I'm going to do an experiment in lab in which I examine the effect of nitrapyrin ( it is a nitrification inhibitor ) on more ammonia-oxidizers bacteria. There are several experiments proved that nitrapyrin inhibits Nitrosomonas nitrification bacteria which are responsible for convert the ammonium to nitrite. Howewer, according to the heterogenity of soils, I guess there is a huge heterogenity of population bacteria. If there are other similar function bacteria in soil which are also responsible this mechanism (converting ammonia to nitrite), the impact of nitrapyrin will be not effective. If Nitrosomonas are inhibited, other bacteria may can multiply.