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2. The total K content of soils frequently exceeds 20,000 ppm (parts per
million). While the supply of total K in soils is quite large, relatively small
amounts are available for plant growth at any one time. That’s because
nearly all of this K is in the structural component of soil minerals and isn’t
available for plant growth.
Potassium (K) is an essential nutrient for plant growth. It’s classified as a
macronutrient because plants take up large quantities of K during their life cycle.

3. • Increases root growth and improves drought resistance.
• Maintains turgor; reduces water loss and wilting.
• Aids in photosynthesis and food formation.
• Reduces respiration, preventing energy losses.
• Enhances translocation of sugars and starch.
• Produces grain rich in starch.
• Increases plants’ protein content.
• Builds cellulose and reduces lodging.
• Helps retard crop diseases.

4. Forms of Potassium
1- Potassium contained in inorganic Matter
A. Mineral K- Primary Minerals
B. Non Exchangeable K in Secondary
Minerals
i. Difficultly Exchange
ii. Fixed
A. Exchangeable K
2-Potassium contained in Soil solution
3- Potassium contained in organic matter

5. Symptoms of potassium
deficiency
Potassium is mobile in plants, and
will move from lower to upper
leaves.
Curling leaves
crinkle

6. Forms of potassium
• Primary minerals (unavailable potassium)
• Secondary minerals and compounds (slowly available potassium)
• Solution potassium (readily available K)
.

8. Crop Plant part Time Sufficiency range
Alfalfa Tops (6 inches new growth) Prior to flowering 2.0 to 3.5% K
Apple Leaf from middle of current
terminal shoot
July 15 to Aug. 15 1.2 to 1.8% K
Blueberry Young mature leaf First week of harvest 0.4 to 0.7% K
Broccoli Young mature leaf Heading 2.0 to 4.0% K
Cabbage Half-grown young wrapper
leaf
Heads 3.0 to 5.0% K
Carrot Young mature leaf Mid-growth 2.8 to 4.3% K
Cauliflower Young mature leaf Buttoning 2.6 to 4.2% K
Corn Whole tops Less than 12 inches tall 2.5 to 3.5% K
Corn Leaf at base of ear Initial silk 1.8 to 3.0% K
Edible bean Most recently matured
trifoliate
Bloom stage 1.5 to 3.3% K
Grape Petiole from young mature leaf Flowering 1.5 to 2.0% K
Pea Recently mature leaflet First bloom 2.0 to 3.5% K
Potato Fourth leaf from tip 40 to 50 days after emergence 4.0 to 6.0% K
Potato Petiole from fourth leaf to tip 40 to 50 days after emergence 8.0 to 10.0% K
Raspberry Leaf 18 inches from tip First week in August 1.1 to 3.0% K
Soybean Trifoliate leaves Early flowering 1.7 to 2.5% K
Spring wheat Whole tops As head emerges from boot 1.5 to 3.0% K
Strawberry Young mature leaf Mid-August 1.1 to 2.5% K
Sweet corn Ear leaf Tasseling to silk 1.8 to 3.0% K
Sugarbeet Recently matured leaves 50 to 80 days after planting 2.0 to 6.0% K
Source: Bryson et al. (2014)
and Rosen and Eliason
(2002).