Potassium

Along with nitrogen and phosphorus, potassium is one of the essential macronutrients required by grass plants. It supports plants in the processes of photosynthesis, water absorption and respiration. Potassium helps in the development of thick cell walls, making the grass plants more resistant to stress and disease. It helps strengthen your lawn by firmly rooting grass, which encourages the uptake of nutrients, such as iron. 

A deficiency of potassium weakens the grass plants and increases vulnerability to drought and disease. Symptoms of potassium deficiency include yellowing leaves, brown tips and weakened plant roots. The grass may also be prone to slow growth and wilting. Sandy soils are prone to potassium deficiency as heavy rainfall may leach the nutrients from the soil. Excessive application of nitrogen can negatively impact the uptake of potassium by the grass plants. 

Potassium is required in large quantities, second only to nitrogen. It is required all year round so needs regular application.