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Abstract
The present work aimed to compare the effectiveness of nitrapyrin (NP),
hiourea (TU), and dicyandiamide (DCD) as nitrification inhibitors (NIs) when
were applied to a sandy soil treated with ammonium sulphate and incubated in the
laboratory at 28 ”C for 40 days. Two greenhouse column experiments were also
carried out to evaluate the efficacy of the three inhibitors in increasing the
efficiency of ammoniacal fertilizers in a sandy soil cultivated with wheat and
maize. The obtained results can be summarized as follows:
In the laboratory experiment, the effectiveness of the three Nls, as indicated
by the percent inhibition of nitrification (PIN),
increasing their application rates. The highest PIN values were recorded in
the soil treated with 100 mg ammonium sulphate (AS)-N + 2 mg NP kg”
soil where they were 92.8 and 18.5% after 7 and 40 days of incubation,
respectively. At the end of incubation period (40 days), the effectiveness of
the three Nls could be arranged on the basis of the average PIN values as
follows: NP > DCD > TU. Concerning soil microorganisms, the use ofNls
decreased the highest average counts of total
compared to the control. The highest counts of ammonia oxidizing bacteria
and nitrite oxidizing bacteria were recorded in the soil treated with AS alone
and were found to be decreased with increasing the inhibitor rate at the end
of incubation period.
2- In the wheat experiment, the highest grain and straw yields were obtained in
the soil treated with 100 mg urea-N kg-1soil plus 20% DCD where the
increases over solo urea were 14.7 and 9.32%, respectively.
3- In the maize experiment, the highest dry matter weight of the plant was
recorded when the soil was treated with 150 mg AS-N kg’ soil plus 20%
DCD.