PANHANDLE PERSPECTIVES: Making decisions about fertilizing and mowing lawns

By Jim Schild and Gary Stone, Extension Educators, UNL Panhandle Research and Extension Center

Fertilizing a turf grass lawn is a lot more than just buying a bag of fertilizer and spreading it all in the spring.

There are several decisions to make. One is how much fertilizer to apply; another is when to apply it. And spring is not the best time to apply most of the year's fertilizer.

The goal of a good fertilizer program is to keep growth at a minimum while maintaining a good, thick, dense, well-colored lawn. To reach the goal, at least two-thirds of the fertilizer should be applied during the fall to thicken the turf and help the grass recover after the summer stress.

A light application of nitrogen is recommended in early May, using fertilizer containing slow-release nitrogen. This will produce a slow growth rate over the summer. Additional fertilizer can be applied in early September to help thicken and stimulate root growth.

The amount and timing of fertilizer application, especially nitrogen fertilizer, will dictate the growth pattern of the grass season-long. Kentucky bluegrass has its peak growth in the spring months of April and May and then a secondary peak during September. Fertilizer applied prior to those peak months stimulates growth and can encourage excessive grass growth.

And excessive lawn growth means more watering and mowing.

Total N (nitrogen) applied during an entire growing season should not exceed 4 pounds per 1,000 square feet for the typical lawn, and a low-maintenance lawn typically should be fertilized at 1 to 1 ½ pound of N per 1,000 square feet during September, with another ½ pound applied with crab grass preventer applied the first of May.

The amount of nitrogen applied can be calculated by using the three numbers on every bag of lawn fertilizer. They indicate the amount of nitrogen, phosphate and potash (N, P and K) respectively, expressed as the percent of total weight. The remainder of the bag's contents consist of inert material.

To apply 1 pound of nitrogen, using a bag of 20-5-5 fertilizer, apply 5 pounds of product. That is 5 pounds of material, of which 20 percent (1 pound) is nitrogen.

A homeowner using the low-maintenance fertilizer regimen in western Nebraska would routinely mow about every five days. A homeowner who applies 4 pounds per 1,000 square feet and uses a mulching mower would typically need to mow every three days.

Following recommended mowing practices also is important. The rule of thumb is never to remove more than one-third of the grass blade at once. Otherwise the grass becomes stunted, goes off color, and requires energy from the root system to initiate regrowth.

Grass height can affect turf health. The recommended blade length is 3 to 3 ¼ inches.

Grass cut to a length of 2 inches increases soil evaporation and also allows sunlight to penetrate into the soil. The sunlight will allow more weeds to germinate. For example, crab grass is more likely to be a problem when turf is mowed at 2 inches than at 3 ¼ inches.

The more a lawn is fertilized and mowed, the more water it will require. In real simple terms, the more you fertilize the more you have to mow. The more you mow, the more you have to water (to recover from the mowing).