3 Land

.3 LAND Land is the basic resource of any nation, but it is the limiting factor utilized for various purposes other than cultivation, such as farm houses, cattle shed. wells, channels, roads, processing yards etc Land is one of the main component of the environment bestdes water, air. flaura and fauna. Land is required by man for a number of .purposes such as Agricultural and horticultural food production. ii) Housing, commerce in relationship to urban and communities. iii) Industrial sites. (iv) Transportation including rails, roads, highways etc. v) Mining vi) For forests vii) For recreation and other purposes. There are numerous problems in the utilization of land. In urban areas where it is densely populated there is scarcity for land with as in rural areas land is available in plenty. Some land is protecte for wild life preservation. Some part of land is utilized for the construction of reservoirs. The disposal of wastes also requires land The changes from one land use to the other use affects the environment. Sometimes it is positive and sometimes negative. Land resources are also related to natural disasters such as volcarn eruptions, earth quakes and landslides. Land also includes waste lands and wetlands. Wasteland is piece of land which is not capable of producing crops which include the degraded forest, over irrigated soils, eroded valleys and water logged marshy land. Wetlands are the parts of aquatic echo systems. In aquatic system water is the main component and it includes the fresh water pond, lakes, rivers, seas etc. When the depth of the water does not exceed 6 m, it may be called as wet land echo system. It is estimated that-the wet land covers about 6% of the worlds land surface. 2.3.1 soil Soil is the most inherent component of the land. Soil is a natural formation resulting from the'tfahsformation of surface rocks by the combination of climate, plant and animal life with aging. Soil may be defined as a natural body formed at the bundry between the lithosphere and the biosphere by interchains all facors involved in soil formation, considering both living dead organism. The composition and the properties of soil are amined relating to the environment. Soil contains not only minerals but also organic and anorganic compounds. Soil is made of rock which has been transformed into other layers due to getation and due to various micro and macro organisms. The soil yer may be divided as (i) Accumulation of organic and human matters. (ii) Intermediate between human and parent rocks. (iii) parent rock weakly altered by soil formation. (iv) Bed rock (combination of hard and rocky materials) .

3.2 Physics of Land The following are the physical properties of soil. 1. Colour

6. Soil air

2. Texture

7. Hygroscopic moisture

3. Porosity

8. Water property of soil

4. Particle size distribution

9. Soil temperature

5. Specific mass of soil

10. Colloidal nature of soil

Colour and Tint The colour and tint of soil depends on the minerals present in and also depends on the humus components. Based on the colour the soil it can be classified into following. 1. Black soil,

2. Grey soil

3. Red soil

4. Yellow or laterite soil

The, grey and black colour of soil indicates the different soil contents of humus and it may also be due to the colour of the parent rock. The red soil indicates the richness of iron or ferric oxide in the soil. The yellow colour indicates the presence of Hydrated. compounds such as Ferric hydroxide. In some tropical areas soils arc also found which indicates the presence of concentration of ferrous compounds such as ferrous oxide. The soil indicates the presence of calcium carbonate in execss. The tint of soil is made up of the combination of two colours. Itcan be brown red, grey black etc., 2. Texture Based on the texture of the soil it can be divided in following groups. 1. Clayey soil (a) Very clayey

(i) Clay (ii) Silly clay

(b) Intermediate

(i) Silty heavy loam (ii) Heavy loam

(c) Sandy clay 2. Loamy Soil (a) Medium Loamy .

(i) Sandy heavy loam (ii) Loam

(b) Slightly loamy 3. Silty soils (a) Silty loam

(i) Sandy loam

(b) Silty clay loam Sandy soils

(i). Loamy Sand (ii) Sand

Soil texture is an important property. Soil texture can be del by the mineralogica! and chemical composition. As soils densely packed structure and capillary pores, they can retain quantities of water. They check the passage of water as capilla are smaller m diameter and they get plugged by swelling. structure of soil has the unique property of absorbing large quantities nutrient. Sandy soils arc very poor in nutrients and need organic ertilizers and minerals for better crop growth. Humus and Humus complexes have better binding properly. Whenever industrial fluent combines with humus, it act: acts as the exchange capacity sulting in total loss in it's binding property. porosity: (P) porosity P of soil many be defined as the ratio of volume voids to the total volume of the given soil mass. p=[d-dv] X 100 here d - Specific mass of soil dv - Volumetric mass of soil The porosity of soil depends upon the texture and the gregation of the soil. 'Soil

Porosity (by volume) (%)

1. Best soil

> 50%

2. Good soil

45 to 50 '

3. Satisfactory soil

40 to 45

4. Unsatisfactory soil

40%

5. Poor soil

<30%

Soil porosity determines its moisture holding capacity of the solids. The pores present in the soil allows the rain water to flow through it for long duration and to retain the rain water. During the ry Season soil, serves as a reservoir of water for all living organisms which depend on soil for their water needs. Even during the dry eriods plats obtain their water requirement through, roots by enetrating deeper into the soil. 4. Particle size distribution The size of the soil particles determines the quantity movement of water and air in the soil, because water and air fill the spaces in between the soil particles. Higher the percentage smaller particles, more the number of pore space (e.g) clayey hence stores more amount of water and air. In turn soils with land particle size have layer space but the pores size are larger, water holding capacity of sandy soils is low compared to class soils

5. Specific mass of soil It is the ratio between the solid phase of soil alone (with air) to the weight of water in same volume at 4°C. where m

= Specific mass of soil

m,

= wt. of solid phase

m,

= wt. of water at 4°C

The specific mass changes with change in the chemi composition of soil and the mineralogical factors. The specific is lower (2 to 4) on humus soil and it is high on rocky soils. 6. Soil air Good aeration of soil is important for maintaining its biologi activities. Good soil aeration is also helpful for better plant grov Soil contains certain gases such as 1. Carbon dioxide

-68%

2. Oxygen

0.3 to 1%

3. Ammonia

<9.1%

4. Methane

<0.05%

7. Hygroscopic moisture (water) The amount of water in soil depends upon the relative humidity of the atmospheric and soil air.The hygroscopic moisture in soil ['depends mainly on the following factors. (i)

humus content

(ii)

chemical composition

(iii)

texture

.

The hygroscopic moisture of soil depends upon the absorptive capacity of the soil. The value is generally about 0.5% to 1% in tropical soils. ' 8. Water property of. soils This represents the water capacity and the water permeability of soils. The water capacity is the amount of water that can be retained by the capillaries when the soil is saturated with water from beneath. It is the maximum quantity of water which the soil can retain within itself. The permeability of water is the capacity of soil to allow water to pass through it. The permeability of soil depends on swelling, aggregation and texture. Higher the permeability of water, the more distinct is the soil structure for a same texture of the soil. The capillarity of soil reflects the energy for retaining water. 9. Soil Temperature The change in temperature, changes the properties of the soil. The colour, moisture, absorbtion and water content of the soil varies with the temperature variations.

10. Colloidal nature of soils The particles size ranging between 0.2 p to 0.001 p are termed as colloidal particles. Based on the colloidal nature of soil, it can be classified into three groups. Type

Particle diameter

Pre colloidal

1 p to 0.2

Colloidal

0.2 p to 0.001µ

Molecular solutions

Close to 0.001 µ

Colloids are charged particles and they can be divided into the groups namely electronegative particles, and clcciroposite particles. Electronegative particles consists of clay minerals, hum acid and complexes of bivalent and trivalent ions with silica. Electropositive soils include hydroxides of iron and Aluminiua Exchange reaction and retaining capacity of soil depend upon the charges 2.3.2 Chemistry of Land The chemical composition of soil is very diversified art depends upon the chemical composition of rock. Generally following chemicals are found in the soil. Table 2.4 The Average content of elements in soils Chemical Element Avg%by wt of soil Oxygen

49

Silicon

33

Aluminium

7.13

Iron

3,8

Carbon

2.00

Calcium

1.37

Potassium

1.3,

Sodium

0.6

Magnesium

0.6

Sulphur

0.08

Nitrogen

0.10

In many soils of arid regions certain water soluble saltsso found 1. Sodium chloride (Nacl) 2. Magnesium Sulphate (Mg S04) 3. Calcium Carbonate (CaCO3) 4. Magnesium Bicarbonate MiUHCO3)2 5. Calcium chloride CaCl2 6. Sodium Sulphate (Na2SO4) 7. Magnesium Carbonate MgCO3 8. Sodium Nitrate (NaNo3) 9. Calcium Sulphate (CaSO4 10. Potassium Nitrate (KNO3) 11. Calcium Bicarbonate Ca(HC03)2 12. Magnesium Chloride (Mgcl2) Of the above salts all the salts are dissolvable in water except CaCa3, MgC03 and CaSO4 Chromium Chromium affects the soil fertility and cultivation. It also inhibits the enzymatic activities, reduce the growth of plants and affects the food chain. The chromium is present in soil due to the entry of industrial wastes from tanneries.s Sodium High sodium content of the effluent cause severe physical impairment of soil like disease in the capillary para space moisture holding capacity and permeability of soil. pH of soil pH of good soils should be about 7, but due to the discharge of effluents into the land, the pH of soil increases orAcidity or Alkalinity of soil Soils are characterized by the following PH values pH Range

Soil

3 to 4.5

strong acid soils

4.5 to 5.5

acid soils

5.5 to 6.5

weak acid soils

6.5 to 7

neutral soils

7 to 7.5

weak alkaline soils

7.5 to 8.5

alkaline soils

8.5 to 13

strong alkaline soils

pH value of soil is of much importance as it regulates cert* properties of soils. If pH is below 7 the composition of cation reve hydrogen and aluminium, the fraction of which increases with decreasing pH. If the pH of soil is above 7, the soils arc saturats with magnesium and calcium. 2.3.3 Biology of land After a long process of weathering and disintegration of rook they arc changed into following types of soils such as sand, si clay and grovel. A large variety of living organisms occur in the soil. They are algae, bacteria, fungi, protozoa, insects, reptile rodents, plants, animal. The inorganic materials are derived from the parent rock an the organic materials are produced by the living organisms duri the life time as well as after their death. These organic matt serves as the source of energy for all living organisms in the so The humus which is a partially decomposed organic matter give the soil loose texture. Because of this loose texture, the soil capable of storing water and nutrients in its pores and also betti air circulation lakes place. The nutrients stored in the soil a regenerated regularly by decay, composition and mineralisations the organic matter, deposits by living organisms. Bacteria Algae and Fungi These are very important in the life of plants and in turn animals because the atmospheric nitrogen is fixed by the Nitrogen fixing bacterias"and blue green algaes: Certain bacteria and fungi use the liirbteins and amino acids in. the dead organ for their own consumption and in turn releases the excess ammonia or ammonium 'Ions''- The Nitrifying bacteria present in the soil oxidises this ammonia'to. nitrite. The other bactcrias present oxidises nitrites,to Nitrates which is another form of nitrogen which can be easily absorbed by the plants. This enhances the plant growth in the soil. Insects Helminths and Rodents These microbes are useful to produce growth producing substances. These microorganisms along with other organics matter binds the soil particles in crumbs or aggregates which prevents the Lexcessive leaching and erosion. Animals -The Burrowing animals creates innumerable passages in the soil which helps in the exchange of gases. Earthworms These are found in all types of soils provided there is sufficient moisture and food in it. They occur in forests, grasslands, gardens, plant nurseries and green houses. The main activity of earthworm in soil involves the ingestion of soil, mixing of different soil components and production of sub surface castings. Earthworms consumes the soil organic matter and convert it into humus with in a short period of time and thereby

increases the soil fertility. Therefore they are called as nature's plaughman. Thus the soil is continuously turned over and over again by these earthworms and the amount brought to the surface is considerable. The earth worm casts contains nutrients in available form and thus helps in promoting the plant growth. Vermicompositing Vermicomposting is a process of convening the organic was materials into valuable vermicompost by culturing the earthwarms known as vermiculture. When other traditional process composting is compared, vermicomposting takes the advantage the biological and physiological characteristics of earthworms, the activities and qualities to enhance the aerobic microbiologie decomposition of organic materials. Composition of organic part and Microorganism The organic matter of the soil contains bulk of water and the following substances. I. Proteins

2. Carbohydrates

3. Lignin

4. Lipids

5. Waxes

6. Resins

7. Tannins

8. Organic acids

The organic part varies from 0.5 to 25 tonnes/hectares depending upon the type of vegetation, climate and soil formation The humus are the dark colloidal substances impregnating the mineral part of the soil, giving a dark colour to its upper surface The humus substances makes the soil more fertile. The humus formed by the organic materials enrich the soils with bases and nutrients such as nitrogen and phosphorous. .They regulate the acidity of the soil and mineral content and the organomineral compounds of iron. The following types of micro organisms are found in soil. 1.Bacteria

2. Fungi

3. Algae

4. Actinomycetes

5. Protozoa The microorganisms present in soil can be broadly divided into