Soil and fertilizer nitrogen transformations under alternate flooding and drying moisture regimes K LSahrawatauthorA study of changes in NH4 + and NO3 ––N in Maahas clay amended with (NH4)2SO4 and subjected to 4 water regimes in the presence and absence of the nitrification inhibitor N-Serve (Nitrapyrin) showed that the mineral N was well conserved in the continoous regimes of 50% and 200% (soil weight basis) but suffered heavy losses due to nitrification-denitrification under alternate drying and flooding. N-Serve was effective in minimizing these losses. Another incubation study with 3 soils showed that after 10 cycles of flooding and drying (either at 60°C or 25°C), the ammonification of soil N was enhanced. Nitrification of soil as well as fertilizer NH4 + was completely inhibited upto 4 weeks by the treatments involving drying at high temperature. Flooding and air drying at 25°C, on the other hand, enhanced ammonification of soil N but retarded nitrification. These treatments, however, enhanced both ammonification and nitrification of the applied NH4 + fertilizer N. Under flooded conditions rate of NH4 + production was faster in soils that were dried at 60°C or 25°C and then flooded as compared to air dried soils. It is concluded that N losses by nitrification-denitrification and related N transformations may be considerably altered by alternating moisture regimes. Flooding and drying treatments seem to retard nitrification of soil N but conserve that of fertilizer NH4 + applied after these treatments. Soil ScienceFertilizer Applications1980KluwerArticle