Feeding Lowcountry grasses

Folks in the North do things a little differently than those in the South.

They wear coats at Halloween. Every car has an ice scraper in the glove box. And they use nitrogen to winterize their lawns in the fall.

Fertilizer schedules are different up North because lawns are predominantly cool-season turf, which are physiologically different than the warm-season turfgrasses we grow in the Lowcountry.

Cool-season turf includes fescue, ryegrass and bluegrass. They go semi-dormant in the winter and tolerate sub-zero temperatures. They utilize nitrogen fertilization in late fall to boost root growth and encourage healthy spring emergence.

Warm-season turf includes centipede grass, St. Augustine and Bermuda. They go completely dormant in winter and can sustain damage when temperatures drop below 20 degrees. Late nitrogen fertilization, however, delays turf dormancy and prevents your lawn from hardening off for low temperatures, which can result in winter damage that becomes visible at spring emergence.

General recommendations are to avoid applying nitrogen two months before cold weather, which was about Sept. 1 in the Lowcountry.

There's nothing wrong with nitrogen-based winterizing fertilizer as long as you live in Ohio. They are not recommended for the Lowcountry.

There are fertilizers, however, that can boost winter hardiness.

There are three numbers on a bag of fertilizer that represent the percentage of the three major nutrients. The first number is percent of nitrogen, the nutrient that influences growth and color. It is typically applied in slow-release fertilizers that make nitrogen slowly available over the course of a month.

Phosphorus is the second number in the fertilizer analysis. It doesn't have a visual impact on turf and is rarely deficient, especially in the Lowcountry where most soil tests often indicate very high phosphorus levels. In fact, the use of phosphorus in fertilizers is being questioned because it contributes to water pollution in ponds, lakes and streams. Some states have made efforts to remove phosphorus from lawn fertilizers.

Potassium is the third number. While it doesn't contribute to the growth or color of turf, it has been shown to improve the stress tolerance. When soil contains adequate levels of potassium, turf is more tolerant of temperature extremes and drought.

Winterizing fertilizers for the Lowcountry should include potassium without nitrogen and phosphorus, a typical analysis being 0-0-25.

You may also use a weed-and-feed product that combines a pre-emergent herbicide with 0-0-7 fertilizer for winter application in early October.

What makes potassium an especially appealing winterizing fertilizer in the Lowcountry is the fact that our soils are commonly potassium deficient.

Sandy soils are susceptible to leaching potassium. A remedy for potassium deficiency is to use fertilizers that contain an equal amount of potassium and nitrogen during the growing season.

Of the three macronutrients discussed, only nitrogen affects color. Dark green is most often the color associated with high quality turf. Iron can be used to achieve darker green color without affecting growth. This is an ideal method for color improvement in late fall when it's too late for nitrogen because iron won't affect winter hardiness.

While there are granular products of iron, liquid applications are most effective; just be sure the product is evenly applied.

A soil test will confirm the nutritional status of your soil. Sample kits can be purchased from Clemson or call Clemson Extension at 722-5940 for more information.

Another option is A and L Laboratories, which as an extensive list of soil and tissue testing services.

Soil tests will reveal nutritional imbalances in addition to recommendations to correct them. It will indicate the soil pH, a measure of the soil's acidity.

On a scale from 0 to 14, a slightly acidic pH (6.5) is ideal. When the pH is too high or too low, it can severely limit nutrient availability, which means a nutrient may still be in the soil but in a molecular form unusable by the plant.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, email him at tony.bertauski@tridenttech.edu.