Soil fertility is the soil's ability to supply essential nutrients for crop growth and is evaluated through various techniques such as visual deficiency symptoms, plant and soil analysis, and chemical testing. Liebig’s Law of Minimum highlights that crop yield is limited by the nutrient in shortest supply, while hidden hunger refers to nutrient deficiencies that do not show obvious symptoms in plants. Effective soil testing and calibration are crucial for optimizing fertilizer application and predicting crop response, ensuring maximum yield.

1. Soil Fertility Evaluation

2. Soil Fertility: it is the potential of the earth or inherent
capacity of the soil to supply plant nutrients in
quantity, forms and proportion required for the growth
and development of the crop.
Fertility is measured by the amount of chemical
elements or compounds required for plant growth
Productivity of a soil is defined as its capacity to
produce plants under specified programme of
management.
It is measured by the yield of the crop per unit area of
the land
Fertility is one of the factors of soil productivity.
Sometimes a soil may be fertile but may not be productive.

3. Liebig’s Law of Minimum- The growth or yield of
a crop is limited by that factor which is present
in relatively least amount.
Eg.
N
Requirement
100
Amount available 40
40%
Justus von Liebig,
1840
P
K
50
25
50%
60
30
50%
So, here N is the factor which limits the crop growth.
“Just as the capacity
of the wooden bucket
to hold water is
determined by the
height of the shortest
stave, crop yields are
restricted by the
nutrient in shortest
supply!”
Liebig was probably the
first to express the yield as
mathematical function of the
given growth factor when a
the other factors kept
constant
y = Ax - B
A,B, = constant
Father of modern Agricultural Chemistry

4. Liebig’s law of minimum
von
Liebig
1803
-1873
N
N
P
P
K Mg S
N
K
N
P
P
K
K Mg S
?

5. Law of diminishing
return :
where increases in yield
of a crop per unit of
available nutrient
decreases as the level
of available nutrient
approaches sufficiency.
“The increase in yield by a unit increment of the deficient factor is
proportional to the decrement of that factor from the maximum.”
Mitscherlich’
s Equation
dy/dx = (A-y)C
(by integration)
y = A (1-10-Cx)
or, log (A-y) = log A – Cx
.
Immobile nutrients
follow (P, K,and Ca
in soil) follow
Mitscerlich’s concept
Yield increases (dy) per unit of available nutrient (dx) decrease as the
current yield (y) approaches a maximum yield (A) with C being a
proportionality constant

6. dy/dx = (A-y)C
∫
dy
=
( A - y) )
∫
Cdx
or, - log (A-y) = Cx +C
If x=0, y=0 , C = - log A
or, - log (A-y) = Cx –log A
or, log (A-y) = log A- Cx
or, log
or,
( A − y)
A
( A − y)
A
= −Cx
= 10
−Cx
or, A - y = A 10
−Cx
or, y = A(1 - 10
−Cx
)

7. Soil Fertility Evaluation:
Evaluation
Several techniques are commonly employed to assess the fertility status of a
soil
(i)Nutrient deficiency symptoms of plants
(ii)Plant analysis and tissue testing
(iii) Methods involving the growing of higher
plants and microorganism
(iv) Soil Chemical analysis
(v) Isotopic dilution method

8. (i) Nutrient deficiency symptoms(NDS) of plants; it may be detected as
complete crop failure at seedling stage, severe stunting of
plants, specific leaf symptoms, internal abnormalities, abnormal
maturity etc. from the visual sysmptoms.
Careful observation of growing plant may help identify specific
nutrient stress
Disadvantages:
(i) Visual symptoms could be caused by more than 1 nutrient, or any of
several nutrients
(ii) Could be related to toxicity or imbalance of another nutrient.
(iii) It is difficult to distinguish among deficiency symptoms. NDS is
sometimes confused with attack of pests and diseases.
Alfalfa: confusion of leaf hopper damage with Boron deficiency
Corn: Sugar accumulation may be due to insufficient supply of P, cool
nights and warm days, N-deficiency, transverse creasing of the leaves

10. 1. Many symptoms appear similar.
For instance, N and S deficiency symptoms can be very alike, depending upon
plant growth stage and severity of deficiencies.
2. Multiple deficiencies and/or toxicities can occur at the same time.
More than one deficiency or toxicity can produce symptoms, or possibly an
abundance of one nutrient can induce the deficiency of another (e.g.
excessive P causing Zn deficiency).
3. Crop species, and even some cultivars of the same species, differ in their
ability to adapt to nutrient deficiencies and toxicities.
For example, corn is typically more sensitive to a Zn deficiency than
barley and will show Zn deficiency more clearly (NM 7).
4. Pseudo (false) deficiency symptoms (visual symptoms appearing similar to
nutrient deficiency symptoms).
Potential factors causing pseudo deficiency include, but are not limited to,
disease, drought, excess water, genetic abnormalities, herbicide and
pesticide residues, insects, and soil compaction.
5. Hidden hunger.
Plants may be nutrient deficient without showing visual clues.
6. Field symptoms appear different than ‘ideal’ symptoms.
deficiency/toxicity symptoms observed in the field may or may not appear
as
they do here. Experience and knowledge of field history are excellent aids
in
determining causes for nutrient stress.

11. Hidden hunger is a term used to describe a plant
that shows no obvious deficiency symptoms, yet
the nutrient content is not sufficient to give the
top profitable yield.
Fertilization with sure rate rather than the
bare economic optimum for an average leaf helps
to obtain the top profitable yield.

12. Detecting hidden hunger in crops is an increasing problem as yield goals rise
and higher profits are sought. In this zone with no symptoms to guide us, we must
turn to more diagnostic chemistry to evaluate needs more accurately. Testing
of plants and soils is helpful for planning or modifying plant nutrient programmes
to avoid this problem in subsequent crops.

13. (ii) Plant anlysis and tissue testing
This technique is based on the concept that if the content of a particular
nutrient in the plant is greater the higher its availability in the soil
(Lundegardh,1945)
Tissue testing:
Only unassimilated portion is measured.
(i) In one test, the plant parts are chopped up and extracted with reagents. The
intensity of colour developed is compared with standards and used as a
measure of the supply of nutrient in question.
(ii) Plant is transferred to filter paper by squeezing the plant tissue with pliers.
The tests for N,P,K are made with various reagents.
Plant analysis:
Both assimilated and unassimilated element are measured. Plant
grown in the soil is ashed and the different nutrient elements are
estimated. Thre is a basic relationship between the content of a plant
nutrient and the growth or yield of the plant
In contrast to soil analysis, tissue analysis
reflects nutrient uptake conditions of the soil.

14. Tissue Tests:
(1)Plant Part to be Selected:
In general the conductive tissue of the latest mature leaf is
used for testing.
(2) Time of Testing:
The most critical stage of growth for tissue testing is at
the time of bloom or from bloom to early fruiting stage.
Nitrates are usually higher in the morning than in the
afternoon if the supply is short.
Test for
Nitrates ……….. Diphenylamine
Phosphates ……. Molybdate + Stannous oxalate test
Potassium …… Sodium cobalti nitrate

15. Tissue Test Interpretation
 Critical nutrient concentration ranges (sufficiency ranges)
 Using Plant Analysis as a Diagnostic Tool
 DRIS (Diagnostic & Recommendation Integrated System)
Crop logging:

16. CNC (Critical Nutrient Concentration):
Concentration that is just adequate for maximum growth or the level of a
nutrient below which crop yield, quality is unsatisfactory.
Havlin et al., 1999

17. The relationship between nutrient content and nutrient availability in the soil
generally follows an asymptotic curve. This means that above a critical nutrient
level in the plant only small changes in plant nutrient content may occur despite
marked increases in nutrient availability in the soil. From this it follows that
leaf or tissue analyses are particularly useful in the range of low
nutrient availability. In the higher range of availability, however, leaf
analysis is not sensitive enough. Here soil analysis is more appropriate.
Relationship between the nutrient content in the soil solution and the nutrient
content of the plant (Mengel and Kirkby,1987)

18. Provisional DRIS
chart for obtaining
the qualitative
order of
requirement for
NPK in sugarcane.

19. Luxury consumption occurs when soil nutrient levels are above
optimum and plants take up more of a nutrient than needed for
functioning and production. K is commonly taken up in excess.

20. Crop logging: (Clements,1960)
It is a graphic representation of the progress of
the crop contain a series of chemical and physical
measurements.
These measurements indicate the general condition of
the plant and suggest changes in the management that are
necessary to produce maximum yield.
A critical nutrient concentration approach is used in the crop log
system and nutrient concentrations in leaf sheaths 3,4,5 and 6 are
utilised for diagnosis of Ca, Mg, S and micronutrient deficiencies.
(Sugarcane)
During the growing season plant tissue is sampled every 35 days and
analysed for N, sugar, moisture and weight of the young sheath
tisue. Analyses are made for P and K at critical times, and
adjustments in management practices introduced as needed

21. Max-Min Temp.
Growth
Nitrogen
Moisture
Total Sugars
K2O
Completed
crop log for
an irrigated
Hawaiian
Plantation.
P index
Clements
(1960)

22. (iii) Methods involving growing of higher plants and
microorganisms
(a) Plants:
(i) Mitscherlich Pot culture method
(ii) Neubauer Seedling method
(b) Microorganisms:
(i) Azotobacter palque method
(ii) Mehlich’s technique for available K2O by
Aspergillus niger method
(iii) Mehlich’s Cunninghamella–Plaque method for P

23. a) (ii) Neubauer Seedling method (Neubauer and Schneider,1932)
It is based on the principle of intensive uptake of nutrient elements by
growing a large no. of seedlings on a small quantity of soil
In this technique, 100 seedlings of rye are made to feed
exhaustively on 100 g of soil mixed with 50 g sand (Nutrient
free quartz) for 17 days in petridishes of (11 cmx7cm).
A blank without any soil is also run.
The total P2O5 and K2O uptake is calculated, and the
blank value is deducted to obtain the root soulble P2O5 and
K2O in 100 g of air dry soil.
These values are designated as the Neubauer numbers
expressed as mg/100 g of dry soil.
K.....20 mg/100g soil
P.....3 mg/100g soils are regarded as satisfactory levels.

24. (b) (ii) Mehlich’s technique for available K2O by
Aspergillus niger method
Critical limits for available K by using Aspergillus niger
To determine Potassium small amounts of soil are incubated
for a period of 4 days in flasks containing appropriate solns.
The weight of the mycelial pad or the amount of potassium
adsorbed by these pads is used as a measure of the nutrient
deficiency.
Weight of Four pads
( g)
K absorbed by
Aspergillus niger per
100 g soils (mg)
<1.4
<12.5
1.4-2.0
12.5-16.6
>2.0
>16.6
Degree of potassium
deficiency
Very deficient
Moderate –slight
deficient
Not deficient

25. (iii) Mehlich’s Cunninghamella–Plaque method for P
The organism Cunninghamella is sensitive to the
phosphorus status of the growing medium. The soil (50 g) is
mixed with the nutrient soln, a paste is made, spread uniformly
in the well of a specially constructed clay dish, inoculated on
the surface of the paste and allowed to incubate for 4½ days
at 28-29°C.
Normally Cunninghamella olegans is used for the test (22
mm diameter size is adequate).
In Calcareous soil Cunninghamella blakesleana is used
(diameter 16 mm is adequate)

26. 4. Soil Chemical analysis

27. 4. Soil Chemical analysis
Objectives of soil testing
Information gained from soil testing is used in many ways:
To build and /or fertility status of a given field
To predict the probability of obtaining a profitable
response to lime and fertilizer
To provide a basis for recommendations on the
amount of lime and fertilizer to apply
To evaluate the fertility status of soils on a
country, soil area or state-wide basis by the use of
soil test summaries.

28. Soil Testing basics
Soil testing starts with
collecting a good sample
Soil testing is not useful without
meaningful samples

30. Calibration and Interpretation
Perhaps the greatest challenge in a soil testing program is calibration of
the tests. It is essential that the results of soil tests be calibrated against
crop responses from applications of the plant nutrients in question.
Calibration:
 It is the process of determining the relationship between the crops
and soils i.e., the correlation of soil test values with the crop response.
 From the calibrated soil test values it is possible to predict the extra
yield that will be obtained from the addition of extra amount of fertilizer
and that the expected yield at that fertility status of the soil.
 It will also can be predict the amount of fertilizer to be added to obtain
an optimum yield.
Soil test values should be
calibrated in each soil and for
each crop.
 Lack of calibration of each soil test
values is one of the most important
reasons as to why soil testing is not so popular.

31. Two methods of approach in Soil test Calibration.
(i)Soil analysis-correlation approach
(ii)Critical soil test level approach
(Crop yield with adequate nutrients- Yield of control)
Percentage yield = —————————————————————— x 100
Crop yield with adequate nutrients
The most common method is to plot soil
test values against percentage yield and
to calculate the correlation coefficient
between soil test values and percent
yield response
However, if the correlation coefficient
obtained from a large no. of
Experiments is statistically significant,
it is acceptable as a guide for the
preparation of a fertilizer schedule.
Yield response to fertilizer in relation to soil test
value (points represent individual soils tested).

32. Based on the contents of available nutrients,
soil test values(N,P,K), the soils are grouped
into classes such as low, medium and high.
In general, the greatest response can be
obtained from the low class and the least
response from the high class in soil
test values.

34. Interpretation of soil test Values:
The interpretation of soil Test values involves determining how much of a
particular nutrient will be needed throughout the growing season to
provide a sufficient supply of this element to the plant for a predicted yield.
The lower the soil test value for a particular nutrient, the higher is the
response to the fertilizer nutrient..
Max. Profit
Max. Profit
1. High - Soil Test Value where
probability of response to additional
fertilizer is small(10%).
2. Medium - Soil Test Value where
probability of response to additional
fertilizer is moderate(50%).
Max. Profit
3. Low - Soil Test Value where
probability of response to
additional fertilizer is good (90%).

35. Rating Chart for soil test values
pHw (1:2.5)
Acidic
< 6.5
EC(dSm-1)
Neutral
Alkaline
6.5 - 7.5
> 7.5
Normal
Critical
Injurious
< 1.0
1.0 - 3.0
> 3.0
Parameters
Low
Medium
High
Org. Carbon
< 0.5
0.5 - 0.75
>0.75
Avail N (kg/ha)
< 280
280 - 560
> 560
Avail P (kg/ha)
< 22
22 - 45
> 45
Avail K (kg/ha)
< 120
120 - 280
> 280
Avail. S (SO4-2) µg g-1
0-10
10-15
>15
Critical limit for Micro Nu
(µg g-1 in soil )(rice)
(DTPA extract)
Fe
2.0
Boron
(µg g-1 in soil )(HWS)
Mn
1.0
Deficiency
< 0.50
Zn
0.86
Cu
0.20
Toxicity
> 4.00

36. Critical Levels developed by
Cate and Nelson (1965)
% yield versus soil test level
Two Groups:
1. probability of response to added fertilizer is small
2. probability of response to added fertilizer is large
Step A.: Calculate Percentage yield values obtained for a wide range in locations
(Crop yield with adequate nutrients- Yield of control)
Percentage yield = ——————————————————————--------- x
Crop yield with adequate nutrients
100
Step B. Soil test values obtained (Check Plot)
Will generate a single % yield and one soil test value for each location
Step C. Scatter diagram, % yield (Y axis) versus soil test level (x axis) should plot
Range in Y = 0 to 100%
Step D. Overlay
(i) overlay moved to the point where data in the +/+ quadrants are at a maximum
(ii) point where vertical line crosses the x = critical soil test level

37. 120
100
Percentage Yield
80
60
40
20
Critical Level
0
0
20
40
60
80
Soil Analysis, ppm P
100
120
140
160
(i) the soils collected from each
field are analysed,
(ii) field experiments are
conducted with the application of
graded dose of fertilizers,
(iii) response curves are fitted.
(iv) A scattered diagram of
percentage yield (y-axis) vs soil
test value (x-axis)is then plotted.
(v)It is divided into four quadrants.
(vi)The point where the vertical
line parallel to the y-axis crosses
the x-axis is defined as the
critical soil test value.
Critical soil test level (Cate and
Nelson) is the level of the nutrient
below which a reasonably
satisfactory economic response
should be expected from the
application of that particular
nutrient and above which the
probability of such response is low.

39. Fried and Dean (1952)
Assuming that plants take up nutrients from two different sources in direct
proportion to the amount available, the A-value was developed as the
expression
A = B(1-y)/y
where; A = amount of available nutrient in the soil
B = amount of fertilizer nutrient (standard) applied
y = proportion of nutrient in the plant derived from the standard
“Lower A values = Higher P Availability”
For specific soil, crop and growing conditions:
A-value is constant
independent of rate of fertilizer application
independent of size of test pot and growth rate
A value developed to determine availability of P in soil
(P supplying power of a given soil).

40. Fried and Dean(1952) used the principles of Isotope dilution to evaluate the
experimentally the availability of soil P to the plants. The method was based on the
principle that a plant confronted with two source of nutrient would utilise them in
direct proportion to their availability. It is to derive an equation for for A-value.
Let the two sources be A and B,
where A= soil P, B= fertilizer P, added to the soil as a standard
Let the respective amount of P in the plant from these two source “A” and “B”
be “a” and “b” respectively.
Then according to their concept:
A:B = a:b
Ab=aB, or
.....................(i)
......................(ii)
A= B. a
b
or,
A = B. a/(a+b)
.............................(iii)
b/(a+b)
Let b/(a+b) = y, and it is the fraction of P in plant derived from fertilizer
(P contribution from fertilizer source)
From IDP,
b/(a+b) = y, or, b= ay+by or, ay= b-by or, a = (b-by)/y
Now, a/(a+b) = (b-by)/y
= 1-y
(b-by)/y +b
From eqn (iii) we get, ,
A = B. (1-y) .....................(Iv)
y
y = Sp / Sf

42. Isotopic Dilution Principle (IDP):
“ For
a given constant amount of radioactivity the specific activity
is inversely proportional to the amount of test substance present”
Assumption : After equilibrium mixing, the system is uniform w.r.t. its specific
activity of the particular element.
Specific activity: It is defined as the amount of radioactive element per unit
mass of the element present. (mCi/g material, Cpm/mg of material)
Suppose , a system contains an unknown amount of A g of test substance. To
this system, added known amount of B g of the same susbstance labelled with
initial specific activity, Si ,
Let, the final specific activity which is measured, be Sf.
According to IDP,
(A+B)Sf= B.Si
(total activity remains constant, irrespective of diln.)
Or,
Or,
A+B = B. Si/Sf
A= B[(S i /S f )-1]

43. The Hungarian chemist George de Hevesy
was awarded the Nobel Prize in Chemistry
for development of radiotracer method,
which is a forerunner of isotope dilution
S

1 − p
Sf

A = B
Sp

 S
f









44. Indicator plants:
Certain plants are very sensitive to deficiency of a specific plant nutrient
and they produce specific symptoms which are different from other
deficiency symptoms. Thus the deficiency of that element can easily be
detected.
The indicator plants are the following

45. (a) (i) Mitscherlich Pot culture method
This is a pot-culture study with 10 pots to hold 6 pounds
(2.72kg) of soil in each of them. The treatments include:
1.No N-1 pot
2.No K2O-3 pots(NP)
3.No P2O5-3 pots (NK)
4.Complete fertilizer- 3 pots (NPK)
Oat will be the test crop and grown upto the maturity. The
yields of NP and NK treatments are expressed as a
percentage of the yield from the complete NPK treatment.
From tables prepared by Mitscherlich, the plant nutrient
reserve and predictions as to the %age increase in the yield
expected from the addition of a given given quantity of
fertilizers can be obtained.

47. Sunflower pot culture technique for Boron
: In this method
500 g soil is taken in small pot and 5 sunflower
seedlings are allowed to grow. The soil is fertilized with a
solution containing all the nutrients except B and
deficiency of B is noticed and ranked.

50. (b) (i) Azotobacter
palque method
(Sackett and Stewart technique,1931)
Winogradsky observed that the growth of Azotobacter
serve to indicate the limiting mineral nutrients in soil.
4 petridish was taken and 50 g soil was added in
each petridish.The petridish contains this nutrient serially
K2SO4 (T1), NaH2PO4(T2) , KH2PO4 (T3), Control(T4) .Soil
inoculated with Azotobacter culture and incubated for 72
hrs at 30°C. The soil is rated from very deficient to not
deficient in the respective elements, depending on the
amount of colony growth.

51. DRIS (Diagnostic & Recommendation Integrated System)
DRIS is a new approach to interpreting leaf or palnt analysis which
was developed by Beaufils at the University of Natal, South Africa.It is a
comprehensive systems which identiifes all the nutritional factors
limiting crop production and in so doing increases the chnaces of
obtaining high crop yields by improving fertilizer recommendations .
To develope a DRIS for a given crop, the following requirements must be met:
(i)All factors suspected of having an effect on crop yield must be defined
(ii)The relationship beteen these factors and yield must be described
(iii)Calibrated norms must be established
(iv)Recommendation suited to particular sets of conditions and based on
correct and judicious use of these norms must be continually refined

52. A provisional chart for obtaining qualitatively the NPK requirements of sugarcane
is given in Figure 1.
A qualitative reading of this chart can be done by using arrows in the
following conventional manner:
Horizontal →for values within the inner circles of the chart,
Diagonal
for values between the two circles
Vertical
for values found beyond the outer circle.
The way in which this chart is used will be illustrated by means of an example.
Assume that the following values are obtained from the analysis of the third leaf
blade of sugarcane:
Because an excess of one plant nutrient corresponds to a shortage of
another, by convention only insufficiencies are recorded for the purpose of
diagnosis and this is done stepwise for each function. Identical diagnoses are
obtained by considering either excesses or insufficiencies or both.

53. Determination of Relative
NPK requirement by using
DRIS Chart:
The chart is constructed of three
axes for N/P, N/K, and K/P,
respectively with the mean value
for the subpopulation of high
yielders located at the point of
intersection for each form of
expression.
This
point
of
intersection of the three axes
therefore
represents
the
composition for which one is
striving and at which one should
achieve the highest yield permitted
by limiting factors other than N,
P,K. Th concentric circles can be
considered as confidence limits,
the inner being set at the mean
±15% and the outer at the mean
±30% for each expression.

54. The value of the function N/P lies in the zone of N insufficiency giving:
while that of N/K lies between the two circles adding a tendency to K
insufficiency
and that of K/P lies in the zone of K
insufficiency giving
Once the three common functions
have been read, the remaining
character is assigned a horizontal
arrow. The final reading then becomes:
which gives the order of requirements
for NPK in terms of limiting importance
On yield - viz. :

55. Table 1. Mobility of nutrients within plants.
Variably
Mobile
Immobile
Mobile
Nitrogen
Copper
Calcium
Phosphorus
Zinc
Boron
Potassium
Sulfur
Manganese
Magnesium
Molybdenum
Iron
Plant nutrients which can move from places where they are stored to places where
they are needed are called plant mobile. N, P,K are always plant mobile nutrients.
Deficiencies are noticeable first on older tissue. Plant immobile element
deficiencies are noticeable first on younger tissue. Ca and B are always plant
immobile nutrients. S,Cl,Cu, Zn, Mn, Fe and Mo are intermediate in plant mobility.
Under certain circumstances the intermediate elements are mobile. Mobility in
intermediate elements may be linked to the breakdown under low N conditions of
amino acids and proteins in older parts of the plant, and the mobility of these
organic compounds to younger parts of the plant in the phloem stream. Under good N
availability, these elements are mostly immobile.

56. Plant Nutrient Deficiency Terminology
Burning:
severe localized yellowing; scorched appearance.
Chlorosis:
general yellowing of the plant tissue; lack of
chlorophyll.
Generalized: symptoms not limited to one area of a plant, but
rather spread over the entire plant.
Immobile nutrient: not able to be moved from one part of the
plant to another.
Interveinal Chlorosis: yellowing in between leaf veins, yet veins
remain green.
Localized: symptoms limited to one leaf or one section of the leaf or
plant.
Mobile nutrient: able to be moved from one plant part to another.
Mottling:
spotted, irregular, inconsistent pattern.
Necrosis:
death of plant tissue; tissue browns and dies.
Stunting:
decreased growth; shorter height of the affected plants.

57. N deficiency in barley. Top leaves are N deficient,
bottom leaf is normal.
Interveinal chlorosis. (Fe deficiency)
P deficiency in alfalfa (L) and normal alfalfa
(R). P deficient leaf is dark green and stunted.
P
deficiency
in corn.
Leaves are
purplish
and tips
are brown
and
necrotic.

58. Interveinal chlorosis (Figure 2)
occurs when certain nutrients [B, Fe,
Mg, Mn, nickel (Ni) and Zn] are
deficient. Purplish-red discolorations
in plant stems and leaves are due to
above normal levels of anthocyanin
(a purple colored pigment) that can
accumulate when plant functions are
disrupted or stressed.
K deficiency in corn. Older leaves
are chlorotic and leaf edges are
burned, but the midrib remains
green.
S deficient wheat plant (left) has
light green leaves and stunted
growth as compared to normal
wheat plant (right).

59. Cu deficiency in wheat: severely affected
Alfalfa with B deficiency; chlorosis of
(L), moderately affected (Centre),
upper leaves and rosetting of leaves near unaffected (R). Deficient wheat shows
base.
melanosis with poor grain production and
fill
Zn deficiency displaying striped
interveinal chlorosis.

60. Mobile
Nutrients

61. Immobile
Nutrients
Initial symptoms occur in middle
laeves with young & /or old
leaves become chlorotic

62. Mineral Deficiency
• The most common deficiencies
– Are those of nitrogen, potassium, and phosphorus
Healthy
Phosphate-deficient
Reddish-purple margins
esp. on young leaves
Potassium-deficient
Nitrogen-deficient
“Firing”…drying along tips
and margins of older leaves
Yellowing that starts at the
tip and moves along the
center of older leaves

63. Extraction of nutrients from a soil-water suspension in an electric field and with a
ultrafiltration.
The principle of this method is based on the use of an electric field to separate
nutrient fractions from a soil suspension. During separation the voltage is
increased from 50 to 400 V, thus increasing the force by which plant nutrients are
desorbed from soil particles.
1. Fraction (intensity): 30 min, 200 V, < 15 mA, 20o C
2. Fraction (quantity): 5 min, 400 V, < 150 mA, 80o C
3. Fraction (micronutrients) : 5 min, 400 V, < 150 mA, 80o C with 0.002 M DTPA.
EUF-desorption
curve for K+
(NEMETH, 1979)

66. Soil test correlation: The process of
determining the relationship
between
plant nutrient uptake or yield and the
amount of nutrient
extracted by a
particular soil test
method.
Soil test calibration.
The process of determining the
crop nutrient requirement at different
soil test values.
Yield response to fertilizer in
relation to soil test value (points
represent individual soils tested).
Soil test interpretation.
The process of developing nutrient
application recommendations from
soil test concentrations, and other
soil, crop, economic,
environmental and climatic
information .
(Crop yield with adequate nutrients- Yield of control)
Percentage yield = ——————————————————————
x 100
Crop yield with adequate nutrients