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Assessment of post-emergence weed management in direct-seeded rice
V. Pratap Singh*, S.P. Singh, Neema Bisht, A. Kumar, Kavita Satyawali and Arunima Paliwal
Department of Agronomy, College of Agriculture, Govind Ballabh Pant University of Agriculture &
Technology Pantnagar, U.S. Nagar, Uttarakhand 263 145
Received: 4 July 2017; Revised: 19 August 2017
ABSTRACT
The present study was carried out at G.B. Pant University of Agriculture and Technology, Pantnagar
during rainy seasons 2014 and 2015 to determine the efficacy of post-emergence application of
cyhalofop-butyl in managing weeds in direct-seeded rice. Eight treatments, viz. cyhalofop-butyl 10% EC
at 65, 75, 80 and 90 g/ha, cyhalofop-butyl 10% EC at 75 and 80 g/ha, hand weeding twice at 20 and 40 DAS
and untreated control were laid out in a randomized block design with three replications. Application of
cyhalofop-butyl controlled grassy weeds better than the non-grassy weeds and recorded maximum
weed control efficiency, higher yield attributes and yield. Application of cyhalofop-butyl in rice did not
show any phytotoxic effect on succeeding wheat.
Key words: Cyhalofop-butyl, Herbicide, Herbicide efficiency index, Weed control efficiency, Yield
Rice (Oryza sativa) is a major cereal crop and
staple food for more than half of the world’s
population. About 90% of the world’s rice is
produced and consumed in Asia (FAO 2014). The
world’s total rice area is 168 Mha and production is
about 722 M tons with the productivity of 4.29 t/ha
(FAOSTAT 2012). Puddling for transplanted rice
cause to dispersion of soil particles and consequent
compaction of the soil and is labour intensive
(Chauhanet al. 2012). The direct-seeded rice (DSR)
cultivation, which does not need puddling and
transplanting was found as feasible alternative to save
water and labour (Ghosh et al. 2016). DSR is a cost
effective rice establishment method where dry seed is
drilled into the non-puddled soil. This provides
opportunities of saving irrigation water by 12-35%,
labor up to 60% and provides higher net returns (US$
30-50/ha) with similar or slightly lower yield of rice
(Kumar and Ladha 2011). Despite multiple benefits of
dry DSR, weed control remains one of the major
challenges for its success in South Asia (Kumar and
Ladha 2011, Rao et al. 2007, Singh et al. 2008).
Since the concept of aerobic rice is new (Belder et al.
2005) growing rice under aerobic conditions on
raised beds or flat land would require suitable,
effective and economic weed-control methods. Both
pre-emergence and post-emergence herbicides can
be used in aerobic rice fields and they are effective, if
properly used (De Datta and Baltazar 1996, Singh et
al. 2006). In spite of use of different chemicals as
pre-emergence and post-emergence, certain weeds
like Leptochloa chinensis and other grassy weeds are
still not controlled. Hence, the present study was
undertaken to determine the efficacy of cyhalofop-
butyl as post-emergence application against grassy
weeds in direct-seeded rice.
MATERIALS AND METHODS
The field experiment was conducted at
GBPUA&T, Pantagar (290N latitude, 27.30E longitude
and at an altitude of 243.8 m above the mean sea
level) during the rainy season of 2014 and 2015. The
climate of Pantnagar is very hot in summers and cold
in winters. The hottest months are May and June,
when the maximum temperature reaches 400C,
whereas during December and January, the coldest
month of the year, the minimum temperature often
remains below 100C and may reach to 10C. The
average rainfall is 1450 mm, 80% of which is
received through the monsoon from June to
September.
The experiment was laid out in a randomized
block design with three replications. Eight treatment
combinations were made up with different
herbicides, hand weeding and weedy check as
follows: Cyhalofop-butyl 10% EC at 65 g/ha,
cyhalofop-butyl 10% EC at 75 g/ha, cyhalofop-butyl
10% EC at 80 g/ha, cyhalofop-butyl 10% EC at 90 g/
ha, cyhalofop-butyl 10% EC (standard check) at 75
g/ha, cyhalofop-butyl 10% EC (std. check) at 80 g/
ha, two hand weeding (20 and 40 days after sowing;
*Corresponding author: vpratapsingh@rediffmail.com
Indian Journal of Weed Science 49(3): 211–215, 2017
DOI: 10.5958/0974-8164.2017.00056.9
212
DAS) and weedy check. Herbicides were applied
using a power operated knapsack sprayer fitted with
a flat fan nozzle and water as a carrier at 500 liter/ha.
In the weedy check, no weeding was done. For
phytotoxicity study, cyhalofop-butyl 10% EC (std.
check) was applied at 160 g/ha in direct-seeded rice.
Rice (‘Sarjoo 52’) was seeded manually in line on 13th
June, 2014 and 11th June, 2015 using seed rate of 50
kg/ha. Row to row spacing was 20 cm with
continuous rice plants in a row. Thinning was done
manually at 15 DAS to maintain plant population.
Irrigation was applied in the field as per requirement.
The soil was loamy, medium in organic matter
(0.67%), available nitrogen (210 kg/ha), phosphorus
(17.5 kg/ha) and potassium (181.2 kg/ha) with pH
7.5. Half of nitrogen, full dose of phosphorous and
potash were applied as basal and remaining half of
nitrogen was applied in two split doses first at active
tillering and second at panicle initiation stage in all
treatments. Observations were taken on density and
biomass of weeds, weed control efficiency (WCE),
herbicide efficiency index (HEI) and weed
persistence index at 45 DAS by placing a quadrate of
0.25 m2 at four randomly selected places. Removed
weed flora was oven dried at 700C for 72 hours. Crop
was harvested on October 27, 2014 and October 25,
2015 and left in the field for 5-7 days for sun drying.
The number of panicles/m2, grains/panicle, 1000
grain weight, grain yield, straw yield and grain straw
ratio was recorded. Data were analyzed by using
standard statistical techniques (STPR package).
Phytotoxic symptoms were recorded in direct-seeded
rice on 3, 7, 14, 21 and 28 days after herbicide
application at a dose of 80 and 160 g/ha of cyhalofop-
butyl by comparing it with weedy check. Carry over
effect of applied herbicides also observed on
succeeding wheat crop.
RESULTS AND DISCUSSION
Relative weed density
At 45 days after herbicide application (DAA) the
experimental area of direct-seeded rice crop was
infested with different grassy and non-grassy weeds
during both the years of experimentation. Among
grassy weeds Echinochloa colona, E. crus-galli and
Leptochloa chinensis were dominant and among non-
grassy weeds Alternanthera sesillis, Caesulia
axillaris, Cyperus iria and Cyperus rotundus were
major weeds. Echinochloa colona, E. crus-galli, L.
chinensis and non-grassy weeds accounted 7.7, 7.7,
9.5 and 75.1% during 2014 and 4.1, 7.6, 4.7 and
83.6% relative weed density during 2015,
respectively in weedy check plot (Table 1).
Density and dry biomass of weeds
During 2014, the minimum density and biomass
of E. colona and E. crus-galli was recorded with the
application of cyhalofop-butyl at 90 g/ha, which was
comparable with its lower dose applied at 80 (both
sponsor sample and std. check) and 75 g/ha while
during 2015, all the herbicidal treatments except
cyhalofop-butyl at 65 g/ha completely eliminated E.
colona whereas the density as well as dry biomass of
E. crus-galli was found minimum with the
application of cyhalofop-butyl at 90 g/ha, which was
at par with its lower dose applied at 75 and 80 g/ha.
All the doses of cyhalofop-butyl except its lower dose
at 65 g/ha recorded complete elimination of L.
chinensis during both the years of experimentation
while during 2015, std. check of cyhalofop-butyl at
75 g/ha also not achieved complete control over its
density and dry biomass. None of the herbicidal
treatments was found effective in controlling the
density and dry biomass of non-grassy weeds over
the weedy check treatment. Minimum density of
grassy weeds is due to selectivity of herbicide. This
herbicide was more effective against the grassy
weeds as compared to broad leaf weeds and sedges
and lowest dry biomass of grassy weeds might be
due to low density of grasses as compared to non-
grassy weeds.
Total weed dry biomass, WCE, HEI and WPI
Minimum total dry biomass of weeds was
recorded with the post-emergence application of
cyhalofop-butyl at 90 g/ha which was significantly
superior to rest of the treatments except twice hand
weeding at 20 and 40 DAS during 2014 while during
2015, cyhalofop-butyl applied at 90 g/ha as post-
emergence was comparable with rest of the weed
management practices except with the application of
cyhalofop-butyl at 65 g/ha. Among different
herbicidal treatments, application of cyhalofop-butyl
at 90 g/ha as post-emergence recorded maximum
weed control efficiency (WCE) of 70.2 and 74.0%
during 2014 and 2015, respectively (Table 3).
Maximum herbicide efficiency index (HEI) was
attained (21.7 and 13.9%) with the application of
cyhalofop at 90 g/ha during 2014 and 2015,
respectively, which was followed by its lower dose
applied at 80 g/ha. During 2014, application of
cyhalofop-butyl at 90 g/ha obtained minimum weed
persistence index (WPI) (0.42%) that was followed
by cyhalofop-butyl (std. check) at 80 g/ha, whereas,
during 2015, cyhalofop-butyl (std. check) at 75 g/ha
recorded lowest weed persistence index (0.32%),
which was followed by cyhalofop-butyl at 90 g/ha
Assessment of post-emergence weed management in direct-seeded rice
213
(Figure 1).Thus, with the increase in herbicide
efficiency index, weed persistence index is
decreases. As compared to 2015, in 2014 greater
herbicide efficiency index as well as weed persistence
index was recorded.
Yield attributes
All yield attributing characters of rice crop, viz.
number of panicles/m2, grains/panicle and 1000 grain
weight were significantly influenced by different
weed control treatments during both the years of
Table 1. Effect of treatment on weed density (no./m2) at 45 days after herbicide application
Treatment
Grasses Non grassy weeds
E. colona E. crus-galli L. chinensis
2014 2015 2014 2015 2014 2015 2014 2015
Cyhalofop-butyl (65 g/ha) 3.2(9.3) 1.7(2.0)
3.0(8.0)
2.4(4.7)
2.5(5.3)
4.7(2.4) 14.5(210.7)
13.4(179.3)
Cyhalofop-butyl (75 g/ha) 2.1(3.3) 1.0(0.0)
2.0(3.0)
1.5(1.3)
1.0(0.0)
1.0(0.0) 13.3(178.7)
13.2(174.7)
Cyhalofop-butyl (80 g/ha) 1.9(2.7) 1.0(0.0)
1.9(2.7)
1.2(0.7)
1.0(0.0)
1.0(0.0) 12.2(150.7)
13.0(168.7)
Cyhalofop-butyl (90 g/ha) 1.5(1.3) 1.0(0.0)
1.5(1.3)
1.0(0.0)
1.0(0.0)
1.0(0.0) 12.6(158.0)
13.4(178.7)
Cyhalofop-butyl (std. check) (75 g/ha) 2.5(5.3) 1.0(0.0)
2.5(5.3)
2.2(4.0)
1.0(0.0)
1.9(2.7) 12.0(142.7)
13.9(191.0)
Cyhalofop-butyl (std. check) (80 g/ha) 1.9(2.7) 1.0(0.0)
1.9(2.7)
1.9(2.7)
1.0(0.0)
1.0(0.0) 12.8(162.7)
13.2(174.7)
Hand weeding 20 and 40 DAS 2.5(5.3) 1.5(1.3)
2.2(4.0)
1.9(2.7)
3.2(9.3)
1.5(1.3) 7.9(62.7) 10.4(108.0)
Weedy check 4.3(17.3)
3.2(9.3)
4.3(17.3)
4.3(17.3)
4.7(21.3)
3.4(10.7)
13.0(168.7)
13.8(190.7)
LSD (p=0.05) 0.60 0.3 0.50 0.6 0.31 0.40 2.1 1.24
Value in parentheses was original and transformed to square root for analysis, DAS- Days after sowing
Table 2. Effect of treatment on weed dry biomass (g/m2) at 45 days after herbicide application
Treatment
Grasses Non grassy weeds
E. colona
E. c
rus
-
galli
L. chinensis
2014 2015 2014 2015 2014 2015 2014 2015
Cyhalofop-butyl (65 g/ha) 5.2(26.7) 2.6(5.8) 5.0(24.0) 3.1(8.5) 3.5(11.4) 2.1(3.4) 8.6(73.0)
8.1(65.2)
Cyhalofop-butyl (75 g/ha) 3.1(8.7) 1.0(0.0) 2.8(7.3) 1.7(2.0) 1.0(0.0) 1.0(0.0) 7.9(61.9)
8.0(63.5)
Cyhalofop-butyl (80 g/ha) 3.0(8.3) 1.0(0.0) 2.8(7.0) 1.3(0.8) 1.0(0.0) 1.0(0.0) 7.8(60.4)
7.8(60.1)
Cyhalofop-butyl (90 g/ha) 2.1(3.9) 1.0(0.0) 2.0(3.7) 1.0(0.0) 1.0(0.0) 1.0(0.0) 7.6(57.3)
7.7(59.0)
Cyhalofop-butyl (std. check) (75 g/ha)
4.1(16.2) 1.0(0.0) 4.0(14.9) 2.0(3.2) 1.0(0.0) 1.8(2.1) 7.5(55.5)
7.7(58.1)
Cyhalofop-butyl (std. check) (80 g/ha)
3.1(8.8) 1.0(0.0) 2.82(7.7) 1.9(2.7) 1.0(0.0) 1.0(0.0) 7.8(59.9)
7.6(57.7)
Hand weeding 20 and 40 DAS 4.2(16.6) 2.6(6.9) 3.6(12.3) 1.9(2.8) 4.2(16.4) 1.7(2.1) 4.8(22.3)
5.2(26.6)
Weedy check 7.8(60.3) 8.3(67.6) 7.1(49.2) 9.8(95.3)
6.7(44.5) 3.4(10.9) 8.0(63.5)
7.3(53.1)
LSD (p=0.05) 1.0 0.9 0.82 0.70 0.27 0.43 0.83 0.85
Value in parentheses was original and transformed to square root for analysis, DAS- Days after sowing
Table 3. Effect of treatments on total weed dry biomass
and WCE at 45 DAA
Treatment
Total weed dry
biomass(g/m2)
Weed
control
efficiency
(%)
2014 2015 2014 2015
Cyhalofop
-
butyl (65 g/ha)
11.7(135
)
9.1(83
)
37.9
63.5
Cyhalofop
-
butyl (75 g/ha)
9.4(87
)
8.1(65
)
60.0
71.1
Cyhalofop-butyl (80 g/ha) 8.8(77) 7.9(61) 64.7 73.2
Cyhalofop
-
butyl (90 g/ha)
8.1(65
)
7.7(59
)
70.2
74.0
Cyhalofop-butyl (std. check)
(75 g/ha) 9.4(87) 8.0(63.4)
60.2 72.1
Cyhalofop
-
butyl (std. check)
(80 g/ha)
8.8(76
)
7.8(60
)
64.8
73.4
Hand weeding 20 and 40 DAS
8.3(67
)
6.3(38
)
68.9
83.1
Weedy check 14.8(218)
15.1(227)
- -
LSD (p=0.05) 0.40 0.77 - -
Value in parentheses was original and transformed to square
root for analysis, DAS- days after sowing, DAA- days
after herbicide application and WCE- weed control efficiency.
study except 1000-grain weight during 2014 (Table
4). Yield attributes data depicted highest value under
twice hand weeding at 20 and 40 DAS during both the
years. Within herbicidal treatments, application of
cyhalofop-butyl at 90 g/ha achieved maximum
panicles number of 232 and 253/m2 during 2014 and
2015, respectively, which was at par with rest of the
herbicidal treatments except cyhalofop-butyl applied
at 65 g/ha. During 2014, cyhalofop-butyl applied at
90 g/ha and during 2015 application of cyhalofop-
butyl at 80 g/ha obtained highest number of grains/
panicle, which was comparable to rest of the
treatments. 1000-grain weight was maximum (24.5
g) with the application of cyhalofop-butyl at 80 g/ha
which was significantly superior to cyhalofop-butyl
applied at 65 g/ha. This might be due to less density
and biomass of weeds, less crop weed competition
during critical period, better environment for rice
V. Pratap Singh, S.P. Singh, Neema Bisht, A. Kumar, Kavita Satyawali and Arunima Paliwal
214
growth at higher doses of cyhalofop-butyl, which in
turn resulted in highest value for yield attributes of
rice crop.
Grain and straw yield
The highest grain yield (4.21 and 4.29 t/ha) was
found with the application of cyhalofop-butyl at 90 g/
ha which was comparable with rest of the herbicidal
treatments except with its lower dose applied at 65 g/
ha (Table 4). The grassy weeds dominant at critical
period of weed competition stage (Table 1 and 2)
were well managed by cyhalofop-butyl. Menono et
al. (2014) also reported that maximum rice yield with
application of cyhalofop-butyl either applied as alone
or in combination. The highest straw yield was
recorded with the application of cyhalofop-butyl at 80
Table 4. Rice yield and yield attributing characters of direct-seeded rice as affected by treatments
Table 5. Effect of various doses of cyhalofop-butyl applied in rice on the succeeding wheat crop, Rabi season
Treatment
Panicles
(no./m2) Grains/
panicle 1000 grain
weight (g) Grain yield
(t/ha) Straw yield
(t/ha) Grain: Straw
2014
2015
2014
2015 2014
2015 2014
2015
2014 2015
2014
2015
Cyhalofop-butyl(65 g/ha) 134
223 92.7
94.5 23.9 23.0 2.97
3.50
4.31 6.30 0.69
0.55
Cyhalofop-butyl (75 g/ha) 225
251 97.7
104.5 24.2 24.3 4.07
4.10
7.36 7.38 0.55
0.56
Cyhalofop-butyl (80 g/ha) 229
252 98.0
106.7 24.2 24.5 4.17
4.16
7.46 7.48 0.56
0.56
Cyhalofop-butyl (90 g/ha) 232
253 99.3
104.5 24.3 24.1 4.21
4.29
7.29 7.73 0.58
0.56
Cyhalofop-butyl (std. check)(75g/ha)
225
238 97.7
103.5 24.1 23.9 4.00
4.02
7.19 7.24 0.57
0.55
Cyhalofop-butyl (std. check)(80g/ha)
227
247 98.7
105.1 24.3 24.4 4.12
4.07
5.99 7.44
0.69
0.55
Hand weeding 20 and 40 DAS 246
265 109.3
111.3 24.1 24.7 4.25
4.34
6.67 7.81 0.64
0.56
Weedy check 112
138 54.0
67.0 23.6 22.2 0.65
1.19
1.17 2.13 0.56
0.56
LSD (p=0.05) 30.5
27.3 6.6 14.2 NS 1.36 0.38
0.29
0.48 0.50 - -
DAS- days after sowing
Treatment
Plant
population
(m2)
Spikes
(no/m2) Grains/spike
1000 grain
weight (g) Grain yield
(t/ha) Straw yield
(t/ha)
2014-
15 2015-
16 2014-
15 2015-
16 2014-
15 2015-
16 2014-
15 2015-
16 2014-
15 2015-
16 2014-
15 2015-
16
Cyhalofop
-
butyl(65 g
/ha)
262
229
296
329
42.6
41.3
44.4
39.4
4.39
4.02
6.41
6.90
Cyhalofop
-
butyl (75 g/ha)
256
224
285
307
43.1
40.5
44.4
40.2
4.30
4.20
6.47
7.14
Cyhalofop-butyl (80 g/ha) 256 225 273 309 43.0 41.5 44.2 39.0 4.46 4.20 6.36 7.15
Cyhalofop-butyl (90 g/ha) 234 230 292 275 41.6 40.5 43.5 40.3 4.14 4.01 6.52 6.81
Cyhalofop-
butyl (std.
check)(75g/ha) 245 223 304 304 42.7 41.0 45.1 39.1 4.52 4.14 6.46 6.98
Cyhalofop-
butyl (std.
check)(80g/ha) 241 225 288 298 42.4 40.4 45.7 39.5 4.10 4.10 7.05 6.97
Hand weeding 20 and 40 DAS 267 222 286 284 42.7 40.7 45.0 39.5 4.18 3.95 6.63 6.72
Weedy check 269 224 280 328 42.1 41.4 45.4 39.5 4.30 4.02 6.74 6.80
LSD (p=0.05) NS NS NS NS NS NS NS NS NS NS NS NS
DAS- days after sowing, NS- non significant
Assessment of post-emergence weed management in direct-seeded rice
215
g/ha in 2014 and 90 g/ha during 2015, which were
significantly superior to cyhalofop-butyl applied at 65
g/ha. The highest grain yield of rice was obtained
with cyhalofop-butyl at 90 g/ha due to better control
of grassy weeds. Maximum grain: straw ratio was
recorded with cyhalofop-butyl at 65 g/ha and
cyhalofop-butyl (std. check) at 80 g/ha (0.69) during
2014 and with application of cyhalofop-butyl at 75,
80 and 90 g/ha as well as twice hand weeding at 20
and 40 (0.56) during 2015.
Phytotoxicity
No phytotoxic symptoms were seen in direct-
seeded rice crop due to application of cyhalofop-butyl
at different doses on 3, 7, 14, 21 and 28 days after
herbicide application during both the years.
Carryover effect
In succeeding wheat crop, the plant population
at harvest as well as wheat yield and yield attributing
characters were not influenced significantly due to
various weed control treatments applied during
preceding rice crop and they were statistically similar
to each other. This concludes that post emergence
application of cyhalofop-butyl against weeds in
direct-seeded rice crop during rainy season was very
safe for growing wheat crop during winter season
(Table 5).
It was concluded that cyhalofop-butyl should be
applied at 75 and 80 g/ha for better control of grassy
weeds and maximum rice grain yield. The succeeding
wheat crop had no phytotoxic effect due to
application of cyhalofop-butyl.
ACKNOWLEDGEMENT
The authors gratefully acknowledge Crystal
Crop Protection Pvt. Ltd. for financial assistance.
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V. Pratap Singh, S.P. Singh, Neema Bisht, A. Kumar, Kavita Satyawali and Arunima Paliwal
... The effective control of grassy weeds by post emergence grass killer i.e. Cyhalofop butyl or Butachlor (pre-emergence) followed by control of broadleaved weeds through 2,4-D might have resulted in minimum weed density in present study as was previously indicated by other researchers Singh et al. 2017). Maximum weed density at 30, 60 and 90 DAS, respectively was observed under weedy check where no weed control was done, while weed free check registered the minimum weed density. ...
... Application of 80 g ha −1 Cyhalofop butyl at 25 DAS fb 0.75 kg ha −1 2,4-D at 35 DAS gave consistently and significantly higher grain yield (Suppl. Figure 3) of rice (Table 6), which was not significantly different with the treatment receiving mechanical weeding with grubber at 20 and 40 DAS. The effective and timely control of weeds with Cyhalofop butyl fb 2,4-D have reduced crop weed competition during the critical crop growth stages and provided better crop growth environment, which ultimately increased the yield components and yield (Menon et al. 2014;Singh et al. 2017). Further, the yield obtained with either 1.5 kg ha −1 Butachlor fb 0.75 kg ha −1 2,4-D or 0.75 kg ha −1 Pretilachlor fb 0.75 kg ha −1 2,4-D were comparable (Table 6), which might be due to similar mode of action of these herbicides. ...
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Weed management in upland rice under subtropical climate with high rainfall is challenging. The diverse weed flora in upland rice ecosystem emerges in several flushes, necessitating sequential application of herbicides. A 4-year study conducted in Meghalaya (950 m above sea level), India indicated that sequential application of Cyhalofop butyl [2-{4-(4-cyano-2-fluorophenoxy) phenoxy} propionic acid, butyl ester (R)], a grass weed killer high efficacy low volume herbicide applied 80 g ha⁻¹ at 25 days after sowing (DAS) and 2,4-D, a broadleaf weed killer herbicide applied 0.75 kg ha⁻¹ at 35 DAS was effective for weed control and produced significantly higher grain yield (3572 kg ha⁻¹) of rice with the highest weed control efficiencies than other treatments. Application of Pretilachlor followed by (fb) 2,4-D or Fenoxaprop-p-ethyl fb 2,4-D yielded significantly higher chlrophyll (chl) a, chl b and total leaf chl content compared with other herbicides at 90 DAS. The highest net energy (111,443 MJ ha⁻¹), energy profitability and benefit:cost ratio was recorded with sequential application of Cyhalofop butyl and 2,4-D. Thus, sequential application of Cyhalofop butyl and 2,4-D could provide a sustainable weed management option in upland rice under high rainfall conditions in the Eastern Himalayas, India.
... Bundle weight was recorded with the help of spring balance and converted into kg ha -1 . [7] , Thakur and Dantre (2018) [9] . ...
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Rice (Oryza sativa L.) is a principal source of food for more than half of the world population, especially in South and Southeast Asia and Latin America. Elsewhere, it represents a high‐value commodity crop. Change in the method of crop establishment from traditional manual transplanting of seedlings to direct‐seeding has occurred in many Asian countries in the last two decades in response to rising production costs, especially for labor and water. Direct‐seeding of rice (DSR) may involve sowing pregerminated seed onto a puddled soil surface (wet‐seeding) or into shallow standing water (waterseeding), or dry seed into a prepared seedbed (dry‐seeding). In Europe, Australia, and the United States, direct‐seeding is highly mechanized. The risk of crop yield loss due to competition from weeds by all seeding methods is higher than for transplanted rice because of the absence of the size differential between the crop and weeds and the suppressive eVect of standing water on weed growth at crop establishment. Of 1800 species reported as weeds of rice, those of the Cyperaceae and Poaceae are predominant. The adoption of direct‐seeding has resulted in a change in the relative abundance of weed species in rice crops. In particular, Echinochloa spp., Ischaemum rugosum, Cyperus diVormis, and Fimbristylis miliacea are widely adapted to conditions of DSR. Species exhibit variability in germination and establishment response to the water regime postsowing, which is a major factor in interspecifically selecting constituents of the weed flora. The relatively rapid emergence of ‘‘weedy’’ (red) rice, rice phenotypically similar to cultivars but exhibiting undesirable agronomic traits, has been observed in several Asian countries practicing DSR, and this poses a severe threat to the sustainability of the production system. Stale seedbeds, tillage practices for land leveling, choice of competitive rice cultivars, mechanical weeders, herbicides, and associated water management are component technologies essential to the control of weeds in DSR. Herbicides in particular are an important tool of weed management, but hand weeding is either partially or extensively practiced in countries of Asia, Africa, and Latin America. Though yet to be globally commercialized, transgenic rice varieties engineered for herbicide resistance are a potential means of weed control. The release of herbicide‐resistant rice for red rice control in the United States has indicated the need to critically examine mitigation methods for the control of gene flow. Integrating preventive and interventional methods of weed control remains essential in managing weed communities in DSR, both to prohibit the evolution of herbicide resistance and to maximize the relative contributions of individual components where herbicides are not widely used. There remains a need to further develop understanding of the mechanisms and dynamics of rice weed competition and of the community dynamics of weed populations in DSR to underpin sustainable weed management practices.
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Irrigated aerobic rice is a new system being developed for lowland areas with water shortage and for favorable upland areas with access to supplementary irrigation. It entails the cultivation of nutrient-responsive cultivars in nonsaturated soil with sufficient external inputs to reach yields of 70–80% of high-input flooded rice. To obtain insights into crop performance, water use, and N use of aerobic rice, a field experiment was conducted in the dry seasons of 2002 and 2003 in the Philippines. Cultivar Apo was grown under flooded and aerobic conditions at 0 and at 150kg fertilizer N ha–1. The aerobic fields were flush irrigated when the soil water potential at 15-cm depth reached –30kPa. A 15N isotope study was carried out in microplots within the 150-N plots to determine the fate of applied N. The yield under aerobic conditions with 150kg N ha–1 was 6.3 t ha–1 in 2002 and 4.2 t ha–1 in 2003, and the irrigation water input was 778mm in 2002 and 826mm in 2003. Compared with flooded conditions, the yield was 15 and 39% lower, and the irrigation water use 36 and 41% lower in aerobic plots in 2002 and 2003, respectively. N content at 150kg N ha–1 in leaves and total plant was nearly the same for aerobic and flooded conditions, indicating that crop growth under aerobic conditions was limited by water deficit and not by N deficit. Under aerobic conditions, average fertilizer N recovery was 22% in both the main field and the microplot, whereas under flooded conditions, it was 49% in the main field and 36% in the microplot. Under both flooded and aerobic conditions, the fraction of 15N that was determined in the soil after the growing season was 23%. Since nitrate contents in leachate water were negligible, we hypothesized that the N unaccounted for were gaseous losses. The N unaccounted for was higher under aerobic conditions than under flooded conditions. For aerobic rice, trials are suggested for optimizing dose and timing of N fertilizer. Also further improvements in water regime should be made to reduce crop water stress.
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Rice (Oryza sativa L.), a staple food for more than half of the world population, is commonly grown by transplanting seedlings into puddled soil (wet tillage) in Asia. This production system is labor-, water-, and energy-intensive and is becoming less profitable as these resources are becoming increasingly scarce. It also deteriorates the physical properties of soil, adversely affects the performance of succeeding upland crops, and contributes to methane emissions. These factors demand a major shift from puddled transplanting to direct seeding of rice (DSR) in irrigated rice ecosystems. Direct seeding (especially wet seeding) is widely adopted in some and is spreading to other Asian countries. However, combining dry seeding (Dry-DSR) with zero/reduced tillage (e.g., conservation agriculture (CA)) is gaining momentum as a pathway to address rising water and labor scarcity, and to enhance system sustainability. Published studies show various benefits from direct seeding compared with puddled transplanting, which typically include (1) similar yields; (2) savings in irrigation water, labor, and production costs; (3) higher net economic returns; and (4) a reduction in methane emissions. Despite these benefits, the yields have been variable in some regions, especially with dry seeding combined with reduced/zero tillage due to (1) uneven and poor crop stand, (2) poor weed control, (3) higher spikelet sterility, (4) crop lodging, and (5) poor knowledge of water and nutrient management. In addition, rice varieties currently used for DSR are primarily selected and bred for puddled transplanted rice. Risks associated with a shift from puddled transplanting to DSR include (1) a shift toward hard-to-control weed flora, (2) development of herbicide resistance in weeds, (3) evolution of weedy rice, (4) increases in soil-borne pathogens such as nematodes, (5) higher emissions of nitrous oxide—a potent greenhouse gas , and (6) nutrient disorders, especially N and micronutrients. The objectives of this chapter are to review (1) drivers of the shift from puddled transplanting to DSR; (2) overall crop performance, including resource-use efficiencies of DSR; and (3) lessons from countries where DSR has already been widely adopted. Based on the existing evidence, we present an integrated package of technologies for Dry-DSR, including the identification of rice traits associated with the attainment of optimum grain yield with Dry-DSR.
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Dry seeding of rice (Oryza sativa L.) in the furrow-irrigated raised-bed planting system (FIRBS) represents a major shift in the production practices for attaining optimal water productivity in the rice–wheat system in the Indo-Gangetic Plains of South Asia. Information on weed management in dry-seeded rice in the FIRBS is lacking. Two experiments were conducted for 2 years, with an objective of identifying appropriate, effective, and economical methods of managing: (1) broadleaf weeds only; and (2) a mixed population of both grass and broadleaf weeds in dry-seeded rice cultivated in the FIRBS. The major weeds associated with dry-seeded rice in the FIRBS during both years were Echinochloa crus-galli (L.) P. Beauv., Echinochloa colona (L.) Link, Dactyloctenium aegyptium (L.) Willd., Leptochloa panicea (Retz.) Ohwl, Caesulia axillaris Roxb., Euphorbia hirta L., Lindernia sp., Commelina benghalensis L., Eclipta prostrata (L.) L., Trianthema portulacastrum L., and Portulaca oleracea L. Triclopyr at 500 g a.i. ha�1, bensulfuron at 60 g a.i. ha–1, ethoxysulfuron at 18 g a.i. ha–1, and 2,4-D (ester) at 500 g a.i. ha–1, all applied at 21 days after seeding (DAS), were equally effective in realizing higher rice grain yields by controlling broadleaf weeds. Among these, ethoxysulfuron at 18 g a.i. ha–1 was found to be least expensive but effective for controlling broadleaf weeds. Effective and economical herbicides identified for managing a mixed population of both grass and broadleaf weeds included fenoxaprop-p-ethyl+ethoxysulfuron at 50+18 g a.i ha–1, applied at 21 DAS, and pendimethalin followed by (fb) chlorimuron+metsulfuron at 1000 fb 4 g a.i. ha�1 applied at 3 fb 21 DAS.
Weed Management in Rice: FAO Plant Production and protection paper 139
  • De Datta
  • S K Beltazar
  • A M Auld
  • B A Kim
De Datta SK and Beltazar AM. 1996. Weed control technology as a component of rice production systems. pp. 27-52. In: Weed Management in Rice: FAO Plant Production and protection paper 139, (Eds. Auld BA and Kim KU), FAO, Rome.
Weed control in wet-seeded rice by post-emergence herbicides
  • S S Menon
  • P Prameela
  • C T Abraham
Menon SS, Prameela P and Abraham CT. 2014. Weed control in wet-seeded rice by post-emergence herbicides. Indian Journal of Weed Science 46(2): 169-171.