NITROGEN MINERALIZATION AND ENZYME ACTIVITIES IN SUBMERGED PADDY SOIL UNDER LONG TERM FERTILIZATION
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Date
1990
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY RAJENDRANAGAR, HYDERABAD.
Abstract
f\ field experiment was conducted during kharif,
1988 in the experimental plots of Long Term Fertilizer Experiment
operating since 1971 on a sandy clay loam soil (Tropaquept)
at Agricultural Research Institute, Rajendranagar
with rice ( Var. Tellaham~n), to study the effect of long
term use c·f fertilizers and manures on soil properties,
yield, upta k~ of N, P, K, nitrogen mineralization and enzyme
activitie!:O viz., dehydrogenase, .urease and phosphatase.
The fertilizer and manurial treatments comprised of 50%
NPK (T
1
), 100·~~ NPK (T..,), 150~~ NPK (T~), 100% NPK coupled
with hand weeding (T
4 t, 100% N PK .f' Zn (T
5
), 100% NP
(T
6
), 100~~ N (T
7
), 100% NPK + FYM (T
8
), 100%' NPK-S (T
9
1
ana a control without fertilization or manuring (T
10
J.
The pH, EC, available N, P, K and nitrogen mineralizahon
of the soil wPre studied in the samples collE>cted at harvest
of rice. The enzyme activity and organic carbon were
studied in the soil samples collected before puddling, 10
days after transplanting (DAT), 50 OAT and at harvest.
The plant s:~mples collected at harvest were used to study
the uptake of N, P and K.
Long tern) u!:.e of fertilizers and manure~ dicf
net have a ny significant infl~.tence on pH, EC and a.vallable
nitrogen cont<:>nt of the soil. The organic carbon content
was the hlcaho:st in the treatment receiving 100% NPK in
conjunction with E"YM ( T
8
) at all stages of sampling. The
available P content was also highest in this treatment.
Besides thes , the grain and straw yields and uptake
:·: . 1
of nutrients viz., N, P, K were highest in T8 indicating
the beneficial effects of application of organic matter along
with 100% NPK through chemical fertilizers. With increase
in level of application from 50 to 100 and 150% NPK, increase
in yield and uptake of N, P and K were noticed.
Nitrogen mineralization studies. revealed that
the ammoniacal, nitrate and nitrite nitro.,;ren contents were
highest in the treatment rece1v1ng FYM at 7 and 14 days
of incubation. There was no appreciable increase in ammoniacal
nitrogen content after 7 days of incubation however,
an increase in nitrate nitrogen was evident between 7
and 14 days of incubation. Total mineral N content increased
with increase in period of incubation from 7 to 14 days.
Significant positive correlations of organic carbon with
ammoniacal, nitrate and nitrite nitrogen contents were
observed.
The dehydrogenase, urease and phosphatase
activities were highest in the treatment receiving 100%
NPK in conjunction with FYM (T ) and these activities
correlated significantly with organ~c carbon at all stages
of sampling. An increase in urease and phosphatase activity
with increase in level of fertilizer from 50 to 100 and
150% NPK was observed. The mean dehydrogenase activity
was maximum before puddling and minimum at harvest
while reverse was the case with urease activity. The mean
phosphatase activity was maximum be fore puddling and
it was lower during crop growth periods i.e. 10 OAT and
50 DAT. The results have confirmed the profound influence
of FYM application along with chemical fertilizers on the
availability of nutrients and soil enzymatic activities.
Conjunctive use of FYM along with optimal levels of NPK
is, therefore, ad vacated as a better agronomic practice
under intensive cropping for maintaining soil fertility
and higher productivity of rice under submerged conditions
in a light textured sandy clay loam soil.
Description
Keywords
NITROGEN, MINERALIZATION, ENZYME, ACTIVITIES, SUBMERGED, PADDY,