Ammonia volatilization from urea as influenced by soil temperature, soil water content, and nitrification and hydrolysis inhibitors
1990
Clay, D.E. | Malzer, G.L. | Anderson, J.L.
Residue cover influences temperature and water gradients in the soil profile. Changes in the physical environment of the soil influence NH3 volatilization from urea-containing fertilizers. Field and laboratory experiments were conducted to investigate the influence of residue-cover-induced changes in soil water and temperature on NH3 volatilization as impacted by urea treatment with a nitrification and urease inhibitor. Fertilizer treatments were urea, urea plus dicyandiamide (DCD), urea plus N-(n-butyl)thiophosphoric triamide (NBPT), and urea plus NBPT and DCD. Following fertilizer application, the soil was either left bare or covered with corn (Zea mays L.) residue. Every 3 h over a 4-d period, water potential, soil temperature, CO2 production, and NH3 volatilization were measured. The influence of fertilizer treatments on soil pH was determined in a laboratory incubation experiment conducted over 8 d under controlled environmental conditions. Treatments were similar to the field experiment, with NH3 volatilization, pH, and CO2 production measured daily. The NH3-volatilization rate in the field was highest 2 d after urea application at a time that corresponded with daily maximum soil temperature and decreasing soil water content. Residue cover reduced NH3 volatilization. Volatilization of NH3 as a result of urea application was not increased when urea was treated with DCD. Ammonia volatilization as a result of urea treatment with NBPT was reduced by 100 times over untreated urea. During an incubation experiment, soil pH increased from 6.5 to 7.2 in the urea-NBPT, and from 6.5 to 9.0 in the urea and urea-DCD treatments. Associated with the pH increase in the urea-NBPT treatment was a reduction in CO2 production when compared with the untreated soil.
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