Potassium (39.10)(+)

Potassium is one of the primary macro nutrients essential for plant growth. Potassium is very mobile in plants. Potassium is important for the plants ability to photosynthesize and the conversion, transportation as well as storage of food/energy for the plant. Potassium plays an important role in conjunction with other nutrients (Calcium & Boron) in the formation of plant cells. It also helps the plant manage Nitrogen. Furthermore, Potassium has an integral part in the plants immune system – it’s ability to fight and repair damage from diseases, insects as well as colder weather and drought (water stress).

Factors affecting Potassium availability

• Dry soils prevent uptake of Potassium.
• High Rainfall or over irrigated soils.
• Dense Clay soil.
• Acidic soils (below 6.5pH) can cause Potassium lockout.
• High levels of other Cations.
• High levels of Sodium in the soil.

Potassium deficiency

Potassium deficiency is most likely to occur with plants grown in poor quality toils. Soils that are too acidic, too dry or too wet. Compacted dense clay soils with poor drainage and aeration can be the main culprits. Nutrient imbalances brought about by uncontrolled feeding can inhibit Potassium availability. Cold soil temperatures early spring and late autumn can impede the uptake of Potassium.

Potassium deficiency on chilli leaf" src="https://www.chillihead.co.za/image/catalog/nutrients/potassium.jpg" style="width: 100%;" />

Symptoms

Older leaves show signs of interveinal as well as marginal chlorosis. This will progress to necrotic spots interveinal as well as marginal necrosis. The leaf may display a rash of white spots on the leaf surface. This will progress to a total scorching of the leaf. Potassium deficient plants have a tendency to be stunted in size and are more prone to disease and slow to recuperate from water stress as well as insect damage.

Treatment
First check your soil pH is correct (6.5-7.5pH). Adjust soil pH if needed. Ensure soil is not waterlogged or dry – ensure watering is consistent. Ensure soil is loamy with a good dose of organic matter. Compacted clay soils will need forking and amending with organic matter. Early season or late season Potassium issues can be due to soil temperatures being too low. Insulate soil – mulch and black plastic sheeting can help insulate as well as raise soil temperatures. If you are supplementing with soluble nutrients, make sure there isn’t a build up of sodium in the soil. This can be sorted with regular watering to leach out salts in the root zone. Also, check that other nutrients are not in excess. A balanced supplement is key. Failing all these checks, if your soil is still low in Potassium, a Potassium specific supplement can be considered (ie Banana peels, Kelp, Rock dust, Potash, Potassium Nitrate). Our advice would be get the soil tested if possible to establish your soil deficiencies or toxicities.

Potassium Toxicity
Potassium does not manifest any toxic symptoms. But, too much Potassium will cause deficiencies with other nutrients (calcium, nitrogen and magnesium).