Potassium

Constraint - Potassium 

Plant use

• Potassium is a macronutrient

• Potassium acts to regulate various metabolic processes such as water regulation, fixation of nitrogen, cell wall development, flowering and seed set, and weather disease and pest resistance

• As such it is essential for correct plant growth and function

Symptoms 

• Smaller sometimes wilted plants 

•  Young plants appear prostrate

• Dull pale yellow to yellow-brown colour begins at leaf edges and develops white dead spots and blotches that gradually join

• Leaf interveinal tissue bulges above the veins and the midrib bends backwards

• Tissue discolouration and death gradually spreads inwards towards the midrib, but leaf veins remain green

• Fewer and thinner flowering stems that set smaller pods

Damage

• Yield penalty can be severe if untreated

Management

A soil test or a plant tissue test should be used to confirm potassium deficiency. Potassium-specific fertilisers can be applied, and will generally correct the deficiency. Insuring adequate moisture for effective potassium uptake; and liming acidic soils to a pH above 5.5 will also increase potassium retention in the soil. Foliar sprays generally cannot supply enough potassium to overcome a severe deficiency and can scorch crops.

Links and Resources

AOF - Nutrition. Potassium Section 5.7 contains limited information on potassium. Published 2006.

DAFWA - Crop Updates Information on potassium field experiments, plant symptoms, trial results, results and discussion, and conclusion. Published 2000.

DEPI VIC - What nutrients do plants require? Potassium Section 6.3.3. Deficiency symptoms, mobility of potassium, susceptibility of plant species to deficiency, the potassium cycle, forms of potassium and their availability, and methods of loss. Page last updated 2013.

GRDC - Best Practice Management Guide. Potassium Page 35 of 92. Role, use, deficiency symptoms, soil tests, and fertiliser recommendations. Published 2009.

IPNI - Canola 4R Guide. Potassium Pages 13-15 of 21. General introductory information, and the right rate, time and place for potassium. Published 2013.