Winterizing Fertilizer for Southern Lawns (09-24-12)
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Any year-round lawn fertilization program should be based on soil test analysis, turf use requirements, and grower expectations. However, applying a late-season or “winterizing fertilizer” application to warm-season turfgrasses in Mississippi often becomes a controversial management practice. The controversy stems from the concerns for potential winterkill, disease promotion, and the effect on total nonstructural carbohydrates. Although some research has indicated that late-fall nitrogen fertilization increased vulnerability to winterkill and promotion of diseases other studies, including those conducted by Mississippi State University have shown no direct correlation to winterkill but instead prolongs fall color and earlier recovery in the spring. Late fall applications of potassium is a standard recommendation and practice as potassium promotes winter hardiness and disease resistance in turf.
Therefore, a fall application of a winterizing fertilizer formulated to contain lower ratios of nitrogen to potassium, and particularly with nitrogen sources that are released slowly may be just what your lawn needs. Time the winterizing fertilizer application when temperatures begin to moderate and days begin to shorten, but before the turf goes dormant.
Regardless of time of year, lush turf growth stimulated by excessive nitrogen may be more susceptible to certain diseases and insects so be prepared to treat accordingly with appropriate fungicides and/or insecticides if conditions warrant.
A strong healthy lawn probably can do just fine without fall fertilization but a weak stressed lawn can still benefit from a boost in nutrients. The first official day of fall was September 22nd so there still are several weeks of growing conditions left for most of the state.
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. firstname.lastname@example.org