Why Potassium in Fertilizer is Important

Experiencing the loss of a lawn due to the challenges posed by summer heat or winter cold can be highly disheartening for both homeowners and lawn care professionals. Dedicated hours of care may be invested in maintaining customers’ lawns, only to see them succumb to the pressures of a demanding season. As a turf-care professional, the primary objective should revolve around ensuring the health of the lawn and soil. A robust and healthy lawn is pivotal in delivering the desired color, growth, and resilience sought by customers. Contrary to popular belief, the green appearance of a lawn during summer or winter does not automatically indicate its overall health. The well-being and resilience of the lawn in challenging seasons hinge on less apparent factors, such as its access to and utilization of potassium—an aspect often overlooked by many landscapers.

Fertilizer serves the purpose of nourishing the lawn by providing vital macronutrients crucial for vertical growth, root development, color, and overall plant functionality. Each fertilizer is composed of various compounds, typically featuring nitrogen (N), phosphorus (P), and potassium (K), indicated by their respective N-P-K percentages on the packaging. In brief, these elements play distinct roles in turfgrass maintenance: nitrogen facilitates the greening and upward growth of the grass, phosphorus is absorbed during germination to promote downward root growth and establishment, and potassium is indispensable for the overall health and functioning of the plant.

Significance of Potassium

While all three macro-nutrients hold importance, potassium is frequently underestimated because its impact on the plant becomes apparent only when a deficiency arises. Potassium plays a pivotal role in the plant’s physiological functions. During photosynthesis, where light is absorbed for energy and carbon dioxide is converted into breathable oxygen, potassium regulates the plant’s response to light by facilitating the opening and closing of stomata—the pores responsible for releasing generated gases outside the plant’s cells.

Moreover, potassium serves as a catalyst for biochemical enzymes involved in Adenosine Triphosphate (ATP) generation, the storage site for the plant’s energy derived from photosynthesis. According to Thiel and Wolf, potassium deficiency significantly contributes to reduced photosynthesis, a well-documented aspect of research (1997). Beyond its role in photosynthesis, potassium is indispensable for processes like nutrient and water translocation within the plant’s cells, maintenance of cell wall turgor pressure, protein and starch production, and waste excretion (Taurus Agricultural Marketing, 2021). Given its involvement in numerous crucial turf processes, potassium plays a vital role in enhancing grass energy production and ensuring survivability during challenging periods.

Indicators and Effects of Potassium Deficiency in Grass

These fundamental plant processes contribute to an overall robust, efficient, and stress-resistant grass plant. Grass suffering from a potassium deficiency manifests symptoms such as chlorosis (yellowing and defoliation), stunted growth, diminished adaptability to environmental fluctuations (temperature and moisture levels), and heightened susceptibility to fungal diseases. Potassium-deprived turfgrass often struggles to withstand the challenges posed by summer or winter stress. If uncertainty persists regarding the potassium content in the soil, seeking guidance from your local turfgrass extension for a soil test is advisable. Soil tests provide valuable information on nutrient levels, including potassium, and offer recommendations for fertilizer applications to rectify deficiencies.

Potassium Sources and Application

Commonly, potassium in fertilizers is derived from naturally occurring inorganic, water-soluble compounds, with potassium chloride (Muriate of Potash or MOP) and potassium sulfate (Sulfate of Potash or SOP) being the predominant forms. The umbrella term “potash” is often used generically to describe various potassium fertilizers, and at times specifically refers to potassium chloride, the most widely utilized potassium fertilizer.

Each type of potash has distinct advantages. Potassium chloride, for instance, boasts three times the water solubility of potassium sulfate, enhancing its availability for plant absorption and suitability for spray applications (International Plant Nutrition Institute [IPNI], 2021). For those employing fertigation systems, potassium chloride stands out as the preferred choice. However, it’s important to note that the high solubility of potassium chloride results in a salinity index three times higher than that of potassium sulfate, potentially jeopardizing the plant’s water and nutrient absorption capabilities, making it susceptible to heat-related stress. Another noteworthy factor is the cost advantage of potassium chloride, which is approximately 40% to 50% less expensive per pound.

On the other hand, potassium sulfate offers the advantage of not posing the same risk of soil over-salinization as potassium chloride. Additionally, it can address sulfur deficiencies indicated in a soil test. Both forms of potassium are often combined in fertilizers to leverage the benefits of each. Natural sources of potassium include compost, seaweed, wood ash, animal feeds, and bedding materials.

In conclusion, fertilizers, whether inorganic or organic, enriched with elevated potassium levels are formulated to provide plants with an ample supply of this nutrient. The goal is to enhance the plant’s resilience, enabling it to endure challenging periods of stress, particularly during the summer and winter seasons.