Kansas

"Winterizer" is a catchy word that sells lots of high-phosphorus lawn fertilizer each year. But, the best winter preparation for tall fescue and Kentucky bluegrass lawns is a fertilizer high in nitrogen--even one with no phosphorus content, said a Kansas State University horticulturist.

Nitrogen is the most important nutrient for turf color, density and growth, said Chip Miller, yard and garden specialist with K-State Research and Extension.

"Nitrogen also is the major lawn nutrient that moves down to plant root systems most readily and the one that grass plants use in greatest quantity. It's pretty well wiped out of the soil by the end of every growing season. So, it's the only lawn food K-State recommends you apply on a regular basis at a standard rate," Miller said.

That recommendation for fescue and bluegrass is 1 to 1.5 pounds nitrogen per 1,000 square feet, applied in September, November and perhaps again in March.

"Potassium is the second most important fertilizer element. It's responsible for making the turf strong, so it can resist damage from stress, wear and winter weather," Miller said. "Normally, plants need less potassium than nitrogen, but you should test your soil to determine the correct amount to apply. Established lawns that already have been fertilized several times often have enough residual potassium and phosphorus for a healthy lawn."

Phosphorus helps lawns with energy-requiring tasks, such as putting out new roots and shoots. Established turfgrass only uses a small amount each growing season. So, unless a soil test indicates otherwise, fall fertilizer applications should have low quantities of phosphorus or none at all.

"Typically, phosphorus applications are most needed around new homes where the contractor has removed or buried the top soil," he said.

"The other end of the scale are those lawns that have received heavy applications of phosphorus on a regular basis. That can lead to a soil buildup of the nutrient - which, in turn, can interfere with plants' uptake of iron and other micronutrients."

Expressed as numbers, the three major nutrients always appear on fertilizer containers in the same order: Nitrogen, phosphorus and potassium (NPK).

"Phosphorus may be listed second, but it's your lawn's third priority," Miller said. "For example, if you can't find an all-nitrogen formulation, a 25-3-8 or similar mix could be a good ratio for routine lawn feedings--fall or spring."