Agriculture Soil Science Study Point For Competitive Exam
Agriculture Soil Science Study Point For Competitive Exam
1.Soil Orders (as per Soil Taxonomy) representing different soil groups
|Genetic System||Soil Taxonomy|
|Alluvial Soils||Entisol, Inceptisol|
|Black (Cotton) Soils||Vertisols|
|Red Soils||Alfisol, Ultisols|
|Laterite and Lateritic Soils||Ultisols|
|Forest and Hill Soils||Alfisols|
|Salt Affected Soils||Aridisols, Inceptisols|
2.Six categories were adopted for this system
|Order||It is highest category, there are 12 soil order|
|Sub-order||63 sub order in this classification|
|Great group||> 240|
|Series||It 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 Order||Word||Derivation||Pronun ciation|
|Inceptisol||Latin||Inceptum means begining||Inception|
|Gelisols||Greek||Gel means ice||Frost churning|
|Histosols||Greek||Histos means tissue||Histology|
|Spodosols||Greek||Spodos means ash /Podzol||odd|
|Vertisols||Latin||verto means turn||Invert|
|Ultisols||Latin||Ultimus means last||Ultimate|
|Mollisols||Latin||Mollis means soft||Mollify|
|Soil Order||Soil Characteristics|
|Entisol||Soils with little horizon development or beginning of soil formation|
|Ineptisol||Soils with altered horizons, but no illuvial horizon containing clay or Fe, Al oxides, may have umbric, ochric or cambic horizon|
|Gelisols||Soils that have permafrost within 100 cm or gelic material with permanent frost within 2 m of the surface|
|Histosols||Soils containing > 30 % organic matter to a depth of 40 cm|
|Spodosols||Soils with spodic horizon with in 2 m.|
|Andisols||Soils that have andic soil properties in 60% or more of the thickness between the soil surface and 60 cm or lithic or paralithic contact|
|Oxisols||Oxide Highly weathered soils of tropical and subtropical regions with oxic horizon|
|Vertisols||Soils with more than 30% clay in all horizons and crack when dry|
|Aridisols||Dry soils, ochric epipedon, some have argillic, nitric or salic horizon|
|Ultisols||Soils in warm humid regions with argillic horizon and low base saturation(<35% at 2 m depth below the surface|
|Mollisols||Dark colored, base rich soils of grass land areas, mollic epipedon, many with argillic, nitric, or calcic horizon.|
|Alfisols||High 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:-
- Suited for cultivation a
- Not suited for cultivation.
The subclasses are further divides in to unit based on a specific management practice.
- 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.
- 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
6.Detailed characteristics of Land Capability Classes (LCC)
|Land Suitable for Cultivation|
|I||Very 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|
|II||Good 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|
|III||Soils 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.|
|IV||These 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|
|V||Land 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.|
|VI||These 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.|
|VII||These 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.|
|VIII||Very 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 Class||Ranges of soil separates (%)|
|Sand||85 – 100||0 – 15||0 – 10|
|Loamy sand||70 – 90||0 – 30||0 – 15|
|Sandy loam||40 – 80||0 – 50||0 – 20|
|Loam||23 – 52||28-50||7-27|
|Sandy clay loam||45-80||0-28||20-35|
|Silty clay loam||0-20||40-73||27-40|
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:
- Sand (size as in beach sand)
- Silt (size like talc/talcum powder)
- 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:-
- Type of aggregates (form),
- Class (average size) and
- 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”.
- 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.
- 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 – 1||Cl;ick|
|Agriculture Soil Science Important Table – 2||Cl;ick|
|Agriculture Soil Science Important Table – 3||Cl;ick|
|Agriculture Soil Science Important Table – 5||Cl;ick|