small valleys carry Fladbury soils and adjacent thin river terrace drift gives Lawford, Wickham and Oxpasture soils.

The association covers about 56 km² in south Wales on Jurassic rocks with small patches on thin strips of Rhaetic clays. It occurs mainly in a thin discontinuous band between Port Talbot and Barry in the Vale of Glamorgan and the component soils were originally mapped as Charlton Bank and Dyffryn series. A small area has also been mapped near Newport. The landscape is mainly low-lying, gently sloping or level but Evesham and Hornton soils occur on moderately sloping ground. Some Evesham soils are slowly permeable and mottled above 40 cm but they are not extensive. Strips of alluvium along valleys carry Fladbury soils and adjacent thin drift gives Lawford, Wickham and Oxpasture soils. East of Port Talbot drift, of local origin, is an important component of the soil profiles and Lawford soils are common.

The association occurs in the east of the region along the foot of the western escarpment of the Yorkshire Wolds, in the Howardian Hills and along the northern edge of the Vale of Pickering on moderate and steep slopes. The Denchworth series is generally associated with Evesham, Wickham, Lawford and Oxpasture soils, but Coombe and Millington soils in chalky drift occur on the upper slopes near the Wolds escarpment.

The association is found in a broken strip in the west of the region, mainly in Northamptonshire and to a lesser extent in Lincolnshire, Bedfordshire and Cambridgeshire. Most of the land is low-lying and gently sloping or level. Denchworth soils are usually the main component but, where loamy drift occurs, Wickham and Oxpasture soils are common. Evesham soils are found mainly in south-west Northamptonshire on moderately steep eroded slopes and small knolls.

Some are slowly permeable and mottled above 40 cm depth and in some places they cover up to a tenth of the land. Where Northamptonshire borders Oxfordshire and Leicestershire, small outcrops of ironstone are included giving Banbury and Irondown soils. In north-west Northamptonshire the soils are largely on Upper Lias which has a higher silt content than elsewhere and Dale soils occur, but their proportion is difficult to estimate. Strips of alluvium along small valleys carry Fladbury soils and adjacent thin river terrace deposits give Wickham, Lawford and Oxpasture soils.

The association is extensive in five counties of the South West, from Axminster, near the south coast, to the vicinity of Moreton-in-Marsh. It is common locally on Lias clays, but is most continuously found on the Oxford and Kimmeridge Clay outcrops from Dorset to north-east Wiltshire. Denchworth and some Wickham soils are present on Lias clay on the slopes surrounding the East Devon Plateau and in west Dorset. In Marshwood Vale, around Kimmeridge, and in the south of Blackmoor Vale, Evesham soils are relatively common on slopes. Around Sturminster Newton and Gillingham, where the Kimmeridge Clay is non-calcareous and contains non-swelling clays and much silt, there are Dale soils. Here large ponds are found in many fields. Some low knolls in the Vale are capped with Plateau Gravels, in which Oak soils are developed.

On Oxford Clay the Denchworth soils usually contain calcium carbonate concretions within 60 cm depth and the associated soils belong to Lawford and Wickham series. North of Trowbridge the climate becomes drier as the broad vale continues towards the Upper Thames valley. From Dorset to Wiltshire, steep slopes are often landslipped, particularly those below the Upper Greensand and facing north-westwards. Around Gloucester and Cheltenham the Lias clay is either covered by drift deposits or is more calcarous and Evesham soils become dominant. However, in the Moreton Vale and northwards Denchworth soils are again extensive, with the associated soils developed in till and Head.

In South East England the association is found on Jurassic and Cretaceous clays mainly between Aylesbury, Stow-on-the-Wold and Reading. It occurs also between Aldershot and Midhurst, to the north of Brighton, from Leatherhead in an are to Ashford and Folkestone, and east of Heathfield. Much of the land is low-lying and gently sloping or level, though between Farnham and Petersfield and near Heathfield, moderate slopes are common.

Langley series is common on small areas of Kellaways Beds near Witney. Between Swindon and Oxford in the Vale of the White Horse on the lowest ground, there are Lawford soils, formerly mapped as Rowsham series , and Wickham and Oxpasture soils are uncommon. Evesham soils occur on Kimmeridge Clay on moderately sloping ground. Kingston series is present on Corallian and Lower Greensand beds and narrow strips of alluvium along small valleys carry Thames and Fladbury soils.

In Surrey, Sussex and Kent, at the foot of the North and South Downs the association is found on the strip of Gault Clay between the Chalk and the Lower Greensand, and in places contains inclusions of Bignor and Buriton soils on narrow outcrops of Upper Greensand. In east Hampshire and West Sussex, the proportion of Wickham soils increases eastwards along the southern flanks of the Rother valley between Petersfield and the Arun. Fladbury, Worminghall and Hurst soils occur in small valleys and on flanking patches of terrace. Similar inclusions are found where the association is over Weald Clay in Surrey and West Sussex. Here, drift free land includes some Dale soils and thin limestone seams within the Weald clay give soils that become calcareous at depth and are more olive in colour. Near Alfold, there are Shabbington soils in river terrace drift. A small area of the association is developed over Purbeck beds in the High Weald.

Soil Water Regime

Denchworth and Lawford soils are slowly or moderately permeable in the topsoil, slowly permeable at depth and are waterlogged for prolonged periods in the growing season (Wetness Class IV to V). Wickham soils have a moderately permeable topsoil but slowly permeable subsoil and are also waterlogged for long periods (Wetness Class IV). Denchworth, Lawford and Wickham soils respond to drainage measures and where annual rainfall is less than 600 mm can be improved to Wetness Class III. Oxpasture and Evesham soils also have slowly permeable subsoils (Wetness Class III) but after suitable drainage they have a drier regime (Wetness Class II or III).

Cropping and Land Use

With efficient underdrainage and careful management, the soils yield moderately good crops of grass, cereals and oilseed rape. Autumn sown crops are favoured as, even with drainage improvements, there is little opportunity to work the land in spring. The timing of cultivations is critical because topsoils are slow to dry and the use of cage wheels is desirable to reduce ground pressure and protect against structural damage. Direct drilling enables more land to be sown in a short period in autumn when soil conditions are optimum. Denchworth soils however have a narrow range of conditions suitable for direct drilling so they are not well suited to the technique. When too wet the slit cut by the disc is smeared and the soil is compacted causing poor germination; when too dry the soil is too hard for good drill penetration. On grassland, surface wetness and weak soil bearing strength limit stocking density and grazing period, although moderately good yields of grass are possible. The soils poach easily particularly in the troughs of ridge and furrow so, where grazing is ill-timed, yields are reduced. Denchworth soils are acid in the surface where unlimed, but pH increases gradually with depth and the soil is often neutral or alkaline within 1 metre. The potassium status is usually good but phosphorus is commonly held in forms not readily available to plants.

Near Gillingham in Dorset ponds in small fields make large scale improvement difficult. In drier districts on the better drained associate soils, some arable crops are grown but even with drainage improvements, difficulties are experienced with spring tillage and, with little opportunity to work the land in spring, autumn-sown crops are favoured. Because the topsoils take a long time to dry out, timing of cultivations is critical and measures to reduce ground pressure, such as cage wheels, are desirable to protect against structural damage. In wetter districts like Blackmoor Vale there are few autumn working days on Denchworth soils so arable cropping is never likely to be successful. The profile available water is adequate for cereals but not for grass.

In the South East the choice of trees for commercial forestry is restricted by prolonged winter waterlogging over the slowly permeable clayey subsoils, and drainage is often needed to reduce surface wetness. Many trees develop shallow root systems and there is a significant risk of windthrow on exposed sites. Old woodland is widespread, often hazel coppice below oak standards. There is also some hornbeam coppice in Kent and Surrey. Dog's mercury (Mercurialis perennis), sanicle (Sanicula europaea), bugle (Ajuga reptans) and primrose (Primula vulgaris) are common herbs. On acidic soils, birch, hazel and oak woodland is characteristic accompanied by tufted hair-grass (Deschampsia cespitosa), common bent-grass (Agrostis capillaris), slender St John's wort (Hypericum pulchrum), common tormentil (Potentilla erecta) and bluebell (Hyacinthoides non-scripta).

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0712b DENCHWORTH

Typical Landscapes

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All information Copyright, Cranfield University © 2017

Citation: To use information from this web resource in your work, please cite this as follows:
Cranfield University 2017. The Soils Guide. Available: www.landis.org.uk. Cranfield University, UK. Last accessed 19/10/2017