NITRIFICATION OF AMMONIATED PEAT AND AMMONIUM-SULFATE IN MINERAL SOILS

Our objective was to model nitrification kinetics of ammoniated peat ( AP), ammonium sulfate (AS) and peat supplemented with ammonium sulfate and hydrated lime (PAS), in four different surface soils. The peat so urce was an acid sapric peat of high ammonia retention capacity. Nitri fication rate was influenced significantly by soil type, N carrier and N application rate. Nitrification of AP showed a lag lasting longer i n coarse-textured soils than in fine-textured soils, whatever N rate w as applied. No lag was observed in AS- and PAS-treated soils. Initial nitrification rate was lowest in AP-treated soils at low N application rates but increased with AP application rate. High application rates of AS and PAS reduced NO3- production considerably. N loss was higher for AS and PAS than for AP treatments. AP and PAS treatments significa ntly increased initial soil pH values. AP tended to decrease soil pH s lightly at the end of the incubation. AP appeared to be an initially s low-release, thereafter a sustained-release N fertilizer.