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Regulation of nitrification of soil-applied urea by some heterocyclics

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Title Regulation of nitrification of soil-applied urea by some heterocyclics
 
Creator Sharma, J P
Singh, Teekam
Kumar, Rajesh
Taneja, H K
Tomar, S S
 
Description 11-17
The nitrogen use efficiency of ammonical fertilizers in soil, particularly in tropics, is only 30-40% of the applied dose. The
factors contributing to the low N-use efficiency include ammonia volatilization, nitrification, denitrification and nitrate leaching
etc. These processes also contribute to health and environmental hazards. Nitrification seems to be the centre point of the
problem leading to inefficient N-use, denitrification and nitrate leaching being just the consequences. Efforts are, therefore,
underway all over the world to retard and regulate the soil microbes driven nitrification phenomenon. Most of the well established
potential nitrification inhibitors are nitrogen containing heterocyclic compounds viz N-serve or nitrapyrin, 2-chloro-6(
trichloromethyl) pyridine, 2-ethynylpyridine, S-ethoxy-3-trichloro-methyl-l,2,4-thiadi'azole (etridiazole), 4-amino-l,2,4-triazole
(ATC), 3-methyl pyrazole-l-carboxamide (MPC), 2,4-diamino-Strichloromethyl triazine and 2-amino-4-chloro-6-methyl
pyrimidine etc. Compounds bearing thiocarbonyl moiety, owing to their tendency to form chelates with ammonia mono
oxygenase (AMO) enzyme generally associated with Nitrorosomonas europea, the primary inhibitor of nitrification phenomenon,
have also been reported to have potential nitrification inhibitory property. But none of the above chemicals have found favour
with the farmers/industrialists due to high application cost. Oxidation of ammonia by Nitrosomonas europea bacteria that initiates
the nitrification as a whole is a two-stage process that involves the initial oxidation of ammonia to hydroxylamine by the
membrane bound enzyme known ammonia mono oxygenase, which has remarkably broad substrate range that can account for
the inhibitory effects of many compounds on this enzyme. Therefore, in our endeavour to develop viable N-regulators for soilapplied
urea some simple heterocyclic molecules were synthesized and evaluated in the laboratory. A series of substituted iso
oxazoles, which was synthesized by condensation of appropriate unsaturated carbonyl compounds with hydroxyl ammonium
hydrochloride, has exhibited wide range of nitrification inhibitory activity. The laboratory incubation experiments were carried
out in a typic Haplustept. The compounds were screened at 10% of applied urea-N dose and incubated for a period of 28 days
at 28±2°C, maintaining moisture at 50% of the water holding capacity of the soil. Evaluated weekly over a period of four
weeks, most of the test compounds had been found to be mild inhibitors of nitrification. 5-phenyl iso oxazole and 3-methyl-5(
4'-methoxy phenyl) iso oxazole were found to be best among the series and were comparable to dicyandiamide the reference
nitrification regulator. During the first week of application, these chemicals showed 78.2 and 82.6% nitrification inhibition,
respectively as compared to 85.1 % by dicyandiamide. The effect however, was considerably reduced by third and fourth week.
The study indicated that the above compounds could be used as nitrification regulators for soil applied urea-N
 
Date 2009-02-19T04:52:17Z
2009-02-19T04:52:17Z
2007-06
 
Type Article
 
Identifier 0771-7706
http://hdl.handle.net/123456789/3186
 
Language en_US
 
Publisher CSIR
 
Source BVAAP Vol.15(1) [June 2007]