Transcript Chapter 1 Introduction - Soil 4234, Soil Nutrient Management

Chapter 2
NUTRIENT GENERAL CHEMISTRY
AND PLANT FUNCTION
What nutrients do plants need?
Plants require 16 nutrients; each is a
chemical element
Plants do not require organic matter,
enzymes or hormones as nutrients taken
up from the soil.
– Plant requirements for these substances is met
by the plant’s own manufacture of them.
Except for carbon (C), hydrogen (H),
oxygen (O), and boron (B) the nutrients
are absorbed primarily as chemical ions
from the soil solution.
Form
Nutrient
Symbol Absorbed Primary Source*
Macronutrients (primary)
H
Hydrogen
H2 O
Rainfall / soil solution
O
Oxygen
H2 O, O2
Rainfall / soil solution
C
Atmosphere
Carbon
CO2
N
Nitrogen
NO3 - and Soil solution
NH4 +
K
Potassium
K+
Soil solution / soil exchange sites
2+
Ca
Calcium
Ca
Soil solution / soil exchange sites
2+
Magnesium
Mg
Mg
Soil solution / soil exchange sites
P
Phosphorus
H2 PO4 and Soil solution
HPO4 2Soil solution
2S
Sulfur
SO4 and
Soil solution
SO2
Atmosphere (minor source)
Micronutrients
Fe
Iron
Fe2+
and Soil solution (chelates)
3+
Fe
Soil solution (chelates)
Cl
Chlorine
ClSoil solution
B
Boron
H3 BO3
Soil solution
Mn
Manganese
Mn2+
Soil solution / soil exchange sites
2+
Zn
Zinc
Zn
Soil exchange sites / chelates
2+
Copper
Cu
Cu
Soil exchange sites / chelates
2Molybdenum Mo
MoO4
Soil solution
Soil
Mobility**
M
M
M and
I
I
I
I
I
I
M
I
I
M
M
I
I
I
I
CHOPKNS CaFe MgB Mn ClCuZn Mo
What makes these nutrients
essential?
Must satisfy three specific criteria:
1. Plants cannot complete their life cycle
without the element.
2. Deficiency symptoms for the element
can be corrected only by supplying the
element in question.
3. The element is directly involved in the
nutrition of the plant, apart from its effect
on chemical or physical properties of the
soil.
What affects the soil availability
of these nutrients?
Most of the nutrients are absorbed as ions from the soil
solution or the soil cation exchange complex.
Understanding the general chemistry of the nutrient ions,
as it relates to their concentration in the soil solution, is
critical to developing an understanding of how to manage
their availability to plants.
What affects nutrient ion solubility?
Solubility is strongly influenced by the charge of the ion.
The first step to understanding solubility of nutrient ions
and molecules is to know ionic and molecular charges.
Help comes from identifying common ions, from group I, II
and VII of the periodic table, that have only one standard
valance in the soil environment.
To know these “standard” ions is as important to basic
chemistry as knowing ‘multiplication tables’ is to basic
mathematics.
www.webelements.com
Elements that have only one valance
state in the soil environment.
Cations
H+
Na+
K+
Mg2+
Ca2+
Al3+
Anions
ClO2WEB ELEMENTS
Oxidation number or oxidation state: charge of an atom that results when the
electrons in a covalent bond are assigned to the more elctronegative atom
Ionic Bond: electrostatic forces that exist between ions of opposite
charge (left side metals combined with right side NM)
Covalent Bond: sharing of electrons between two atoms
Metallic Bond: each metal atom is bonded to several neighboring atoms
(give rise to electrical conductivity and luster)
A positively-charged ion, which has
fewer electrons than protons, is
known as a cation
A negatively charged ion, which has
more electrons in its electron shells
than it has protons in its nuclei, is
known as an anion
Ion/molecule
Name
Oxidation State
NH3
ammonia
-3
NH4+
ammonium
-3
N2
diatomic N
0
N2O
nitrous oxide
+1
NO
nitric oxide
+2
NO2-
nitrite
+3
NO3-
nitrate
+5
H2S
hydrogen sulfide
-2
SO4=
sulfate
+6
N: 5 electrons in the outer shell
loses 5 electrons (+5 oxidation state NO3)
gains 3 electrons (-3 oxidation state NH3)
O: 6 electrons in the outer shell
is always being reduced (gains 2 electrons to fill the outer shell)
H: 1 electron in the outer shell
N is losing electrons to O because O is more electronegative
N gains electrons from H because H wants to give up electrons
oxidation state - the degree of oxidation of an
atom or ion or molecule; for simple atoms or ions
the oxidation number is equal to the ionic
charge; "the oxidation number of hydrogen is +1
and of oxygen is -2"
The oxidation state or oxidation number is
defined as the sum of negative and positive
charges in an atom , which indirectly indicates
the number of electrons it has accepted or
donated.
Oxygen:
Hydrogen:
Nitrogen:
oxidation number = -2
oxidation number = +1
oxidation number = 0
N is losing electrons to O because O is more electronegative
N gains electrons from H because H wants to give up electrons
N
NH3
NO3
NH4
H or O
Charge = 0 3(+1) = 3
Charge = -1 3(-2) = -6
Charge =+1 4(+1) = 4
Oxidation State
3-(0))= +3
-6- (-1)) = -5
4 – (+1)) = 3
-3 N gains 3
+5 N loses 5
-3 N gains 3
Oxidation State
Cr(OH)3,
O has an oxidation number of −2
H has a state of +1
So, the triple hydroxide group has a
charge of 3×(−2 + 1) = −3. As the
compound is neutral, Cr has to have
a charge of +3.
Using this information, we can determine the charge of molecules or the
oxidation state of elements in a charged molecule
Ex: CO3=, we should be able to determine, by difference, that the
oxidation state of C is 4+
(3*-2=-6) -2 showing = +4
CaCl2 is an uncharged calcium chloride molecule
The chemical formula, name, and charge of
each molecule should be carefully studied
(memorized). Significance of each to soil
fertility is presented and discussed in later
chapters.
NH4 + (ammonium)
NO3 - (nitrate)
NO2 - (nitrite)
NH3 0 (ammonia)
SO4 2- (sulfate)
PO4 3- (phosphate)
HPO4 2- (phosphate)
H2 PO4 - (phosphate)
CO3 2- (carbonate)
HCO3 - (bicarbonate)
MoO4 2- (molybdate)
H3 BO3 o (boric acid)
General effect of ion charge on
solubility
Availability of nutrient ions to plants
and the solubility of compounds they
come from, or may react to form,
can be discussed from the
perspective of the general reaction:
An+ + Bm-
  AmBn
Reactant ions An+ and Bm- combine to form a
compound (usually a solid) predicted by their
electrical charges.
The higher the charge of either the cation or anion,
the greater is the tendency for the compound or
solid to be formed.
When the solid is easily formed, only small
concentrations of the reactants are necessary for
the reaction to take place. Because of this, the
compound or solid that forms is also relatively
insoluble (it will not easily dissolve in water), or it
does not easily break apart (reaction to the left).
Conversely, if the cation and anion are both singlecharged, then the compound (solid) is not as easily
formed, and if it does form, it is relatively soluble.
An+ + Bm-
  AmBn
“Real life” examples of chargeinfluenced solubility
A common compound that
represents single charged ions is
sodium chloride (NaCl, table salt),
whose solubility is given by the
equilibrium reaction,
An+ + Bm-
  AmBn
Na+ + Cl-
  NaCl
Examples
Common table salt is very soluble and easily
dissolves in water. Once dissolved, the solid
NaCl does not reform until the ions, Na+ + Cl-,
are present in high concentration.
When water is lost from the solution by
evaporation the solid finally reforms as NaCl
precipitate.
Iron oxide or rust, represents multiple charged
ions forming a relatively insoluble material.
When iron reacts with oxygen and water (a
humid atmosphere), a very insoluble solid, rust
or iron oxide, is formed
2 Fe3+ + 3 O2- + 3 H2O =  Fe2 O3 . 3H2O (rust)
2 Fe(OH)3
How does all this relate to nutrient
availability?
With regard to solubility of inorganic compounds, we may expect that
when both the cation and anion are single charged, the resulting
compound is usually very soluble.
Examples are compounds formed from the cations H+, NH4+, Na+, K+ and
the anions OH-, Cl-, NO3-, H2PO4-, and HCO3- (bicarbonate). Note that
NH4+, K+, Cl-, NO3-, and H2PO4- are nutrient ions.
Because monovalent ions are very soluble, when a monovalent cation
reacts with OH- to form a base, the base is very strong (e.g. NaOH,
KOH).
Strong Acid
Strong Base
Strong Electrolyte
Weak Electrolyte
Similarly, when a monovalent anion reacts with H+ to form an acid, the
acid is a strong acid (e.g. HCl, HNO3). The monovalent molecules H2PO4, and HCO3-, which are products of multi-charged ions that have already
reacted with H+, are exceptions.
Except for H+ and OH-, whenever either the cation or anion is single
charged and reacts with a multiple charged ion, the resulting compound
is usually very soluble. Another exception to this rule is for F-, which
reacts with Al+++ to form insoluble AlF3, a reaction important to soil test
extractants of P in acid soils
Multiple charged ions
Divalent cations Mg 2+ , Ca2+ , Mn2+ , Fe2+ , Cu2+ , Zn2+
Divalent anions SO42-, CO32- (carbonate), HPO42-, and MoO42Trivalent cations Fe 3+ and Al 3+
Trivalent anion PO43When monovalent anions Cl- or NO3- react with any of the multicharged cations Mg 2+ , Ca2+ , Mn2+ , Fe2+ , Cu2+ , Zn2+ Fe 3+ and Al
3+ the solid compounds are all quite soluble.
Similarly, when any of the monovalent cations NH4+, Na+, or K+
reacts with any of the multi-charged anions SO42-, CO32-, HPO42-,
MoO42-, or PO43-, the solids are all quite soluble.
If both the cation and anion are divalent, the resulting compound will
be only sparingly soluble. An example is gypsum (CaSO4*2H2O).
If one of the ions is divalent and the other is trivalent, the compound
will be moderately insoluble. An example is tricalcium phosphate,
Ca3(PO4)2.
If both the anion and cation are trivalent, the compound is very
insoluble. An example is iron (ferric) phosphate, FePO4
AlPO4 ?
How can these general rules be
simplified?
Once charges of the ions in a compound are known, we can get
some idea of the compound solubility by simply adding the
charges.
For example, if the sum of the anion and cation charges is 2, then
the compound is very soluble (e.g. NaCl).
As the sum of the charges increases, the solubility of the
compound decreases.
Whenever one of the ions is monovalent the compound is usually
very soluble (e.g. KCl, CaCl2, and FeCl3 are all soluble even
though the sum of charges is 2, 3, and 4, respectively).
Many examples where these simple rules are a good predictor of
solubility. The sum of charges in CaSO4 is 4, and it is less soluble
than CaCl2.
The sum of charges in Ca(H2PO4)2 is 3 (Ca 2+ and H2PO4-) and it is
more soluble than CaHPO4 where the sum of charges is 4 (Ca 2+
and HPO42-). Similarly, Ca3(PO4)2 has a charge sum of 5 (Ca 2+
and PO43-) and is less soluble than CaHPO4.
Relative solubility of compounds formed
from the reaction of anions (An-) and
cations (Mn+) of different charges.
M 3+
M 2+
M+
A-
A 2-
A 3-
A 2-
A 3-
1. All compounds w ith a monovalent ion are soluble.
M 3+
M 2+
M+
A-
2. Compounds w ith both ions divalent are sparingly soluble.
M 3+
M 2+
M+
A-
A 2-
A 3-
3. Compounds w ith one divalent ion and one trivalent ion are moderately
insoluble.
M 3+
M 2+
M+
A-
4. Compounds with both ions trivalent are insoluble.
A 2-
A 3-
Why are some nutrients mobile
and some immobile in the soil?
With a general understanding of nutrient ion
solubility, it is now easier to examine the relative
nutrient mobility in soils.
Bray: Nutrient management is closely linked to
how mobile the nutrients are in the soil.
Relative mobility of nutrients in soils is governed
primarily by
– inorganic solubility
– ionic charge
– ionic adsorption (e.g., cations on the soil cation
exchange sites), and
– biological immobilization
Are all highly soluble nutrients
mobile in the soil?
Monovalent nutrient ions have a good chance of being
mobile in soils.
Monovalent anions, Cl- and NO3-, are mobile in the soil
because they are not adsorbed on ion exchange sites.
They have the wrong charge (-) for adsorption on cation
exchange sites and they are too weakly charged, compared
to SO4 -- for example, to be adsorbed on anion exchange
sites.
Furthermore, most soils have limited anion exchange
capacity (tropical soils are an exception).
Monovalent cation nutrients, K+ and NH4+, are highly water
soluble, but relatively immobile in soils because they are
adsorbed on cation exchange sites. These nutrient ions
become more mobile in sandy, low organic matter soils that
have extremely low cation exchange capacity.
Plants absorb B as the uncharged, undissociated, boric acid
molecule (H3BO3). Since this form of B is highly watersoluble and has no charge, it is mobile in soils.
Are all divalent and trivalent
nutrient ions immobile in the soil?
Divalent and trivalent nutrient ions are immobile in soils (exception SO42-)
In tropical soils, are enough anion exchange sites to provide significant
adsorption of SO42- and cause it to be somewhat immobile. Although
sulfate compounds, such as CaSO4 and MgSO4 are relatively insoluble, the
equilibrium concentration of SO42- with these solid compounds is far
greater than that needed for plant growth. Phosphate is immobile in soils
because it tends to form insoluble compounds with Ca in neutral and
calcareous soils and Al and Fe in acidic soils (described in more detail in
the chapter on P). Molybdate (MoO4 --) reacts to from insoluble solids
similar to the solid-forming reactions described for phosphate.
The divalent cation nutrients, Ca 2+ , Mg2+ , Cu2+ , Mn2+ , and Zn2+ are
adsorbed on cation exchange sites in soils, which prevents them from
being mobile. In addition, when divalent and trivalent anions are present,
these cations will react to form sparingly soluble and insoluble solids (e.g.
Ca3(PO4)2).
Iron absorption by plants involves both Fe2+ and Fe+3 .
Both are immobile in soils.
Reduced form is usually not present in significant amounts, but could be
absorbed on cation exchange sites.
Trivalent iron forms insoluble solid oxides (rust) that prevent the ion from
being mobile.
Reduced (Fe++) Oxidized (Fe+++)
gains electrons loss of electrons
Ferrous
Ferric
http://www.swarthmore.edu/NatSci/prablen1/Geology_Pict
ures/geologypictures.html
Mortar
The dry mix of hydrated lime and sand is mixed to form mortar. The initial
mix is plastic yet stiff. Slowly, the hydrated lime reacts with the CO2 in air
to form a hard and almost impervious mass of calcium carbonate:
Ca(OH)2 + CO2 -> CaCO3 + H2O
One could consider this as reforming the limestone from which the lime was
originally obtained.
CaCO3 + heat -> CaO + CO2
CaCO3 (calcite or aragonite) is relatively stable and durable under ambient
conditions; witness limestone cliffs, marble, crustaceans, coral, etc.
Acidic precipitation is the enemy of mortar and all other CaCO3-based
materials
Cement
Concrete is a mixture of cement, sand, water and
stone (aggregate).
Ordinary Portland Cement is a mixture of five
compounds in these approximate amounts:
– 55% Ca3SiO5 20% Ca2SiO4 8% Ca4Fe2Al2O10
– 12% Ca3Al2O6 5% CaSO4*2H2O
Ordinary Portland Cement can be modeled as its
most abundant and important component
tricalcium silicate, Ca3SiO5, and tricalcium
dialuminum oxide, Ca3Al2O6.
– When formed into a paste with water, these compounds
hydrate to form a rigid gel and matte of crystals.
Manufacture of Cement
1. Fire limestone + shale at 1400-1500oC. Shale
is a sedimentary rock made up mostly of quartz
and clay minerals such as kaolinite,
Al2Si2O5(OH)4.
3
9
2
–
CaCO3 + SiO2 + heat -> Ca3SiO5 + 3 CO2
CaCO3 + Al2Si2O5(OH)4 +heat -> Ca3Al2O6 +
Ca3SiO5 + 9 CO2 + 2 H2O
The product is called clinker because it is a partially
fused mass of material
2. The clinker is ground with the additional
gypsum to the consistency of flour. The gypsum
is needed to control the rate of hardening.
How does cement work?
Mix water plus cement to make a paste in
the ratio of about 2.5 parts of cement to 1
part of water (by weight). At first the
paste can flow because the water acts as
a lubricant for the cement grains.
After a few hours (the induction period)
the cement grains start reacting with the
water (hydrating) and filling the spaces
between grains with a hard mass of
calcium-silicate-hydrate gel and crystals of
a complex calcium aluminum sulfate
hydroxide hydrate known as ettringite.
How does cement work?
(Reactions)
Ca3SiO5 + 3 H2O -> Ca2SiO4*2H2O(gel) +
Ca(OH)2 rigid gel
or
– 2 Ca3SiO5 + 7 H2O -> Ca3Si2O7*4H2O(gel) + 3
Ca(OH)2
– and
2 Ca3Al2O6 + 3 CaSO4*2H2O + 24 H2O ->
Ca6Al2(SO4)3(OH)12*26H2O Ettringite
What are the plant concentrations,
functions and deficiency symptoms of
the essential nutrients?
Plant concentration of nutrients is helpful in managing
nutrients that are mobile in the soil.
For these nutrients, the crop requirement can be
estimated by multiplying yield times plant concentration.
Nitrogen
Nitrogen component of all amino acids
part of all proteins and enzymes
Plants contain from 1 to 5 %N
Wheat (2.35%) Corn (1.18%N) Soybeans (5.2%N)
Young legumes contain about 4 % N (25 % crude
protein) and recently fertilized turf may contain 5 % N.
Nitrogen is a structural component of many plant
compounds including chlorophyll and DNA.
Deficiencies of N are the most common, worldwide, of
any of the nutrients.
Nitrogen
Wherever non-legumes are grown in a high-yielding
monoculture system, and the crop is removed in harvest as
a part of the farming enterprise, N deficiencies occur within
a few years. (Straw, Residues)
Deficient plants are stunted
Low protein content
develop chlorosis (yellowing) at the tip, progressing along
the mid-rib toward the base of the oldest leaf.
http://www.nue.okstate.edu/Spatial_N_Variability.htm
Nitrogen
If the deficiency persists, the oldest leaf
becomes completely chlorotic, eventually
dying, while the pattern of chlorosis begins
developing in the next to oldest leaf. The
pattern of chlorosis develops as N is
translocated to newly developing tissue (N is
mobile in plants). Nitrogen deficiency reduces
yield and hastens maturity in many plants.
Nitrogen Deficiency.
Shows up as chlorosis (yellowing) at the
tip of the oldest leaf.
– Progresses toward the base of the leaf along
the midrib (corn).
– Chlorosis continues to the next oldest leaf,
after the oldest leaf becomes almost
completely chlorotic, if deficiency continues.
Nitrogen Deficiency in Corn.
chlorosis (yellowing) at the tip of the oldest
leaf.
Nitrogen Deficiency in Corn.
Chlorosis continues to the
next oldest leaf
Phosphorus
The P content of plants ranges from about
0.1 to 0.4 %, and is thus about 1/10th the
concentration of N in plants.
Storage and transfer of energy as ADP
(adenosine di-phosphate) and ATP
(adenosine tri-phosphate). High-energy
phosphate bonds (ester linkage of
phosphate groups) are involved
ATP
Biochemical reaction illustrating the
release of energy and primary
orthophosphate when ATP is
converted to ADP (R denotes
adenosine).
O
O
O



R-O-P-O-P-O-P-OH  energy +



OH OH OH
ATP
O


R-O-P-O-P-OH +


OH OH
ADP
O
O

O-P-OH

OH
Primary ortho phosphate (H2 PO4 -)
Phosphorus
Plant symptoms of P deficiency include poor
root and seed development, and a purple
discoloration of oldest (lower) leaves. Purple
discoloration at the base of plant stalks
(corn) and leaf petioles (cotton) is
sometimes a genetic trait that may be
incorrectly diagnosed as P deficiency.
Phosphorus Deficiency.
CORN
purple coloring and sometimes
yellow on lower (oldest) leaves.
Phosphorus Deficiency.
Deficiency in Oklahoma cultivated soils is
related to historical use of P-fertilizers.
– P builds up in soils when high-P, low-N
fertilizers are the only input.
10-20-10 and 18-46-0.
Rate of P Applied
So, we know that plants have 1/10
the amount of P as N
If both N and P were deficient,
would we apply
a.
b.
c.
d.
1/10 the amount of N
1/5 the amount of N
1/2 the amount of N
Doesn’t matter, Bray said so
Potassium.
The content of K in plants is almost as high as for N,
ranging from about 1 to 5 %. Potassium functions as a cofactor (stimulator) for several enzyme reactions and is
involved in the regulation of water in plants by influencing
turgor pressure of stomatal guard cells.
Potassium is mobile in plants and the deficiency
symptoms are similar to those for N, except the chlorosis
progresses from the tip, along the leaf margins (instead of
the midrib), toward the base of the oldest leaf.
Leaf margins usually die soon after chlorosis develops,
resulting in a condition referred to as “firing” or leaf burn.
Deficiencies are related to soil parent material, fertilizer use
and cropping histories.
Potassium Deficiency.
Common in crops grown in weathered
soils developed under high rainfall.
– Symptoms are chlorosis at the tip of the oldest
leaf (like N), that progresses toward the base
along the leaf margins.
Potassium Deficiency.
Common in crops grown in
weathered soils developed under
high rainfall.
K Usually
adequate
K Usually
deficient
Potassium Deficiency.
– Chlorosis at the tip of the oldest leaf
progressing toward the base along the leaf
margins (corn, alfalfa).
Calcium and Magnesium
Calcium deficiencies are rare, although the
concentration of Ca is relatively high (0.5 %) in
plants. The primary function is in the formation
and differentiation of cells. Deficiency results in
development of a gelatinous mass in the region of
the apical meristem where new cells would
normally form.
N
N
Mg
N
N
R
R
Chlorophyll, showing the importance of N (apex of four pyrrole rings)
and Mg (centrally coordinated atom in the porphyrin type structure). R
indicates carbon-chain groups.
Mg cont.
Magnesium is present at about 0.2%, or one-half
the concentration of Ca in plant tissue.
Soil Mg levels are considerably lower than for Ca,
and Mg deficiency does occasionally occur.
Magnesium functions as a co-factor for several
enzyme reactions and is the centrally coordinated
metal atom in the chlorophyll molecule
Intermediately mobile in plants, leading to
deficiency symptoms of interveinal chlorosis in
lower leaves.
Deficiencies may be expected in deep, welldrained soils developed under high rainfall that
are managed to produce and remove high forage
yields (Example?)
Magnesium and Sulfur
additions.
Lime, especially dolomitic, adds Mg.
Rainfall adds 6 lb/acre/yr of S.
– Like 120 lb of N (crop needs 1 lb S for
every 20 lb N).
Magnesium Deficiency in
Alfalfa.
Magnesium and Sulfur
deficiencies.
Occur on deep, sandy, low organic
matter soils in high rainfall regions
with high yielding forage production.
– Storage capacity for Mg and S is low.
– Large annual removal of nutrients.
Sulfur
Sulfur is present in plant tissue in
concentrations ranging from 0.1 to 0.2
%, similar to that for Mg. The function
of S in plants is similar to that for N,
component of three amino acids,
cystine, cysteine, and methionine,
which are important in the structural
changes and shapes of enzymes
Sulfur NCSU
Sulfur Deficiency in Corn.
Overall light green color, worse
on new leaves during rapid
growth.
Sulfur Deficiency in Wheat.
Overall light green color, worse
on new leaves during rapid
growth.
Zinc
Deficiency in
Corn (Kansas).
Note short
internodes (stunted
plants).
Note “bronze”
coloring of leaf.
Zinc Deficiency in Cotton
(Mississippi)
Zinc deficiencies.
Usually found in high pH, low organic
matter soils, and sensitive crops.
– Pecans, corn, soybeans and cotton.
– Crop symptoms are shortened
internodes and bronze coloring.
Correcting Zinc Deficiency
in Crops.
Broadcast and incorporate 6 to 10 lb
of Zn as zinc sulfate preplant.
– This rate should eliminate the deficiency
for 3 to 4 years as compared to 1 to 2
lb applied annually.
Foliar apply low rate to pecans
annually.
Micronutrient cation elements
Immobile in plants and function as co-factors in
enzyme reactions (Mn and Zn) or oxidationreduction reactions
Deficiency symptoms are found on the newest
leaves.
For Fe deficiency, the symptoms are a dramatic
interveinal chlorosis (yellowing) of the newest
leaves.
Iron deficiencies.
Limited to high pH soils and sensitive
crops.
– West-central and western Oklahoma.
– Grain sorghum, sorghum sudan, and wheat
(also pin oak, blueberries and azaleas).
– Crop symptoms are chlorosis between veins of
newest leaves
Iron Deficiency in Corn.
Note yellowing (chlorosis)
between veins.
Iron Deficiency in Peanuts
Note yellowing (chlorosis) between
veins of newest leaves.
Correcting and Minimizing Iron
Deficiency in Crops.
Select tolerant varieties and crops.
Incorporate several tons of rotted
organic matter per acre of affected
soil.
Use a foliar spray of 1 % Fe as iron
sulfate.
– Usually will require repeat spraying and
will not be economical.
Molybdenum
Plants require Mo at tissue concentrations of
about 0.1 to 0.2 ppm. It functions in critical
enzymes related to N metabolism; nitrate
reductase, which reduces nitrate to amino-N, and
nitrogenase, which is required for N2 fixation by
legumes.
Deficiency symptoms are similar to that
described for N deficiency. Molybdenum appears
to be mobile in plants (translocated from old to
new tissue). Deficiencies are rare and are
associated with very acid soils and soils that have
a high content of iron oxides.
Boron
Of the remaining micronutrients, B is the most
commonly deficient. However, even its
deficiency is somewhat rare and most common in
regions of relatively high rainfall (> 40 inches per
year).
It is found at tissue concentrations of about 20
ppm and is believed to function in sugar
translocation, although it is extremely immobile
in plants. Deficiency symptoms include poor root
and internal seed development (“hollow heart” in
peanuts)
Correcting Boron Deficiency
in Crops.
Apply ½ to 1 lb B according to soil
test.
– May be applied as addition to N-P-K
blend or foliar spray in-season.
– Excessive rates may kill crop.
Applications may be needed each
year.
BORAX
Boron Deficiencies.
Occasionally found in peanuts grown in
sandy, low organic matter soils.
– Responsible for “hollow heart”.
Chlorine
Since its discovery as an essential plant nutrient in the mid
1950’s, the function of Cl in plants has been somewhat of a
mystery.
Required in plant tissue at concentrations of only about 100 ppm
(1 lb Cl/10,000 lb plant material).
Yield response associated with application rates 20 to 50 times
higher than that required to supply plant concentration
requirements.
Believed to function in internal water regulations and as a counter
ion associated with excess cation uptake.
Deficiencies have been reported in small grains (wheat and
barley) grown in the central Great Plains (far from Cl containing
ocean sprays and hurricanes) in soils that do not require annual K
fertilization.
The most common K fertilizer is KCl. Some crops also show a
positive response to Cl fertilizer because of disease suppression
(not a nutritional response). Chloride deficiency symptoms
appear as chlorotic, leaf-spot lesions on older leaves (chloride is
mobile in plants).
Chloride Research-Kansas State University
Chlorine Deficiency.
Occasionally found in wheat grown in
sandy, low organic matter soils.
Chlorine Deficiencies.
Symptoms are yellow “blotches’ on
mature leaves.
Chlorine Deficiencies.
Limited to areas where potassium (K)
fertilizer is not used.
– K fertilizer is usually potassium chloride.
– Soil test Cl is < 20 lb/acre in top 2 feet.
What are the Primary Nutrients
needed by all crops
*Range of total amount in soil. From Chemical Equilibria
in Soils. W.L.Lindsay, 1979. Wiley & Sons.
Nutrient
Soil (lb/a)*
Crop
(lb/a)**
Nitrogen (N)
400 – 8,000
80
Potassium (K)
800 - 60,000
40
Phosphorus (P)
400 – 10,000
12
**Calculated for 2 ton crop yield (67 bushel wheat).
Secondary Nutrients Needed
by all Crops
* Range of total in soil. From Chemical Equilibria in Soils.
W.L.Lindsay, 1979. Wiley & Sons.
Nutrient
Soil (lb/a)*
Crop (lb/a)**
Calcium
14,000 – 1,000,000
16
Magnesium
1,200 - 12,000
8
Sulfur
60 – 20,000
6
**Calculated for 2 ton crop yield (67 bushel wheat).
Micronutrients Needed by all
Crops
Nutrient
Soil (lb/a)*
Crop (lb/a)**
Iron
14,000 – 1,100,000
1
Manganese
40 – 6,000
0.8
Copper
4 - 200
0.08
Zinc
20 - 600
0.6
Boron
4 - 200
0.08
Chlorine
40 – 1,800
4
Molybdenum
0.4 - 10
0.0008
*Range of total in soils. From Chemical Equilibria in Soils.
W.L.Lindsay, 1979. Wiley & Sons.
**Calculated for 2 ton crop yield (67 bushel wheat).
Review: Nutrients Needed
by all Crops
Primary
Secondary
Micro
Nitrogen (N)
Calcium (Ca)
Iron (Fe)
Potassium (K)
Magnesium (Mg)
Zinc (Zn)
Phosphorus (P)
Sulfur (S)
Manganese (Mn)
Copper (Cu)
Chlorine (Cl)
Boron (B)
Molybdenum
(Mo)
Nutrients are grouped
according to crop removal.
Primary (N, P, K).
– Removed in largest amount by crop.
Most commonly deficient.
Secondary.
– Removed in moderate amount by crop.
Micro.
– Removed in minute amount by crop.
Nutrients not found deficient in
Oklahoma crops.
Calcium.
– Liming prevents Ca deficiency.
Manganese.
Copper.
Molybdenum.
Nutrients seldom found deficient
in Oklahoma crops.
Magnesium.
Sulfur.
Iron.
Zinc.
Boron.
Chlorine.
Nutrients often Deficient in
Oklahoma crops.
Nitrogen (N).
– Legumes like soybeans and alfalfa get
their N from microorganisms
(rhizobium) that fix N from the
atmosphere.
Phosphorus (P).
Potassium (K).