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

0721e WENALLT

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Soil and site characteristics

Slowly permeable seasonally waterlogged reddish loamy upland soils with a peaty surface horizon. Some patches of peat soils and some soils with thin ironpan. Very acid where not limed.

Geology

Drift from reddish sandstone and siltstone

Cropping and Land Use

Wet moorland of poor grazing value; coniferous woodland, military use.

Component soil series

Subgroup Series name Percentage WRB 2006 link
7.21 WENALLT 70% Chromic Dystric Histic Stagnosols
10.13 CROWDY 15% Ombric Sapric Histosols
6.51 CRAY 10% Placic Histic Stagnic Albic Podzols

Covers 234 km2 in England and Wales

Soilscapes Classification

19
Slowly permeable wet very acid upland soils with a peaty surface

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0721e WENALLT

Detailed Description

The Wenallt association consists of very acid wet peaty soils in reddish drift, mainly on moorland at 300 to 500 m O.D. It is mapped only in south Wales and south-west Shropshire over or adjacent to the Old Red Sandstone outcrop and is most extensive on the gentle dipslopes and footslopes of the range of hills extending from the Black Mountain near Ammanford to the Brecon Beacons. Loamy cambic stagnohumic gley soils, belonging to the Wenallt series, predominate and the main ancillary soils are raw oligo-amorphous peat soils, Crowdy series, and ironpan stagnopodzols, Cray series. Cambic stagnogley soils of the Fforest series with mineral topsoils occur on enclosed land. The soils are all developed in thick till or solifluction deposits and have impermeable subsoils often with a fragipan which holds up surface water.The peaty topsoils are commonly 15 to 30 cm thick over a gleyed and bleached subsurface horizon depleted of iron. In the Wenallt series this overlies a dense gleyed horizon with orange and reddish mottles and prismatic structures, whereas in the Cray series there is a thin ironpan over an often ungleyed subsoil. Both series pass to little altered drift within a metre depth. The particle-size class of the soils varies with the source of the drift, but over much of the association the incorporation of coarse sandstones and conglomerates of the Upper Old Red Sandstones gives coarse textured soils, commonly sandy loam over sandy clay loam which are frequently bouldery (Wright 1981). Elsewhere the particle-size class is clay loam or silty clay loam. Although the association is most common on gentle moorland slopes, it is also mapped on steep-sided hills where drift is thick. The Cray series is a common associate, typically on better drained sites as on the edges of solifluction lobes. The Crowdy series is also common, especially above 400 m O.D. usually in depressions as basin peat but also as blanket peat. Upslope the association passes to the Lydcott association of stagnopodzols on red sandstone, the boundary being along a concave break of slope and spring line, with a vegetation change from Molinia to Vaccinium heath or Nardus grassland.


Soil Water Regime

They are wet for most of the year (Wetness Classes V-VI) and the winter run-off is very rapid, a dense drainage pattern of rills and streams being characteristic of most slopes.

Cropping and Land Use

The climate is cold and wet with annual rainfall about 2,000 mm and soil moisture deficits less than 40 mm. The semi-natural vegetation is Molinia grassland with some Nardus and moist heather moor of moderate or poor grazing value. Wet flushes and hollows are usually dominated by rushes and bog-mosses. Most of the land is used for common grazing but recreation and military training are also important activities and much is within the Brecon Beacons National Park. Wetness, boulders and poor nutrient status make grassland improvement costly. Conventional drainage techniques are prohibitively expensive on large areas of moorland, yet without removing excess water there can be little significant pasture improvement. Some farmland has been drained then rotavated shallowly rather than ploughed. Careful grazing management is required as the organic topsoil is soft and easily poached. Some of the land is used for forestry, the largest areas being Glasfynydd Forest owned by the Forestry Commission and private forests on Fan Fraith and Fan Gihirych. Sitka spruce is the preferred species and site preparation involves deep ploughing and opening deep drains to remove surface water and encourage root penetration as windthrow is a hazard.

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0721e WENALLT

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