Turf managers have utilized late season nitrogen fertilization, sometimes referred to as fall fertilization, for years. This type of fertility program involves the application of much of the season’s nitrogen during the late season months of September through December. It is important that late season fertilization not be confused with dormant and / or winter fertilization. The latter method implies that fertilizer applications are made after the turf has lost most or all of its green color and is not actively growing. This differs notably from the late season concept, which requires that nitrogen be applied before the turf loses its green color in the late fall.

Late season fertilization is popular because many of the agronomic and aesthetic advantages attributed to its use are not realized when spring and / or summer fertilization are practiced. Advantages of the late season concept include:

• Better fall and winter color

• Earlier spring green-up

• Increased shoot density

• Improved fall, winter, and spring root growth

• Enhanced storage of energy reserves (carbohydrates) within the turf plant

Quality

Turf fertilized in September and again during October, November, or December is generally shown to possess better fall and winter color than a turf that was not fertilized at that time. In addition, signs of spring green-up have been shown to occur two to six weeks earlier if the turf has been fertilized the previous fall. Most importantly, the enhanced rate of spring greening is realized without stimulating excessive shoot growth that accompanies the early spring nitrogen applications called for in most turf fertility programs.

Timing

The late-season nitrogen fertilization concept is designed to apply nitrogen during that period of the year (late fall) that will favor root growth over shoot growth, and favor a positive carbohydrate balance. Shoot growth of cool season grasses occur most readily in the temperature range of 50-65ºF. Root growth of cool season grasses will continue at soil temperatures close to freezing. When air temperatures in late fall consistently drop below 50ºF shoot growth slows or ceases but soil temperatures are still in the favorable range for significant root, rhizome, and stolon growth. LSF capitalizes on this differential in optimum temperatures for growth of roots versus shoots. Wait until the grass stops growing but it’s still nice and green.

Fertilizer Rate & Fertilizer Type

In addition to timing, fertilizer rate and fertilizer type is critical to successful LSF. The most efficient nitrogen fertilizers for LSF are those independent of temperature for nitrogen release.

Nitrogen rates should be in the range of 1- 1 ½ pounds of actual nitrogen per 1,000 square feet.

Proper rate and nitrogen source will result in significant carryover of nitrogen for early spring greenup the following season. The standard spring fertilization rate can typically be reduced to one half or less, or eliminated, thus avoiding a spring fertilization flush. Don’t couple LSF with traditional spring nitrogen fertilization rates. This defeats the purpose of the LSF strategy.