The objective of this experiment is to study the effect of different concentrations of urea-N on the amount of the available ammonium remained and that of nitrate formed so that to calculate the nitrification rates directly in the soil. Five concentrations of urea-N (0,75,150,225,300) ppm urea-N are used in a CRD factorial experiment with three replicates. Each treated soil is moistened to 90% of it’s field capacity and incubated at room temperature for forty days started during which the amount of nitrate formed was measured at a 10-day intervals water is added to maintain the moisture by weighing the plates every two days.
The following results are recorded:-
1-The results show that was ( 39.8%) of the added nitrogen for the soil taken from Karna, followed by Souq Al-Shiyokh (29.6%), and less than that is registered for the soils taken from Hay and Rafiaee (24.2% and 23.7%) respectively , which is then decreased in the following periods of incubation.
2-Generally the rates of nitrification in soil are proportional to the calcium carbonate and organic matter contents of the soil.