As CSR Activities Soil
analysis has been taken by NFCL in INDIA
A
brief about soil, soil analysis methodologies, Application & critical analysis
& Fertilizer Recommendation for Farmers soil.
Dr. Amar Nath Giri (EHSQ)
Soil may be defined as a thin
layer of earth crust which serves as a natural medium for the growth of the
plants. Soil consists of organic matter Soil
organisms - Micro flora and Micro fauna. Soil water Soil air Inorganic matter - Macro
nutrients and Micro nutrients Organic Matter the plants and animals grown
in weathered material and the organic residues left behind decay with time and
become an integral part of the soil. The main source of soil organic matter is
plant tissue. Animals are subsidiary source of soil organic matter. The micro flora like bacteria, fungi, algae,
actinomycetes, and micro fauna like protozoa, nematodes, macro fauna like
earthworms, ants etc. play an important role in formation of organic matter.
The organic matter influences the soil in respect to colour, physical
properties, supply of available nutrients and adsorptive capacity. IN NFCL we
are considering the significant parameters which is useful to analysis maximum
quality of the soil which used to be beneficial to provide real solution for
healthy Crop & fruits , cereals, vegetables.
Objective of Soil
Testing:
Appropriate fertilizer dozes
used to be recommended on the basis of soil testing such as In Normal soil (pH-
6 to 6.5) all Nitrogenous fertilizer, Super phosphate, Ammonium phosphate etc.
can be used. Similarly in the soil having less than 6.00 pH value, Calcium ammonium
nitrate, Sodium nitrate, phosphetic fertilizer. Super phosphate, Murate of
potash etc can be applied. In the soils having more than 8.5 Ph value, Urea,
Ammonium sulphate, Amonium chloride, Super phosphate, Amonium phosphate, Murate
of potash etc are recommended. The water logged soils can be applied Urea,
Ammonium sulphate, Super phosphate, Ammonium phosphate, Ammonium chloride etc.
To identify the quantity of organic carbon in the soil is one of the major objectives of soil testing, because growth of crop & availability of nutrients are based on organic carbon. The ratio of organic carbon & nitrogen is 10-12:1. The propagation of useful bacteria also depends on it.
To identify the quantity of organic carbon in the soil is one of the major objectives of soil testing, because growth of crop & availability of nutrients are based on organic carbon. The ratio of organic carbon & nitrogen is 10-12:1. The propagation of useful bacteria also depends on it.
Soil
testing recommends the ingradiant required reclaiming the acidic soil or saline
soils etc. The deficiency of micro element like Znic, Copper, Boron, Molybdenum,
Iron, Cobalt, Silicon, Manganese & Chlorine etc also adversely affect the
crop condition & ultimately the production.
In NFCL soil testing
laboratories pH, Ec, Organic carbon (as an index of available nitrogen), available
phosphorus, and available potassium are estimated. If necessary micro nutrients
like Fe, Cu, Mn, Zn and B are estimated, Ca, Mg and S are also estimated if any
deficiency symptoms are observed on crops. pH (potential of hydrogeni) is
estimated by a glass electrode pH meter in 1:2 soil water suspensions.
Electrical conductivity is measured by a conductivity meter in 1:2 soil water suspensions.
Available nitrogen is estimated by Subbaiah and Asija
(1956) method (distillation of soil
with alkaline potassium permanganate solution). But in most of the laboratories
organic carbon is taken as an index of available nitrogen content of soil
assuming C: N
ratio is 10. Organic carbon is determined by chromic acid oxidation
by rapid titration (Walkley and Black (1934) rapid titration). Phosphorous is determined by Olsen's (1954) using 0.5 M sodium bicarbonate as extracting and phosphorus
is analyzed calorimetrically. Neutral normal ammonium acetate solution is the
most widely used extractant for available potassium which is analyzed by flame
photometer. Micro nutrients are extracted by DTPA and determined by atomic
absorption spectrophotometer .
When land is brought
under cropping, grain or fruit and sometimes the entire plants are removed (harvested)
from the land. Hence, the soil losses a considerable amount of its nutrients
(up take by plants). If cropping is continued over a period of time, without
nutrients being restored to the soil, its fertility will be reduced and crop
yields will decline. Apart from removal by crops, nutrients may also be lost
from the soil through leaching and erosion. Even to maintain soil productivity
at the existing levels, it is necessary to restore to the soil, the nutrients
removed by crops as also those lost through leaching and erosion.
Continued maintenance of a
high level of soil fertility is an indispensable for profitable land use and
sustained agricultural production. From time to time the inherent fertility of
soil has to be evaluated.
A
brief About Indian Soil and its qualification:
Classification of Indian Soils
There are 8 major group of soils in
India
which are furnished below
Red Soils: Red colour is due to
various oxides of iron. They are poor in N, P, K and with pH varying 7 to 7.5.
These soils are light textured with porous structure. Lime is absent with low
soluble salts. Red soils occur extensively in Andhra Pradesh,
Assam, Bihar, Goa, Parts of
kerala, Maharastra, Karnataka, Tamilnadu and West Bengal.
Most of the red soils have been classified in the order ' Alfisols'.
Lateritic Soils
Seen in
high rainfall areas, under high rainfall conditions silica is released and
leached down wards and the upper horizons of soils become rich in oxides of
iron and aluminium. The texture is light with free drainage structure. Clay is
predominant and lime is deficient. pH
5 to 6 with low in base exchange capacity,
contained more humus and are well drained. They are distributed in summits of
hills of Daccan karnataka, Kerala, Madhyapradesh, Ghat regions of Orissa,
Andhra pradesh, Maharastra and also in West Bengal, Tamilnadu and Assam. Most of
the laterite soils have bee classified in the order ' ultisols' and a few under
' oxisols'.
Alluvial Soils
These
are the most important soils from the agriculture point of view. The soils are
sandy loam to clay loam with light grey colour to dark colour, structure is
loose and more fertile. But the soils are low in NPK and humus. They are well
supplied with lime; base exchange capacity is low, pH ranges from 7 to 8. These
soils are distributed in Indo-Gangetic plains, Brahmaputra
valley and all most all states of North and South. Most of the alluvial soils
have been classified in the orders ' Entisols', ' Inceptisols' and ' Alfisols'.
Black Soils
This is
well known group of soils characterised by dark grey to black colour with high
clay content. They are neutral to slightly alkaline in reaction. Deep cracks
develop during summer, the depth of the soil varies from less than a meter to
several meters. Poor free drainage results in the soils, base exchange is high
with high pH and rich in lime and potash. Major black soils are found in
Maharastra, Madhyapradesh, Gujarat and
Tamilnadu. Cotton is most favorable crop to be grown in these soils. These
soils are classified in the order 'Entisols', ' Inceptisols' and ' vertisols'.
Forest Soils
This
group of soils occur in Himalayas. Soils are
dark brown with more sub-soil humus content. They are more acidic.
Desert Soils
These
soils are mostly sandy to loamy fine sand with brown to yellow brown colour,
contains large amounts of soluble salts and lime with pH ranging 8.0 to 8.5.
Nitrogen content is very low. The presence of Phosphate and Nitrate make the
desert soils fertile and productive under water supply. They are distributed in
Haryana, Punjab, Rajasthan. They are
classified in the order ' Aridisols' and ' Entisols'.
Peaty and Marshy Soils
These
soils occur in humid regions with accumulation of high organic matter. During
monsoons the soils get submerged in water and the water receipts after the
monsoon during which period rice is cultivated. Soils are black clay and highly
acidic with pH of 3.5. Free alluminium and ferrous sulphate are present. The
depressions formed by dried rivers and lakes in alluvial and coastal areas some
times give rise to water logged soils and such soils are blue in colour due to
the presence of ferrous iron. Peaty soils are found more in Kerala and marshy
soils are found more in coastal tracks of Orissa, West
Bengal and South - East coast of Tamilnadu.
Saline - Sodic Soils
Saline
soils contain excess of natural soluble salts dominated by chlorides and
sulphates which affects plant growth. Sodic or alkali soils contain high
exchangeable sodium salts.
Both
kinds of salt effected soils occur in different parts of India like Uttarpradesh, Haryana, Punjab,
Maharastra, Tamilnadu, Gujarat, Rajastan and
Andhra pradesh. These soils are classified under ' Aridisols', ' Entisols' and
' Vertisols'.
Classification of Soils In Andhra
Pradesh There are five important types of soils in Andhra Pradesh. They are Red soils , Black soils, Alluvial soils , Laterite soils . Saline soils.
The characters of these soils are
same as given under Indian soils.
Soil
degradation
Soil degradation involves a
number of physical, chemical and biological processes, which may act singly or
jointly. In Andhra Pradesh state, soil erosion by water due to intense storms
and soils with poor surface structural stability are the most obvious forms of
land degradation. The other forms of degradation seen in our state are salinisation,
alkalisation, laterisation and inundation of the total area
of 18.52 million hectares in
14 districts surveyed so far, 19.6% suffers from soil degradation of one type
or the other.
Current records indicate
that 1,14,000 hectares of land are affected by water logging and salinity in
Guntur and Prakasam districts under the Nagarjuna sagar Right Bank Canal
Command. More than 60,000 hectares are alkaline in
the districts of Anantapur, Kurnool,
Medak, Nalgonda and Mahaboobnagar.
Salt affliction in soils may
occur as a result of a variety of causes, namely, capillary rise from subsoil
containing salt, indiscriminate use of canal water for irrigation, weathering
of rocks in salts transported by rivers from upstream regions to plains, salt
impregnated sands transported by coastal winds, in-site decomposition of soil
minerals and intrusion of sea water. The extent of saline and alkaline tracts
in irrigated areas (under canal and tank or reservoir command areas) is about 5,30,000
hectares.
Response:
Unfortunately, the response to the changes in soils leading to
degradation has been painfully slow. Nonetheless, systematic watershed
development and command area development programmes have earnestly attempted to
set matters right. Some steps have also been taken to rationalise energy and
water use through tariff structure. The present infrastructure of seven research stations in
different agro climatic zones in the state by the Department of Agriculture
helps in monitoring the changes in soil content but needs further strengthening
by way of interlocking with Agricultural Universities, Non-governmental organizations
, Fertilizer Industries Experts and
Institutions.
As industry & Nutrient solution provider in INDIA as
Eco-efficient way for best plant growth, good soil health & maximum
utilization of fertilizer by the plant and least environmental effects NFCL is
day by day improving the Quality of UREA & other fertilizers and asking
soil sample from farmers all over INDIA for analysis & best Soil recommendation provider.
There are different methods for soil
fertility evaluation as listed below: Soil Test
Interpretation and Fertilizer Recommendations
From the results of analysis of soil
samples sent by the farmer and information sheet supplied by him, soil test
reports are prepared in the laboratories. Copies of these reports are sent to
the concerned farmer.
Soil test reports are
usually in three main parts. First part indicates results of analyses of the
soil sample. Most laboratories give actual analyses as well as the ratings.
Second part is fertilizer recommendations for the crop based on soil analyses,
history of the field like cropping pattern, manures and fertilizers earlier
applied, etc. This part indicates quantities of nitrogen (N), Phosphate (
P205), Potash(K20), Zinc (Where facilities exist ) and also of lime or gypsum
to be applied per hectare.
The third part of the report usually
indicates time and methods of fertilizer application and other practices
required to make the fertilizer use more efficient.
During
the relatively short period that soil testing service has been in operation in
this country a large number of soil samples have been analyzed in various
laboratories. Based on the results of these analyses , soil fertility maps have
been prepared indicating the nutrient status of nitrogen, phosphorus, potassium
and zinc in different parts of the country. It must however, be noted that this
is only a broad classification , since it is based on limited soil sample
analysis.
Soil Composition
Soil Organisms: Soil is the
habitat for enormous number of living organisms. Some of these organisms are
visible to naked eye where as others can be seen by microscope only. Roots of
higher plants are considered as soil macro flora while bacteria, fungi, algae
and actinomycetes are considered as soil micro flora. Protozoa and nematodes
are the significant soil micro fauna where as the earthworms, moles and ants
constitutes soil macro fauna.
Soil Water: In order to function
as a medium for plant growth, soil must contain some water. The main functions
of water in the soil are as follows:
Promotes
many physical and biological activities of soil.
Acts as
a solvent and carrier of nutrients.
As a
nutrient itself.
Acts as
an agent in photosynthesis process.
Maintains
turgidity of plants.
Acts as
an agent in weathering of rocks and minerals.
Soil Air
Oxygen
is essential for all biological reactions occurring in soil. Its requirement is
met from the soil air. The gaseous phase of soil acts as a path way for intake
of oxygen which is absorbed by soil micro organisms, plant roots and for escape
of carbondioxide produced by the plants.
This
two way process is called soil aeration. Soil aeration become critical for the
plant growth when water content is high, because water replaces soil air.
Soil Inorganic Matter
The
inorganic constituents of the soil comprises carbonates, soluble salts, free
oxides of iron, aluminium and silica in addition to some amorphous silicates.
The inorganic constituents form the bulk of the solid phase of the soil. Soils
having more than 20% of the organic constituents are designated as organic
soils.
Soil pH
The
negative logarithm of hydrogen ion (H +) concentration is called pH. Soil pH
may be acidic, basic or neutral.
Soil Fertility
Soil
fertility deals with the nutrient status or ability of soil to supply nutrients
for plant growth under favorable environmental conditions such as light,
temperature and physical conditions of soil.
Soil Productivity
Soil
productivity is defined as the capability of the soil for producing a specified
quantity of plant produce per unit area and the ability to produce sequence of
crops under a specified system of management.
Problem Soils
The
soils which owe characteristics that they can not be economically used for the
cultivation of crops without adopting proper reclamation measures are known as
problem soils.
Acid Soils
Those
soils with pH less than 6.5 and which respond to liming may be considered as
acid soils.
Reasons for Acidity Humus decomposition
results in release of large amounts of acids. There by lowering the pH.
Rainfall: In areas with more than 100 cm
rainfall associated with high R.H., Ca, Mg is dissolved in water and leached
out due to this base saturation of soil decreases. Application of elemental
sulphur under goes reactions resulting in formation of H2SO4.
Continuous
application of acid forming fertilizers like ammonium sulphates or ammonium
chlorides results in depletion of Ca by CEC (cation exchange capacity)
phenomenon. Parent Material : Generally rocks are considered as acidic, which
contain large amount of silica (Si O2) when this combined with water, acidity
increases.
Characteristics : PH is less than 6.5
This
soils are open textured with high massive Structure. Low in Ca, Mg with
negligible amount of soluble salts. These
soils appear as brown or reddish brown, sandy loams or sands. Injury to
Crops
Direct Affects
Plant
root system does not grow normally due to toxic hydrogen ions. Permeability of
plant membranes are adversely affected due to soil acidity. Enzyme actions may
be altered, since they are sensitive to PH changes.
Indirect Affects
Deficiency
of Ca and Mg occur by leaching. Al, Mn and Fe available in toxic amounts. All
the micro nutrients except molybdenum are available. So 'Mo' deficiency has
been identified in leguminous crops. Phosphorous gets immobilized and its
availability is reduced. Actvity
of Micro Organisms Most of the activities of beneficial organisms like
Azatobacter and nodule forming bacteria of legumes are adversely effected as
acidity increases. Crops Suitable
For
Cultivation in Acid Soils
Amelioration
Lime as
reclaiming agent : Lime is added to neutralize acidity and to increase the PH,
so that the availability of nutrients will be increased. Basic slag obtained
from Iron and steel industry can be substituted for lime. It contains about
48-54% of CaO and 3-4% MgO. Ammonium sulphate and Ammonium chloride should not
be applied to acid soils but urea can be applied. Calcium Ammonium Nitrate
(CAN) is suitable to acid soils. Any citrate soluble phosphate fertilizer is
good source of phosphorous for acid soils. Eg. Dicalcium phosphate (DCP),
Tricalcium phosphate (TCP) Potassium sulphate is a suitable source of 'K' for
acid soils. But MOP is better than K2So4 because Cl of MOP replaces -OH ions,
their by release of -OH ions tends to increase the PH.
Alkaline Soils :
Alkali
soils are formed due to concentration of exchangeable sodium and high pH.
Because of high alkalinity resulting from sodium carbonate the surface soil is
discoloured to black; hence the term black alkali is used.
Reasons for Alkalinity
The
excessive irrigation of uplands containing Na salts results in the accumulation
of salts in the valleys. In arid and semi arid areas salt formed during
weathering are not fully leached.
In
coastal areas if the soil contains carbonates the ingression of sea water leads
to the formation of alkali soils due to formation of sodium carbonates.
Irrigated soils with poor drainage.
Characteristics
Injury to Crops
High
exchangeable sodium decreases the availability of calcium, magnesium to plants.
Dispersion of soil particles due to high exchangeable 'Na' leads to poor
physical condition of soil, low permeability to water and air, tends to be
sticky when wet and becomes hard on drying.
Toxicity
due to excess hydroxyl and carbonate ions. Growth of plant gets affected mainly
due to nutritional imbalance. Restricted root system and delay in flowering in
sensitive varieties.
Typical
leaf burn in annuals and woody plants due to excess of chloride and sodium.
Bronzing
of leaves in citrus. It effects the solubility of zinc( Zn). Crops
Suitable for Cultivation in Alkaline Soils Barley,
Sugarbeet, Cotton, Sugarcane, Mustard, Rice, Maize, Redgram, Greengram,
Sunflower, Linseed, Sesame, Bajra, Sorghum, Tomato, Cabbage, Cauliflower,
Cucumber, Pumpkin, Bitterguard. Beetroot, Guava, Asparagus, Banana, Spinach,
Coconut, Grape, Datepalm, Pomegranate.
Amelioration
The
process of amelioration consists of two steps. To convert exchangeable sodium
into water soluble form. To leach out the soluble sodium from the field.
Amendments used for reclamation of Alkali soils.
Gypsum
It is
slightly soluble in water. So it should be applied well in advance.
Requrement
For
every 1 m.e of exchangeable Na per 100 gm of soil, 1.7 tonns of Gypsum/ acre is
to be added.
Application
Saline Soils
The
saline soils contains toxic concentration of soluble salts in the root zone.
Soluble salts consists of chlorides and sulphates of sodium, calcium,
magnesium. Because of the white encrustation formed due to salts, the saline
soils are also called white alkali soils.
Reasons For Salinity
In arid
and semi arid areas salts formed during weathering are not fully leached.
During the periods of higher rainfall the soluble salts are leached from the
more permeable high laying areas to low laying areas and where ever the
drainage is restricted, salts accumulate on the soil surface, as water
evaporates
The
excessive irrigation of uplands containing salts results in the accumulation of
salts in the valleys. In areas having salt layer at lower depths in the
profile, seasonal irrigation may favour the upward movement of salts. Salinity
is also caused if the soils are irrigated with saline water. In coastal areas the ingress of sea water
induces salinity in the soil.
Characteristics
Injury to Crops
High osmotic pressure decreases
the water availability to plants hence retardation of growth rate. As a result
of retarded growth rate, leaves and stems of affected plants are stunted.
Development of thicker layer of surface
wax imparts bluish green tinge on leaves Due to high EC germination % of seeds
is reduced.
Crops Suitable For Cultivation In
Saline Soils
Barley,
Sugarbeet, Cotton, Sugarcane, Mustard, Rice, Maize, Redgram, Greengram,
Sunflower, Linseed, Sesame, Bajra, Sorghum, Tomato, Cabbage, Cauliflower,
Cucumber, Pumpkin, Bitterguard. Beetroot, Guava, Asparagus, Banana, Spinach,
Coconut, Grape, Datepalm, Pomegranate.
Amelioration
The
salts are to be leached below the root zone and not allowed to come up. However
this practice is some what difficult in deep and fine textured soils containing
more salts in the lower layers. Under these conditions a provision of some kind
of sub-surface drains becomes important.
The
required area is to be made into smaller plots and each plot should be bounded
to hold irrigation water.
Separate
irrigation and drainage channels are to be provided for each plot. Plots are to
be flooded with good quality water upto 15 - 20 cms and puddled. Thus, soluble
salts will be dissolved in the water. The
excess water with dissolved salts is to be removed into the drainage channels.
Flooding
and drainage are to be repeated 5 or 6 times till the soluble salts are leached
from the soil to a safer limit. Green
manure crops like Daincha can be grown upto flowering stage and incorporated
into the soil. Paddy straw can also be used.
Super phosphate, Ammonium sulphate or Urea can be applied in the last
puddle. MOP and
Ammonium chlorides should not be used.
Scrape
the salt layer on the surface of the soil with spade.
Grow
salt tolerant crops like sugar beet, tomato, beet root, barley etc
Before
sowing, the seeds are to be treated by soaking the seeds in 0.1% salt solution
for 2 to 3 hours.
If the
requirement is 3 tonnes/ acre- apply in one dose.
If the
requirement is 3 to 5 tonnes/acre- apply in 2 split doses.
If the
requirement is 5 or more tonnes/ acre - apply in 3 split doses.
Use of Pyrites (Fe S2)
Sulphur present in pyrites causes decrease in pH of soil due to
formation of H2SO4.
H2So4 + Ca Co3 -- Ca S04 Ca So4 +
Na --- Na So4 + Ca ( leachable)
Application
of sulphur. Application of molasses. Drainage channels must be arranged around
the field. Growing the green manure crops and incorporate in the field.
Objectives
of Soil Testing - The objectives
of soil testing area as follows:
To estimate the available
nutrient status, reaction (acidic/alkaline) of a soil. To evaluate the
fertility status of soils of a country or a state or a district.
By soil test summaries the
fertility status i.e., available nitrogen status or available phosphorous
status or available potassium status expressed as HIGH, MEDIUM or LOW.
Delineating areas of nutrient (e.g.,N, P, K) sufficiency or areas of nutrient
(e.g.,N, P, K) deficiency, Determining nutrient (e.g.,N, P, K) requirement for
the deficient areas etc.
3. to prepare a basis for fertilizer
recommendation, lime recommendation or gypsum recommendation.
The main purpose of soil
testing is to evaluate the fertility status of the soil. It provides a basis
for fertilizer, lime and gypsum recommendation. Laboratory test is a means of
making an inventory of the chemical conditions of soil and determining
treatments, if any, are needed.This service is generally rendered free of cost
Under Social Corporate Responsibility. Attachments –Annexure 1. In the soil
testing laboratory, soil samples are analyzed for the following five individual
soil properties: pH or soil reaction which indicates whether the soil is
acidic, alkaline or normal
Total
soluble salts which indicates whether the soil is saline or normal:
Organic
carbon (as a measures of available nitrogen)
Available
phosphorus
Available
potash
Fertilizer Recommendation
Analysis Procedure AnneXure -2
Rating of Soil Test Results- On the basis of soil test results,
the soils are grouped into different categories. The categories with respect to
organic carbon, available PO, KO and N are a
follows:
Categories
|
Organic Carbon (%)
|
Available N (kg ha-)
|
Available PO (kg
ha-)
|
Available KO (kg ha-)
|
High
|
Above 1.5
|
Above 450
|
Above 90
|
Above 340
|
Medium
|
0.75-1.5
|
280-450
|
45-90
|
150-340
|
Low
|
Up to 0.75
|
Below 280
|
Below 45
|
Below 150
|
The categories of soils with respect to soil pH are as
follows:
Soil pH
|
Categories
|
Conductivity
|
Categories
|
Below 5.5
|
Acid
|
Below
1
|
Normal
|
5.5-6.5
|
Slightly acid
|
1 - 2
|
Critical for germination
|
6.5-7.5
|
Neutral
|
2 -.3
|
Critical for growth of salt-sensitive crops
|
7.5-8.5
|
Tending to become alkali
|
Above 3
|
Injurious to most crops
|
Above 8.5
|
Alkali
|
||
Ratings of soil test parameters
Quadratic
Response Equation
Y = A + b1SN + b2SN2 +
b3 SP + b4SP2 + b5SK
+ B6SK2 + b7FN + b8FN2 + b9FP + b10FP2 + b11FK + b12FK2 + b13FNSN +
b14FPSP + b15FKSK
Where,
Y = Crop Yield (kg/ha)
A = Intercept
bi = Regression coefficients (kg/ha)
SN, SP, SK = Soil available N, P and K (kg/ha) respectively
FN, FP, FK = Fertiliser N, P and K (kg/ha) respectively
A = Intercept
bi = Regression coefficients (kg/ha)
SN, SP, SK = Soil available N, P and K (kg/ha) respectively
FN, FP, FK = Fertiliser N, P and K (kg/ha) respectively
Mitcherlich-Bray equation
Availble
Nutrient
|
High
|
Low
|
Medium
|
N(Nitrogen)
|
63.10%
|
25.57%
|
11.33%
|
P(Phosphorous)
|
42.33%
|
37.66%
|
20.01%
|
K(Potassium)
|
12.93%
|
36.65%
|
50.42%
|
Log (A-Y) =
Log A - c1b - cx
Where,
A = theoretical
maximum yield
b = native soil nutrient
Y = yield obtained
x = added fertiliser
c1 = efficiency factor for soil nutrient
c = efficiency factor for added nutrient
b = native soil nutrient
Y = yield obtained
x = added fertiliser
c1 = efficiency factor for soil nutrient
c = efficiency factor for added nutrient
Target Yield Equation
FD = NR/CF
*100*T -CS/CF*STV
Where,
FD = Fertiliser
N or P2O5 or K2O (kg/ha)
NR = Nutrient requirement of N or P2O5 or K2O (kg/t)
CF = Contribution from fertiliser N or P2O5 or K2O (%)
CS = Contribution from soil N or P2O5 or K2O (%)
STV = Soil test value of N or P X 2.29 or K X 1.21 (kg/ha)
NR = Nutrient requirement of N or P2O5 or K2O (kg/t)
CF = Contribution from fertiliser N or P2O5 or K2O (%)
CS = Contribution from soil N or P2O5 or K2O (%)
STV = Soil test value of N or P X 2.29 or K X 1.21 (kg/ha)
Conception of Soil Testing
In most of the soil testing laboratories in India,
the soil pH, electrical conductivity, oxidizable organic carbon, available
nitrogen, available phosphorous and available potassium are determined by
chemical analytical methods within a short period. Hence, Soil testing is the
rapid chemical analysis of a soil to estimate the available nutrient status,
reaction and salinity of the soil.
Method of Collection of Soil Samples - Collection for field crops
Equipments
Spade
Polythene bucket
12 inches scale
Ball point pen/Lead pencil
A sheet of thick paper
Polythene sheet (2ft x 2ft)
Procedure
Determine the soil unit (or plot).
Make a traverse over the soil unit (or plot).
Clean the site (with spade) from where soil sample is to
be collected.
Insert the spade into soil.
Standing on opposite side, again insert the spade into
soil.
A lump of soil is removed.
A pit of vee (V) shape is formed. Its depth should be
0-6" or 0-9" or 0-12". (i.e., depth of tillage).
Take out the soil-slice (like bread-slice) of ½ inch thick
from both the exposed surface of the pit from top to bottom. This slice is also
termed furrow-slice. To collect the soil-slice spade may be used. Collect the
soil samples in a polythene bucket.
Collect furrow-slices from 8-10 or sometimes 20-30 sites.
Select the sites at random in a zigzag (or criss-cross) manner. Distribute the
sites throughout the entire soil unit (plot). In lieu of spade auger may be
used. Do not take the prohibited samples and local problem soils.
Furnish the following information in two sheets of thick
paper with the sample. One sheet is folded and kept inside the bag. Another
sheet is folded and attached with the bag.
Informations
Name and address of the farmer (or farm owner).
Name of the block.
Plot number or any other number that identifies the plot
(or Soil unit).
Soil texture (sandy/clay/loam).
Availability of irrigation facilities.
Availability of drainage system.
Upland/Mediumland/Lowland.
Depth of soil sample.
Information of the previous crop.
Name and variety of the crop.
Dose of organic manure, if applied.
Dose of fertilizers, if applied.
Yield.
Informations of the crop that will be grown.
Name and variety of the crop.
Season (pre Kharif/Kharif/rabi).
Problem, if any.
Date of sample collection.
Signature of the farmer (or farm owner).
Collection for plantation crop
Dig a well (pit) of 1.8 meter depth. (Depth may vary
depending on root-depth).
Collect the soil-slice of ½ inch thick from the exposed
surface of pit at different depths as follows: 0-15, 15-30, 30-60, 60-90,
90-120, 120-150 and 150-180 cm.
Collection for local problem soils - Local problem soils are treated as
separate soil units (plots). Hence, separate composite samples are collected
from problem soils. The problem soil samples are not mixed with normal soils
(i.e., non problem soils). Both surface soil and subsoil samples are collected.
fThe categories of soils with respect to conductivity
(total soluble salts) in mmhos/cm (dSm-1) followed are as follows:
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Analysis Procedure Annezure -2
pH-(potentia
of hydorgenii), EC, OC ( Organic carbon), Phosphorus As P2O5, Potassium as K2O.
Potassium
Along with N and P, potassium (K) is also
of vital importance in crop production. Most soils contain relatively large
amounts of total K (1 - 2%) as components of relatively insoluble minerals,
however, only a small fraction (about 1%) is present in a form available to
plants, i.e., water-soluble and exchangeable K. Highly weathered acid soils (of
tropical regions) are more frequently deficient in plant available K, whereas
soils of arid and semi-arid areas tend to be well supplied with K.
Nevertheless, extractable-K, or
exchangeable plus water-soluble K, is often considered the plant-available
fraction and is routinely measured in the region's laboratories. Water-soluble
K tends to be a large proportion of the extractable K fraction in drier-region
soils.
Where levels of extractable-K values are
less than 100 to 150 ppm; K deficiency is likely and fertilization is required
to maximize crop production with irrigation or high K requiring crops, the critical level should be
even higher.
1 Extractable Potassium
This fraction of soil K is the sum of
water-soluble and exchangeable K. The method uses a neutral salt solution to
replace the cations present on the soil exchange complex; therefore, the cation
concentration determined by this method are referred to as
"exchangeable" for non-calcareous soils. For calcareous soils, the
cations are referred to as "exchangeable plus soluble" (Richards, 1954).
Apparatus
Flame photometer with
accessories.Centrifuge, capable of 3000 rmp.Mechanical shaker, reciprocating.
Reagents
A.
Ammonium Acetate Solution (NH4OAc), 1 N
• Add 57 mL concentrated acetic acid (CH3COOH) to
800 mL DI water, and then add 68 mL concentrated ammonium hydroxide (NH4OH), mix
well, and let the mixture cool.
Adjust to pH 7.0 by adding more acetic acid
or ammonium hydroxide, and bring to 1-L volume with DI water.
B.
Standard Stock Solution
• Dry about 3 g potassium chloride (KCl) in
an oven at 120°C for 1 – 2 hours and cool in a desiccator, and store in a
tightly stoppered bottle.
• Dissolve 1.907 g dried potassium chloride
in DI water, and bring to 1-L volume with DI water. This solution contains 1000
ppm K (Stock Solution).
• Prepare a series of Standard Solutions
from the Stock Solution as follows: Dilute 2, 4, 6, 8, 10, 15 and 20 mL Stock
Solution to 100-mL final volume of each by adding DI water or 1 N ammonium
acetate solution. These solutions contain 20, 40, 60, 80, 100, 150, and 200 ppm
K, respectively.
Note
Standard solutions for measuring soluble-K should be prepared in DI water, but for measuring
extractable-K the standards should be made in ammonium acetate solution.
Procedure
1. Weigh 5 g air-dry soil (< 2-mm) into
a 50-mL centrifuge tube, add 33 mL ammonium acetate solution, and shake for 5
minutes on a shaker. The tubes should be stoppered with a clean rubber or
polyethylene stopper, but not corks, which may introduce errors.
2. Centrifuge until the supernatant liquid
is clear and collect the extract in a 100- mL volumetric flask through a filter
paper to exclude any soil particles. Repeat this process two more times and
collect the extract each time.
3. Dilute the combined ammonium acetate
extracts to 100 mL with 1 N ammonium acetate solution.
4. Run a series of suitable potassium
standards, and draw a calibration curve.
5. Measure the samples (soil extracts), and
take the emission readings on a Flame Photometer at 767-nm wavelength.
6. Calculate potassium (K) concentrations
according to the calibration curve.
CALCULATION
For Extractable Potassium in soil:
Where: A = Total volume of the extract (mL)
Wt = Weight of air-dry soil (g)
2 Soluble
Potassium
This fraction is a measure of the amount of
K extracted from the soil by water.
Procedure
1. Weigh 5 g air-dry soil (<2 mm) into a
250-mL Erlenmeyer flask, add 100 mL DI water, and shake for 1 hour.
2. Filter and measure soluble-K on a Flame
Photometer.
CALCULATION
A Extractable K (ppm) = ppm K (from calibration
curve) × .... Wt
A Soluble K (ppm) = ppm K (from calibration
curve) × ... Wt
For Soluble Potassium in soil:
3 Exchangeable
Potassium
Exchangeable K, or that held on the
exchange sites or surfaces of clay minerals, is normally the dominant portion of
total extractable K. It can be deduced by difference. For Exchangeable
Potassium in soil:
Note
1. Exchangeable sodium (Na), calcium (Ca)
and magnesium (Mg) can be measured in the same way as derived for exchangeable
potassium (K). Extractable-Na, Ca, and Mg are measured in the ammonium acetate
extract and soluble Na, Ca, and Mg in the water extract. The difference will
represent exchangeable Na, Ca, and Mg.
2. A range of 20 to 200 ppm of Na standards
may be prepared in ammonium acetate solution for extractable Na and in
de-ionized water for soluble Na.
3. After extraction, the filtrate
containing K, Mg, Ca and Na should not be stored for longer than 24 hours unless it is refrigerated
or treated to prevent bacterial growth.
4. Soils can be stored in an air-dry
condition for several months without any
Exchangeable K (ppm) = Extractable K (ppm)
- Soluble (ppm) ....... (40)
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