SOIL HORIZONS AND SOIL SAMPLING METHODS

Done by

Pragna Prathap

2012-20-119

Weathered layer of the earth’s crust with living organisms and products of their decay are intermingled

SOIL

What makes up soil?

It is the vertical section of soil

through all its horizon and

extending up to the parent

material. A vertical exposure of the

horizon is termed as soil profile

Soil profile

Soil horizon

They are the layers of the different types of soil found at different depths in the soil profile.

SOIL HORIZONS

Master horizons• A,B and C are the master

horizons.• Typically found in all soils

THE “ORGANIC MATTER” HORIZON

surface-layer, at depths of 0-2 feet

dark in color, soft in texture

Several o-layers can occur in some soils,

consisting only of o-horizons

O- Organic Horizon

Oi

Oa

Ob

slightly decomposed (litter)

intermediate decomposition

highly decomposed

“TOPSOIL” OR “BIOMANTLE” HORIZON

Topmost layer of mineral soil, at depths of 2-10 feet It consists of mixture of humified organic matter and mineral matter.

It is darker in colour

Smallest and finest soil particles

A Horizon

Horizon “A”

E Horizon• zone of eluviation [loss (by water) of suspended

materials]

• Small layer between A & B horizons

• At depths of 10-15 feet

• Clay and sesquioxides are leached out leaving resistant minerals such as quertz.

• It is light in colour than A horizon, mainly sand & silt

• Soil particles larger than in A horizon but smaller than in B horizon

B Horizon• It is the zone of illuviation(accumulation of

suspended materials).• It is also called sub-surface horizon• At depths of 10-30 feet• Rich in clay and minerals like Fe & Al• Accumulation of clay and sesquioxides

occur.• Some organic material may reach here

through leaching• Plant roots can extend into this layer• Red/brown in color due to oxides of Fe &

clay

C HorizonThe “Regolith” Horizon• At depths of 30-48 feet• Made up of large rocks or lumps of

partially broken bedrock • Least affected by weathering and have

changed the least since their origin• Devoid of organic matter due to it being

so far down in the soil profile• not affected by soil-forming processes

R HorizonThe “Bedrock” Horizon• At depths of 48+ feet• Deepest soil horizon in the soil profile• No rocks or boulders, only a continuous

mass of bedrock• Colors are those of the original rock of

the area

SOIL SAMPLING

• Main purpose is to evaluate the

fertility status of the soil

• It provide a basis for fertilizer,

lime and gypsum

recommendation

Principles to be followed

The sample collected should be true representative of the area

• Sample each field separately divide the field suitably and sample each area.

• Avoid drawing sample from spots which do not represent the field.

Eg: bunds, hedges ,near manure pit etc.

• Do not sample the field with in 3 months of fertilizer or lime application.

• Take sample from ,

15 cm depth- ordinary crop

25 cm depth- perennial crop

5 cm depth-pasture and Lawn

• In line sown crop take-take sample

between the line

Soil Sampling Tools

soil sampling probe (tube)

A soil probe works best in well cultivated soils without rocks but is difficult to use in rocky, very dry or very wet soil,soil probe provides a continuous soil core with minimal disturbance to the soil

Auger An auger is better for less well

cultivated or rocky soils. Commonly used for obtaining

disturbed soil samples at or near the surface.

shovelIf the soil texture is very coarse or there are many coarse fragments, a shovel can be used instead of a soil sampling tube or auger.

Procedure for sampling

• Scrape the litter from the surface of the soil

• Then dig a ‘V’ shaped cut to the required depth(15-20cm)

• Cut a thin slice(1 inch) from one side of the hole

• Collect the soil and put it in a clean bucket

• Collect atleast 10 samples like this

• Break all bumps and mix well in the container

• reduce the size of the sample by successive quartering to about 500g

• Dry the sample in shade for 1-2 hours by spreading over a paper or a polythene sheet

• Use polythene bags for bagging the sample

• Then put it in a cloth bag

• Fine a paper tag for identification

• Fill the information sheet and send it along with soil sample to the soil testing laboratory

Information sheet contain following details

1. Name of the farmer, address2. Village, taluk, district, survey

number3. Wet/dry/garden land4. Area of the field5. Depth of sampling6. Processed crop or variety7. existing crop or variety8. Cropping history of the field for 3

years9. Signature of farmer

Typical information sheet

TYPICALSOIL ANALYSIS REPORT

If the soil is destroyed, then our liberty of

action and choice are gone

Thank You