Turf and Landscape - Know Your Soluble Fertilizers 3

This is the third in a series on soluble fertilizers for use in turf and landscapes. This post is on ammonium nitrate, a nitrogen fertilizer.

Ammonium Nitrate is typically marketed in prilled form containing 33-34% N. It is highly soluble and is also marketed in solution form; generally it will be offered in combination with urea containing 28, 30 or 32% N. Prilled ammonium nitrate may be bright white in color, indicating that the prill has been coated with magnesium chloride, or beige in color, indicating that the product has been coated with a mixture of clays. Both of these coatings reduce the hygroscopicity of the product and improve handling properties. Ammonium nitrate and urea cannot be mixed together in dry form because of severely reduced handling properties. Ammonium nitrate produces only 1.8 pounds of acidity per pound of N applied upon nitrification, and thus is not as acidifying as ammonium sulfate. The salt index of ammonium nitrate, 2.99, is less than that of ammonium sulfate and thus there is less potential for turfgrass burn immediately after application. Ammonium nitrate generally does not impart as dark green a color as does ammonium sulfate and the longevity of the response is not as great.

Reprinted from "Selected Fertilizers Used in Turfgrass Fertilization" by J.B. Sartain & J.K. Kruse, University of Florida Cooperative Extension.

Turf and Landscape - Know Your Soluble Fertilizers 2

This is the second in a series on soluble fertilizers for use in turf and landscapes. This post is on urea, a nitrogen fertilizer.

Urea is a white crystalline solid, generally marketed in prill form, containing 45-46% N. It has good physical properties and is not as hygroscopic as ammonium nitrate. It produces 1.8 pounds of acidity per pound of N and has a salt index of 1.62; thus it can be applied to turfgrass with little threat of burn when applied at recommended rates. If left on the soil surface, significant quantities of N may be lost by volatilization. Therefore, urea should always be watered in with the proper amount of water. Urea is a non-ionic compound when placed into solution and will leach rapidly through the soil profile if excess water is applied. Remember that one inch of water will effectively wet the top ten inches of a Florida sand soil profile. Urea is highly soluble and one of the materials of choice in N solution fertilizers. Generally speaking urea does not produce as good a turfgrass response as does ammonium sulfate or ammonium nitrate, but because of its ease of application in solution form, its high solubility, its low burn potential and low cost per pound of N, it is a popular soluble N source, particularly by lawn care maintenance personnel.

Reprinted from "Selected Fertilizers Used in Turfgrass Fertilization" by J.B. Sartain & J.K. Kruse, University of Florida Cooperative Extension.

Turf and Landscape - Know Your Soluble Fertilizers 1

This is the first in a series on soluble fertilizer sources for use in turf or landscapes.

Ammonium Sulfate is a white crystalline material containing 20-21% N and 24% S. If produced in the pure crystalline form it is seldom marketed. The marketed product may be grayish in color due to carbon contamination during manufacture. Nitrification of ammonium sulfate produces acidity in the soil. Upon conversion to nitrate, the ammonium ion produces 5.35 pounds of acidity per pound of N applied, thus making ammonium sulfate the most acidifying N source available. This acidifying property makes ammonium sulfate the desired N source on alkaline turfgrass soils. When applied on high pH soils, particularly those containing free calcium carbonate, ammonium sulfate should always be watered in to limit volatile loss of N. Ammonium sulfate has a high burn potential with a salt index of 3.25, therefore, it should not be applied at high rates to avoid potential turfgrass burn. Due to limited solubility ammonium sulfate is not often applied in solution form. Ammonium sulfate imparts a dark green color in turfgrasses which tends to last for at least 30 days when applied at recommended rates. Turfgrass responses to ammonium sulfate tend to last for a longer period than for the other soluble N sources, and for this reason ammonium sulfate tends to be the preferred soluble N source of many turfgrass managers.

Reprinted from "Selected Fertilizers Used in Turfgrass Fertilization" by J.B. Sartain & J.K. Kruse, University of Florida Cooperative Extension.

Turf and Landscape - Reminder to Get all Late N and P Fertilizer Applications Done Before December 7

Nutrient management regulations in Delaware restrict the application of fertilizers containing nitrogen and/or phosphorus between December 7 and February 15. The following is information about the regulation.

Turf managers and landscapers are reminded that regulations in Delaware state that no nitrogen or phosphorus fertilizers may be applied to impervious surfaces, frozen ground, or between December 7 and February 15.

The following is the regulation from the Delaware Department of Agriculture and the Delaware Nutrient Management Commission.

6.0 Nutrient Handling Requirements
6.1 As required by 3 Del.C §2201 et.al, Nitrogen and Phosphorus fertilizers shall be applied according to a Nutrient Management plan.
6.2 For land areas not required to have a Nutrient Management plan, applications of Nitrogen and Phosphorus fertilizers by anyone holding a commercial nutrient handler or nutrient consultant certification, or anyone required to be certified at said level pursuant to 3 Del.C. §2242 and section 4.0 herein, are prohibited when one of the following conditions exist:
6.2.1 The surface area of application is impervious such as sidewalks, roads and other paved areas and the misdirected fertilizer is not removed on the same day of application;
6.2.2 The surface area is covered by snow or frozen; or
6.2.3 The date of application is between December 7 and February 15.

Turf and Landscape - Slow Release Fertilizers: Polymer Coated Fertilizers 1

This is the first in a series on slow release fertilizers for turf and landscapes. This post contains information on one of the newer polymer coating technologies.

Reactive Layer Coating. A relatively new coating technology known as reactive layer coating (RLC) polymerizes two reactive monomers as they are applied to the fertilizer substrate in a continuous coating drum. These in situ reactive layer polymerizations form an ultra-thin membrane coating which controls nutrient release by osmotic diffusion. A number of these products are being marketed under the trade name Polyon. These include coated basic fertilizer materials, i.e., urea, potassium nitrate, potassium sulfate, potassium chloride, ammonium sulfate, ammonium phosphate and iron sulfate, in various particle sizes. Coating weights on urea vary from 1.5 to 15%, depending on the release duration desired.

Nutrients are released from Polyon-coated fertilizers by osmotic diffusion. The RLC process permits application of ultra-thin, and hence lower cost, membrane coatings, which distinguishes this technology from many other polymer-coated fertilizers. The coating thickness determines the diffusion rate and the duration of release. Polyon-coated urea at 4% coating (44%N) will release at twice the rate and will have half the duration as an 8% coating (42% N).

During the manufacturing process two polymers react to form a polyurethane coating which is chemically bonded to the fertilizer core. The advantage of RLC technique is that the liquid coating materials can be applied and polymerized to the desired coating thickness in a continuous coating process drum without the need for solvents and associated recovery equipment. As a result, production costs are lower than many of the other commercial polymer-coated fertilizer technologies.

Reprinted from Selected Fertilizers Used in Turfgrass Fertilization by J. B. Sartain and J. K. Kruse, University of Florida Extension.

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.

Turf and Landscape - Nitrogen and Phosphorus Winter Application Restrictions

Turf managers and landscapers are reminded that regulations in Delaware state that no nitrogen or phosphorus fertilizers may be applied to impervious surfaces, frozen ground, or between December 7 and February 15. The following is the regulation from the Delaware Department of Agriculture and the Delaware Nutrient Management Commission.

6.0 Nutrient Handling Requirements
6.1 As required by 3 Del.C §2201 et.al, Nitrogen and Phosphorus fertilizers shall be applied according to a Nutrient Management plan.
6.2 For land areas not required to have a Nutrient Management plan, applications of Nitrogen and Phosphorus fertilizers by anyone holding a commercial nutrient handler or nutrient consultant certification, or anyone required to be certified at said level pursuant to 3 Del.C. §2242 and section 4.0 herein, are prohibited when one of the following conditions exist:
6.2.1 The surface area of application is impervious such as sidewalks, roads and other paved areas and the misdirected fertilizer is not removed on the same day of application;
6.2.2 The surface area is covered by snow or frozen; or
6.2.3 The date of application is between December 7 and February 15.