THE POTENTIAL FOR VOLATILIZATION LOSSES OF APPLIED NITROGEN FERTILIZERS FROM NORTHERN IDAHO SOILS

Up to 70% applied ammonium-based nitrogen (N) fertilizers can be lost by volatilization in agricultural soils. The purpose of this experiment was to determine the effects of fertilizer treatment, water potential, and time on volatilization losses in three northern Idaho soils under laboratory conditions maintained at 25-degrees-C. A completely randomized block factorial design with repeated measures (3 soils x 4 fertilizer treatments x 2 soil water potentials x 3 replications-measured at 0, 2, 4, 8, and 16 d) was utilized in this study. The four fertilizer treatments consisted of 200 kg N/ha applied as: (1) surface-applied ammonium nitrate (AN), (2) surface applied ammonium sulfate (AS), (3) surface applied urea (Ysur), and (4) incorporated urea (Uinc). Data were analyzed by SAS-GLM and Omega squared (omega2) values were used to identify the impact of each main effect and interaction. A 4-factor interaction of fertilizer treatment (NM x soil (SL) K water potential (WP) x time of incubation (IT), four-3 factor interactions, six-2 factor interactions and four main effects were found to be significant in this study. Due to the number of significant sources of variation, omega2 values were used to assess their relative importance. The soil x fertilizer treatment interaction accounted for 27.3% of the variation in this study. Nitrogen loss after 16 d of incubation from the Usur treatment was 37.8% in the Devoignes silt loam, 18.7% in the Santa silt loam, 4.9% in the Schnoorson silt loam. Volatilization of N from the Uinc and AS treatments was greater in the Devoignes silt loam than the Santa and Schnoorson soils. Conversely, differences in volatilization losses from AN were not observed among the three soils. Fertilizer treatment was the second most important factor accounting for 21.4% of the variability. Losses of 20.5, 2.6, 1.9, and 1.3% were observed for the Usur, Uinc, AS, and AN treatments, respectively. This study demonstrated that: (1) volatilization losses may be significant for surface applications.of urea on some Idaho soils; however, incorporation of urea will reduce this hazard, and (2) volatilization losses are minimal when AN and AS are the N fertilizer sources.