soil horizons and soil sampling methods
TRANSCRIPT
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