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Agricultural Soil Science Important Points (2)

Agricultural Soil Science 

Agricultural Soil Science Important Point

1.Classification of Soil Particle Size

ClassificationDiameter (mm) (AgriExam.Com)
IISSUSDA
Gravel>2.0>2.0
Coarse Sand0.2 – 2.00.5 – 1.0
Fine Sand0.02 – 0.20.1 – 0.25
Silt0.002 – 0.020.002 – 0.05
Clay<0.002<0.002

2.Soil Classification Based on pH

Soil type (AgriExam.Com)pH range
Extremely acidic<4.5
Moderately acidic4.5-5.5
Slightly acidic5.5-6.5
Neutral6.5-7.5
Slightly alkaline7.5-8.5
Moderately alkaline8.5-9.5
Extremely alkaline>9.5

Agricultural Soil Science Important Points

3.Density of Different Soil

SoilParticle density (cm/cc)Bulk density (cm/cc)
Normal Soil2.651-1.6
Sandy Soil2.61.6
Silty Soil2.71.3
Clay Soil2.81.1

4.Total pore space of soil

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SoilPore space
Sandy20-30%
Loamy30-50%
Clay50-60%

5.Specific heat

MaterialSpecific heat (Cal./gm)
Water1
Organic matter0.462
Clay soil0.22
Air24
Humus0.4
Ice0.5

6.Heat Capacity

MaterialHeat Capacity (Cal./cm3)
Organic matter0.60
Water1
Air0.003

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7.Cation Exchange Capacity (CEC) of Soils

Soil textureCEC (meq/100 gm)
Sand (light colour)3-5
Sand (dark colour)10-20
Loam10-15
Silt loam15-25
Clay and clay loam20-50
Organic soil50-100

8.Conversion factors

Conversion factors (AgriExam.Com)
NNox 0.22
NoN x 4.54
PP2O5 x 0.44
P2O5P x 2.27
KK2O x 0.83
K2OK x 1.20
CaCaO x 0.71
CaOCa x 1.40
MgMgO x 0.61
MgOMg x 1.63
OMOC x 1.724
OCOM x 0.58

OM= Organic matter

OC = Organic carbon

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9.Soil Test Rating Chart for Available Nutrients

NutrientLow levelMedium levelHigh level
N<250 kg/ha250-500 kg/ha>500 kg/ha
P<20 kg/ha20-50 kg/ha>50 kg/ha
K<125 kg/ha125-300 kg/ha>300 kg/ha
Zn/Cu<0.5 ppm0.5-1.0 ppm>1.0 ppm
Mn<1.0 ppm1.0-3.0 ppm>3.0 ppm
B<0.33 ppm0.33-0.67 ppm>0.67 ppm
OC<0.5%0.5-0.75%>0.75%

Agricultural Soil Science Important Points

10.Soil colour

It is found out by using Munsell Colour Chart. Three variable are used to denote soil colour.

Component of Soil Colour (AgriExam.Com)
HUEDenotes the dominant spectral colour (Yellow, red blue, brown etc.)
VALUEDenotes the lightness and darkness of colour
CHROMADenotes purity of colour

11.Antagonistic Effect

Excess of nutrient (AgriExam.Com)Causes deficiency
CaP
Ca, MgK
K, NH4Mg
Fe, SO4Mo
PZn
N, P, KCu
NO3Fe
Zn, AlCu
N, K, CaB

12.Different nutrient test method in soil

Nutrient Determination Analyzing Process
Total Nitrogen in soilKzeldahl Process
Available N Alkaline Permanganate method
Phosphursus in acid condition Bray No.1
Phosphursus in neutral and alkaline condition Olsen’s Method
K & NaFlame photometer
Sulphate sulphure (SO4) Terbimatric Method
Organic carbona)Walke & Black method
b)Rapid Oxidation process (KMnO4)
c)Morgan’s method
Available K (Potash)Ammonium Acetate

 

Important Table – 1Cl;ick
Important Table – 2Cl;ick
One LinerCl;ick
Fertilizers classificationCl;ick

 

Updated: 2021-04-03 — 2:55 pm

2 Comments

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  1. Plz share somthng about entomology…m waitng😕

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    IBPS AFO pre Exam
    IBPS AFO mains Exam
    Note
    Mock test
    Join karna chahta hu sir …

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