Weed Science

A field experiment was conducted to test the efficacy of different herbicides and cultivars during boro seasons of 2009 and 2010 on clay loam soils at BHU, Varanasi. The herbicides used were butachlor 1500 g/ha (pre-emergence) fb 2,4–D 500 g/ha + NIS (0.25%) at 20-25 DAT, pretilachlor 750 g/ha (pre-emergence) fb azimsulfuron 35 g/ha + NIS (0.2%) at 15 DAT, penoxsulam 22.5 g/ha + NIS (0.25%) at 15 DAT, ethoxysulfuron 18 g/ha + fenoxaprop + safner 56 g/ha + (NIS 0.25%) at 15 DAT, propanil 3000 g/ha + trichlorpyr 500 g/ha + NIS (0.25%) at 20-25 DAT and pyrazosulfuron 20 g/ha (pre-emergence) fb bispyribac 25 g/ha + NIS (0.25%) at 25 DAT under ‘Gautam’, ‘Prabhat’ and ‘Krishna Hamsa’ cultivars. Weed count and its dry matter under ‘Prabhat’ cultivar were lower than that with other two cultivars for both Echinochola and Cyperus spp. resulting in higher weed control efficiency with Prabhat as compared to other two cultivars whereas, significantly highest grain yield of 4.15 t/ha was obtained in Gautam cultivar due to higher growth and yield attributes. The application of ethoxysulfuron + fenoxaprop was most effective in minimizing population of Cyperus spp. and its dry matter with highest WCE. ‘Gautam’ cultivar with highest net return of Rs. 24,898/ha and benefit cost ratio of 1.19 and pretilachlor fb azimsulfuron with net return of Rs. 27,461/ha  and benefit: cost ratio of 1.32 were found most profitable among the cultivars and herbicidal treatments, respectively.

In this study, beneficial effects of multifaceted growth promoting isolates for rice were investigated under two different salt concentrations in pot culture conditions. Two most salt tolerant isolates (TRY2) Serratia sp. and Bacillus sp. (TRY4) were selected and their growth promoting characters were studied under slight and moderate NaCl concentration. Isolates Serratia sp. and Bacillus sp. were able to fix the nitrogen and solubilise phosphate, synthesise IAA, acc deaminase regardless of NaCl concentration in most cases, under conditions of salinity. In pot experiments, plant growth (plant height, dry weight, and chlorophyll content) was promoted by bacterial inoculation with 2.9 and 5.8 g NaCl/kg soil. In this study, uptake nutrients (N+, P+, and K+) were increased regardless of NaCl concentration with inoculation of Serratia sp. and Bacillus sp. and uptake of Na+ was reduced with treatments receiving 5.8 NaCl/kg soil with Serratia sp. and Bacillus sp. isolates used as inoculants as compared to control. The present observations showed that strains Serratia sp. and Bacillus sp. partially alleviated the saline stress in rice, likely through the integration of several mechanisms that improve the plant response.

Field experiments were conducted in Safsaf area in Libya during growing season of 2009-10 and 2010-11.  The field infested with many weeds of mixed flora was used to investigate the efficacy of clodinafop, isoproturon and their sequential application in ‘Zorda’ cultivar of durum wheat during different crop growth stages that is seedling, tillering and elongation in the presence or absence of diammonium phosphate (DAP) at 2.5 t/ha. Results revealed that all weed control treatments reduced weed density and dry weight recorded at 60 days of sowing.  The least weed density was recorded from sequential application of clodinafop and isoproturon compared to weedy check.  Herbicide application at seedling stage of crop growth in the absence of DAP was more effective in reducing weeds density and their dry weight.  Crop height, effective tillers, biological yield, grain and straw yield, seed and harvest index increased due to sequential application of clodinafop and isoproturon during seedling stage in the presence of DAP compared to weedy check and elongation stage in the absence of DAP.

An experiment to evaluate the bioefficacy of pinoxaden in combination with broad-leaved herbicides 2,4-D, metsulfuron and carfentrazone  in wheat was conducted at  Hisar during 2006-07 and 2007-08. Dominant weed flora of the experimental fields were Phalaris minor among grassy weeds and Chenopodium album, Melilotus indicia and Rumex dentatus among broad-leaved weeds. The tank mix application of pinoxaden with broad-leaved herbicides proved significantly effective in reducing density and dry weight of weeds and gave 85-100 % control of broad-leaved and 100% control of P. minor. Tank mixing of carfentrazone with pinoxaden although caused injury in terms of yellowing of tips but injury symptoms disappeared within 15 days after spray and did not result in any detrimental effect on grain yield of wheat. Application of broad-leaved herbicides 7 days earlier than pinoxaden or 7 days after application of pinoxaden also proved effective in controlling P. minor and broad-leaved weeds. Tank mixture of 2,4-D with pinoxaden did not result any antagonistic effect as anticipated as is evident by number of spikes, plant height, and number of grains per panicle and grain yield with use of 2,4-D were at par with weed free check.

A field experiment was conducted on durum wheat during 2005-06 and 2006-07 to study the effect of resource conservation techniques (RCTs), cultivars and pendimethalin herbicide on weeds and yield of durum wheat. Zero tillage (ZT) significantly reduced the population of Phalaris minor and dry matter of grassy weeds as compared to conventional tillage (CT) and furrow irrigated raised bed system (FIRBS), however, density and dry matter of broad-leaved weeds was higher under ZT that under CT and FIRBS. Grasses were predominant under FIRBS as compared to CT. Cultivar ‘PDW 291’ had less density and dry weight of weeds having superior yield attributes and produced significantly higher grain yield over ‘WH 896’ and ‘WH 912’. Pre-emergence application of pendimethalin (1.5 kg/ha) reduced the density and dry matter accumulation by grassy as well as broad-leaved weeds effectively and increased the wheat grain yield by 25% over weedy check.

Eight weed control treatments in soybean and three in wheat were evaluated in soybean-wheat cropping system during 2009-10 and 2010-11 at Palampur. Commelina benghalensis followed by Echinochloa colona were the most competitive weeds in soybean. In wheat, Phalaris minor and Avena ludoviciana were the most predominant weeds. Pendimethalin fb chlorimuron reduced dry weight of Aeschynomene, Ageratum, Cyperus, Echinochloa and Panicum significantly over the unweeded check. Isoproturon 1000 g/ha + 2, 4-D 500 g/ha reduced dry weight of Phalaris minor over the weedy check. In soybean, application of pendimethalin fb chlorimuron-ethyl allowed weeds to remove 89.2, 89.1 and 88.9% less N, P and K, respectively as compared to the unweeded check. Application of isoproturon 1000 g/ha + 2,4-D 500 g/ha reduced N, P and K depletion by weeds by more than 24% over the unweeded check. Application of pendimethalin fb chlorimuron-ethyl resulted in 187.5% higher N and 166.3% higher K uptake by soybean over weedy check. Unchecked weed growth reduced P uptake by 62.4% as compared to pendimethalin fb chlorimuron ethyl. Isoproturon 1000 g/ha + 2,4-D 500 g/ha and isoproturon 750 g/ha + 2,4-D 500 g/ha resulted in significantly higher N, P and K uptake by wheat over unweeded check. Weedy check reduced soybean equivalent yield by 37.4 and 28.8% during 2009 and 2010, respectively. Imazethapyr fb imazethapyr produced higher soybean equivalent yield (3.34 t/ha) during 2009, whereas, pendimethalin fb chlorimuron (3.16 t/ha) was better during 2010. Isoproturon 1000 g/ha + 2,4-D 500 g/ha ( Rs. 1,17,736) and isoproturon 750 g/ha + 2,4-D 500 g/ha ( Rs. 1,16,861) resulted in higher net returns and  net per  invested as compared to weedy check.

A field experiment was conducted during winter season of 2005-06 and 2006-07 to evaluate the effect of nitrogen levels and weed control on weed growth, productivity and economics of wheat. The treatments comprised of 4 levels of nitrogen, viz. 0, 40, 80, and 120 kg/ha in main plots and 5 weed control methods, viz. weedy control, 2,4-D Na 0.75 kg/ha as post-emergence, isoproturon 1.0 kg/ha as post-emergence, isoproturon 1.0 kg/ha + 2,4-D Na 0.75 kg/ha as post-emergence and weeding by Dutch hoe at 15, 30 and 45 days after sowing. Maximum density and dry weight were recorded with 120 kg N/ha and minimum under N0. Increasing levels of nitrogen from 0 to 40, 40 to 80 and 80 to 120 kg/ha increased weed density by 33.7, 39.9 and 47.3% and weed dry matter by 35.2, 24.9 and 13.5%, respectively while N up take by 68.8, 56.7 and 18.7% phosphorus 13.2, 4.6 and 4.4% and potassium 16.2, 7.0 and 8.7% over preceding lower levels. 120 kg N/ha recorded significantly higher grain (2.90 t/ha) and straw (4.6 t/ha) yield, net return ( 26,616/ha) and B:C ratio (1.52).

A field experiment was conducted during Rabi season of 2006-07 and 2007-08 at Gwalior (M.P.) to evaluate the effect of herbicides on weed control and yield of wheat (Triticum aestivatum L.) and residues of herbicides in post harvest soil, grain and straw of wheat. Ten treatments consisting of post emergence application of two doses of isoproturon (1.0 and 2.0 kg/ha), clodinafop- propargyl (60 and 120 g/ha),  fenoxaprop -p-ethyl (60 and 120 g/ha) and sulfosulfuron (25 and 50 g/ha)  along with two hand weeding and weedy control were evaluated in randomized block design with four replications. Samples of post harvest soil, grain and straw of wheat with higher dose of herbicides were analysed for herbicide residues by HPLC using PDA detector. Lowest weed population and weed dry weight at 60 days after sowing was recorded in isoproturon at both concentrations while lowest weed biomass at harvest and weed control efficiency was recorded in sulfosulfuron 25 g/ha followed by two hand weeding. Highest wheat yield (5.4 t/ha) was recorded in two hand weeding which was at par with sulfosulfuron 50 g/ha. clodinafop 60 g/ha, sulfosulfuron 25 g/ha and isoproturon 2.0 kg/ha. A reduction of 55.4% in wheat yield in weedy check was observed as compared to two hand weeding. A residue of 0.006, 0.041 and 0.022 µg/g isoproturon was in post harvest soil, wheat grain and straw while residues of 0.021 and 0.096 (µg g/g) clodinafop was present in soil and grain at higher level of application.  

A field experiment was conducted to explore the feasibility of growing lentil with integration of weed management practices using   herbicide, increased plant population and manual weeding at Meerut during 2008-09 and 2009-10. The experiment was laid out in randomized block design with four replications and ten treatments. The major weeds in experimental field were Chenopodium album, Phalaris minor, Anagalis arvensis and Convolvulus arvensis were recorded with some other minor weed species. Lowest weed density (4 m2) and dry weight (2.64 g/m2) was recorded where pendimethalin  was applied 0.75 kg/ha as PE plus one hand weeding, which was statistically on par with pendimethalin 1.0 kg/ha. Whereas, the highest grain yield of 1662 kg/ha was recorded by pendimethalin 0.75 kg/ha plus one hand weeding, which was statistically at par with weed free as well as pendimethalin 1.0 kg/ha. Increased seed rate of 25% significantly decreased the weed dry weight (32.0%) and increased seed yield (22.8%) in comparison to their respective treatments. On an average of 37.7% yield reduction was recorded due to weed infestation. The highest gross returns of  Rs. 23,268, net returns of  15,918 and B:C was recorded by pendimethalin 0.75 kg/ha PE + one hand weeding.

A field experiment was conducted to study the integrated weed management in groundnut (Arachis hypogaea L.) for consecutive two Kharif seasons in 2010 and 2011 at Rahuri with combination of 12 weed management treatments in three replications. Weed free check (two hand weeding at 20 and 40 DAS and manually uprooting of weeds at 60 DAS) was found more effective to control weeds in groundnut and recorded lowest weed density, wed dry matter and weed index and highest weed control efficiency. It was also recorded significantly highest growth and yield attributes in groundnut over all the other treatments viz. plant height, dry matter weight of plant, number of pods/plant and pod yield/hectare. Though highest gross monetary returns (Rs. 1,09,845/ha) was recorded in treatment weed free check, maximum net monetary returns (Rs.  61,460/ha) and B:C ratio (2.42) were recorded in the treatment application of pendimethalin 1.5 kg/ha as pre-emergence  + imazethapyr  0.150 kg/ha as post-emergence + one hand weeding  at 40 DAS which was found most economically feasible weed management practice for groundnut.

A field study was conducted during spring season in 2007-08 and 2008-09 at Muzaffarnagar to evaluate the influence of nutrient and weed management practices on yield attributes, yield, quality, nutrient uptake and economics of sugarcane. Results showed that application of 125% of recommended dose of fertilizer (RDF) enhanced the cane yield to the tune of 15.52 and 3.60% over 75 and 100% RDF owing to remarkable improvement in cane length, cane girth, cane weight and NMC. Sucrose, available sugar and commercial cane sugar (CCS) yield were also improved by 17.3, 23.4 and 42.6% over 75% RDF while 2.73, 3.15 and 6.84% over 100% RDF, respectively under application of 25% higher RDF. The values of juice extraction and purity per cent were remained statistically unchanged under 100 and 125% RDF but significantly improved over 75% RDF. The uptake of NPK in cane, green tops, trash as well as in total produce along with net return and B:C ratio were also noticed higher under fertility enrichment with 125% in comparison to lower ones. Weed free treatment produced maximum values of cane and CCS yield, yield components, juice extraction and nutrient uptake which was followed by application of glyphosate  1.0 kg/ha at 25 days after planting followed by one hand weeding at 60 DAP and performing of three hand weeding at intervals of  30, 60 and 90 days after planting (DAP).  Although, the higher B:C ratio was registered  under application of glyphosate  1.0 kg/ha, at 25 DAP followed by one hand weeding at 60 DAP owing to lower cost of cultivation. Consequently, application of 125% recommended dose of N: P2O5 :K2O  along with glyphosate applied 1.0 kg/ha at 25 DAP followed by one hand weeding at 60 DAP proved valuable in enhancing the yield, quality and economics of spring planted sugarcane.

Four herbicides (oxyflurofen 0.25 kg/ha, pendimethalin 1.50 kg/ha, trifluralin 1.50 kg/ha and metachlor 1.50 kg/ha) at recommended rates alone and at half of the recommended rates integrated with one hand weeding were compared with hand weeding 30, 60, 90 days after planting (DAP) and untreated check in silty clay loam soil during Rabi 2008-09 and 2009-10 at Palampur. Phalaris minor followed by Avena ludoviciana were the predominant associated weeds. All treatments resulted in significantly lower density of Phalais minor, Alopecurous myosuroides and Coronopus didymus. Metolachlor 1.50 kg/ha effectively reduced the density of Poa annua.  Metolachlor + hand weeding, pendimethalin and pendimethalin + hand weeding effectively reduced the density of Stellaria media. Integration of hand weeding with half dose of oxyflourfen, pendimethalin and metolachlor resulted in significantly higher yield of garlic than their respective higher dose alone. Weed index was lowest and weed management index (WMI), agronomic management index (AMI) and integrated weed management index (IWMI) were highest under pendimethalin + hand weeding. Herbicide efficiency index (HEI) was highest with oxyflourfen + hand weeding. Pendimethalin + hand weeding gave highest net return due to weed control (NRwc) and was followed by pendimethalin and metolachlor + hand weeding. Pendimethalin gave highest marginal benefit cost ratio (MBCR) of 40.7 followed by pendimethalin + hand weeding and metolachlor + hand weeding. Weeds reduced the garlic bulb yield by 72.5% over the best treatment pendimethalin 0.75 kg/ha + HW.

Herbicidal potential of CFCF (cell free culture filtrate) of Phoma herbarum (FGCCPH#27) against Parthenium hysterophorus was determined by shoot cut, seedling and detached leaf   bioassays. Maximum mortality was shown by the inoculum formulated with sucrose + Tween-20 followed by Tween-80. Triton-X was found to be highly inhibiting in its action. Maximum average leaf area damage (LAD) of 85% on the seventh day and 65% of leaf damage by fourth day was observed when treated with CFCF obtained from 14 day’s old fermented broth at 50% concentration followed by 75 and 100%. Maximum phytotoxicity was obtained from 14 day’s old fermented broth with sucrose + tween 20  0.5% as formulating agent. Chlorophyll and protein contents were also significantly affected when treated with CFCF. The contents were gradually decreased with increased incubation. Maximum reduction was recorded in shoots treated with CFCF obtained from 14 days old fermented broth at 50% concentration followed by 75% and 100 % (Table 4). 14 days old fermented broth showed the maximum biological activity as depicted by the significant reduction in the chlorophyll and protein content of the host leaves. While extract obtained from 7 days old broth failed to show any remarkable reduction in these contents at similar concentration. The effect was comparatively more on chlorophyll-a and total chlorophyll while chlorophyll-b and protein contents were less affected.

Chlorimuron-ethyl was found very effective to control broad-leaved weeds and sedges, however it was less effective on grassy weeds. Chlorimuron-ethyl 12 g/ha was found much effective than lower dose for controlling the existing weed flora with higher crop yield and benefit: cost ratio.

A field experiment was carried out on the medium black soil of Junagadh Agricultural University, Junagadh (Gujarat) during summer season of 2011. The relative efficacy of pendimethalin, oxyfluorfen, fenoxaprop-p-ethyl, quizalofop-ethyl was tested applied alone or in combination with hand weeding and intercultural 30 days after sowing (DAS) to control weeds in summer green-gram. Two hand weeding with two interculturing at 20 DAS and 40 DAS proved its superiority over rest of the weed management in summer green gram.  Among herbicidal treatment, application of quizalofop-ethyl at 20 DAS and fenoxaprop-p-ethyl at 20 DAS was found to be relatively more effective in controlling weeds than their sole application.

A field experiment was conducted during Kharif 2009 to evaluate the economic feasibility of weed management practices in soybean (Glycine max) grown in red loamy soils of western zone of Tamil Nadu. Early post- emergence (EPOE) application of imazethapyr reduced the density and dry biomass of broad-leaved weeds as well as grasses significantly as compared to pre-emergence herbicide under study. The lowest weed density and biomass were recorded with hand weedings twice on 30 days after sowing (DAS) followed by imazethapyr at 200 and 100 g/ha. Imazethapyr at 100 g/ha was found to be the economic method of weed management by giving higher net returns with grain yield.

A field experiment was conducted during Kharif season 2012 at the Main Research Station, Hebbal, Bengaluru, to know the effect of weed management practices on weed flora and weed growth in irrigated organic finger millet. All weed management treatments had significantly lower total weed density and weed dry weight as compared to unweeded control. Stale seed bed technique + inter cultivation twice at 20 and 35 DAP (23.9/m2 and 10.3 g/m2) significantly lowered the total weed density as well as weed dry weight and was at par with hand weeding twice at 20 and 30 DAP (22.6/m2 and 9.4 g/m2, respectively). Higher total weed density and weed dry weight was found in unweeded check (245.9/m2 and 105.1 g/m2). Highest weed control efficiency was found in manual weeding (93.2%) followed by stale seedbed combined with inter cultivation twice (91.6%) and passing wheel hoe twice with one manual weeding (88.7%). Grain yield was significantly higher in hand weeding twice (5.46 t/ha) followed by stale seedbed combined with inter cultivation twice (5.36 t/ha).

Fifteen demonstrations on integrated weed managment technology were laid out during Kharif  2010 to 2012 in sorghum at randomly selected farmers field from various districts of Marathwada region of Maharashtra with an objective to show the performance of IWM in sorghum. The IWM was found effective in increasing grain yield of sorghum from 18-50% over farmers practice depending upon weed intensity. 

Weed-free check treatment recorded significantly lowest total weed count/m2 and its dry weight at harvest      followed by oxyflourfen pre-emergence 0.10 kg/ha  fb imazethapyr post-emergence 0.10 kg/ha (immediate after harvest of Ist cut) and one hoeing at 3 week after sowing and one hand weeding at 5 week after sowing which were at par with each other. The weed control efficiency was highest in weed free check and significantly superior to all the treatments. Significantly minimum weed index of berseem, green forage yield and seed yield were  observed in treatment oxyflourfen  pre-emergence 0.10 kg/ha  fb imazethapyr post-emergence 0.10 kg/ha and it was at par with treatment one hoeing at 3 week after sowing and one hand weeding at 5 week after sowing and imazethapyr post-emergence 0.10 kg/ha. The economic studies indicatesed that oxyflourfen pre- emergence 0.10 kg/ha fb as post-emergence imazethapyr 0.10 kg/ha immediate after harvest of Ist cut was most cost effective and remunerative. The maximum net monitory returns of  Rs. 64,658/- with B:C ratio of 2.01 was fetched by the treatment oxyflourfen pre-emergence 0.10 kg/ha followed by imazethapyr as a post- emergence application 0.10 kg/ha immediate after harvest of Ist cut was found effective and remunerative followed by treatment  one hoeing at 3 week after sowing and one hand weeding at 5 week after sowing.