1.
Compiled & Edited Dr Syed Ismail,MAU
Parbhani
Plant Nutrients
1
Nutrient movement,
absorption, supply,
uptake and transformation

2.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Objectives
 Knowledge of essential elements for plant
growth
 Mechanisms by which plant roots contact,
absorb nutrients
 Methods of nutrient cycling and loss
 Materials used in fertilizers
 Understanding of the behaviors of nutrients
in the soils
 Fertilizer applications
 Importance of
macro/secondary/micronutrients in plant
development 2

3.
Essential Nutrients
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
What is an essential plant nutrient?
von Liebeg’s ‘Law of the Minimum’
Plant growth progresses to
the limit imposed by the
nutrient in least supply
3

4.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Von Liebeg’s ‘Law of the
Minimum’
Plant growth progresses to the limit
imposed by the nutrient in least supply
4

5.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Forms in which nutrients
exist
 cation – positively charged ion
 anion – negatively charged ion
 neutral – uncharged
• Plants used the mineralized from of a
nutrient
– It does not matter to the plant where it comes from
5

6.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Essential Elements
 17 elements known to be essential
 C, H, O
 Photosynthesis
 Light energy used, H split off of water
 H combined with C & O to make CO2
(diffused through leaf stomata)
 Results in CHO + other organic
molecules
6

7.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Essential Elements
 Macronutrients
 N, P, K
 Secondary Nutrients
 Ca, Mg, S
 Micronutrients
 B, Cl, Cu, Fe, Mn, Mo, Ni, Zn
 Others as needed as beneficial
7

8.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Mechanisms of Nutrient
Uptake
Nutrients reach root surfaces by three
mechanisms
 Mass flow – movement of nutrients in water
flowing toward the root
 Diffusion – movement down a
concentration gradient from high - low
 Interception – roots explore new soil areas
containing unused soil nutrients
 All three in constant operation
 Root hairs primarily responsible for the
uptake
8

9.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
9

10.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Mechanisms of Nutrient
Uptake
 Absorption of Nutrients into Roots
 Movement through cell wall easy
 Movement into cytoplasm much harder
 Nutrient must go through passageway, or
bond w/ carrier to get through cell
membrane
 Some actively pulled into cell
 Electrical balance also involved
10

11.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Mechanisms of Nutrient
Uptake
 Absorption through Leaves
 Leaf stomata
 Exchange of H20, O2, & CO2
 Some soluble elements can be absorbed in
small amounts
 Mostly micronutrients
 Macros typically need in too high quantities to
foliar feed
11

12.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
IMPORTANCE OF NITROGEN IN THE
ENVIRONMENT
 N2 comprises 80% of the atmosphere
 N2 can not be used by most organisms
 N2 is not a problem until its in a reactive form like NH3
or NO3 and is out of balance in nature
 N is the major component of proteins and nucleic
acids
 Often the most limiting nutrient for plant growth
 When out of balance, N can have both direct and
indirect negative impacts on the environment
12

13.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
THE NITROGEN CYCLE
13

14.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
N CYCLE
 N enters the cycle through:
 N fixation
 Fertilization
 N fixation
 Non-biological
Lightning Burning fossil fuels
N2 + O2 2 NO
2NO + O2 2 N O2
2 N O2 + H2O HNO3 + HNO2
HNO3 H+
+ NO3
-
(Nitrate; Readily
used by
plants)
 Biological N fixation
Microorganisms
Nitrogenase
N2 + 6 e-
+ 8H+
2NH3 (Ammonia)+ H2
Fe, Mo 14

15.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
 Biological N fixation
 Symbiotic N fixers
 Responsible 70% of all N fixation
 Microorganisms
 Rhizobium bacteria
 Infect roots of legume plants
 Frankia bacteria
 Infect the roots of certain trees
 Process
 Bacteria reduce N2 to NH3
 Plants take up NH3 and combine it with Carbon skeletons to produce amino
acids
 Other plants only have access to this fixed N by the plant dying and
becoming part of the soil organic matter-N pool
 High levels of N will reduce biological N fixation
 Free living N fixers
 Responsible for 30% of world N fixation
 Microrganisms
 Cyanobacteria
 Found in rice paddies
 Azospirrilium, Azobacter, and Clostridium bacteria
 Found in soil
 Generate NH3 for their own use.
15

16.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
N fertilizer
 Produced by the Haber-
Bosch process
 Developed in 1913
 Process
High pressure High
temperature
N2 + 3H2
Fe catalyst NH3
 Primarily responsible for
the green revolution, but
also responsible to large
increase of reactive N in
our environment
16

17.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Ammonification (Mineralization)
 N in plant protein may become part of the soil’s OM
nitrogen pool by microbial degradation of:
 Dead plant litter
 Undigested protein in animal feces
 OM-nitrogen converted to ammonia by soil bacteria
 Process
R-NH2 NH3 + R
 Done by both aerobic and anerobic bacteria
 Increased by:
 Increased soil OM-N pool
 Increased soil temperatures
 Soil pH > 7
 High soil moisture
 NH3 rapidly converted to NH4
+
at pH < 7.5
 NH4
+
is relatively stable
 N is digested by animals is excreted as urea (mammals) or
uric acid (poultry)
17

18.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
O Urease
H2N – C – NH2 2NH3 + CO2
Urea
O
H
C N 5 steps w/
H N C Urease
C O 4NH3 + 5CO2
O C C
N N
H H
Uric acid
18

19.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
FATE OF AMMONIA RELEASED BY
MINERALIZATION
 Use by plants
 Immobilization
 Bacteria incorporate N into their own cells and
contribute to soil OM-N pool
 Occurs in soils containing high C:N ratios
 Leaching
 Occurs in sandy soils
 Have a low capacity for binding NH4
+
 Ammonium cations may leach into ground water as
precipitation infiltrates soils
 Soils that are high in clay or organic matter can bind
NH4
+
which can only be lost with erosion
19

20.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
 Nitrification
 Highest proportion of NH4
+
is converted to NO3 by
aerobic bacteria
Nitrosomas Nitrobacter
O2 H O2
NH4 O2 NO3
 Rapid under conditions of:
 Warm temperatures
 Well aerated soils
 Neutral pH
 Moist soils
 High fertility
 Slow under conditions of:
 Cold temperatures
 Saturated soils
 Low pH
 During nitrification, soil pH may decrease as NH4 is converted
to NO3
20

21.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Volatilization
 NH4
+
is not volatile
 In soils with high pH (> 7.0), NH4
+
is converted to NH3
which can volatize into the atmosphere as a gas
 NH3 is also released when the urea (in mammals) or
uric acid (in poultry) excreted in urine mixes with the
urease or uricase enzymes produced by the bacteria,
outdoor lots, manure storage structures, and in fields
after application
 Amounts of NH3 volatilized
 20 to 70% of the N in manure
 Ammonia losses from animal agriculture represents 75%
of all NH3 emitted in the U.S.
 Rate of NH3 volatilization is increased by:
 Soil pH > 7.0
 Soil temperatures > 50 F
 Greater air movement 21

22.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
FATE OF NO3 PRODUCED DURING
NITRIFICATION
 Use by plants
 Leaching into groundwater
 NO3 is highly soluble in water and does not bind to soil
particles
 During periods of excessive precipitation, NO3
transported to ground water as water infiltrates the soil
 Carries Ca, Mg, and K cations out of the soil reducing
fertility while leaving Al which is toxic to plants
 NO3 may be transported to surface waters via tile
drainage
 Factors that lead to increased leaching in spring
 Build up on NH4
+
in soil during winter
 Increased NO3 in soil as nitrification increases with
increased soil temperatures
 Low utilization of NO3 by immature plants
 High soil moisture
22

23.
Compiled & Edited Dr Syed
 Denitrification
 Conversion of NO3 to N2 in anerobic conditions in soil or
manure storage areas
 Process
C6H12O6 + 4 NO3 6CO2 + 6H2O + 2N2 + NOx
NOx = NO, NO2 or N2O
 N2 and NOx are gases released into the environment
 N2 is inert in the environment
 NOx has numerous adverse effects on the environment
 Denitrification is increased by:
 High soil N levels
 Anerobic soils
 Flooded soil
 Compacted soil
 Warm temperatures
 High OM in soil
23

24.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
POSITIVE EFFECTS OF INCREASING THE
AMOUNTS OF REACTIVE N IN THE
ENVIRONMENT
 Increased yields and nutritional value of feeds
 Increased wealth of the human population
 Increased productivity of N-limited crops and
ecosystems
 Increased yields per acre
 Could reduce cultivation of marginal and forested lands
 Increased carbon sequestration
24

25.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
ADVERSE EFFECTS OF NITROGEN IN
THE ENVIRONMENT
25

26.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
ADVERSE EFFECTS OF NITRATE (NO3) IN THE ENVIRONMENT
 Enters drinking water supplies
 Hazard (Blue Baby Syndrome)
 Formation of methemoglobin that prevents hemoglobin in red
blood cells from carrying oxygen to peripheral tissues
Normal:
O2
Hemoglobin in Oxygenated hemoglobin
red blood cells
Peripheral tissue
(Uses O2)
Nitrate toxicity: Gut bacteria
NO3 NO2 O2
Hemoglobin in Methemoglobin
red blood cells
Peripheral tissue
 Hazardous level: 10 ppm in water
26

27.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
ADVERSE EFFECTS ON AMMONIA IN THE ENVIRONMENT
 Hazards :Odor and Direct toxin
 Physiological effects and amounts
 Livestock (<100 ppm, usually found in livestock facilities)
 Eye irritation
 Respiratory tract irritation
 Reduced disease resistance
 Humans (OSHA limit is 50 ppm)
 9 ppm
Eye, nose and throat irritation
 50 – 150 ppm
Severe cough and mucous production
Nasal irritation
 > 150 ppm
Scarring of the upper and lower respiratory tract
Pulmonary edema
Chemical burns of eyes
 500 ppm
Acute death
27

28.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Nitrogen Gains &
Transformations
N is the key nutrient in plant growth
management
 Most commonly deficient nutrient,
controlling factor in plant growth
 Constituent of: proteins, chlorophyll,
nucleic acids
 Plants :sufficient N have thinner cell
walls & are more succulent plants
 N deficiency = poor plant yields
28

29.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Nitrogen Gains &
Transformations
 Much soil N isn’t in a form that can be
absorbed
 Most immobile in organic matter
 N2 gas in the atmosphere
 Must be fixed by soil bacteria first
 Unique nutrient
 Can be absorbed soluble organic form
 NH4, NO3
 Soluble, mobile, easily leached
 Can be easily denitrified by soil microbes
29

30.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Nitrogen Gains &
Transformations
 Deficiency symptoms: poor, spindly,
stunted growth
 NH4 & NO3 are not necessarily
interchangeable
 NH4 saves the plant energy
 NO3 is more stable in the soil
 Fixation of N Gas
 Primary source of soil N
 Taken by soil microbes, converted to NH4
30

31.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Nitrogen Gains &
Transformations
 Wide variation in how much N is fixed
due to: soil, fertilizers used, crops, etc.
 Mineralization of N
 Release of N from decomposition of
organic materials
 Mineralization – conversion of organic N
to NH4 form
 Soil organic matter contains ~5%N
 Only small % of organic matter
decomposes each yr
31

32.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Nitrogen Gains &
Transformations
 Nitrification of Ammonium
 Nitrification – oxidation of ammonium to
nitrate by bacteria, other organisms
 Rapid microbial transformation (usually 1-
2d)
 Most is complete w/in 1-2 wks
 Some absorbed, some adsorbed quickly
 Slowed by anaerobic conditions, dry,
cold, toxic chemicals
32

33.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Nitrogen Gains &
Transformations
 Other Fixation Reactions Involving
Soil N
 Immobilization – soluble N held in plant
materials or microbes
 N not available to plants
 N can be fixated to clay particles
 N can be consumed by decomposing
microbes and held until they die
33

34.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Nitrogen Losses from the
System
 Leaching of Soil N
 NO3 – readily leached form of N, toxic to
young mammals
 Nitrate lost due to negative charge
 Ammonium held due to positive charge
 Leaching rates increase as percolation rates
increase, when plant growth rates aren’t
quick enough to keep up N production
 Losses from crop covered soils usually low
34

35.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Nitrogen Losses from the
System
 Losses from heavily fertilized, wet soils high
 Nitrification Inhibitors
 Chemicals used to inhibit nitrification
 N-Serve, Didin coating, coaltar coating,
Urea brackets
 Inhibit the first step of nitrification, slow the
release of N to the soil
 N-Serve more volatile & can evaporate slowly
 DC, CC – stable, easy to handle, can be applied
as coatings to granules
35

36.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Nitrogen Losses from the
System
 Gaseous Losses of Soil N
 Denitrification – change by bacteria of
NH4 to N gas
 Biological process
 Can be most extensive gaseous N loss
 Especially poorly aerated/wet soils
 Rapid process
 Substantial N loss can occur in <1d
 ~10-20% normal
 ~40-60% in extreme conditions, 100% in
wetlands
36

37.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Nitrogen Losses from the
System
 Three reasons large amounts of N lost:
 Lack of adequate free O in the soil
 Energy source of organic matter for the
bacteria
 Warm, slightly acidic soils
 Ammonia Volatilization
 Occur when ammonium is in alkaline
environment
 Chemical process
 Losses occur from surface applications of
ammonium/urea
 Can be ~30%, normally <10%
37

38.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Nitrogen Losses from the
System
 Most extensive under following conditions:
 High pH, calcareous soils
 Fertilizer left on soil surface
 High temps
 Low CEC soils
38

39.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Ammonia & Aqueous N
 Anhydrous Ammonia (NH3)
 Most common N fertilizer in Europe
 >90% of all N fertilizers made up of some form
of ammonia
 82% N
 Manufactured from atmospheric N using
natural gas to supply H (Haber Process)
 First usable fertilizer product of this process
 Other N fertilizers require more processing
39

40.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Applied : chisels to ~5”
 Pressured liquid in the tank, gas at
atmospheric pressure
 Least expensive N fertilizer (per unit N)
 Very dangerous to handle
 Burns
 Blindness
 Inhalation risks
 Safety precautions
 Wear proper safety equipment (gloves,
goggles)
40

41.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Keep away from flames
 Keep away from ammonia clouds
 Have water available
 Store in proper tanks, don’t overfill
 Paint tanks white to reflect heat
 Inspect tanks regularly for leaks/problems
 Solid Fertilizers
 Urea
 Synthetic, organic fertilizer
 Cheaper per kg than any other solid N fertilizer
 46% N
 Must be converted in the soil to NH4
41

42.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Readily soluble & leachable
 Stabilized & can be stored when converted in the
soil to NH4
 Popular
 Cheapest solid N source
 Soluble in water
 Convenient for application in sprinkler, spray,
solution, drip
 Major pollutant of surface waters
 Not really discussed in depth in this unit
 Ammonium Sulfate
 21% N
 High cost
 Less popular
42

43.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Commonly used in rice
 Ammonium is all available to plant
 Sulfate keeps it from being denitrified
quickly
 Strongest acidic N fertilizer
 UAN
 Urea-Ammonium Nitrate solution
 28% N or 32% N
43

44.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Organic Wastes
 Considered controlled-release fertilizers
 Nutrient concentration is low
 Depends on decomposition rates
 May carry undesirables
 Weed seed, diseases, soluble salts, etc.
44

45.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Controlled-Release N Fertilizers
 Standard N fertilizer crop use rates ~30-
70%
 Rest is leached, denitrified, etc.
 Slow-release N fertilizers used to control
proportion of fertilizers available at one
time
 More efficient use of N means more cost
savings & less pollution
45

46.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying
Nitrogen
 Slow-release N products most commonly used in
turf grass
 Urea-Formaldehydes
 Varying rates of urea & formaldehyde
 Greater urea, more available N
 Environmental conditions must favor microbe
activity to release N
 Losses may be ~20%
 Polymer-coated N
 Soluble form of N (urea) diffuses through
polymer membrane
 Reliable, consistent control of N release
46

47.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Phosphorus
 Traditionally, second-most prescribed
nutrient in the soil
 Essential part of nucleoproteins in cell
nuclei
 Carry DNA
 Main component of cell energy
currency (ATP)
47

48.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Phosphorus
 Roles in:
 Cell division
 Root growth
 Plant maturation
 Energy transformation w/in cells
 Fruit/seed production
 Animal/human nutrition
 Growth of bones & teeth
48

49.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Phosphorus
 Young plants absorb soil P readily
 Most critical for plants to have available
P sources early in development
 Wheat from tillering to flowering
 Corn ~3 wks into growing season
49

50.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
Soil forms of P very low solubility
P applied through fertilizer often combines
with substances to reduce solubility
Most P supplied to plants by diffusion in the
soil
 Diffusion rates extremely slow (0.02 -0.1
mm/hr)
Major problem to keep P soluble & available
to the plants in soils
Soil P doesn’t leach
50

51.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
 Mineral P
 Available P critical
 Supply of P in soils is low
 Phosphates in soils not readily available
 While there is lots of P in the soil,
minutes fractions actually available
 Original natural source of P – apatite
(rock phosphate)
 Along with others, these can be used as
low-quality fertilizer sources
51

52.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
 Soluble phosphate often reacts with
other soil substances to form insoluble
compounds
 Also readily adsorbs to other molecules
like Ca,Fe,Al etc
 Soil P most available at pH ~6.5
 Phosphates in Anaerobic Soils
 Phosphates more soluble than in aerated
soils
 Iron phosphates are soluble in flooded
soils, less tie-up for P
52

53.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
 Works out good for rice growers
 Organic Soil P
 Phosphatases used by plant roots &
some microbes to split P from organic
residues – making it available for
absorption
 P in organic residues tends to more
soluble, therefore, more useful to plants
 May comprise >50% of soluble soil P
53

54.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
 The more favorable conditions are for
microbe decomposition > available soil P
54

55.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Managing Soil P
Mycorrihzae helps plants access soil P
 Fumigated soils, non-healthy microbe
population soils - < access to soil P -
<growth
 Soil pH influences
 Changes solubilities of Fe, Ca, Al, &
affects soil bacterial growth
55

56.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
 ~6.5 pH optimal for P availability
 Phosphate fertilizer effectiveness
 Most efficient use when banded
 Want to place ~2” away from root zone on
either side
 Only 10-30% of soil applied P is actually
used
56

57.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
The P Problem
 Excess P retained in the soil
 Can cause Zn deficiency
 P pollution from runoff
 Maximizing P efficiency
 Maintain soil pH 6-7
 Promote healthy soil organic matter content
 Band P fertilizer for row crops, broadcast &
incorporate for non-row crops
57

58.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Materials Supplying P
 Mixed with sulfuric acid to form
superphosphate
 8-9% P, 48% gypsum
 Mixed with phosphoric acid to form triple
superphosphate
 20-22% P (40-45% phosphate)
 Mixed N-P Fertilizers
 Monoammonium & Diammonium
Phosphate fertilizers
 Apply N & P with same product
58

59.
Soil Potassium
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
59

60.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
Ranks 2nd
to N in plant use & fertilizer
applied
Chemical compounds of K very soluble,
but mineral form is not
 Can see considerable soil amounts of K, but
much of may not be available
 Decomposition of plant residues provides
much soluble K
60

61.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
61
 First recognized by Home (1762)
 Isolated by Sir Humprey Davy (1807)
 After 30 years J. von Liebig pointed out importance.
 Symbol K- Kalium (german).
 Uptake of K > N by 60 %.
For a crop production, a 3-pronged role of potassium is
emerging in
Its ability to increase crop yields
Its ability to improve crop quality
Its role in helping the crop plants to combat a variety
of climatic and biological stresses.
Efficient use of K by making use of available results of research.

62.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
Roles of K
 Cell division
 Formation of CHO’s
 Movement of sugars
 Enzyme actions
 >60 enzymes known to need K for activation
 Disease resistance
 Cell permeability
 Important for water balance
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63
Deficiency of K
 Reduction in growth rate and vigor.
 Darkening of the leaves.
 Appearance of white, yellow or orange chlorotic spots
or stripes on older leaves, usually starting from the leaf
tips and margins
 The chlorotic areas become necrotic. The tissue dies
and leaves dry up (firing or scorching).
 The symptoms spread to younger leaves and finally the
plants can die.
 Decreased drought resistance.
 Roots are poorly developed and often affected by rot.
 Disease incidence increases and crop quality is severely
reduced.

64.
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66.
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67.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 Forms of Soil K
 Most K used by plants in exchangeable
or soluble form
 K Losses & Gains
 K may be taken up in excess amounts by
plants – Luxury Consumption
70
 The mineral K (92%).
 The non-exhcnageable K or K-fixed in between clay
plates (6.2%)
 The exchangeable clay (1.6%)
 The K present in soil solution (0.2 %)

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71
Reserve mineral K (92%)
Total K
Non-exchangeable K (6.2%)
Exchangable K (1.6%)
Solution K (0.2%)

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Ismail,MAU Parbhani
72
Plant & animal
residues
Soil organic
matter
Soil solution
K+
-------------------------
non-exchangable K+
-------------------------
-
-------------------------
weathering
Fixation
Release
leaching
Desorption
Adsorption
Plant uptake
2:1 CLAY MINERALS
Exchangeable K+
MINERAL K+
K equilibrium & cycling in soils

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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 May be expensive waste of K fertilizer
 May inhibit Mg absorption
 Soluble K losses
 Immobilized by microbes
 Leached
 Trapped in soil clay layers
 Eroded
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71.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 K gains
 Mineralization of organic matter K
 Can be used ~ as fast as water moves through
soils
 Held on cation sites in the soil
 Soil K is relatively stable & not volatile
with temp changes
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 Supplying K to Plants
 K fertilizers usually water soluble
 May not be very mobile in the soil
 Is held on cation sites, or will replace other ions
on those sites
 Needs to be supplied in the root zone to be most
effective
 Acidic soils often result in K deficiencies
 Abundance of soil Ca, Mg, or K may antagonize
uptake of one of the others
 Competition for plant absorption
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73.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 KCl –easily available K fertilizer source
 Can choose sulfate or nitrate forms to add
additional nutrients…but more costly
 Managing Soil K
 Crop harvesting removes much K from
the soil each year
 Highest K requirement during vegetative
growth
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 K Management keys
 Maximize efficient use of added K
 Minimize luxury consumption
 Split applications – especially in sandy soils
 Maximize use of natural K (organic matter
sources)
 Maintain soil pH 6-6.5 – reduces leaching
losses
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75.
Method of K fertilizerMethod of K fertilizer
applicationapplication
 Apply K in the root zone, NPK complexes-
drilled or applied in furrows.
 Avoid applying K to leaves, seeds or roots.
 Broadcasting is effective if done before or
during soil preparation.
 Side banding several weeks or months after
emergence.
 Side banding below the soil surface where
possible is the best method
 K can also be applied through drip irrigation.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
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76.
Interaction with other nutrients
 K & N- positive interaction.
 K & Mg- antagonistic interaction.
 K & Na- K maintains Na-K ratio.
 K & Zn- strong synergism.
 K & B- positive interaction.
 K & Fe- negative interaction.
Compiled & Edited Dr Syed
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil K
 Materials Supplying K
 Potash
 Most potash imported from Canada
 Muriate of potash (KCl) – principle source
 60% potash
 Potassium sulfate – 2nd
most used K fertilizer
 Potassium-magnesium sulfate – provides 3
nutrients
 Potassium nitrate – adds N with K
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78.
Common K fertilizersCommon K fertilizers
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
81
Fertilizers K2O (%)
Potassium chloride 60-62
Potassium sulfate 50-52
Potassium magnesium sulfate 22
Potassium nitrate 44
Potassium hydroxide 83
Potassium carbonate < 68
Potassium orthophosphates 30-50
Potassium polyphosphates 22-48
Potassium thiosulfate 25
Potassium polysulfide 22

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Compiled & Edited Dr Syed
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82
relative share of different fertilizers
straight MOP
17-17-17
12-32-16
15-15-15
10 26 26
19-19-19

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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Ca
Occurs in many minerals, more plentiful
in soils than any other plant nutrient
Ca deficiency is rare due to wide range
of Ca sources in soils
 Mobility of Ca
 Taken up as Ca
 Strongly adsorbed to cations
 Large amounts may be leached simply due
to large supply in the soil
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Ca
 Mass flow usually supplies enough Ca to
root zone
 Only absorbed through root tips
 Plant Need for Ca
 Dividing cells – forms Ca pectate which
cements cells together
 Physical integrity & normal cell function
 Deficiencies
 Deformation of new leaves/necrotic
appearance
 Death of buds
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Ca
 Used more than Mg, less than K
 Needs to be supplemented in
greenhouses
 Ca deficiency common due to not enough
fertilization with higher Ca sources
 Ca Fertilizers
 Limestone
 Usually only used on soils if they’ve
become acidic
 Can use gypsum if pH raise not needed
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83.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mg
 Mobility of Mg
 Most soluble/exchangeable forms
supplied in the soil
 Reacts similar to Ca
 Lower total leaching loss, less present
 Plant Need for Mg
 Most supplied to the roots by mass flow
 1/5 of Mg used by plants for chlorophyll
 Stabilizes ribosome structure
 Enzyme activator
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84.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mg
 Readily mobile in the soil
 Deficiency symptoms
 Interveinal chlorosis of older leaves
 Hypomagnesia (grass tetany)
 Can occur in livestock grazing soils low in
Mg
 Mg can be tied up by heavy applications
of K and/or ammonium fertilizers
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85.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mg
 Mg Fertilizers
 Dolomitic limestone
 Ca with Mg
 Can also use Mg salts
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil S
Constituent in 2 of the 20 amino acids
Essential part of proteins
Also found in vitamins, oils
Much overlooked
Factors increasing need for S fertilizers
 Lower amounts of sulfate added incidentally
with other nutrients
 Lower pollution from sulfur oxides into air
 Higher plant yields, greater demands on
soils
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil S
 Sources of S
 Availability of soil S hard to determine –
major portions come from organic
matter
 Depends on decomposition, climate, temp,
etc.
 Rainfall
 Can be toxic to fish, if S is too high
 S also supplied as part of other fertilizers
 Like SSP can supply 12% of S
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil S
 Characteristics of Soil S
 Decomposition can release much S
 Exists in many chemical forms,
depending on the soil
 Easily leached
 Waterlogged soils can cause soil S
sources to convert to sulfide – toxic gas
to plants
 Acidifies the soil
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil S
 Managing Soil S
 Reduced air pollution, purer fertilizers, better
understanding = reduced incidental S additions
 Some increased reports of S deficiencies
 Sulfur Fertilizers & Amendments
 Select ammonium sulfate or potassium sulfate
fertilizers
 SSP
 Gypsum
 Others can be recommended
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Ismail,MAU Parbhani
Soil B
Essential for:
 Cell wall formation, sugar movement,
pollination
Deficiencies:
 Terminal bud death
 Reduced flowering, retention of flowers
 Reduced pollen germination
 Less fruiting
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil B
 Soil Chemistry of B
 Forms a weak acid
 Deficiencies common in high rainfall
areas
 Various borates (forms) may exist in
different soils
 Sources for B
 Primary rocks & minerals
 Combined in soil organic matter
 Adsorbed in soil clays
 Boric acid
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil B
 Boron Deficiency & Amendments
 Deficiency in grapes greatly reduces
yield
 Cost to supplement relatively
inexpensive
 If over-supplemented can be toxic
 Fine line between adequate & excess amounts
 Supplemental B supplied by borax
 Very soluble
 11% B
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Cl
Found in soil as Cl-
 Soluble, mobile
 Not very reactive in the soil
Osmotic role – maintains/equalizes cell
charges
 Unique Features of Cl
 Cycles easily
 Supplied by manures, KCl, rainfall, etc.
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Ismail,MAU Parbhani
Soil Cl
 Can accumulate to toxic amounts
 Especially in soils high in soluble salts
 Some diseases linked to Cl deficiencies
(stripe rust, take-all root rot, leaf rust)
 Cl Amendments
 Deficiencies rarely seen in the field
 Cl typically supplied incidentally with
other fertilizers
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Ismail,MAU Parbhani
Soil Cu
Essential for many enzymes
Very low solubility
 Solubility related to soil pH
Strongly adsorbed to soil clays
 Problem Soils & Susceptible Plants
 Deficiencies:
 Common in organic soils
 Bonds strongly to organic substances & won’t
become soluble
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Cu
 Sandy soils
 Calcareous soil – pH 8-8.4
 High competition with other metals
 Less common than other micro
deficiencies
 Symptoms of deficiency
 Yellowing of younger leaves
 Off-color (bluish/green)
 Small dead spots
 Leaf curling
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Cu
 Sensitive plants:
 Alfalfa
 Rice
 Wheat
 Oats, etc.
 Cu Amendments & Their Use
 Successful, when applied
 Often only need supplement few ppm/ha
 CuSO4
 Can be applied as foliar treatment
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Fe
Important part of energy-providing
reactions
 Much Fe association with chloroplasts
Very low solubility
 Difficult to keep Fe soluble for plants to
absorb
Very low amounts needed for plants
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Fe
 Fe in Soil Solution – Chelates &
Availability
 pH has dominant effect of iron solubility
 Highly soluble at pH – 3
 Solubility decreases by factor of 1000/pH
unit rise
 At normal pH – soluble iron very low
 Fe needs mostly provided by soil organic
matter, stays bonded to something else
to keep it soluble
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Fe
 Some supplied in chelate form
 Keep metals in a mobile/soluble form
 Move to plant roots by diffusion or mass
action
 Problem Soils, Susceptible Plants, &
Fe Amendments
 Deficiencies common in calcareous soils
 High P levels also antagonize Fe
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Fe
 Fe deficiency symptoms:
 Interveinal chlorosis
 Soluble chelate supplementation will
often correct deficiencies
 Foliar sprays
 May need to be repeated
 Soil applications have longer residual, but
much slower acting
 Keep organic matter high
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mn
Involved in enzyme systems
Solubility increases w/ pH increases
Organic matter decomposition aids Mn
solubility
 Toxicity, Problem Soils, & Deficiency
Symptoms
 Toxic concentrations more common than any
other micro
 Soils may naturally have high Mn
 Conditions can cause Mn toxicity easily
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mn
 High Mn soils may show toxicities at pH
just below 6, excessive water, or even at
high pH’s
 Deficiency symptoms – chlorosis of
younger leaves
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mo
Exists & needed in minute amounts
Important for enzyme function & N
fixation
Strongly adsorbed, yet soluble
 Problem Soils & Susceptible Plants
 Deficiencies common in acid/sandy soils
 Susceptible crops:
 Soybeans, alfalfa, corn, tomatoes, etc.
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Mo
 Toxicities usually only show up in grazing
animals
 Known to happen on soils with high organic
matter & neutral/alkaline pH
 Problem related to imbalances of Cu & Mo
 Stunted growth, bone deformation
 Feed, inject Cu will often correct
 Mo Amendments
 Foliar sprays
 Soil application lower rates
 Lime acidic soils
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Zn
Essential for enzyme systems
 Zn in the Soil Solution
 Quite immobile in the
soil
 Can become deficient in
flooded soils
 Problem Soils &
Susceptible Plants
 Deficiencies:
 Occur in basic soils,
limed soils, cropping
with high Zn demand
crops (citrus,corn,
fruits, etc.)
 Most expected at high
soil pH & CaCO3
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Zn
 Cotton responds to Zn supplementation
Symptoms:
 Interveinal chlorosis in young & old leaves
 Reduced stem elongation
 Bunched leaves
 Small, thick leaves
 Early defoliation
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Soil Zn
 Zn Amendments
 ZnSO4 most commonly used to cure
deficiencies
 Foliar application for treatment
 Soil application if problem is anticipated
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Other Beneficial Elements
 May not be essential for all plants, but may
be essential for certain species
 Co
 Essential for microbes involved with N fixation
 Can be deficient in high Ca soils, sandy, leached
soils
 Si
 Very abundant in the environment
 Can be deficient in very weathered soils
 Appears to strengthen cell walls
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Other Beneficial Elements
 Na
 Essential for desert species to maintain
turgor
 Growers usually reluctant to add
 V (Vanadium)
 Essential for algae, microbes
 May substitute for Mo in enzyme activation
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Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Other Beneficial Elements
 Ni
 Raised to essential status in 1983
 Scientists still argue over its roles
 Suspected roles in plant metabolism
 Enzyme activator
 No fertilizer with Ni currently available
 Soybeans have demonstrated a positive
response to Ni treatment
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112.
Compiled & Edited Dr Syed
Ismail,MAU Parbhani
Thanks
115