PERFORMANCE OF AEROBIC RICE (Oryza sativa L.) UNDER DRIP IRRIGATION WITH DIFFERENT LEVELS OF NITROGEN
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Date
2024-03-06
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Acharya N G Ranga Agricultural University
Abstract
The present investigation entitled “Performance of aerobic rice (Oryza
sativa L.) under drip irrigation with different levels of nitrogen” was carried
out during two consecutive rabi seasons of 2019-20 and 2020-21 on sandy clay
loam soils of wetland farm of S.V. Agricultural College, Tirupati of Acharya
N.G. Ranga Agricultural University, Andhra Pradesh.
The experiment was laid out in split-plot design with three replications.
The treatments consisted of four main plots (Irrigation regimes) viz., I1 (Drip
irrigation at 1.25 Epan), I2 (Drip irrigation at 1.5 Epan), I3 (Drip irrigation at 1.75
Epan) and I4 (Drip irrigation at 2.0 Epan) and four sub plots (Nitrogen levels)
viz., N1 (75 % RDN - 90 kg N ha-1), N2 (100 % RDN - 120 kg N ha-1), N3 (125 %
RDN - 150 kg N ha-1) and N4 (150 % RDN – 180 kg N ha-1).
Irrigation regimes and nitrogen levels significantly influenced the growth
parameters, yield attributes (except panicle length with irrigation regimes), yield,
nutrient uptake, nitrogen use efficiency, water use efficiency, economics and
post-harvest nutrient status of the soil. However, harvest index (HI) was not
significantly influenced by irrigation regimes and nitrogen levels, but relative
water content (RWC) of leaf was influenced only by irrigation regimes.
Scheduling drip irrigation at 2.0 Epan (I4) resulted in higher values of
growth parameters (plant height, number of tillers m-2, LAI, LAD, dry matter
accumulation, root dry weight), SPAD chlorophyll meter reading (SCMR),
relative water content (RWC) of leaf, yield attributes (number of panicles m-2
,
panicle weight, total number of grains panicle-1, number of filled grains panicle-1
and test weight), grain and straw yields, NPK uptake and nitrogen use efficiency,
which was however comparable with drip irrigation at 1.75 Epan (I3). The lower
values of all the above parameters were observed with scheduling drip irrigation
at 1.25 Epan (I1). However, higher number of chaffy grains panicle-1, chaffy
grains percentage, post-harvest soil available NPK were recorded with
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scheduling drip irrigation at 1.25 Epan (I1) and lower values of these parameters
were observed with drip irrigation at 2.0 Epan (I4) which was however
comparable with 1.75 Epan (I3).
Among the different nitrogen levels, 180 kg N ha-1 (N4) resulted in higher
growth parameters (plant height, number of tillers m-2, LAI, LAD, dry matter
accumulation and root dry weight), SPAD chlorophyll meter reading (SCMR),
yield attributes (number of panicles m-2, panicle weight, total number of grains
panicle-1, number of filled grains panicle-1 and test weight), grain and straw
yields, nitrogen uptake and post-harvest soil available N, which was significantly
superior to remaining lower nitrogen doses, except in case of some growth
parameters (plant height during both the years, tillers m-2 during the first year,
LAI, LAD and root dry weight during both the years of study and in the pooled
mean) at 30 DAS, SPAD at 30 DAS during both the years of study, tillers m-2 at
90 DAS during the first year of study, yield attributes (excluding panicle weight),
and nitrogen uptake by plant at 30 DAS during the second year, wherein it was
on par with 150 kg N ha-1 (N3). The lower values of all the above parameters
were observed with 90 kg N ha-1 (N1). However, number of chaffy grains, chaffy
grains percentage (%), nitrogen use efficiency, post-harvest soil available P2O5
and K2O were higher with 90 kg N ha-1 (N1), and the lower values of these
parameters were recorded with 180 kg N ha-1 (N4), which was however
comparable with 150 kg N ha-1 (N3) in case of post-harvest soil available P2O5
during the first year of study and in the pooled mean and in case of post-harvest
soil available K2O during both the years of study and in the pooled mean, and
chaffy grains percentage (%) during the first year of study.
With respect to interaction effect, scheduling drip irrigation at 2.0 Epan
along with 180 kg N ha-1 (I4N4) resulted in higher values of growth parameters,
yield attributes (number of panicles m-2, panicle weight, total number of grains
panicle-1 in the pooled mean and number of filled grains panicle-1), grain and
straw yields, and nutrient uptake which was however statistically at par with drip
irrigation at 1.75 Epan along with 180 kg N ha-1 (I3N4) except in case of growth
parameters at 30 DAS, plant height at 60 DAS during both the years and in the
pooled mean and at harvest in the pooled mean, tillers m-2 at 60 DAS during the
second year of study and at 90 DAS and harvest in the pooled mean, LAD at 60-
90 DAS interval in the pooled mean and at 90 DAS-harvest interval during the
second year of study and in the pooled mean and root dry weight at 60 DAS
during the second year of study, wherein significant variation was observed. In
case of nutrient uptake, significant difference was observed between I4N4 and
I3N4 with respect to nitrogen uptake at 60 DAS during both the years of study
and in the pooled mean, total N, P and K uptake at harvest during both the years
of study and in the pooled mean, P uptake by straw at harvest during the first
year of study and in the pooled mean, and K uptake by straw at harvest during
both the years of study and in the pooled mean. Drip irrigation at 1.25 Epan
along with 90 kg N ha-1 (I1N1) resulted in the lower values of above parameters.
Weed density in aerobic rice was significantly influenced by nitrogen
levels at different stages, but influenced by irrigation levels only at 60 DAS
during both the years of study and in the pooled mean, and at 90 DAS during the
second year of study. Higher weed density was observed with drip irrigation at
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2.0 Epan (I4) which was however comparable with 1.75 Epan (I3) and 1.5 Epan
(I2), and the lower weed density was recorded with 1.25 Epan (I1). Among the
nitrogen levels, significantly higher weed density was observed with 180 kg N
ha-1 (N4) over other nitrogen doses except at 60 DAS during the first year of
study, wherein it was comparable with 150 kg N ha-1 (N3). Whereas at 90 DAS, it
was comparable with both 150 (N3) and 120 kg N ha-1 (N2).
With respect to interaction effect of irrigation regimes and nitrogen levels
on weed density at 60 DAS during both the years of study and in the pooled
mean, higher weed density was observed with drip irrigation at 2.0 Epan along
with 180 kg N ha-1 (I4N4), which was however comparable with 1.75 Epan along
with 180 kg N ha-1 (I3N4), 2.0 Epan along with 150 kg N ha-1 (I4N3) and 1.5 Epan
along with 180 kg N ha-1 (I2N4). The lowest weed density was recorded with drip
irrigation at 1.25 Epan along with 90 kg N ha-1 (I1N1).
Weed dry weight was considerably influenced by nitrogen levels at
different growth stages, but by irrigation regimes only at 60 DAS during the first
year of study and in the pooled mean. Among the different irrigation regimes,
higher weed dry weight was recorded with drip irrigation at 1.5 Epan (I2)
followed by 1.75 Epan (I3) and 2.0 Epan (I4), which were comparable. The
lowest weed dry weight was observed with 1.25 Epan (I1) irrigation regime. At
different stages, higher weed dry weight was observed with 180 kg N ha-1 (N4)
and the lowest value with 90 kg N ha-1 (N1). But at 60 and 90 DAS, application
of 180 kg N ha-1 (N4) was comparable with 150 (N3) and 120 kg N ha-1 (N2).
Days to 50 % flowering was significantly influenced by irrigation regimes
only in the pooled mean. Significantly higher number of days to 50 %
flowering was observed with drip irrigation at 1.25 Epan (I1), whereas, both 2.0
Epan (I4) and 1.75 Epan (I3) irrigation regimes recorded lower number of days to
attain 50 % flowering. Among the different nitrogen levels, 90 kg N ha-1 (N1)
took more number of days to flower, whereas earlier flowering was noticed with
180 kg N ha-1 (N4), which was however comparable with 150 kg N ha-1 (N3) and
120 kg N ha-1 (N2) during the second year of study, and with 150 kg N ha-1 (N3)
in the pooled mean. Number of days to maturity did not differ significantly due
to different irrigation regimes and nitrogen levels.
Water requirement of aerobic rice varied with different drip irrigation
schedules. Higher water requirement was registered with the drip irrigation
schedule of 2.0 Epan (I4), while the lower water requirement was with drip
irrigation at 1.25 Epan (I1). Water use efficiency was found to be higher with drip
irrigation scheduled at 1.25 Epan (I1) which was however comparable with drip
irrigation at 1.5 Epan (I2). The lower value of water use efficiency was recorded
with drip irrigation scheduled at 2.0 Epan (I4). Among the nitrogen levels, 180 kg
N ha-1 (N4) recorded higher value of WUE, which was however at par with 150
kg N ha-1 (N3) during the first year of study and significantly different during the
second year and in the pooled mean. The lower value of water use efficiency was
recorded with 90 kg N ha-1 (N1). Among the interactions, higher water use
efficiency was recorded with the drip irrigation schedule of 1.5 Epan along with
180 kg N ha-1 (I2N4) and the lower value was observed with drip irrigation at 2.0
Epan along with 90 kg N ha-1 (I4N1).
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The higher gross returns were realized with drip irrigation at 2.0 Epan (I4)
which was however comparable with drip irrigation at 1.75 Epan (I3). The higher
net returns were recorded with drip irrigation at 2.0 Epan (I4) in the first year of
study, but with 1.75 Epan (I3) during the second year and in the pooled mean.
Net returns in 2.0 Epan (I4), 1.75 Epan (I3) and 1.5 Epan (I2) irrigation regimes
were comparable. Whereas, higher value of B : C ratio was recorded with the
drip irrigation schedule of 1.75 Epan (I3) which was however comparable with
2.0 Epan (I4) and 1.5 Epan (I2). The lower values of all the economic parameters
were observed with the drip irrigation schedule of 1.25 Epan (I1).
Among the different nitrogen levels, 180 kg N ha-1 (N4) resulted in higher
gross returns, net returns and B : C ratio. However, it was comparable with 150
kg N ha-1 (N3), during the first year of study in case of net returns, and during the
first year and in the pooled mean in case of B : C ratio. The lower monetary
returns were observed with 90 kg N ha-1 (N1). Among the interaction
combinations, drip irrigation schedule of 2.0 Epan along with 180 kg N ha-1
(I4N4) resulted in higher gross returns, net returns and B : C ratio, whereas the
lower values were recorded with 1.25 Epan along with 90 kg N ha-1 (I1N1).
Based on the outcome of the investigation, it could be inferred that drip
irrigation at 2.0 Epan (I4) resulted in higher growth and yield parameters, yield
and gross returns. However, drip irrigation at 1.75 Epan (I3) can be practiced
considering higher B : C ratio and water use efficiency. Application of 180 kg N
ha-1 (N4) can be practiced as it results in superior growth and yield attributes,
yield and water use efficiency along with higher monetary returns. Combination
of scheduling drip irrigation at 1.75 Epan along with 180 kg N ha-1 (I3N4) can be
recommended over 2.0 Epan along with 180 kg N ha-1 (I4N4) considering their
parity in yield and monetary returns and higher water use efficiency in case of
I3N4. However, under water scarce conditions, combination of 1.5 Epan along
with 180 kg N ha-1 (I2N4) may be practiced for getting higher yield and monetary
returns