Plants need balanced nutrition to thrive, just like people.  One of the important nutrients for plant growth and development is Potassium (K), which is a component of most standard lawn fertilizers.  To use Potassium fertilizers correctly, it is important to understand how Potassium functions in plants, and how to recognize the signs of Potassium deficiency.

Potassium in Fertilizer

Potassium is one of the "big three" nutrients found in most lawn fertilizers.  Most fertilizer analysis gives the N-P-K number, which indicates what percentage of each nutrient is in the fertilizer.  The percentage of Potassium is indicated by the last number in the N-P-K analysis.

Potassium Function in Plants

Potassium is integral to many growth processes in plants, including:

• Photosynthesis
• Starch and protein production
• Enzyme reactions
• Water movement
• Protein synthesis
• Cell wall components
• Fruit development

Recognizing Potassium Deficiencies

(See above picture.) Potassium deficiency is a serious problem for all plants, because it is involved in so many different plant processes.  Plants experiencing potassium deficiencies will show the following symptoms:

• Yellowing and curling of edges of lower (older) leaves
• Sometimes leaves will turn purple
• More likely to occur in times of drought stress
• Leaf edges looked burned

There are a number of things that can cause potassium deficiency.  Sandy soils tend to be more deficient in potassium, because it is leached easily from soils that do not have a high CEC (Cation Exchange Capacity).  Adding organic matter to the soil can help in potassium retention.  Soils with a low pH (acidic soils) sometimes have enough Potassium, but it is not available to plants.  It is important to test the soil pH to see if the potassium is there, but not available.

Correct Application of Fertilizers

Many soils are deficient in Potassium, but it is always a good idea to look at the soil test before adding any fertilizer.  Flowers, fruits and vegetables need more potassium fertilizers during flowering and fruiting.  General lawn fertilizers will usually have a balanced analysis, and will have enough Potassium for the average lawn, unless the soil is severely depleted or the pH is off.  Apply potassium fertilizers that are balanced with Nitrogen and Phosphorous, and your soil will receive its necessary requirements to support plant growth.