Name: manzoor nabiCourse: forestryRoll no: 04

Acidic,Salic,

AndAlkali Soils

MEWARUNIVERSITY

Define soil acidity?• Soil acidity may be defined as the soil

system`s proton(H ions) donating capacity

during its transition from a given state to a

reference state.

• Soil acidity involves intensity and quantity

aspects.The intensity aspect is universally

characterised by the measurements of H

ion activity,expressed as pH. Soil acidity is a

major problem in relation to plant growth

and therefore, acid soils are called a

problem soil

Characteristics of acid soils?1.The pH is low,high exchangeable H and Al,

low CECand high base unsaturated are the

characteristics of acid soils .

2.Adverse effect is due to toxic concentration

of Al,Mn and Fe and deficiency of Ca and Mg

3.Acid soils are low in available P and have

high P fixing capacity

4.Available micronutrients status is adequate

except molybdenum .

5.Population of bacteria and actinomycetes is

lower and those of fungi higher.

Define saline soil?

Saline soil may be defined as a soil having a

conductivity of the saturation extract greater

than 4dS/m (0.4S/m or 4mmhos/cm) and

abn exchangable sodium percentage (ESP)

less thann 15. The pH is usually less than 8.5.

Formerly these4 soils were called white

alkali soils because of surface crust of white

salts.

Characteristics of saline soils:Saline soils contain neutral soluble salts of

chlorides and sulfates of sodium, calcium magnesium .

The electrical conductivity of saturated extract of the soil is more than 4dS/m

ESP is less than 15 and pH is less than 8.5.Because of the presence of excess salts and low amount of Na, these soils are in a flocculated state and their permeability is higher than alkali soils.

Their physical conditionis good and water can pass through them .

These soils have a white crust of salts on their surface.

Define alkali soil?Alkali or sodic soil is defined as a soil having

a conductivity of the saturation extract less

than 4dS/m (0.4S/m or 4mmhos/cm) and an

exchangeable sodium percentage (ESP)

greater than 15.The pH is usually between

8.5-10.0.Formerly these soils were called

black alkali soils and the soil is called solod,

soloth or degraded alkali or sodic soil

Characteristics of alkali or sodic

soils?

Most of the Na is in exchangeable form

EC of saturated extract is less than 4dS/m.

ESP is more than 15and pH more than 8.5.

Such soils are not in a good physical condition and the surface of these soils is sometimes black due to dispersion of organic matter and humus .

Such soils if ploughed when wet , turn into slick furrow slice referred to as slick spots.

Define saline-alkali soil?Saline-alkali soil is defined as a soil having

a conductivity of the saturation extract greater than 4dS/m (0.4S/m or 4mmhos/cm )and an exchangeable sodium percentage (ESP) greater than 15.The pH is variable and usually above 8.5 depending on the relative amount of exchangeable sodium and solube salts .When soils dominated by exchangeable sodium, the pH will be more than 8.5 and soils dominated by solubesalts, the pH will be less than 8.5.

Characteristics of saline-alkali soils?

These soils have both soluble salts and

exchangeable sodium.

The soils reaction becomes strongly alkaline

because of hydrolysis of exchangeable sodium

.

The physical condition of the soil is deteriorated.

The EC of saturated extract is more than

4dS/m,ESPis more than 15 and PH is around8.5.

They are transitional soils that they may be

converted into saline or into sodic soils.

Formation of saline and alkali soils ?1. Weathering of rocks and minerals:-The soluble

salts released during weathering leach down with rain water , but again move upward due to high temperature and accumulate as white crust forming a saline soil.

2. Hydrolysis of sodium saturated exchange complex in the formation of an alkali soil:-Sodium carbonate undergoes hydrolysis to form sodium hydroxide,which dissociates to increase concentrationof hydroxyl ions in soil solution.

Micelle (Na+H2CO3 Micelle)Na+H+Na2CO3

Na2CO3+2H.OH 2 NaOH+H2CO3

2NaOH 2 Na+OH-

Formation of OH results in an increase in pH

3.Salty underground water :-If the ground

water is salty move upward with water and get

deposited when water evaporates

4.Arid and semi arid climate :-The low rainfall

is not sufficient to leach down the soluble

weathered products and hence the salts

accumulate in the soil.

5. Use of basic fertilizer:-Basic fertilizers

like NaNO3 and basic slag may develop

soil alkalinity.

Thank you