To study the effect of the compound AM (2 amino-4 chloro-6-methyl
pyrimidine) as an inhibitor of the nitrification process, a pot experiment was conducted
in a greenhouse using a clay loam collected from Agric. Res. Center Farm at Giza.
The added AM levels were 3, 6, 9 and 12% of fertilizer added to the soil as
ammonium sulfate or urea. Cotton plants c.v.Giza79 up to 120 day age was used a
test plants. The obtained data could be summarized in the followings:- Addition of AM in rates of 9 or 12% of the added fertilizer resulted in
depression of plant growth and uptake. It may be due to an inhibition effect of nitrifying
bacteria and also due to an adverse effect on root system. The level of 3% was found
to be best treatment followed by 6% where nitrogen efficiency ratio (NER) increased
by either ammonium sulfate or urea especially with 3% level of AM application. Nitrification rate increased by time in the most treatments as affected with
AM limitation of nitrogen release from the both used fertilizers. Generally, it could be
recommended with application of AM in a rate corresponding of 3% of added
ammonical or amide fertilizers to control the release of their nitrogen and thus
increased NER.