Soil science

Soil and land, though related to different entities.

• Land is 2 dimension entity representing geographical area and landscape.

• Soil is three dimensional body with length breadth and height.

Soils are formed by weathering process of rocks, Which in the words of Hans jenny can be depicted by the equation.

Definition of soil.

• soil is natural body composed of inorganic or organic constituent having a different genesis and a distinct nature of its own.-------Dokuchaev(1900)

• Father of soil science is Dokuchaiev.

soil is the unconsolidated mineral method on the immediate surface of the earth that serve as a natural medium for the growth of land plants.

Component of soil

Soil consists of four major component.

1. Inorganic = 45%
2. , organic, = 5%
3. air,.     = 25%
4.  water. =. 25%

Inorganic soil

Inorganic substance are 45 percent present.

It is composed of small Rock fragments and minerals of various kind example 

1. gravel 
2. ,cobbles, and
3.  stones.

inorganic fraction of soil is is essential for plant growth and development.

• Primary minerals are sand and silt.

Organic matter

Plant and animal residue are disintegrated and decompose.

other organic compound synthesized by soil microbes.

Soil water

Soil water is held in soil Pore.

soil water with its soluble constituent make up soil solution which is the critical medium for supplying nutrient to growing plant.

Soil air

Soil air occupies those soil pores are not filled with water.

Soil air is always differ from atmosphere in composition for root and microbial activity.

• Carbon dioxide several hundred times higher than 0.033 %
• Oxygen content usually less than 20% .

Soil texture

•  the relative proportion of various soil separate namely sand ,silt and clay in a given soil .

the size particle or separate in mineral soil is not easily change. so the proportion of each size group in a given soil can not be altered easily.that is why soil texture is considered

Soil texture classes

the group based on the relative proportion of the various soil particle are known as soil texture classes.

soil texture classes name are used to give an idea of the soil of the texture makeup of the soil and to indicate their physical property.

Soil texture classes may be broadly  group into.

Sandy soil

soil having at least 70% sand particle and 15% or less clay particle by weight.

Water holding capacity is low.

nutrient supplying ability and nutrient retention power is very low.

Productivity of soil is very low.

Low chemical activity 

resistance to weathering

Non sticky and

 plastic in nature

Loamy soils

Mixture of sand silt and clay particle in about particle in equal proportion.

Ideal loam soils are gritty and cohesive.

Medium water retention capacity.

Medium plant water available 

Low stickness

Medium CEC

Ideal soil for crop production.

Supply nutrient is medium.

Clay soil

Soil must contain at least 35% of clay particle.

In most cases not less than 40 per cent of clay particle.

Clay soil are fine particle.

Water holding capacity is very good.

CEC, nutrient retention, are very good.

Silty soils

Soil having at least 80% silt and 12% or less clay.

Silty soils are silky and 

buttery and 

some plasticity cohesion and adsorptive capacity.

Medium water available for plant.

Branch of soil science.

Pedology

Study of soil natural body and does not focus primary immediate practical use.

Soil chemistry

Deal with chemical constituent ,chemical properties and chemical reaction of soil relation to crop need.

Soil microbiology

Deal with microscopic population of soil.

It importance in plant nutrition and crop production.

Soil genesis.

Study of the mode of origin of soil.

Soil structure

The arrangement of primary soil particles such as sand, silt and clay into stable aggregate.

Soil structure Denotes

1.  size shape and arrangement of particle and aggregate
2. size shape and arrangement of voids or space separating the particle and aggregate.
3. Combination of voids and aggregate of structure

Peds

Natural aggregate which vary in their water stability.

Clod

Used for a coherent mass of soil broken into a any shaped by artificial means such as  tillage.

Fragment

Broken ped

Concretion

Coherent mass formed with in soil by the precipitation of certain chemical dissolve in percolating water.