Mowing and nitrogen source effects on ammonia volatilization from fertilizers applied to turfgrass
Type of DegreeThesis
DepartmentAgronomy and Soils
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Although ammonia (NH3) volatilization can be a pathway of nitrogen (N) loss from turfgrass systems, the magnitude of this loss has not been well quantified, especially from N sources other than urea. The objective of this research was to evaluate NH3 volatilization as affected by N source and mowing. The laboratory study consisted of two mowing treatments (mowed or not mowed) and six N sources: 1) urea (46-0-0), 2) sulfur coated urea (39-0-0); 3) polymer coated urea (41-0-0), 4) methylene urea (40-0-0), 5) ammonium nitrate (34-0-0), and 6) composted sewage sludge (6-0-0). The 12 treatments were applied at a N rate of 14.7 g m-2 to the surface of a 10 cm diameter bentgrass plug contained in 1 L jars. Jars were sealed, and NH3 volatilization over 10 days was measured via boric acid trapping. Two experiments were conducted, each with a different soil: a loamy sand (Exp. 1), and an 80% sand/20% peat (v/v) greensmix (Exp. 2). In Exp. 1, mowing never affected NH3 volatilization, so mowing was eliminated from Exp. 2. Over the ten day measurement period, urea had greatest total NH3 volatilization, with most released in the first two days. Polymer coated urea released the least NH3, with greatest release nine and ten days after treatment. In descending order, amounts of NH3 volatilization were: urea, sulfur coated urea, methylene urea, composted sewage sludge, ammonium nitrate, and polymer coated urea. The objective of the field study was to determine the amount of nitrogen (N) lost through NH3 volatilization from three N sources previously used in the laboratory experiment. Treatments were applied to existing turfgrass stands of Tifway hybrid bermudagrass, Emerald zoysiagrass, and both bermudagrass and zoysiagrass in fall 2005, spring 2006, and fall 2006, respectively, near Tuskegee, AL. Fertilizer treatments included: urea (46-0-0), methylene urea (40-0-0), and polymer coated urea (41-0-0) and were applied at a rate of 14.7 g m2 of N. Ammonia was captured using a passive micrometeorological system and differences in N sources were observed over a 10-d period. In 2005, urea released the highest proportion of applied N (11.7 %). Mass of NH3 released from methylene urea (7.4 %) was not different from that released from urea (P < 0.10). Polymer-coat urea differed from urea in the amount of NH3 volatilized, but did not differ from methylene urea (P < 0.10). In spring 2006, NH3 volatilization from N sources was in the order: urea (20.1%) > methylene urea (7.4%) > polymer coated urea (4.4%) (P < 0.10). Nitrogen sources followed the same trend in fall 2006: urea (15.7%) > methylene urea (4.2%) = polymer coated urea (4.4%) (P < 0.10).