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Agriculture Soil Science Important Study Table (6)

Agriculture Soil Science Study Point For Competitive Exam

Agriculture Soil Science Important Study Table (6)

Agriculture Soil Science Study Point For Competitive Exam

 1.Soil Orders (as per Soil Taxonomy) representing different soil groups

Genetic SystemSoil Taxonomy
Alluvial SoilsEntisol, Inceptisol
Black (Cotton) SoilsVertisols
Red SoilsAlfisol, Ultisols
Laterite and Lateritic SoilsUltisols
Desert soilsAridisol
Forest and Hill SoilsAlfisols
Salt Affected SoilsAridisols, Inceptisols

 2.Six categories were adopted for this system 

CategoriesFeatures
OrderIt is highest category, there are 12 soil order
Sub-order63 sub order in this classification
Great group> 240
Sub-group> 1000
Family
SeriesIt is most specific and lowest category (> 200 in India)

Note:- The smallest unit of soil classification is the soil series
Soil orders in the 7th approximation and their derivation

 3.12 Soil orders With Characters 

Soil OrderWordDerivationPronun ciation
EntisolNonsense symbolRecent
InceptisolLatinInceptum means beginingInception
GelisolsGreekGel means iceFrost churning
HistosolsGreekHistos means tissueHistology
Spodosols GreekSpodos means ash /Podzolodd
AndisolsJapaneseAndAndo
OxisolsFranceOxideOxide
VertisolsLatinverto means turnInvert
AridisolsLatinAridusArid
UltisolsLatinUltimus means lastUltimate
MollisolsLatinMollis means softMollify
AlfisolsNonsense symbolPedalfer
Soil OrderSoil Characteristics
EntisolSoils with little horizon development or beginning of soil formation
IneptisolSoils with altered horizons, but no illuvial horizon containing clay or Fe, Al oxides, may have umbric, ochric or cambic horizon
GelisolsSoils that have permafrost within 100 cm or gelic material with permanent frost within 2 m of the surface
HistosolsSoils containing > 30 % organic matter to a depth of 40 cm
SpodosolsSoils with spodic horizon with in 2 m.
AndisolsSoils that have andic soil properties in 60% or more of the thickness between the soil surface and 60 cm or lithic or paralithic contact
OxisolsOxide Highly weathered soils of tropical and subtropical regions with oxic horizon
VertisolsSoils with more than 30% clay in all horizons and crack when dry
AridisolsDry soils, ochric epipedon, some have argillic, nitric or salic horizon
UltisolsSoils in warm humid regions with argillic horizon and low base saturation(<35% at 2 m depth below the surface
MollisolsDark colored, base rich soils of grass land areas, mollic epipedon, many with argillic, nitric, or calcic horizon.
AlfisolsHigh base status (>35%) soils of the humid and sub humid regions with an ochric epipedon and argillic (or nitric) horizon.

 4.Land Capability Classification 

  • Land capability classification (LCC) may be defined as a system of grouping land in to various classes based on inherent limitations imposed on sustained use by soil attributes, topography, drainage and climate.

The capability classes falls in two groups:-

  1. Suited for cultivation a
  2. Not suited for cultivation.

The subclasses are further divides in to unit based on a specific management practice.

  1. Thus land is classified in to eight land capability classes under two broad groups as:Land suitable for agriculture and other uses which include class I to class IV lands.
  2. Land not suitable for agriculture but very well suited for forestry, grass land and wild life which include class V to class VIII lands.

 5.On map, the capability classes are indicated in different colours 

Land ClassColour
IGreen
IIYellow
IIIPink
IVBlue
VDark green
VIOrange
VIIRed
VIIIPurple

 6.Detailed characteristics of Land Capability Classes (LCC) 

LCCCharacteristics
Land Suitable for Cultivation
IVery good cultivable, deep, nearly level productive land with almost no limitation or very slight hazard. Soils in this class are suited for a variety of crops, including wheat, barely, cotton, maize, tomato and bean. Need no special practices for cultivation
IIGood cultivable land on almost level plain or on gentle slopes, moderate depth, subject to occasional overland flow, may require drainage, moderate risk of damage when cultivated, use crop rotations, water control system or special tillage practices to control erosion
IIISoils are of moderate fertility on moderate steep slopes subject to more sever erosion and severe risk of damage but can be used for crops provided adequate plant cover is maintained, hay or other sod crops should be grown instead of row crops.
IVThese are good soils on steep slopes, subject to severe erosion, with severe risk of damage but may be cultivated occasionally if handled with great care, keep in hay or pasture but a grain crop may be grown once in 5 or 6 years.
Land unsuitable for cultivation but suitable for permanent vegetation
VLand is too wet or stony which make it unsuitable for cultivation of crops, subject to only slight erosion if properly managed, should be used for pasture or forestry but grazing should be regulated to prevent cover from being destroyed.
VIThese are shallow soils on steep slopes, used for grazing and forestry; grazing should be regulated to preserve plant cover; if the plant cover is destroyed, use should be restricted until cover is re-established.
VIIThese are steep, rough, eroded lands with shallow soils, also includes droughtly and swampy land, severe risk of damage even when used for pasture or forestry, strict grazing or forest management must be applied.
VIIIVery rough land, not suitable even for woodland or grazing, reserve for wild life, recreation or wasteland consideration.

7.Composition Of Sand Silt & Clay Related To Textural Class

Textural ClassRanges of soil separates (%)
SandSiltClay
Sand85 – 1000 – 150 – 10
Loamy sand70 – 900 – 300 – 15
Sandy loam40 – 800 – 500 – 20
Loam23 – 5228-507-27
Silt loam0-5050-880-27
Silt0-2080-1000-12
Sandy clay loam45-800-2820-35
Clay loam20-4515-5327-40
Silty clay loam0-2040-7327-40
Sandy clay45-650-2035-45
Silty clay0-2040-6040-60
Clay0-450-4040-100

Soil Texture:-
Soil texture refers to relative proportion of mechanical / soil separates below 2 mm in diameter (viz. sand, silt and clay).
Three size classes are particularly important:

  1. Sand (size as in beach sand)
  2. Silt (size like talc/talcum powder)
  3. Clay (small particles which stick together, like modeling clay).

Soil Structure and Consistency:-

  • The term soil structure refers to the arrangement of primary and secondary particles in to a certain structural pattern.
  • The primary particles are sand, silt and clay whereas the secondary particles are the cluster of the primary particles which are called aggregates and peds.
  • Structure can be modified by cultivation and tillage operations while texture is an inherent property of soil and cannot be modified within short period of time.

Soil structure is most usefully described in terms of:-

  1. Type of aggregates (form),
  2. Class (average size) and
  3. Grade (degree of aggregation)

Types of Soil Structure:-
Based on the shape and arrangement of peds or aggregates, soil structure is classified into four principle type –plate like, prism like, block like and spheroidal structure.

1. Plate like:-

  • In this type, the aggregates are arranged in relatively thin horizontal plates or leaflets. The horizontal axis or dimensions are larger than the vertical axis
  • It is commonly found in forest soils, in part of the A- horizon, and in claypan soils. When the units/ layers are thick they are called “ platy” and when they are thin then it is “ laminar”.

2. Prism-like:

  • In prism like structure, the vertical axis is more developed than horizontal, giving a pillar like shape. They are commonly found in the subsurface horizons of semiarid and arid regions.
  • The prisms having rounded tops are called columnar and mostly occur in subsoils of salt-affected soils. When the tops are flat or level the structure is termed as “ prismatic”.

3. Block like:-

  • The structure is blocky when soil particles cling together in nearly square or angular blocks having more or less sharp edges.
  • The peds have sizes varying from 1 cm to 10 cm. There are two types- angular blocky and sub-angular blocky.
  •  They are commonly found in the B-horizon where clay has accumulated.

4. Spheroidal:-

  • Here the individual particles of sand, silt and clay are grouped together in small, nearly spherical grains.
  • When the peds or aggregates are relatively non-porous, they are called granules and porous granules are termed as crumbs.
  • They are commonly found in the A-horizon of the soil profile.

Agriculture Soil Science Study Point

Agriculture Soil Science Important Table – 1Cl;ick
Agriculture Soil Science Important Table – 2Cl;ick
Agriculture  Soil Science Important Table – 3Cl;ick
Agriculture  Soil Science Important Table – 5Cl;ick

 

Updated: 2020-02-25 — 4:03 pm

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