Influence of nitrification inhibitor on hydrolyzed products of urea

An incubation study on urea hydrolysis revealed that the
conversion of ammonia to nitrate is much faster in Munnar
soils than in the soils of other regions. The higher rate of
nitrification in Munnar soil is an unwanted phenomenon
as far as the tea crop is concerned. Tea soils are known
to prefer ammoniacal nitrogen than nitrate nitrogen.
Most of the studies indicate that nitrification inhibitors,
when supplied to soil in conjunction with N-fertilisers or
animal wastes, reduce nitrate leaching and nitrous oxide
emission, leading to increased plant growth. However,
this always is not the case. There are reports on variable
effects of nitrification inhibitors on N loss and plant yields.
Hence, effectiveness of nitrification inhibitor should be
tested locally. The present trial dicyandiamide (DCD),
a nitrification inhibitor was used to control nitrification
process of soils collected from Munnar. To determine
the effect of nitrification inhibitor on urea hydrolysis,
two separate test portions were prepared with 10 g of soil.
To the first set of soils, 0.1 g of urea and 0.005 g of
dicyandiamide were added and to the second set of soils,
0.1 g of urea was added all the samples are incubated
simultaneously at 25°C. The amount of ammoniacal
nitrogen and nitrate nitrogen formed were estimated
at 5 days interval.

On 0th day, even though fertilisers were not applied,
the nitrate nitrogen concentration was four times
higher than that of ammonium nitrogen (data available
on request). Application of urea had brought down the
concentration of NO3--N by about 50 % on the third day,
while ammonium nitrogen content increased drastically.
When DCD was not added along with urea, there was a
sharp fall in the content of ammonium nitrogen in course
of the time, while nitrate nitrogen content increased.
Application of DCD along with urea prevented the
formation of nitrate ions, which resulted in the
accumulation of ammonium ions. Therefore,
it is concluded that the application of DCD blended
urea could result in higher agronomic efficiency of
urea nitrogen in the tea soils of Munnar.