Turf - Considerations in Fertilizing Turfgrass in Lawns

The following are some considerations in fertilizing turfgrass in lawns from Virginia Tech.

1) After choosing the appropriate program of fertilization for a lawn, you should then determine the amount and frequency of fertilization that is proper. This will be influenced by the quality desired, source of nitrogen, soil type, type of turfgrass, length of growing season, traffic, shade, and whether clippings are recycled. Evaluate your lawn situation based on these factors and how each affects the amount and frequency of nitrogen application. Choose the amount and frequency that best suits your situation.

2) Fertilizer "Burn" - The primary advantage of slowly-available nitrogen sources is that they can be applied at higher rates, which reduces the total number of times the fertilizer must be applied. When properly applied, they also reduce the chances of foliar burning that is common with ammonium nitrate and urea. Foliar burning is the brownish discoloration that occurs on grass blades as a result of contact with soluble fertilizer. It can be minimized by watering the lawn immediately after fertilizing.

3) Soil Type - Sandy soils will generally leach more nitrogen than silt loam and clay loam soils. Therefore, more frequent nitrogen applications are often required in sandy soils when quickly-available sources of nitrogen are used. Leaching can be minimized by using slowly-available nitrogen sources, which in turn can reduce possible contribution to the problem of nitrogen-enriched water in nearby streams.

4) Type and Age of Turfgrass - Nitrogen application to coolseason grasses such as Kentucky bluegrass, tall fescue, perennial ryegrass, and the fine fescues (creeping red fescue, hard fescue, sheep fescue and chewings fescue) is best done in the late summer and fall period. Warm-season grasses perform best when nitrogen is applied in the mid-spring to mid-summer period. Newly established lawns or lawns lacking density or ground cover will benefit from properly timed applications of nitrogen until ground cover and density have reached a desirable level. Mature zoysiagrass, centipedegrass, and fine fescue lawns require lower levels of nitrogen than Kentucky bluegrass, tall fescue, perennial ryegrass, or bermudagrass.

5) Traffic - Where heavy traffic or use is anticipated, higher rates of properly timed nitrogen can be beneficial in generating recuperative potential.

6) Shade - Grasses growing in heavily shaded areas require only 1/2 to 2/3 as much nitrogen as grasses growing in full sun. Shade also affects the timing of nitrogen applications. Since grass plants in shade can best use nitrogen when sunlight can reach the grass leaves, fertilizer applications should be timed after the majority of leaves have fallen from the trees in the fall. Applications made in October and November are generally most effective. In heavily shaded areas with fine fescue turf, it may be beneficial to reduce fertilization rates even further or omit applications until leaf collection is finished in the fall.

7) Quality Desired - Turfgrass quality is a measure of density, color, uniformity (free of weeds and off-type grasses), smoothness, growth habit, and texture. If high levels of turfgrass quality are desired, a commitment must be made to proper turfgrass species and variety selection, frequent mowing, and to slightly higher rates of nitrogen and increased application frequency. Additionally, irrigation, aeration and pesticide application may at times enhance quality.

8) Clipping Recycling - Significant amounts of nitrogen and potassium are returned to a lawn when clippings are returned. Recycling turfgrass clippings contributes very little to thatch, provides nutrients and organic matter and an environmentally friendly method of clipping disposal. If clippings must be collected, higher rates of nitrogen and potassium applications may be necessary.

9) Micronutrients - Fertilizers that contain micronutrients are most suited for application on sandy soils. Foliar spray application of iron on high quality cool-season turf during the fall, winter, and summer seasons will improve color, vigor and root growth. Three to four foliar applications of 2 ounces of iron sulphate per 1,000 sq ft during fall and winter and another three to four applications during the summer, at the same rate, will give maximum results. Iron chelates provide similar results. However, since there are a number of different iron chelates available, refer to product guidelines for their use. Application of iron in winter, if turf is brownish, may result in a gray-green appearance.

10) Fertilizer application equipment and methods - Nitrogen fertilizer will "green-up" a lawn. Therefore, it is important to uniformly apply nitrogen-containing fertilizers. This will eliminate streaking caused by different shades of green turf in the lawn. Proper application of nitrogen fertilizers by hand is difficult, even for a trained professional. Drop-type or rotary spreaders should be used. When using drop-type spreaders, be sure to overlap the wheel tracks, since all the fertilizer is distributed between the wheels. Drop-type spreaders are not as easy to maneuver around trees and shrubs as rotary spreaders. Rotary spreaders usually give better distribution where sharp turns are encountered because they tend to cover a broader swath and fan the fertilizer out at the edges of the swath. It is advisable to apply one half of the material in one direction and the other half in a perpendicular direction until one is experienced with a spreader. This will minimize streaking. Avoid application of any fertilizer to non-turfed areas (driveways, roads or bare soil) since it is then prone to runoff into drainage ways at which time it can enter water supplies.

Extracted from "Lawn Fertilization in Virginia" Authors: J.M. Goatley Jr., Extension Specialist, Turf; D.R. Chalmers, Extension Agronomist, Turf; J.R. Hall III, Extension Agronomist, Turf; and R.E. Schmidt, Professor, Department of Crop and Soil Environmental Sciences, College of Agriculture and Life Sciences, respectively; Virginia Tech.