Nitrogen is one of the most essential nutrients for turfgrass, and it comes in several forms that vary in how they are made available to plants. These forms can be broadly classified into quick-release and slow-release types.
Quick-release Nitrogen (Soluble Nitrogen)
Urea is a synthetic organic nitrogen compound that dissolves rapidly in water, making it quickly available to turfgrass plants. Once applied, it converts to ammonium, which plants can easily uptake. Containing 46% nitrogen—one of the highest concentrations available in fertilizers—urea allows turfgrass managers to apply less material while still delivering an effective dose of nitrogen, improving efficiency.

Classified as a quick-release nitrogen source, urea is relatively inexpensive compared to other nitrogen fertilizers, making it a cost-effective choice for maintaining lawns. It can be used in various environmental conditions and turfgrass types, applied during crucial growth periods such as early spring or fall. In soil, urea is converted into ammonium and nitrate, forms of nitrogen that promote microbial activity, benefiting soil health and nutrient cycling.
Ammonium Sulfate (NH₄)₂SO₄ is a fast-acting nitrogen source that is immediately available to plants and can acidify the soil, making it useful when a quick response is desired. In addition to 21% nitrogen, ammonium sulfate contains 24% sulfur, an essential nutrient that aids protein synthesis and chlorophyll formation. This dual nutrient content enhances turfgrass color, growth, and overall health, especially in sulfur-deficient soils.

The acidifying effect of ammonium sulfate lowers soil pH, which is beneficial in alkaline soils, making other nutrients like iron, manganese, and phosphorus more available to turfgrass and improving nutrient uptake. Additionally, it helps reduce certain soil-borne diseases that thrive in alkaline conditions. Unlike urea, ammonium sulfate has a much lower risk of volatilization (the conversion of nitrogen into ammonia gas), especially in high-pH soils, reducing nitrogen loss to the atmosphere and increasing nitrogen availability to plants. The combination of nitrogen and sulfur promotes a deeper green color in turfgrass and enhances plant density, which is particularly important for high-visibility areas like golf courses, sports fields, and ornamental lawns.
Ammonium Nitrate (NH₄NO₃): A combination of ammonium and nitrate nitrogen, it is highly soluble and provides an immediate nitrogen source to the turfgrass, making it ideal for a quick greening response. Ammonium nitrate provides two forms of nitrogen: ammonium (NH₄⁺), which is readily available for plant uptake and can be retained in the soil, and nitrate (NO₃⁻), which is immediately available and highly mobile in soil water.

This combination ensures both a quick response and sustained nitrogen availability to the turfgrass. The nitrate content of ammonium nitrate leads to a rapid green-up reaction, as it is immediately absorbed by plant roots for quick growth and improved color, making it an ideal choice for fast results, such as recovery after stress or dormancy. Meanwhile, the ammonium portion is more stable in the soil and is gradually converted to nitrate over time.
Calcium Nitrate (Ca(NO₃)₂) provides fast nitrogen availability through nitrate, which is immediately available for plant uptake. Calcium nitrate provides nitrogen in the nitrate form (NO₃⁻) and calcium (Ca²⁺), both of which are crucial nutrients for healthy turfgrass growth. Nitrate nitrogen is immediately available for plant uptake, promoting rapid growth and green-up, especially in cool-season grasses during active growth periods.

Slow-release Nitrogen
Sulfur-coated Urea (SCU) is urea coated with sulfur to slow the release of nitrogen, allowing it to become gradually available to the turfgrass as the sulfur coating breaks down. This provides a slow and steady release of nitrogen over time, reducing the risk of nitrogen leaching and promoting sustained growth without rapid surges. The sulfur coating also reduces the risk of fertilizer burn, which can occur with fast-release nitrogen sources, making it particularly beneficial when applied during hotter months or on sensitive turfgrass species.

The controlled release of nitrogen allows the turfgrass to utilize the nutrient more efficiently over a longer period, reducing the need for frequent fertilization and leading to more consistent turfgrass health and appearance. SCU provides extended feeding, lasting anywhere from 8 to 12 weeks, depending on environmental conditions, making it ideal for maintaining turfgrass during rapid growth or in areas where frequent fertilization is impractical.
Polymer-coated Urea (PCU): Urea granules are encased in a polymer coating, which controls the release of nitrogen over time based on moisture and temperature. This provides a slow and controlled release of nitrogen, similar to sulfur-coated urea (SCU), but with greater precision. The release rate, influenced by soil moisture and temperature, ensures nitrogen is available to the turfgrass only when conditions are optimal for growth, reducing the risk of nutrient loss through leaching or volatilization.

PCU can release nitrogen for up to 12 to 16 weeks or more, depending on the coating thickness and environmental conditions, reducing the need for frequent applications and promoting consistent turfgrass growth while minimizing labor costs. The slow release also significantly reduces the risk of fertilizer burn, making it safer for sensitive turfgrass, especially in warmer weather or drought conditions. Additionally, the gradual release allows the turfgrass to absorb nutrients more efficiently, enhancing turf color, growth, and stress tolerance over the long term.
Urea-formaldehyde (UF) provides a slow, controlled release of nitrogen through microbial activity in the soil, making it an excellent choice for long-term feeding. The nitrogen is gradually released as the urea-formaldehyde breaks down, with availability extending over several months, depending on soil temperature and microbial activity. This makes UF ideal for providing consistent nutrition to turfgrass without the need for frequent reapplication. Its slow release also minimizes the risk of nitrogen leaching into groundwater, ensuring more of the nutrient is absorbed by the turfgrass and less is lost to the environment.
Unlike quick-release nitrogen sources that can burn turfgrass, UF has a low salt index, reducing the likelihood of fertilizer burn, especially in hot or dry conditions. The gradual breakdown of UF ensures that nitrogen is available when the turfgrass needs it most, leading to more efficient nitrogen use, reduced waste, and healthier, more consistent growth.
Isobutylidene Diurea (IBDU) is a synthetic slow-release nitrogen source that breaks down chemically through hydrolysis, offering a controlled release independent of microbial activity. This chemical process, which relies on soil moisture rather than microbial activity, ensures a more predictable and consistent nitrogen release, particularly in cool or wet conditions where microbial activity may be slower.

IBDU can provide nitrogen to turfgrass over an extended period, often lasting several months, reducing the need for frequent applications and supporting sustained growth while lowering labor and application costs. Its slow breakdown also minimizes nitrogen loss through leaching or volatilization, making it an environmentally friendly option that reduces the risk of groundwater contamination and ensures more nitrogen is available for turf uptake.
Natural Organics (composted materials): Organic nitrogen sources, such as manure-based fertilizers and composted materials, release nitrogen slowly through microbial decomposition in the soil. Natural organic fertilizers, offer numerous benefits for turfgrass management, including improved long-term soil, environmental sustainability, and balanced nutrient availability. As these fertilizers break down gradually over time, they provide a steady supply of nutrients, supporting consistent turf growth while reducing the risk of nutrient leaching and fertilizer burn. This slow release helps maintain even growth, avoiding spikes of rapid growth followed by deficiencies.

Additionally, organic fertilizers add organic matter to the soil that may increase water-holding capacity, and help with aeration. These improvements benefit turfgrass roots by enabling them to penetrate deeper into the soil and access more nutrients and moisture. The addition of organic matter also supports the ideal conditions of beneficial soil microorganisms, which are crucial for nutrient cycling and soil fertility. Furthermore, natural organics are more environmentally friendly than synthetic fertilizers, as they reduce the risk of nutrient runoff, which can lead to water pollution in nearby rivers and lakes.
Slow-release nitrogen forms, such as those coated or organic sources, can reduce the risk of leaching and volatilization. Each form of nitrogen serves a specific purpose, depending on the management goals (e.g., quick greening or long-term feeding) and environmental conditions (e.g., temperature and soil moisture).
Types of Nitrogen Fertilizer for Turfgrass Growth
Nitrogen (N) fertilizers are essential for promoting healthy turfgrass growth, and different types of nitrogen fertilizers provide unique benefits based on their release rates, environmental impact, and nutrient availability. The choice of nitrogen fertilizer depends on the specific needs of the turfgrass, ecological conditions, and management goals. Slow-release and natural organic options are often preferred for sustainable turfgrass health and minimal environmental impact, while fast-release and liquid fertilizers are more suited for quick fixes or rapid greening.