1. Lecture 3 Plant nutrition

2. Potassium deficiency Symptoms - mottled or marginal chlorosis, which
then develops into necrosis on tips,
margins and between veins
- symptoms initially on more mature
(“older”) leaves
- leaves may curl and crinkle
- stems may be slender and weak, with
abnormally short internodal regions
- in K-deficient corn, nodes may have
increased susceptibility to root-rotting
fungus present in the soil
- this together with stem weakness
results in bending of stems to the
ground (lodging)
Soybean
Corn

3. Iron deficiency Symptoms
- strong chlorosis at the base of the leaves with some green netting
- deficiency starts out with
interveinal chlorosis of the
youngest leaves, evolves into an
overall chlorosis, and ends as a
totally bleached leaf
- bleached areas often develop
necrotic spots
- because iron has a low mobility,
iron deficiency symptoms appear
first on the youngest leaves
- iron deficiency is strongly
associated with calcareous soils
and anaerobic conditions, and it is
often induced by an excess of
heavy metals

4. Analysis of plant tissues reveals mineral deficiencies

5. Influence of the pH on the availability of nutrient
elements in organic soils
- main losses of nutrients from
agricultural systems is due to leaching
that carries dissolved ions, especially
nitrate, away with drainage water
- in acid soils, leaching may be
decreased by the addition of lime –
a mix of CaO, CaCO3 and Ca(OH)2 –to make the soil more alkaline,
because many elements form lesssoluble
compounds when the pH is
higher than 6
- width of the shaded areas in the graph
indicates the degree of nutrient
availability to the plant root

6. • Inorganic fertilizer… – Straight fertilizer..Super phosphate,
Treating nutritional deficiencies
• Inorganic fertilizer…
– Straight fertilizer..Super phosphate,
ammonium nitrate
– Compound fertilizer (i.e. contain two or more
mineral nutrients)
• Organic fertilizer
– Residues of plant and animals
– Mineralization (organic compounds broken
down by microorganisms)

7. • Deficiency can be prevented • Not tied up in soils (Fe, Mn and Cu)
Foliar application of fertilizers
• Uptake is faster
• Deficiency can be prevented
• Not tied up in soils (Fe, Mn and Cu)
• Expensive
• Vineyards

8. The principle of cation exchange on the surface of a soil particle
- cations are bound to
the surface of soil
particles, because the
surface is negatively
charged
- addition of a cation
such as K+ can displace
another cation
such as Ca2+ from its
binding on the surface
of the soil particle and
make it available for
uptake by the root
- mineral anions (NO3
_, Cl_) tend to be
repelled by the negative charge of the
surface and remain dissolved in soil
solution; capacity of exchange of anions
is smaller than of cation