Permanent Link: http://ufdc.ufl.edu/IR00003127/00001
 Material Information
Title: Anhydrous Ammonia as a Nitrogen Source for Florida Agricultural Crops
Physical Description: Fact Sheet
Creator: Kidder, Gerald
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
Publication Date: 2000
Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status: Published
General Note: "First printed January 1984 as "Notes in Soil Science #14." Revised and reprinted September 2000 as SL178."
General Note: "SL178"
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Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00003127:00001

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SL178 Anhydrous Ammonia as a Nitrogen Source for Florida Agricultural Crops1 G. Kidder2 1. This document is SL178, a fact sheet of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First printed January 1984 as "Notes in Soil Science #14." Revised and reprinted September 2000 as SL178. Please visit the EDIS Web site at http://edis.ifas.ufl.edu. 2. Gerald Kidder, professor, Soil and Water Science Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611-0290. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences/University of Florida/Christine Taylor Waddill, Dean. Why Anhydrous Ammonia Anhydrous ammonia (NH3) is the primary product in the commercial synthesis of nitrogen (N). It contains 82% N. It is handled as a liquid under pressure at normal environmental temperatures. It is the least expensive form of commercial fertilizer N because it does not require additional processing after production, labor in handling is minimized, and transportation cost per unit of N is less than for other N sources. On the other hand, application equipment is specialized and relatively expensive, and the NH3 must be injected into the soil which increases the energy required and application costs. Anhydrous ammonia is the most widely used source of N for direct application in the United States. It has not been used extensively in Florida because research conducted during the 1950's indicated relatively large volatile losses during its application to sandy soil. Even when higher rates of anhydrous ammonia are applied to compensate for losses due to volatilization, this source of N may still be the least expensive N source. A brief review of existing data on anhydrous ammonia will permit Florida extension agents, fertilizer dealers, and farm managers to make more intelligent decisions with respect to use of this N source. Florida Research Results Experiments with anhydrous ammonia were conducted on several coarse-textured mineral soils. Both perennial forage crops and clean-cultivated annual crops were grown. The anhydrous ammonia was injected to a standard 6-inch depth in all studies. The primary factor that controlled retention and loss of N was the amount of anhydrous ammonia applied per unit of injector row. That amount (concentration) is determined by the pounds of N being applied per acre and the distance between injectors. The greater the rate per acre at a given injector spacing, or the further apart the injector spacings at a given rate per acre, the greater was the percentage lost. Moisture content of the soil ranging from field capacity to almost air dry did not affect retention of N but did affect the shape and size of the retention zone. In very moist soil, the retention zone was narrower


Anhydrous Ammonia as a Nitrogen Source for Florida Agricultural Crops 2 than in dry soil, but in no case did the N move laterally more than 4 inches from the line of injection. Researchers were also concerned about the potentially adverse effect on micronutrient availability of the temporarily high pH (>9.0) in the NH4+retention zone. This was found to not be a problem because of the relatively small volume of soil actually affected by the anhydrous ammonia and the short duration of the alkaline pH condition. Managing Anhydrous Ammonia Applications The management practices discussed below should be used to give the best results when fertilizing with anhydrous ammonia. Emphasis is given to pastures because they represent the crop where most anhydrous ammonia fertilization in Florida is occurring. First and foremost, keep the rate of application in the injector row as low as possible. We know that the lower the concentration in the injector slot, the lower will be the percentage of N loss. At a desired rate of N per acre, this is accomplished by having injector spacings close together. Figure 1 was developed from Florida data to show the expected N volatilization loss at injector spacings and application rates that might be used. For example, if 100 pounds of N per acre are applied at an 18-inch spacing in a pasture, about 22% loss (i.e., 22 pounds of N) would be expected. At a 13.5-inch spacing, the expected loss would drop to 15%. If a 36-inch injector spacing is used for a row crop and 60 pounds of N per acre are applied, the expected loss would be between 20 and 25% of the applied N (i.e., 12 to 15 pounds of N per acre loss). Figure 1. Percentages of applied nitrogen lost by volatilization with increasing ammoniacal-nitrogen rates at four injector spacings. Set injector knives as close together as practical to increase the probability of roots encountering the fertilizer N. Lateral diffusion of ammonia is only 3 or so inches from the injector line, so pastures plants half way between widely spaced injector lines would not receive fertilizer. Injection depth should be no shallower than 6 inches to provide sufficient soil depth for reaction of the ammonia with the soil. Vapor visible behind the injector knife indicates excessive escaping ammonia and the need to make adjustments in the applicator. Another symptom of escaping ammonia is a burned appearance of grass next to the injector slot. While the damage is temporary and of minimal importance, it is an indication of escaping ammonia. Check injection depth and packer wheels. Correction may require spacing knives closer together to lower application rates per unit length of row. Summary The decision of whether or not to use anhydrous ammonia is primarily one of cost and convenience. A producer should consider the application costs, and the cost per pound of N including the extra N that will be needed to compensate for the N lost by volatilization. Volatilization losses are most strongly influenced by the rate of N applied per acre and the injector spacing. Acknowledgment Original text was written in 1984 by Dr. W.G. Blue, then Professor, now Professor Emeritus, Soil Science Department. References Blue, W.G., and C. F. Eno. 1954. Distribution and retention of anhydrous ammonia in sandy soils. Soil Sci. Soc. Am. Proc. 18:420-424. Blue, W.G., and C.F. Eno. 1954. Some aspects of the use of anhydrous ammonia on sandy soils. Soil Crop Sci. Soc. Fla. Proc. 12:157-164. International Fertilizer Industry Association. 2000. Nitrogen, phosphate, and potash statistics.


Anhydrous Ammonia as a Nitrogen Source for Florida Agricultural Crops 3 Available at http://www.fertilizer.org/stats.htm (verified 11 Aug. 2000). Nommik, H., and K. Vahtras. 1982. Retention and fixation of ammonium and ammonia in soils. p. 123-171. In F.J. Stevenson (ed.) Nitrogen in Agricultural Soils. ASA, CSSA, SSSA, Madison WI. Nelson, D.W. 1982. Gaseous losses of nitrogen other than through denitrification. p. 327-363. In F.J. Stevenson (ed.) Nitrogen in Agricultural Soils. ASA, CSSA, SSSA, Madison WI.