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Effects of Soil Temperature and Moisture Content on Ammonia Volatilization from Urea-Treated Pasture and Tillage Soils
S. J. McGarry, P. O'Toole and M. A. Morgan
Irish Journal of Agricultural Research
Vol. 26, No. 2/3 (1987), pp. 173-182
Published by: TEAGASC-Agriculture and Food Development Authority
Stable URL: http://www.jstor.org/stable/25556191
Page Count: 10
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The effects of temperature (8°, 13° and 18°C), soil moisture content (SMC) (35, 60 and 85% of field capacity (FC)) and simulated rainfall (35/85% FC) on ammonia volatilization from urea-treated pasture and tillage counterparts of Borris, Clonroche, Fontstown and Screen soils were investigated under controlled laboratory conditions. Maximum ammonia loss rates did not develop until 3-6 days after urea application at 8°C in all soils, presumably due to delayed urea hydrolysis, and at all temperatures in Clonroche and Fontstown soils apparently because of their low urease activities and high cation exchange capacities (CECs). Otherwise, maximum loss rates occurred within 3 days at 13°C or at 18°C. Simulated rainfall reduced NH₃ volatilization in all soil-temperature treatments. Total ammonia losses after 16 days ranged from 0.05 to 32.2% of the applied urea-N (1000 mg N kg⁻¹ soil). The [soil × temperature × SMC] interaction was highly significant (p <0.001): losses increased with increasing temperature and decreasing soil moisture content except at 85% FC when similar losses occurred at 13°C and 18°C in each soil, except Screen. The results suggest that serious ammonia volatilization from fertilizer urea can occur not only under warm-dry conditions, but even under cool-wet conditions. The influence of soil physical and chemical properties on ammonia volatilization, however, was much larger than the temperature and SMC effects. Ammonia volatilization in each tillage soil, except Fontstown, greatly exceeded that in its pasture counterpart, especially at 18°C/35% FC. The findings suggest that recently reseeded, coarse-textured tillage soils are more prone to ammonia loss through volatilization from urea fertilizer than their counterparts under continuous pasture, especially under warm, dry conditions.
Irish Journal of Agricultural Research © 1987 TEAGASC-Agriculture and Food Development Authority