Golf Course Management

MAR 2015

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03.15 GOLF COURSE MANAGEMENT 93 Ammonia volatilization losses from fertilized turfgrass as affected by nitrogen source Elizabeth Guertal, Ph.D. The loss of nitrogen to the air as ammonia gas (via urease activity) can be a substantial pathway of nitrogen loss, especially if urea is applied to the surface without further incor - poration. The objective of this work was to examine ammonia loss as affected by nitrogen sources, some of which contain various vola - tilization inhibitors (urease inhibitors). Our ammonia volatilization experiment consisted of three separate experiments, all using a standard laboratory bench procedure for the evaluation of nitrogen loss via volatil - ization. Treatments were: (1) granular urea, (2) urea + Ca-Aminoethylpiperazine (Ca- AP)/Ca-Heterpolysaccharides, (3) urea with maleic-itaconic copolymer (Mal-IcoP), and (4) urea with N-(n-butyl) thiophosphoric tri - amide (NBPT). All inhibitors were applied at labeled rates. All fertilizers were applied as granular products to the turf surface at a rate of 1 pound nitrogen/1,000 square feet (4.88 grams/square meter) to tall fescue, with no additional water applied after application. The underlying soil was a loamy sand with a soil pH of 6.2. The volatilization system that was used for all experiments consisted of a series of 16 2-liter glass canning jars, all attached to an air source via a 16-outlet manifold. A plug of turf was placed in each jar, the jar sealed, and air was allowed to fow along the top of the turf in each jar. This method collected ammonia via an ammonia trap system. Air fow was generated by passing 100 milliliters/ minute air stream through a 5N sulfuric acid air scrubber and across each jar, with resul - tant NH 3 trapped in 100 milliliters of 0.01 nitrogen boric acid. The boric acid trap was changed every other day for 11 days, with collected samples titrated to the original pH of the boric acid using 0.01 nitrogen sulfu - ric acid to determine ammonia collected. For each experiment, there were three replicates for each nitrogen source. Each experiment was conducted for 11 days. The fgure below is the average of all three experiments. The only nitrogen source with a volatil - ization inhibitor that signifcantly reduced ammonia loss (as compared to the urea-only control) was the urea that contained the ure - ase inhibitor N-(n-butyl) thiophosphoric tri- amide. Materials with other volatilization in- hibitors did not reduce volatilized ammonia as compared to the urea treatment. Maximum volatilization always occurred by day 3 of the study and had largely reduced to nonmeasur - able levels by 11 days after fertilization. These are very typical responses, and the amount of volatilization and the time over which it oc - curred are similar to those measured in dozens of other volatilization experiments conducted in our laboratory. Typical nitrogen losses from urea applied to the surface were around 20% of nitrogen applied. This was reduced to around 10% of nitrogen applied when the urease inhibitor N-(n-butyl) thiophosphoric triamide was added to the urea. (Report) In addition to urease inhibitors, methods for reducing volatilization losses of nitrogen can include the use of other nitrogen sources that do not contain urea, slow-release nitrogen sources, foliar fertilization or simply applying water to move urea farther into the soil, away from a zone of high urease activity. Prelimi - nary work at Auburn has shown that applica- tion of 1 ⁄8 to ¼ inch (0.3175 to 0.635 centime- ters) of irrigation following urea fertilization will reduce volatilization losses. Beth Guertal, Ph.D. (guertea@auburn.edu), is a professor in crop, soil and environmental sciences at Auburn Univer - sity in Auburn, Ala. Volatilization N loss from fertilized tall fescue Figure 1. Cumulative ammonia loss from tall fescue as affected by various ammonia volatilization inhibitors in a laboratory study. 0 5 10 15 20 25 0 5 10 15 20 25 1 3 5 7 9 11 Days after initial fertilization Nitrogen loss (% of nitrogen applied) Urea Urea + Ca-AP Urea + Mal-IcoP Urea + NBPT

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