Sulfur is a secondary nutrient for turfgrass, required in smaller amounts than primary nutrients like nitrogen, phosphorus, and potassium, but its presence is nonetheless significant. This element supports the fundamental biological processes that keep a lawn healthy and vibrant. Sulfur application is often used as a soil amendment to adjust soil chemistry, which can indirectly improve the lawn’s appearance and resilience. Understanding its role and applying it at the correct time are important steps in lawn care.
Why Sulfur is Necessary for Lawn Health
Sulfur is necessary for the growth and function of turfgrass. It is a necessary component for the synthesis of certain amino acids, which are the foundational building blocks for all proteins within the plant. Without adequate sulfur, the grass cannot produce the full complement of proteins needed for normal growth.
The nutrient is also involved in activating various enzymes that regulate plant metabolism. Furthermore, sulfur is required for the formation of chlorophyll, the green pigment responsible for capturing sunlight during photosynthesis. A deficiency leads to a visible yellowing of the grass blades, known as chlorosis, often starting in the younger leaves.
Determining the Need for Sulfur
Applying sulfur without understanding the soil’s current condition can be wasteful or detrimental. The only accurate way to determine if sulfur is necessary is by performing a professional soil test. This test provides the current soil pH level and the concentration of various nutrients, including sulfur.
Sulfur is primarily applied as a soil amendment to lower high, alkaline pH levels (typically above 7.0). High pH soils often lock up nutrients like iron and manganese, making them unavailable for grass roots to absorb. The goal of applying elemental sulfur is to adjust the pH into a slightly acidic range (6.0 to 6.8), which optimizes the turfgrass’s ability to take up these essential nutrients.
The sulfur requirement depends on the soil test results and the desired pH change. Elemental sulfur works slowly because soil bacteria must convert it into sulfuric acid through microbial oxidation. Soil texture also influences the amount needed, as clay or organic matter-rich soils require more sulfur to achieve a pH change than sandy soils.
Optimal Timing for Sulfur Application
The most effective time to apply elemental sulfur is when soil conditions support the microbial activity required for its slow conversion. The optimal windows for application are generally in the late fall or early spring.
Applying sulfur during these cooler months ensures the soil is moist and temperatures are moderate, ideal for bacterial oxidation. For cool-season grasses, a fall application is beneficial, allowing microbial action to work slowly over the winter. Warm-season grasses benefit from a spring application just before active growth, giving the sulfur time to work before peak summer heat.
Avoid applying elemental sulfur during periods of peak summer heat or drought. High temperatures stress the grass, and lack of moisture limits microbial action, reducing effectiveness. Rapid oxidation in high heat can potentially harm the turf, so the goal is a gradual change over several months.
Application Methods and Safety
Sulfur is commonly available in two main forms for lawn application: elemental sulfur pellets and sulfate forms (e.g., gypsum or potassium sulfate). Elemental sulfur is used to modify soil pH and is typically applied as a granular product using a broadcast or drop spreader. Sulfate forms are readily available for immediate plant uptake and generally correct nutrient deficiencies, but they do not achieve significant pH reduction.
When using granular elemental sulfur, the spreader must be calibrated to ensure even distribution and prevent over-application. The amount applied should never exceed the soil test recommendation; a common maximum rate is 5 to 10 pounds per 1,000 square feet per application to avoid damaging the grass. After spreading, the product should be watered into the soil immediately to begin the dissolution process.
Proper safety precautions should be followed when handling sulfur products. Wear personal protective equipment, such as gloves and a dust mask, to prevent skin irritation or inhalation of fine particles. Keep children and pets off the treated area until the product has dissolved into the soil.