Transcript Role and deficiency symptoms of Potassium in Rice_0

Role and deficiency symptoms of
potassium (K) in rice
Role and deficiency symptoms of potassium in rice
Role of Potassium
Essentially involved in osmoregulation
and enzyme activation.
Regulates transpiration by stomata and
transport of assimilates.
Provides strength to plant cell walls .
Increases leaf area and chlorophyll
content.
Delays leaf senescence, and hence
contributes
to
greater
canopy
photosynthesis and crop growth.
Increases the number of spikelets per
panicle, percentage of filled grains, and
1,000-grain weight.
Improves the plant’s tolerance of adverse
climatic conditions, lodging, insect pests,
and diseases
Role and deficiency symptoms of potassium in rice
It is important to note that:
 Deficiency symptoms tend to occur in older leaves first,
because K is very mobile within the plant and is remobilized
to young leaves from old leaves.
 Yield response to K fertilizer is only observed when the
supply of other nutrients, especially N and P, is sufficient.
 K deficiency is often not detected because its symptoms are
not as easy to recognize as those of P and N deficiency, and
symptoms tend to appear during later growth stages.
Role and deficiency symptoms of potassium in rice
K deficiency symptoms
Leaf tips are yellowish brown, and
later margins may dry up.
Symptoms appear first on older
leaves, then along the leaf edge, and
finally on the leaf base.
Upper leaves are short, droopy, and
dark green in affected plants.
Older leaves change from yellow to
brown and, if the deficiency is not
corrected,
discolouration
gradually
appears on younger leaves.
Yellow stripes may appear along leaf
interveins, and lower leaves may
bend downward.
Role and deficiency symptoms of potassium in rice
K deficiency symptoms
When K deficiency is severe, rusty brown spots appear on the tips of
older leaves and later spread over the whole leaf, causing it to turn
brown and eventually dry up.
Irregular necrotic spots may also occur on panicles.
Stunted plants , smaller leaves, short and thin stems.
Increased incidence of lodging.
Tillering reduced under very severe deficiency.
Early leaf senescence, leaf wilting, and leaf
rolling, especially when temperature is high
and humidity is low.
Role and deficiency symptoms of potassium in rice
K deficiency symptoms
Increased percentage of sterile or
unfilled spikelets caused by poor
pollen
viability
and
retarded
carbohydrate translocation.
Reduced 1,000-grain weight.
Unhealthy root system (many black
roots, reduced root length and
weight), causing a reduction in the
uptake of other nutrients.
Increased incidence of diseases,
particularly brown leaf spot,
bacterial leaf blight, sheath
blight, sheath rot, stem rot, and
blast
Role and deficiency symptoms of potassium in rice
K deficiency in rice
Source:
http://www.plantmanagementnetwork.
org/pub/cm/research/2004/meter/1879
4E8480852573EC000E
Source:
http://www.ipni.net/ipniweb/portal.nsf
/0/9AD9BD18794E8480852573EC00
0EC596
Role and deficiency symptoms of potassium in rice
Toxicity Symptoms of Potassium
Excess potassium may cause deficiencies
in magnesium and possibly calcium.
Role and deficiency symptoms of potassium in rice
Causes of K deficiency
Lower K-supplying capacity of soil.
Inadequate
fertilizers.
use
of
mineral
K
Low recovery efficiency of applied K
fertilizers because of high K-fixation
capacity of soil or leaching losses.
Complete removal of previous crop
straw/ residues.
Wide Na:K, Mg:K, or Ca:K ratios in
soil, and sodic/saline conditions.
Presence of excessive amounts of reduced
substances in poorly drained soils (e.g.,
H2S, organic acids, Fe2+), causing retarded
root growth and hence K uptake.
Role and deficiency symptoms of potassium in rice
Causes of K deficiency
Imbalanced fertilization, especially
excessive use of N or N and P
fertilizers
with
insufficient
K
application.
In direct-sown rice during early growth
stages, when the plant population is
large and root system is shallow.
Cultivar differences in susceptibility to
K deficiency and response to K
fertilizer. Hybrids need more K than
inbred varieties of rice.
Role and deficiency symptoms of potassium in rice
Occurrence of K deficiency
Soils particularly prone to K deficiency include the following types:
 Soils inherently low in K.
 Coarse-textured soils with low CEC and small K reserves (e.g.,
sandy soils ).
 Highly weathered acid soils with low CEC and low K reserves,
e.g., acid upland soils and degraded lowlands.
 Lowland clay soils with high K fixation because of the presence
of large amounts of 2:1 layer clay minerals.
Role and deficiency symptoms of potassium in rice
Occurrence of K deficiency
 Soils rich in K content but very wide (Ca + Mg)/K ratio
(e.g., some calcareous soils).
 Wide (Ca + Mg)/K ratios result in stronger K
adsorption to cation exchange sites and reduce the
concentration of K in the soil solution.
 Leached, acid sulphate soils with a small base cation
content.
 Organic soils with small K reserves.
Role and deficiency symptoms of potassium in rice
Corrective measures (K)
Follow strictly the fertilization schedule
recommended for
rice, particularly
suitable for the region.
Apply optimum doses of N and P
fertilizers and correct micronutrient
deficiencies.
Increase K uptake by improving soil
management practices on root health (e.g.,
deep tillage to improve percolation and to avoid
excessively reducing conditions in soil).
Addition of straw of previous crops/ residues
and organic manures.
Role and deficiency symptoms of potassium in rice
Sources of potassic (K) fertilizers
Name
Potassium chloride
Formula
Content
Comments
KCl
50% K
Muriate of potash (60% K2O)
Potassium nitrate
KNO3
37% K, 13% N
In compounds (44% K2O)
Potassium sulfate
K2SO4
40–43% K, 18% In compounds (50% K2O)
(Muriate of potash)
S
Langbeinite
K2SO4, MgSO4 18% K,
Quick-acting
11% Mg, 22% S
Compound fertilizers
N+P+K
Variable
Common in rice
Role and deficiency symptoms of potassium in rice
Appropriate K management results in better yield of rice