Weed Science

Different doses of bispyribac-sodium 20, 25 and 30 g/ha were evaluated against mixed weed flora in transplanted rice under mid-hill conditions of Himachal Pradesh during 2010 and 2011. Major associated weeds were Echinochloa colona (31.1%) and Commelina benghalensis (7.3%) among grasses, Cyperus iria (26.9%) and Scripus (9.3%) among sedges and Ammania baccifera (8.8%) among broad-leaved weeds. Bispyribac-sodium 20-30 g/ha effectively controlled E. colona. Cyhalofop-butyl/butachlor fb metsulfuron-methyl was comparable to bispyribac-sodium in controlling C. benghalensis. Bispyribac-sodium brought about significant reduction in the count of Cyperus sp. up to 60 days after transplanting (DAT). Bispyribac-sodium 30 g/ha behaving statistically similar with bispyribac-sodium 20 and 25 g/ha resulted in significantly lower total weed count and total weed dry weight. There was no phytotoxicity of bispyribac-sodium on rice and no residual toxicity on succeeding crop of wheat. Bispyribac-sodium, farmer’s practice, cyhalofop-butyl fb metsulfuron-methyl and cyhalofop-butyl fb 2,4-D were comparable in influencing rice grain yield. Rice grain yield was positively associated with plant height, panicle length, effective tillers and spikelets/panicle and was negatively associated with weed count and weed biomass. With one weed per m2 increase up to harvest, grain yield of rice was expected to decrease by 15.3 kg/ha. Bispyribac-sodium at 30 kg/ha was the best in terms of net returns due to weed management. Cyhalofop-butyl fb metsulfuron-methyl gave the highest net profit/rupee invested. Herbicide efficiency index (HEI) was highest and weed index was lowest under bispyribac-sodium 30 g/ha. Weed management index (WMI) and agronomic management index (AMI) were highest under cyhalofop-butyl fb metsulfuron-methyl.

Fourty field demonstrations on chemical weed control practices were laid at four villages of Delang block of Puri district in transplanted rice during Kharif season of 2010 to 2012 to analyze the performance and profitability of new generation herbicides, viz. oxadiargyl, pyrazosulfuron-ethyl, pretilachlor and chloromuron-ethyl + metsulfuron-methyl at 70, 25, 750 and 4 g/ha, respectively on weed growth and productivity of transplanted rice at farmer’s fields. The farmers’ fields were found infested with mixed flora of grasses, sedges and broad-leaved weeds. The herbicides used for demonstrations were found to be highly effective in controlling weeds and thereby increasing grain yield of rice by 23–42% over farmers’ practice based on the intensity and growth of different weed flora. The economic benefits of herbicide demonstration over the farmers’ practice varied from Rs. 4,362 - 9,343/ha.

Field experiments were conducted during Rabi 2011-12, Kharif  2012 and Rabi 2012-13 to evaluate the bioefficacy of carfentrazone-ethyl at 20 and 25 g/ha on 15-20 DAS with 2,4-D Na salt 800 g/ha on 20-25 DAS, weed free situation and un-weeded check as treatments in randomized block design replicated four times. Fimbristylis miliacea, Cyperus difformis, Cyperus iria, Schenoplectus pungens were the major sedges and Monochoria vaginalis, Ludwigia perennis and Sphenoclea  zeylanica were the dominant broad-leaved weed species. Application of carfentrazone-ethyl 20 g/ha on 15-20 DAS proved effective in controlling sedges and broad-leaved weeds in direct-seeded rice. Carfentrazone-ethyl 40 DF 20 g/ha recorded higher grain yield (3.68 t/ha) with weed control efficiency of 90.7% and weed index of 9.5. It was comparable with 2,4-D Na salt 800 g/ha (3.65 t/ha) with weed control efficiency of 96.7% and weed index of 10.5. There was 72% reduction in grain yield due to the infestation of non-grassy weeds in direct-seeded rice. Weed free situation recorded the highest grain yield (4.07 t/ha) but its B: C ratio was lower than carfentrazone-ethyl 20 g/ha and 2,4-D Na salt 800 g/ha.  Carfentrazone-ethyl, both at 20 and 25 g/ha did not exhibit any phytotoxic effect in rice plant.

A field experiment was conducted at Kotwa, Azamgarh during rainy season of 2008 and 2009 to evaluate the comparative efficacy of various planting methods and weed control measures on weeds density growth, yield attributes, grain yield and economics of rice variety ‘Godawari’. Four main rice establishment techniques comprised with six sub-plot weed control practices was laid out in split plot design and replicated thrice. Echinichloa colona, E. crusgalli, Cyperus rotundus, C. difformis and Commelina benghalensis were predominant weed species. Among the rice establishment techniques, puddled transplanted practices proved best for reducing weed dry matter accumulation and produced significantly highest mean grain yield (3.89 t/ha) along with yield contributing parameters in comparison to rest planting methods. Direct drum-seeded rice under puddled condition were observed to be significantly superior and recorded 2.82 t/ha more mean grain yield over direct-dry seeding. Application of pretilachlor 750 g/ha pre-emergence followed by cyhalofop-butyl 60 g/ha post-emergence at 25 DAS/DAT was found quite effective against mixed weed flora which recorded statistically similar grain yield to that of repeated hand weedings. The integration of herbicide with tools, viz. pretilachlor 750 g/ha supplemented with mechanical weeding at 25 DAS/DAT again found equally effective in increasing the grain yield as pre- and post-emergence applied herbicides.

A field experiment was conducted at village Binuria of the district Birbhum, West Bengal, India during rainy seasons (Kharif) of 2008 and 2009 to study the effect of crop establishment methods and weed management practices on weed growth and productivity of aromatic rice cv. ‘Basmati 370’. Three crop establishment methods viz. drum seeding (DS), system of rice intensification (SRI) and conventional transplanting (CTR) were assigned in main plots and six weed management practices, viz. weed-free check (WFC), unweeded check (WC), pyrazosulfuron-ethyl (PSE) at 20 g/ha, cono weeder (CW) twice at 15 and 30 DAS/DAT, combination of pyrazosulfuron-ethyl (PSE) at 20 g/ha and cono weeder twice (PSE + CW) and metsulfuron -methyl 10% + chlorimuron- ethyl 10% (Almix) at 4 g/ha in sub-plots, replicated thrice. Cynodon dactylon, Echinochloa colona and Oryza rufipogon under grasses, Hydrolea zeylanica, Ludwigia parviflora, Sphenoclea zeylanica, Monochoria vaginalis, Sagittaria sagitifolia and Marsilea quadrifolia among broad-leaved and Cyperus iria, C. difformis and Fimbristylis miliacea among the sedges were predominant weeds. Hydrolea zeylanica was the most pre-dominant species in SRI as well as conventional transplanting method while Fimbristylis miliacea in drum seeding. SRI recorded significantly lower number of total weeds at 60 DAT, the highest number of panicles (231/m2), filled grains (98/panicle) and grain filling efficiency (84.79%) producing the highest grain yield (3.23 t/ha), 19.68 and 25.8% higher than that of CTR and DS methods respectively. Pyrazosulfuron-ethyl in combination with cono-weeder recorded the lowest weed population and dry weight at 40 DAS/DAT, higher grain yield (2982 kg/ha), 20.58% more over weedy check and was equivalent to sole application of pyrazosulfuron- ethyl and metsulfuron-methyl + chlorimuron-ethyl.

A field experiment was conducted to study the performance of cultivar and weed management practices under stale seed bed in dry direct seeded rice. The treatment consisted of combination of two methodsof rice sowing i.e. dry seeding after stale seed bed by glyphosate 1 kg/ha and shallow tillage and two weed management treatment (weedy and two hand weeding) in main plot and four cultivars viz. ‘BPT-5204, Sarjoo -52, PRH-10’ and ‘HUBR2-1’ in sub-plot replicated thrice in split plot design. The results revealed that ‘Sarjoo-52’ was found to be more competitive than other cultivars in terms of grain yield and economics. Studies on competitive traits revealed that number of grains/panicle had highest direct positive effect whereas number of panicles/m2 via number of grains/panicle had more indirect effect on grain yield.

A systematic study on herbicide adoption by farmers in rice and wheat growing areas of Haryana conducted during 2008-2009, revealed  that in Sirsa and Fatehabad districts of state,  95% farmers applied herbicide to control weeds in transplanted rice whereas in north-eastern Haryana, all farmers applied herbicides in rice crop. In Sirsa and Fatehabad districts, EC formulation of butachlor was the choice of 45% farmers followed by anilofos (26%), pretilachlor (12%) and oxadiargyl (8%). In Karnal, Kurukshetra, Ambala and Kaithal districts, pretilachlor was the first choice of 42% farmers followed by butachlor (24%) None of the farmer used anilofos. Even 11% farmers used pyrazosulfuron not approved by CCS HAU, Hisar for effective weed control. Twenty two (22) per cent farmers also applied post-emergence herbicide bispyribac- sodium in addition to pre-emergence herbicide because of poor control given by pre-emergence herbicides. In all 50-60% farmers applied herbicides timely (3 DAT). In Sirsa and Fatehabad, splash method of herbicide application is most popular used by  54% farmers where as, in north-eastern Haryana mixing of herbicide with DAP at 3-7 DAT, is most popular method used by 61% farmers. None of farmer in north-eastern districts used sand mix application of herbicide in rice which was the only method approved by CCSHAU, whereas in Sirsa and Fatehabad, only 8% farmers used this technology. In wheat, 94 -96% farmers of state used herbicide to control P. minor and other weeds. In Hisar, sulfosulfuron was the choice of majority of farmers (56%) followed by clodinafop (28%) where as in Kurukshetra district 44 % farmers used sulfosulfuron + metsulfuron (RM), 14% meso+iodosulfuron (Atlantis) and 16% used various brands of sulfosulfuron and only  20% used clodinafop. None of farmer used fenoxaprop and only 4% farmers of Hisar used isoproturon. In Kurukshetra, 66% farmers used flat fan nozzle but in Hisar majority of farmers (52%) used hollow cone nozzle which is the main reason for poor efficacy of herbicides at farmer’s fields. Eighty six farmers in Kurukshetra used recommended brands of sulfosulfuron+ metsulfuron (RM) as against 25% of sulfosulfuron.

Bio-efficacy of ready-mix formulation of clodinafop-propargyl 15% + metsulfuron-methyl 1% WP was studied against complex weed flora in wheat during 2006-07 and 2007-08 at Hisar, India.  Among different herbicidal treatments, clodinafop 0.06 kg/ha was found very effective (95-98%) only against grassy weeds. Metsulfuron 0.004 kg/ha was effective (88-90%) only against broad-leaf weeds. Sequential application of clodinafop 0.06 kg  fb metsulfuron 0.004 kg/ha being statistically at par with clodinafop- propargyl + metsulfuron- methyl at 0.06 + 0.004 kg/ha and above proved very effective against complex weed flora and the control of grassy and broad-leaved weeds to the extent of 95%. clodinafop- propargyl + metsulfuron- methyl being at par with clodinafop fb metsulfuron 0.06 and 0.004 kg/ha recorded the number of spikes, 1000-grain weight and grain yield of wheat statistically similar to that of weed free check. There was no additional gain in grain yield of wheat by using higher doses of clodinafop- propargyl + metsulfuron- methyl beyond 0.06 + 0.004 kg/ha. Weeds allowed growing throughout the crop seasons resulted into 42.9 and 45.1% reduction in the grain yield of wheat during 2006-07 and 2007-08, respectively. There was no residual impact of clodinafop-propargyl + metsulfuron-methyl at x dose (0.06+ 0.004 kg/ha) and 2x dose (0.12 + 0.008 kg/ha) on succeeding crops of sorghum and moongbean. HPLC analysis indicated that there were no residues of clodinafop-propargyl + metsulfuron-methyl (x and 2x doses) at wheat harvest in soil, grains and straw. There was also no adverse effect of herbicides on physico-chemical properties of soil.

A field experiment was consisted of four intercropping systems, viz. sole chickpea, sole mustard, chickpea + mustard (additive series) and chickpea + mustard (replacement series) and six weed management practices viz. weedy check, weed free, pendimethalin 1 kg/ha as pre-emergence (PE), fluchloralin 1 kg/ha as pre-plant incorporation (PPI), isoproturon 0.75 kg/ha as post-emergence (POE) and quizalofop-ethyl 50 ml/ha as post-emergence. These treatments were evaluated under split plot design with three replications. Results revealed that sole stands of chickpea and mustard removed highest amount of N, P and K which were followed by additive series and replacement series whereas among the weed management practices, highest amount of N, P and K was removed by weed free treatment followed by pendimethalim 1kg/ha and fluchloralin 1 kg/ha while the lowest N, P and K was removed by isoproturon 0.75 kg/ha followed by quizalofop-ethyl 50 ml/ha. Among the different intercropping treatments, weeds removed significantly highest N, P and K from sole mustard followed by sole chickpea, replacement series and additive series. Among weed management practices, the uptake of N, P and K in weeds was found to be significantly less in all the weed management practices as compared to weedy check treatment.

The effect of chemical weed management practices in lentil was studied during 2010-11 and 2011-12 at Agra (Utter Pradesh). The treatments included: control, pendimethalin 0.50 kg/ha, pendimethalin 0.75 kg/ha, pendimethalin 1.0 kg/ha, pendimethalin 1.25 kg/ha, pendimethalin 1.50 kg/ha and hand weeding. All herbicidal treatments including hand weeding significantly controlled the weeds. Among all the treatments hand weeding gave the highest weed control (84.8%) and produced lower weed biomass (54.0 g/m2). It gave maximum net income (Rs. 30,850) with CBR of 1:4.4. Pendimethalin 1.5 kg/ha controlled the weeds effectively but germination of seeds were affected. Highest grain yield (1.50 t/ha) was recorded from hand weeding plot with 48.6 and 52.0% increase in yield during 2011 and 2012, respectively.

A field study was conducted during 2010-11 and 2011-12 to evaluate the effect of integrated weed management on two lentil associated weeds viz., Chenopodium spp., Cyperus spp. and economics of the weed management packages. Two hand weedings (HW) at 30 and 45 DAS was the most effective method for containing Chenopodium  spp. and Cyperus spp. counts and dry matter from 60 DAS to harvest. Imazethapyr 2EC and pendimethalin controlled the intensity and corresponding dry matter of Chenopodium   significantly but poorly affected Cyperus which was better suppressed with treatment where mechanical weeding was either a component or as a sole treatment. Among sole herbicides, imazethapyr was the most effective for Cyperus and Chenopodium  weed control whereas, pendimethalin incorporated integrated package was effective on Chenopodium  while imazethapyr associated integrated system was effective on Cyperus weeds.  Average weed control efficiency at 75 DAS and crop harvest reflected that two HW was most efficient for control of Chenopodium  (77.6%) and Cyperus (75.3%) followed by pendimethalin 1 kg/ha supplemented with imazathapyr 37.5 g/ha on both the weed species (75.3 and 81.2%), respectively. The effect of sole chlorimuron and quizalofop-ethyl on both the weeds were least, but better than control. Pendimethalin 1 kg/ha fb mechanical weeding recorded better yield attributes, highest yield of lentil and cost: benefit ratio (1.37 t/ha and 2.80) but minimum weed index (4.53),  next to hand weeding. Hand weeding performed well in all aspects except the lower benefit cost ratio. Hence, integration of pendimethalin 1 kg/ha with mechanical weeding (hoeing) was considered to be the profitable treatment besides being more ecofriendly than chemical-chemical sequential application.

A field experiment was conducted to study the non-chemical methods of weed management in organically grown maize during the year 2010 and 2011. Among the 9 weed management treatments, soybean intercropping + one mechanical weeding ( 20 DAS) and  2 mechanical weeding (20 and 40 DAS) +  mash intercropping being at par with each other resulted in significantly lower weed dry weight, higher yield attributes and maize equivalent yield over other treatments. One mechanical weeding at 20 DAS gave highest benefit-cost ratio of 4.3 followed by 2 mechanical weeding at 20 and  40 DAS and soybean intercropping + 1 MW (20 DAS), which gave the benefit : cost ratio of 2.3.

Field experiments were carried out during 2009-10 and 2010-11 at Mountain Livestock Research Institute, Manasbal, Sher-e-Kashmir University of Agricultural Sciences and Technology Kashmir, India to find out the suitable weed management practices and cropping system of fodder oat. The green fodder yield and dry matter accumulation of oat was significantly higher under oat sole than oat + vetch (2:1) and oat + vetch (1:1), however was at par to oat + vetch 4:1. The magnitude of increase in green fodder yield with oat sole was 0.96, 12.71 and 15.51% than 4:1, 2:1 and 1:1 cropping system, respectively. Application of pendimethalin 0.75/ha recoded 7.76, 24.46 and 98.6% superiority over application of butachlor 2 kg/ha, wheel hoe and weedy check, respectively. The oat sole with application of pendimethalin 0.75/ha recorded highest gross profit (Rs. 76,903/ha), net returns (Rs. 49,363/ha) and B:C (2.79) than other treatment combination.

Study on phytoremedial capability of water hyacinth as a safe  organic manure source was done at the Regional Agricultural Research Station, Kumarakom during 2010-12. The heavy metals and other minerals in water hyacinth were Fe (33038 ppm), Al (13075 ppm), Ca (2234.80 ppm), Mn (1440.1 ppm), Mg (1608.3 ppm), Zn (77.08 ppm), Cu (49.80 ppm), Cr (23.37 ppm), As (5.276 ppm), Pb (0.531 ppm),  and Hg (0.151 ppm). The heavy metal contents in all the three forms of composts were almost  similar, except for Fe, Cr and Cd. The biomass yield of Amaranthus viridis in a pot culture study was higher in water hyacinth than  ordinary compost during the initial harvest, while yields for the final harvest and total yields were significantly higher for the farmyard waste compost. The heavy metals Pb, Hg and Cd content in Amaranthus remained unaltered by the organic sources, while As, Cr and Ni content were enhanced significantly by the water hyacinth treatments.

Metribuzin alone 210 g/ha resulted in significantly lower population of Phalaris minor than alone application of clodinafop 60 g/ha, pinoxaden 40 g/ha and sulfosulfuron 25 g/ha. Application of sulfosulfuron + metsulfuron 32 g/ha  and 25 + 210 g/ha resulted in significantly lower population of P. minor and C. album, respectively. Sulfosulfuron + metsulfuron 32 g/ha resulted in 89.2% WCE which was at par with sulfosulfuron + metribuzin  25 + 210 g/ha. Weed control treatments produced significantly higher grain yield as compared to weedy check. Sulfosulfuron 25 g/ha being significantly superior to alone application of metribuzin 210 g/ha, clodinafop 60 g/ha and pinoxaden 40 g/ha produced higher wheat grain yield, which was evident from the higher WCE  as compared to other herbicides. Ready-mix application of sulfosulfuron + metsulfuron at 32 g/ha produced the highest grain yield (6.42 t/ha) among different herbicide treatments but it was statistically at par with weed free.  

A field experiment was conducted at Research Farm,  JNKVV, Jabalpur, Madhya Pradesh during Kharif  2012 to see the effect of integrated weed management on growth, development and seed yield of fodder maize. The lowest  weed density and weed biomass was recorded under weed free treatment closely followed by atrazine 1.0 kg/ha + hand weeding. All the treated plots receiving either manual weeding or herbicidal treatments and integration with hand weeding produced higher yield over weedy check plots. The maximum seed and stover yields were noted in hand weeding at 20 and 40 DAS followed by atrazine 1.0 kg/ha + hand weed at 30 DAS. The B: C ratio (1.71) was higher in the tank mixed application of atrazine 0 .75 kg/ha + alachlor 2.25 kg/ha.

Among the different chemical weed management practices atrazine 1000 g/ha PE fb HW at 30 DAS recorded minimum number of monocot and dicot weed. Pendimethalin treated plots showed poor germination which might be due to the phytotoxic effect of herbicide. Further, interculturing fb HW at 20 and 40 DAS registered higher grain (7.82 t/ha) and stover yields (19.44 t/ha) which was closely followed by atrazine  1000 g/ha PE fb HW at 30 DAS

The field was mainly infested with monocot weeds like Echinochloa colona, Dinebra retroflexa and Cyperus iria, whereas dicot weeds Eclipta alba and Alternanthera philoxeroides were less dominant in soybean. The application of quizalofop-p-ethyl 37.5 g/ha + chlorimuron 24 g/ha gave satisfactory control of weeds and it gave highest crop biomass (592 g/m2), seed yield (1.59 t/ha) and net monetary returns (15,918/ha) followed by imazethapyr 75 g/ha which registered the crop biomass (557 g/m2), seed yield (1.52 t/ha) and net monetary returns (14,712/ha). However, 2 hand weedings checked the weed growth and recorded significantly higher seed yield (1.87 t/ha) over rest of the treatments, but net monetary return (15,594/ha) were lower than application of quizalofop-p-ethyl 37.5 g/ha + chlorimuron 24 g/ha.

A field experiment was conducted at Junagadh during 2012-13 to evaluate bio-efficacy of pre-and post-emergence herbicides under irrigated conditions of south Gujarat (India). Significantly higher chickpea seed yield (1.39 g/ha) was recorded with application of pendimethalin 38.7% CS at 1.0 kg/ha as pre-emergence (PE) + 1 hoeing at 30-35 DAS and remained at par with pendimethalin (1.0 kg/ha) as PE + 1 HW at 25-30 DAS (1.36 g/ha) and oxyfluorfen 23.5% EC (0.25 kg/ha) as PE at 20 DAS + hoeing at 30-35 DAS (1.21 g/ha). Pre-application of pendimethalin 30% EC + imazethapyr 2% (Velor 32 at 1.0 kg/ha) significantly enhanced branching in chickpea but proved phytotoxic under south Gujarat conditions. One hand weeding was found inadequate for getting higher chickpea seed yield as weedy situation prevailing throughout the crop period caused 54.7% reduction in seed yield of chickpea.

A field experiment was conducted to study the persistence of imazethapyr applied to soybean in sandy clay loam soil. The herbicide was applied as post-emergence 20 days after sowing at 100 and 200 g/ha. The residue analysis of imazethpyr 200 g/ha applied as post-emergence 20 days after sowing was carried out in soil samples collected at 15, 30, 45, 60 and 75 days after application and in soil, grain and plant samples after harvest. The residue level of imazethapyr in soil was found 0.017, 0.016, 0.015, 0.012 and 0.011 µg/g at 15, 30, 45, 60 and 75 days after herbicide application. At harvest the residue was below detectable limit.  However the residue level of 0.082 and 0.023 µg/g were detected in soybean grains and straw, respectively which were below the maximum residue limit