Chemical & microbial analysis of

Farm Soil & Forest Soil

- Ishan O. Trivedi

What is soil ?• Soil is a heterogeneous mixture of silicate particles,

humus, and a variety of insoluble salts and oxides of metals called the solid phase, a liquid phase and a gaseous phase.

• Types of soil texture:1. Clayey2. Sandy3. Loamy

We performed soil analysis to…

• Analyze physiochemical parameters of soil.

• Analyze microbial parameters of soil.

• Study relationship between soil organic content and micro-organisms.

Every soil is a unique combination

of minerals, micro and macro

Organisms.

Also, soil is a/an:

Great integrator

Producer andabsorber of gases (CO2 and others)

Medium for plant growth

Medium of crop production

Home to organisms(plants, animals and micro-organisms)

Waste decomposer

Snapshot of geologic, climatic, biological, and human history

Source material for construction, medicine, art, etc.

Filter of water and wastes

Essential natural resource

Medium of heat andwater storage

Why we specifically chose forest and farm soil ?

• To analyze forest Biota:

- Forest is the richest biodiversity holder. - Forest is the source of timber & medicines to humans. We analyzed what

problems the trees may be facing in the forest and their solutions. - We searched for methods to maximize the growth of beneficial micro-organisms.

• To analyze farm fertility and types of organisms in it:

- Farm is the source of crops for us. Healthy soil gives rise to healthy crops. - Different organisms are favoured in various pH, chloride content, organic

content etc. Knowing this helped in identifying the useful organisms and provided methods of manipulation to favour these organisms.

- Earth worms are favoured in soil rich in organic content.

Characterization and Sampling Options

Soil Pit

Auger

Exposed Profile (road cut)

Surface Sample

Physical analysis

Soil type• Clay soil: Clay soils are made of very small particles.

They feel slick and sticky when wet. Clay and silt hold moisture well, but resist water infiltration, especially when they are dry. Often puddles form on clay or silt soils, and they easily become compacted.

• Loam soil: Loam soil is a mixture of sand, silt or clay, and organic matter. Loam soils are loose and look rich. When squeezed in your fist, moist loam will form a ball which crumbles when poked with a finger. Loam soils normally absorb water and store moisture well. Loam soils can be sandy or clay based, and will vary in moisture absorption and retention accordingly.

• Sandy soils: Sandy soils contain large particles which are visible to the unaided eye, and are usually light in color. Sand feels coarse when wet or dry, and will not form a ball when squeezed in your fist. Sandy soils stay loose and allow moisture to penetrate easily, but do not retain it for long term use

Farm &forestsoil

Soil Structure:

Granular Blocky

Prismatic Columnar

Forest & farm soil

Chemical analysis

Soil pHPrinciple:A pH meter measures the potential difference

between reference solution and test solution and accordingly displays it in the form of pH.

Materials:

• Soil sample, D/w, rotatory shaker, pH meter, pH tablets.

Method:

• Dissolve 10gm soil in 100ml D/w.• Put it on a rotatory shaker for 1 hour.• Allow the soil to settle for 10 minutes.• Calibrate the pH meter on atleast 2 buffers,

usually pH 4 and pH 7 using standard pH tablets.

• Put the combined electrode in the suspension about 3 cm deep.

• Take the reading after 30 secs.• Remove the combined electrode and rinse it

with D/w.

Soil chloridePrinciple:

AgNO3 first reacts with chloride ions to form AgCl. Once all chloride ions have reacted, AgNO3 reacts with K2CrO4 to form brick red precipitates of Ag2CrO4

Materials:

• Soil sample, D/W, rotatory shaker, K2CrO4, AgNO3.

Method:• Take 10 gm soil and mix with 50 ml D/w.• Take 5 ml sample and add 20 ml D/W.• To this add 1-2 drops of K2CrO4

• Titrate with the help of AgNO3 until yellow to brick red.

• Calculation:• Soil chloride Cl-/gm = (x*y*35.5)/1000 X= pipette reading Y= Normality (1N)

Total soil acidityPrinciple:

Principle of normality.N1V1=N2V2

Materials:

• 0.05N NaOH, methyl orange indicator, phenolphthalein, soil sample, D/W.

Method:

• Prepare 100 ml colourless sample from 1 gm soil sample with the help of D/W.

• Add 2-3 drops of methyl orange. If solution turns yellow, methyl orange acidity is absent.

• If solution turns pink, titrate with 0.05 N NaOH till yellow colour is obtained. Take this value as titer value “A”.

• Now add 2-3 drops of Phenolphthalein indicator. If pink colour develops, phenolphthalein acidity is absent.

• If soln. is colourless, titrate with 0.05N NaOH until pink colour is obtained.

• Record B which is known as phenolphthalein acidity.

Calculation:• Methyl orange acidity: Mg/liter= (a*NNaOH*1000*50)/VSample

• Phenolphthalein acidity: Mg/liter= (b*NNaOH*1000*50)/VSample

Total acidity = [(a+b)*NNaOH*1000*50] / VSample.• Convert into “mg/gm” units.

Total soil alkalityPrinciple:

Principle of normality.N1V1=N2V2

Materials:• Soil sample, D/w, phenolphthalein indicator, 0.1N HCl,

methyl orange

Method:• Prepare 100 ml colourless sample from 1 gm soil sample

with the help of D/W.• Take 100 ml of sample. Add 1-2 drops of phenolphthalein.• Titrate against 0.1 N HCl if pink colour develops.• Record this as result “a”. This is phenolphthalein alkality.• Then add 1 drop of methyl orange. If it gives light yellow

colour, again titrate against 0.1 N HCl until the light yellow colour is changed to red.

• Note the result “b”. This is methyl orange alkality.

Calculation:• Phenolphthalein alkality: Mg/liter = (a*NHCl*1000*50)/VSample

• Methyl orange alkality: Mg/liter = (b*NHCl*1000*50)/VSample

• Total alkality = [(a+b)*NHCl*1000*50]/VSample.

Total Organic carbon:Principle: Oxidation of organic matter with know volume of K2Cr2O7 and knowing

the unreduced K2Cr2O7 by reduction with FAS.

Materials: 

-   0.01 M K2Cr2O7 solution.-   Sulphuric acid reagent (500ml H2SO4 + 5.5gm Ag2SO4, Allow it to react overnight).-   Ferrous ammonium sulphate (0.1M).

Method:-   1 gm soil sample + 10ml potassium dichromate + 7ml Sulphuric acid

reagent + 2ml O-Phosphoric acid-   Allow it to react on COD digester at 1500C for 1 hour.-   Allow it to cool.- Add 1 to 2 drop of ferroin indicator.- Titrate with 0.1M ferrous ammonium sulphate.- Colour change : Bluish green to reddish brown. Record it as result “B”.- Run a blank experiment with all above ingredients except soil. Note it

as result “A”.

Calculation:- In mg O2/liter = [(A – B) * M *8000] / Vsample. A = ml Ferrous ammonium sulphate used for blank experiment. B = ml Ferrous ammonium sulphate used for sample.

Microbiological analysis

Standard plate count.

• Principle: Law of serial dilution.• Media used: Nutrient agar, Czapek Dox agar, Soil agar, Actinomycete agar.

Interpretation of results• pH:

Soil chlorides

Total alkality

Total acidity

Total organic carbon

ConclusionChemical analysis:

• Farm soil. This soil is nearly ideal for growing leguminous plants. Currently, ground nut

is being grown at the site. Soil structure, pH, chloride content, sodium content, molybdenum content etc.

are all normal.Soil is falling short of organic matter. This is restricting growth of non-symbiotic

nitrogen fixing bacteria and earthworms.Organic matter need to be added along with liming, if necessary, to make it an

ideal soil.

• Forest soil. This soil is having high organic content. The pH is almost neutral. High

amount of organic acids is the reason. Nitrogen fixing bacteria may find it difficult to survive if the pH falls further.

Soil needs liming or extraction of excess organic matter.

Microbiological analysis:

• High organic matter was found in forest soil but farm soil was more workable ( aeration, water content, tillage etc.).

• Soils receiving well decomposed organic manures have better soil aggregates than those receiving saw dust and other types of not so easily decomposable organic wastes.

• Samples have been collected from two organic content rich soil regions like farm and forest. Forest soil is rich organic matter, 0.28 gm/ dry wt. whereas in farm soil, it is 0.12 gm/dry wt. Heterotrophic count on N. agar shows high population of bacteria & count on soil agar shows high population of nitrogen fixing & biodegrading bacteria.

• Moderate alkaline pH favours high population of actinomycetes in forest soil whereas comparative high population of fungal indices in forest may be due to high plant biodiversity at forest.

• The organic matter in soils is potential source of plant growth. Microbiological decomposition of organic matter is an essential step to release the bound nutrients in organic residues in an easily available form.

• We concluded that the number of actinomycetes increases in presence of decomposing organic matter.

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