Saturday, 15 July 2006

Differences in the Temperature Quotients of Ammonia Emission on the Fertilized Soils from Florida and Washington.

Guodong Liu1, Yuncong Li1, and Ashok Alva2. (1) Univ of Florida/TREC, 18905 SW 280th Street, Homestead, FL 33031, (2) USDA-ARS, 24106 North Bunn Road, Prosser, WA 99350-9687

Temperature is a very important factor for ammonia emission but not well understood yet. This research was conducted with Biscayne Marl Soil and Krome Gravelly Loam from Florida and Quincy Fine Sand and Warden Silt Loam from Washington. The soils were weighed (300 g dry weight) and placed in a 500 ml plastic bottle with about 60 cm2 surface area. Potassium nitrate, ammonium nitrate, ammonium sulfate and urea were applied to the soils at 45 mg per bottle (equivalent to 75 kg ha-1 based on surface area) with 20% and 80% Field Capacity (FC). The soils were incubated at either 11, 20 and 29 oC that are, respectively, the minimum, average and maximum temperatures in-season of potato growth in Washington State. The temperature quotient (also called temperature coefficient) for a 9 oC is called Q9. The Q9 depicts the changed strength of ammonia volatilization under different temperatures. Further, an active temperature quotient is proposed herewith to draw both of changed strength and direction of the ammonia emission when temperature is changed. The volatilized ammonia was trapped in a sponge in the bottle mouth. The sponge was spiked with 0.8 ml trapping solution containing phosphoric acid-glycerol mixture. The trapped ammonia was extracted in 25 ml 1 mol/L KCl. The volatilization was measured in a Rapid Flow Analyzer on day 1, day 3, day 7, day 14 and day 28. The results showed: 1. the active temperature quotients of ammonium sulfate and ammonium nitrate were 3 to 6-fold higher than that of urea because the latter does not have instant ammonium. 2. The active temperature quotients were much higher in the range between 20 to 29 oC than that in the range between 11 to 20 oC when inorganic ammonium fertilizers were applied. 3. Warden Silt Soil from Washington was very positively responsive to temperature increasing but Biscayne Marl Soil from Florida responded negatively. 4. The active temperature quotients of the tested soils decreased with time. This suggested that higher temperature mainly boosted the ammonia emission in the initial period of the treatments.

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