Role in the plant: Potassium is involved in the opening and closing of the stomata in the leaves of the crop which helps regulate respiration and water loss. It is also involved in enzyme activity, the production of proteins and moving sugars around the plant. Thus Potassium is an important component of fruit quality.
Deficiency symptoms: Scorching/death around the periphery of the older leaves. Plant wilting can be more severe under dry conditions.
Toxicity symptoms: not common. Calcium and Potassium ratios are important and high potassium levels may affect calcium and magnesium availability to the plant. Contact an agronomist or soil scientist for more info.
Soils that have calcium most prevalent: Soils with high clay and or organic matter levels.
Management remarks: Potassium can be top-dressed to the crop. In high rainfall areas with sandy textured soils split applications will achieve the best results, however, this can sometimes be very expensive to achieve on low-value crops. Potassium I most frequently required up until plant flowering.