role of potassium in plant growth
TRANSCRIPT
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ROLE OF POTASSIUM IN PLANT GROWTH
PresenterAyesha Iftikhar
DEPARTMENT OF SOIL SCIENCE
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History of PotassiumPotassium symbol K comes from “Kalium” the name of the element in Germany and Scandinavia.Potassium metal was first isolated in 1807 by Sir Humphry Davy who derived it from caustic potash by the use of electrolysis of the molten salt with the newly discovered voltaic pile.
Potassium was the first metal that was isolated by electrolysis.
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Introduction▪ Potassium is an essential plant
nutrient and is required in large amounts for proper growth and reproduction of plants.
▪ It affects the plant shape, size, color, taste and other measurements attributed to healthy produce.
▪ Plants absorb potassium in its ionic form, K+.
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Percentage of potassium in soil
Portion of total K Form of K90 to 98 percent Potassium containing minerals (Micas,
Feldspars, etc.)1 to 10 percent Clay minerals (Illitic types)
0.1 to 2 percent Exchangeable K+ and Soil solution K+
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Roles of Potassium in PlantsIn Photosynthesis, potassium regulates
the opening and closing of stomata, and therefore regulates CO2 uptake.
Potassium triggers activation of enzymes and is essential for production of ATP.
Potassium plays a major role in the regulation of water in plants (osmo-regulation).
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(Cont.)Known to improve drought resistance.
Potassium is essential at almost every step of the protein synthesis.
In starch synthesis, the enzyme responsible for the process is activated by potassium.
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Deficiency Symptoms of Potassium▪ Chlorosis
▪ Slow or Stunted growth
▪ Poor resistance to temperature changes
▪ Poor resistance to drought
▪ Defoliation
▪ Other symptoms▪ Poor resistance to pests▪ Weak and unhealthy roots▪ Uneven ripening of fruits
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K Deficiency Symptoms in Field Crops
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Potassium in soilsThe total K content of soils frequently exceeds 20,000 ppm (parts per million).
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1) Unavailable Potassium90-98% of total soil K is found in this form.
Feldspars and micas are minerals that contain most of the K.
Plants cannot use the K in this crystalline-insoluble form.
Over long periods of time, these minerals weather (break down) and K is released.
As these minerals weather, some K moves to the slowly available pool. Some also moves to the readily available pool.
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2) Slowly Available PotassiumThis form of K is thought to be trapped between layers of clay minerals and is
frequently referred to as being fixed.
Growing plants cannot use much of the slowly available K during a single growing season.
This slowly available K is not measured by the routine soil testing procedures.
Slowly available K can also serve as a reservoir for readily available K.
While some slowly available K can be released for plant use during a growing season, some of the readily available K can also be fixed between clay layers and thus converted into slowly available K
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3) Readily Available PotassiumPotassium that is dissolved in soil water (water soluble) plus that held on the
exchange sites on clay particles (exchangeable K) is considered readily available for plant growth.
The exchange sites are found on the surface of clay particles.
This is the form of K measured by the routine soil testing procedure.
Plants readily absorb the K dissolved in the soil water.
As soon as the K concentration in soil water drops, more is released into this solution from the K attached to the clay minerals.
The K attached to the exchange sites on the clay minerals is more readily available for plant growth than the K trapped between the layers of the clay minerals.
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Potassium Releasing From MicaIts behavior in soil is influenced mostly by cation exchange reactions than by microbial activity.
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Factors affecting Potassium Uptake1) Soil Moisture
2) Soil Aeration and Oxygen Level
3) Soil Temperature
4) Soil pH
5) Leaching
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Inorganic sources of KMaterial Chemical Formula K2 O Content %
potassium chloride KCl 60 %
potassium-magnesium sulfate K 2 SO 4 -2MgSO 4 20 %
potassium nitrate KNO 3 44 %
potassium sulfate K 2 SO 4 50 %
Common fertilizer sources of K.
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Organic sources of KBreak down of crop residuesManures
A. Majority of K is solublea. 80% of total K in manure available the year of applicationb. 10% of total K is available 2nd year after applicationc. 5% of total K is available 3rd year after application
B. Book valuesa. Dairy solids- 9 lb K2O/tonb. Dairy liquids-20 lb K20/1000gal
C. Book solids
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Potassium losses from SoilErosion: Erosion is one of the main pathways
through which K is lost from the soil.
Runoff: Runoff is one of the main pathways through which K is lost from the soil.
Leaching: Annual leaching loss of K from the soils in a humid region under agricultural production (receiving only a moderate rate of K fertilizer) is usually about 25 to 50 kg K/ha.
Harvesting: Plants take up very large amounts of K.
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Influence of Potassium on Crop QualityThe economic return from the investment in K can originate from:
(1)Improvement in total yield; (2)A greater percentage of total yield which is marketable; (3)Better crop quality; (4)Lower cost per unit of production; (5)Disease resistance; (6)Stress tolerance; (7)More effective use of other inputs such as nitrogen (N).
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CornEarlier silking and longer grain fillUniform maturity and grain moistureImproved stalk quality and reduced
lodgingMore kernels per ear and better test
weightImproved N use effectiveness
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WheatImproved grain proteinBetter milling and baking qualitiesMore efficient use of NImproved disease resistance
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SoybeansImproved seed sizeFewer shriveled and moldy beansImproved oil and protein contentMore and larger nodules for N fixationBetter tolerance to pests and
improved resistance to disease
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Application of Potassium FertilizerIncorporate for most of crops
Top-dressing effective on perennial basis
Broadcast__when large amounts of K required unless soil has high fixing capacity
Banding___Ridges till or no till soil with low subsoil K
Starter care must be taken when applied near seed
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Management Practices for PotassiumSuggested management practices for K vary with crop.
The best strategy would be to apply potash fertilizers before seeding followed by annual top-dress applications.
The annual applications should be based on the results of routine soil tests for K.
Any potash needed for small grain production can be applied in a band near the seed at planting or broadcast and incorporated before planting.
When applied in a band, the recommended broadcast rate of potash can be reduced by one-half without causing a reduction in yield.
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Environmental effects of PotassiumPotassium has no known deleterious effect on the quality of
natural and drinking waters and it does not induce eutrophication in rivers and lakes.
Under regular agricultural practices, small amounts of potassium ions is leached into deeper soil layers and finally reaching the aquifers, which presents no ecological threat; K in drinking water and/or food is no hazard for human health provided renal function is normal.
adequate supply of potassium and better nitrogen management, nitrogen use efficiency significantly increases, and consequently the disposed N to the environment is reduced.
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Thank you !Any Question ..?