Fall Strategies for Better Fields Next Spring
Dr. John R. Street and Pamela J. Sherratt
The Ohio State University Department of Horticulture & Crop Science
The fall season provides optimum conditions for lawn renovation practices. The aims are to return the lawn to 100% grass cover of desirable species, to restore soil textural and physical properties through soil cultivation practices, and to return the playing surface to a stable and wear tolerant state. Carrying out key maintenance operations in the fall can provide early spring growth. Three of these important operations are (1) late season fertilization, (2) coring/aerification, and (3) weed control.
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:
The timing of LSF should be made when vertical shoot growth has stopped, but the turf leaves are still green. Vertical shoot growth of cool season grasses will generally slow and stop at air temperatures of 45-50ºF. A properly timed LSF will extend the “greening” time of the turf longer into the late fall and early winter without additional top growth. The green leaves remain photosynthetically active producing carbohydrates. This carbohydrate will be more efficiently used to support root, rhizome, and stolon growth during the late fall and winter period. LSF also assists in building food reserves for the following season. It is critical that the nitrogen be applied prior to dormancy for maximum efficiency of applied nitrogen. Poor timing is a common LSF mistake. Once the leaf tissue has turned brown, photosynthesis will no longer occur. Remember ? “late-season” fertilization is not dormant fertilization.
Urea, more water-soluble methylene ureas, IBDU, and SCU are less dependent on temperature for nitrogen release and, therefore, make excellent LSF nitrogen sources.
Nitrogen rates should be in the range of 1- 1 ½ pounds of actual nitrogen per 1,000 square feet. Higher rates typically provide a better LSF response in the late fall and a better carryover response into late winter/early spring. For cool season grasses, nitrogen is the key nutrient for the LSF response with standard maintenance fertilizer ratios being acceptable.
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.
In summary, LSF lengthens the fall/winter green period and enhances the rate of spring green-up without stimulating excessive shoot growth, thus allowing the turf plant to maintain higher levels of carbohydrates than then spring/summer fertilization is used. Nitrogen applied during early spring increases shoot growth rates and decreases the levels of available carbohydrates in the plant, resulting in depressed root growth rates. LSF has no similar negative effects on root growth. No winter damage or snow mold injury typically occurs as a result of LSF. The turf manager must maintain a good carbohydrate reserve/balance and maximum root mass. Proper timing and rate of application are important in successful long-term programs. Always remember: greener is not always better. A happy medium must be reached between agronomics and aesthetics.
Some degree of soil modification would substantially improve the soil. Historically, the principal goal in soil modification was to replace the existing native soil that typically exhibits cohesive (silt/clay) behavior with a rootzone having properties of a granular (sand) nature. This goal is achieved by establishing sufficiently high sand contents in the rootzone. The recommended sand content for high traffic areas generally exceeds 75% by weight.
In addition to a soil modification program, mechanical cultivation techniques can be adopted that are effective at improving the physical condition of compacted rootzones. Regular core cultivation done throughout the year will keep the lawn free draining and in good shape. Soil cultivation carried out in the fall is sometimes done many times to get maximum results.
Which type of machine is best suited to relieve compaction? In essence, to relieve compaction the soil must be physically displaced to create fracturing so that the same mass of soil occupies a greater volume (e.g. verti-drain, shatter-tine), or the soil must be removed so that a smaller mass of soil occupies the same lawn volume (e.g. hollow core, deep drill).
Timing? Cultivation is best accomplished when the soil is moist but not wet. Moist soil facilitates deeper penetration of the tines. Cultivators will not effectively penetrate dry, compacted soils. It is suggested that several passes (three or four) be made over the lawn in varying directions, for best results. Following soil cultivation, many lawn managers apply a topdressing of sand/sand-based material to reestablish surface levels and maintain correct soil physical properties.
Thus, there are several key advantages to late fall coring. Late fall coring can be followed by dormant over-seeding. Second, a more heavy/intensive coring can be performed with lawns not under schedule for early spring play. Third, more vigorous cultivation like deep tining can be performed that might otherwise significantly interfere with play during the active planting season. Fourth, coring at this time of year results in considerable freezing and thawing of moisture in the holes, resulting in additional fracturing of the soil. Fifth, prolific rooting can occur in the coring holes and adjacent fractured soil. This is more beneficial in the late fall than any other time since root growth of cool season grasses is occurring readily with cooler temperatures.
Late season fertilization (LSF) is a good agronon practice to couple with late core cultivation. LSF stimulates root growth during the fall, early winter, and the spring. The core holes and adjacent fractured soil provide great open channels for the development of roots. Corrective applications of fertilizer can also be applied at this time to facilitate deeper placement.
The Lesco product, Corsair (chlorsulfron) continues to be available for selective tall fescue control in established Kentucky bluegrasses. However, this product should not be used on athletic lawns containing appreciable perennial ryegrass.
The plant growth regulators Scott’s TGR, Dow AgroSciences’ Cutless, and Syngenta’s Primo are capable of assisting in the suppression of annual bluegrass and the conversion to more desirable turfgrass. This approach has been used in the golf course industry with mixed swards of annual bluegrass and creeping bentgrass to convert to bentgrass. The PGR approach has not been used extensively in Kentucky bluegrass turf on athletic lawns for several reasons: (1) Kentucky bluegrass is less aggressive than bentgrass, (2) suppressive applications for Pao need to be made in spring and fall when play is active, and (3) the suppression of the desirable grass may reduce recuperative potential. However, several recent research reports refute point 3.
Prograss (ethofumesate) is a postemergence selective herbicide capable of eliminating annual bluegrass from Kentucky bluegrass, perennial ryegrass, and others. It is most efficacious in the fall and requires 2-3 sequential applications. Managers that have chosen this approach are reporting fair to good results. It can be broadcast or spot treated.
Late fall applications of longer residual preemergence herbicides can be used to reduce annual bluegrass and other annual grassy weed development in the spring. This approach is not appropriate where late-season over-seeding or spring seeding is practiced.
Best management practices for cool-season grasses in the fall and late fall require:
Information provided by Lloyd Royse of Royse Sports Turf
Mowing - In late fall mowing heights should start to be lowered. Lowering the height .25” each time you mow (down to 2.25”), will allow more of the stored nutrients to enhance the root system while also preventing severe winter injury to the grass tips. Be sure your mower blades are sharpened for the winter but leave your mower height at 2.25” for your first mowing of the following spring season.
Watering - Supplemental watering will not be needed during the late fall and winter. Do remember to have all your lawn sprinklers and systems winterized.
Leaves Leaves will not affect today’s application but do not allow them to become so thick, that they block the sunlight to the turf. Doing so will cause adverse coloring and thinning of the grass plants.