SUSTAINABLE CROPPING SYSTEMS FOR IRRIGATED SPECIALTY CROPS AND BIOFUELS
Location: Vegetable and Forage Crops Production Research
Title: Effects of temperature and soil type on ammonia volatilization from slow-release nitrogen fertilizers
Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 13, 2010
Publication Date: February 11, 2011
Citation: Fan, X.H., Li, Y.C., Alva, A.K. 2011. Effects of Temperature and Soil Type on Ammonia Volatilization from Slow-Release Nitrogen Fertilizers. Communications in Soil Science and Plant Analysis. 42:10, 1111-1122.
Interpretive Summary: Emission of ammonia from ammonium sources or ammonium forming nitrogen fertilizers applied to soil is termed as “Volatilization loss of nitrogen”. This form of emission contributes to air quality concerns and also decreases nitrogen uptake efficiency. In this study, ammonia emission has been monitored in sandy and loamy soils over 78 days period at 20 and 30o C. Four slow release nitrogen fertilizer sources were evaluated: two were liquid forms (Nitamin 30L, and RUAG 521 G30) while the remaining two were granular forms (Nitamin 42G, and Nitroform). The urea form of nitrogen was only 5% in Nitroform, while it was 36 to 82% in the remaining three sources used in this study. Ammonia volatilization was much greater from a sandy soil as compared to that from a loam soil. The rate of conversion of ammonium nitrogen into nitrate form (i.e. nitrification) was greater in the loamy soil as compared to that in the sandy soil. This explains, in part, lower cumulative ammonia volatilization from the former as compared to that from the latter soil. Ammonia volatilization was greater from the nitrogen products with greater percent of total nitrogen in urea form.
Ammonia (NH3) volatilization is the major pathway for mineral nitrogen (N) loss from N sources applied to soils. The information on NH3 volatilization from slow-release N fertilizers is limited. Ammonia volatilization, over a 78-d period, from four slow-release N fertilizers with different proportions of urea and urea polymer [Nitamin 30L (liquid) (L30), Nitamin RUAG 521G30 (liquid) (G30), Nitamin 42G (granular) (N42), and Nitroform (granular) (NF)] applied to a sandy loamy soil was evaluated. An increase in temperature from 20 to 30 °C increased cumulative NH3 volatilization loss in the sandy soil by 1.4-, 1.7-, and 1.8-fold for N42, L30, and G30, respectively. Increasing the proportion of urea in the slow-release fertilizer increased NH3 volatilization loss. At 30 °C, the cumulative NH3 volatilization over 78 d from a sandy soil accounted for 45.6%, 43.9%, 22.4%, and <1% of total N applied as N42, L30, G30, and NF, respectively. The corresponding losses in a loamy soil were 9.2%, 3.1%, and 1.7%. There was a significantly positive correlation between NH3 volatilization rate and concentration of NH4-N released from all fertilizers, except for NF (n = 132; r = 0.359, P = 0.017 for N42; r = 0.410, P = 0.006 for L30; and r = 0.377, P < 0.012 for G30). Lower cumulative NH3 volatilization from a loamy soil as compared to that from a sandy soil appeared to be related to rapid nitrification of NH4-N in the former soil than that in the latter soil. These results indicate the composition of slow-release fertilizer, soil temperature, and soil type are main factors to dominate NH3 volatilization from slow- release fertilizers.