Bahiagrass response and N loss from selected N fertilizer sources

The increasing cost of commercial fertilizers and environmental problems associated with improper fertilization management have prompted the need to re-examine commercial N sources that can effectively supply N to pastures while minimizing N losses. This 3-year study evaluated the effects of selected N sources on bahiagrass (Paspalum notatum Flugge) responses, soil properties and N losses. Treatments consisted of a factorial combination of 6 N sources [(i) ammonium nitrate (AN), (ii) ammonium sulphate (AS), (iii) urea (U), (iv) urea treated with Agrotain (U + Agrotain), (v) SuperU and (vi) ammonium sulphate nitrate] and 3 N levels (0, 60 or 120 kg ha(-1) year(-1)), replicated three times. Bahia-grass dry-matter yield (DMY), crude protein (CP) concentration, N uptake and recovery were not affected by N source, with the exception of AN that resulted in reduced DMY in 2010 compared with the other sources. Bahiagrass DMY, CP concentration, N uptake and recovery increased linearly as N levels increased. Nitrogen fertilization showed no effect on soil pH or soil N accumulation. Soil pore-water N concentrations from treatments fertilized with N were similar to the control plots indicating no threat to the environment. At the N levels evaluated in this study, selection of N source should be based on the fertilizer cost.