|
ANALYSIS
REPORT ON SOIL FROM LAKE AT TWISSELLS MILL
Background
Representative
samples were taken by ADAS of soil dredged from a 2 acre
lake at Twissells Mill. The soil consists of
sediment carried by water into the lake and deposited
there over many years. Such sediment from lakes,
rivers and canals has traditionally been used as a soil
improver or topsoil by farmers and growers. Silt
deposited by rivers on flood plains has made these areas
fertile and ideal for agricultural/horticultural use in
many areas of the world
Two
samples of the soil were analysed by Direct
Laboratories to assess their physical and chemical
properties. The results were compared with the
requirements of the British Standards for Topsoil
(3882). The British Standard classifies soils in
relation to their agricultural potential, hence to meet
'Premium' grade relatively high nutrient levels and a
neutral pH are required. Nutient levels and the
soil pH can easily be raised by addition of fertiliser
and lime to the soil hence it is the other, physical
properties, such as the soil texture and stone content
that are of much greater significance to the potential
purchaser of a topsoil.
Analysis
Results
Physical
analysis
The
two samples (A and B) show some variation in clay
content. The low clay material (sample A) is
typical of the majority of the soil seen on site and
this would have a higher value as a topsoil. The
texture of this is a sandy silt loam, which is ideal for
a wide range of horticultural and landscaping purposes.
The
stone content of both samples if very low, which is very
desirable, especially if the soild was to be used as
part of a horticultural growing medium because stones
damage mixing equipment. A high quality retail
bagged topsoil should also have a very low stone
content.
The
Organic Matter (humus) content of the soil is moderate
and could easily be increased by addition of
organic material, such as green compost, spent mushroom
compost or forest brash/bark.
The
samples contain no foreign matter such as glass or
plastic. Many 'topsoils' which originate from
'brown-field' sites are contaminated with building
rubble etc. hence a clean topsoil with no such
contamination is very desirable to end users.
Chemical
analysis
The
soil has a low (acid) pH and a very low calcium
carbonate (chalk) content. this is very unusual in
topsoils in the South-east of England as many contain
chalk naturally or have been limed for agricultural
purposes. Where acidic soils do occur they are
usually very light in texture (sandy) and often have a
high stone content so are less suitable for
horticultural uses. It is easy to raise the pH of
an acid soil by adding lime but very difficult and
rarely economic to lower a soil's natural pH. Acid
soils are useful as constituents of 'John Innes' type
growing media (to avoid the pH of the end product being
too high) and for gardeners/landscapers who wish to grow
acid-loving plants such as Rhododendrons, Azaleas,
Camellias and heathers.
The
nutrient levels in the soil are relatively low but could
easily be raised by incorporation of fertilisers or
blending with nutrient compost/manure so are not of
significance.
Conclusions
The
dredged soil could be a valuable raw material for a
growing media manufacturer. It would also be
suitable as an acidic topsoil for the horticultural
market, either sold screened and bagged for retail sales
or in bulk loads to landscapers.
Topsoil
sold to gardeners typically has a retial price of around
£3 per bag (25kg), which is equivalent to £120/tonne.
The
unique properties of your topsoil would help you to
achieve theses high market values as much of the topsoil
currently available in the South-east of England is of
poor quality. It often originates from construction
sites and is contaminated with foreign matter, such as
brick, concrete or glass fragments. Soil from
agricultural land frequently has a pH that is much
higher than that of your material and it is therefore
unsuitable for some types of plant. The low pH and
lack of stones will therefore be very helpful attributes
when finding markets for the Twissell Mill topsoil.
Susie
Holmes
Soil
Science Consultant
ADAS
Horticulture Ltd
Click
here for: TOPSOIL
ANALYSIS Sample A
TOPSOIL
ANALYSIS Sample B
|