Soil Associations

1025 Mendham

Soil and site characteristics

Deep peat soils associated with clayey over sandy soils, in part very acid. High groundwater levels. Risk of flooding.

Geology

Fen peat and river alluvium

Cropping and Land Use

Permanent grassland; cereals, sugar beet and potatoes with groundwater control.

Component soil series

Subgroup	Series name	Percentage	WRB 2006 link
10.25	MENDHAM	36%	Drainic Rheic Sapric Thionic Histosols
8.15	SHOTFORD	34%	Clayic Thionic Fluvic Gleysols
10.24	ADVENTURERS'	20%	Drainic Rheic Sapric Histosols

Covers 75 km² in England and Wales

Soilscapes Classification

27	Fen peat soils

1025 Mendham

Detailed Description

The Mendham association consists of deep peaty and clayey soils, sometimes extremely acid, and commonly with a high groundwater-table and a risk of flooding. It covers 88 km² in Suffolk and Norfolk mainly along the river Waveney from its source to Lowestoft, but also along the streams that reach the sea between Lowestoft and Aldeburgh. The soils are formed in the sedge-carr peat and clayey river alluvium of the present floodplains. In many places sulphidic salts occur, in the lower reaches of the rivers probably derived from past tidal incursions, and upstream possibly from the chalky till of the surrounding upland. On oxidation of the sulphides, mainly pyrites, following drainage, the soils become extremely acid and so check plant growth. Systematic sampling and measurement of pH values suggests that, in present drainage conditions, the extremely acid Mendham series, earthy sulphuric peat soils, and the Shotford series, sulphuric alluvial gley soils in clayey alluvium overlying pyritic sands and gravels, cover about a sixth of the land but with further drainage this proportion could increase to nearly half as the earthy eutro-amorphous peat soils of the Adventurers' series, which are most extensive at present, become acid following oxidation of pyrites. Other soils include Fladbury series in clayey river alluvium, Midelney series in thin clayey alluvium resting on peat and, under grassland, Wensum series in which a surface mat is commonly well formed. There are smaller areas of the sandy Isleham series and loamy Hopsford series and some Wigton Moor soils.

In the Waveney valley and the lower parts of the Suffolk coastal rivers, Isleham soils on the margins of the wide flood plains are separated by Mendham and Adventurers' series from Shotford and Fladbury soils, which, with narrow outer fringes of Midelney series, are found nearest the rivers. At the confluence of the larger tributaries, as near Harleston, Shotford and Fladbury soils extend across the valleys. Downstream, river alluvium usually merges with marine alluvium which fills the width of the river mouths. Sulphuric soils are everywhere patchily distributed. Soil patterns are less clear where the valleys are narrow and their full width is often nearly filled by Hopsford and Wigton Moor series. Locally spoil from river and ditch dredgings is mixed in the topsoil. On the coast, small areas of Mendham and Adventurers' series are affected by brackish groundwater.

Soil Water Regime

Excepting the better drained Hopsford series, these soils are mostly severely waterlogged or waterlogged for much of the year (Wetness Class V and VI). In some localities drainage has been improved by deepening and cleaning rivers and ditches but not in conservation areas, as at Minsmere near Leiston, or where there is insufficient outfall, for example near Harleston in the Waveney valley and at Heveningham on the river Blyth. Near Beccles, pumped drainage has controlled the water levels in permeable Mendham, Adventurers' and Isleham soils, which are now well drained (Wetness Class I). Where there are less efficient pumps, at Carlton Colville near Lowestoft and upstream from Beccles, the soils remain occasionally waterlogged.

Cropping and Land Use

Arable crops, including field vegetables, are grown on improved land, but grassland or rough grazing is more common with carr woodland in the wetter places including some of the coastal peat areas. Access to grassland is difficult in winter and there is a serious risk of poaching. Where well drained, the peat soils are easily worked and can be cultivated within a few days of rain. In these conditions there is ample time for autumn landwork and spring cultivations. The soils have a large water holding capacity. In many localities, drainage has led to oxidation of sulphides causing extreme acidity and restricting root growth, so giving rise to moisture stress and reducing yields. The acidity causes the mobilization of iron, and ochre is deposited in ditches and in tile drains which become blocked and ineffective. In dry seasons arable peat soils are also at risk in spring when seed beds can be blown away by strong winds.

1025 Mendham

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

Eastern Region

Typical Landscapes

Eastern Region

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