2. 4-0 when USe1 as tank mixture or one week before application of fenoxaprop and clodinafop-propargyl reduced efficacy of these herbicides against A. ludoviciana and Pha/aris minlJ/: whereas efficacy of sulfosulfuron used as tank mixture or one week after 2, 4-0 application was not affected. Efficacy of 2. 4-0 against broadleaf weeds Chenopodium alhum L.. Meli/o/us indica and Rumex re/I'O[/exus L. was same either used as tank mixture or in sequential application before or after these grassy herbicides. Sequential application or 2, 4-0 one week after spray or fenoxaprop and clodinafop-propargyl did not reduce ertlcacy of these herbicides and gave grain yield of wheat at par with weed-free check.

Post-emergence application of carfentrazone at 20 g ha- I provided 92-100'% control of all broad leaf weeds including hard to control weeds Malwa parvif/ora ane Convolvllilis arvel/sis in wheat with no residual effect on succeeding sorghum crop_ Metsulfuron and 2. 4-D were not effective against Malwa parvif/ora and COl/volvllllls arvel/sis_ Carfentrazone at 20-35 g/ha was very safe to wheat crop_

Tillage practices and weed control treatments had marked effect on weeds density and total weed dry matter production in wheat. The' lowest density of Phalaris minOl; CVilodon doelylon. Cvperus rOlundus. Anagallis orvensis and Chenopodium album was rccorded in zero tillage. The maximum density of weed species was observed in conventional tillage. Weed dry matter production was significantly less in zero tillage and more in conventional tillage. Sulfosulfuron at 33.3 g ha" had minimum density of all the major weeds and dry matter production by weeds. Conventional tillage recorded maximum number of carheads n1"'. grains pcr carhead. test weight and grain yield. whieh were minimum in zero tillage treatmcnt. Sulfosulfuron recorded maximum values of all the yield attributes and gave highest grain yield.

Pcndimethalin at 1.0 kg ha" on beds as prc-emergence followed by cultivation in furrows wa; effective (WeE 62.0%,) against grassy and non-grassy weeds resulting in lower total wecds density (35.0 No. Ill") which was statistically at par with sulfosulfuron at 25 g ha', lralkoxydim at 350 g ha" and hand weeding at 30 DAS. Maximum grain yield was obtaincd in bed planted wecd-free plOI (3725 kg ha") which was at par with pendimethalin at 1.0 kg ha" on bcd as pre-emergencc followed by cultivation in furrows, sulfosultllron at 25 g ha", tralkoxydim at 350 g ha" and c1odinafop at 60 g ha".

Different tillage practices did not influence the population and dry maller of weeds and yield of wheat. Infcstation of weeds caused 65'% reduction in wheal grain yield. Post-emergence application of c1odinaf()p at 0.06 kg ha" fb 2, 4-D at 0.50 kg ha' significantly reduced the population and dry matter of weeds and increased the grain yield of wheat. This combination proved more effcctive than isoproturon at 1.0 kg ha:'+2, 4-D at 0.50 kg ha·'.

Effect of rice establishment methods and weed management practices on weeds and grain yield of rice was studied. The maximum reduction of weed species was obtained with application of herbicides as pre-emergence supplemented by two hand weedings at 30 and 60 days after seeding/days after transplanting under all the establishment systems of rice. The maximum weed dry matter reduction was achieved due to herbicide supplemented with two hand weedings in transplanted rice followed by herbicide as pre-emergence supplemented with two hand weedings in wet seeded rice and zero till rice. The highest grain yield (4623 kg ha") was achieved by the application of herbicide supplemented with two hand weedings in transplanted rice which was significantly higher than the other treatments. Among the direct seeded rice, the highest yield (4222 kg ha') .was recorded under wet seeding (WSR) employed with two hand weedings (We. - two hand weedings) and on par with application of herbicide followed by one hand weeding (We,) ullder transplanting (TPR).

Uncontrolled weeds caused 31% reduction in grain yield of rice. Pyrozosulfuronethyl at 20. 25 or 30 g ha" was as effective as butachlor at 1250 g ha-' but superior to hand weeding and rotary paddy weeder in reducing weed growth and increasing grain yield of rice. The yield obtained from hand weeding was comparable to rotary weeder.

Quinclorac at 187 g ha" applied three days after transplanting gave effective control of grasses and broad leaf weeds and provided adequate control of sedges. It was non-toxic to crop. and resulted in higher grain yield (6664 kg ha") and monetary returns (Rs. 32191 ha") than weedy check and was on par with weed-free check.

Post-emergence application or triazolopyrimidine sulfonamide at 15 to 25 g ha" I applicd at 15 days after transplanting (DAT) was more effective in reducing the weed growth and increased crop growth, yield and yield components than pre-emergence herbicides (aniloros. butachlor and pretilachlor) and was on par with hand weeding done at 20 and 40 DAT.

The dominant weed nora were Echinocloa colona (L.), Cyperus djffiJrmis L. and Al/ll/lania hraccif'era (L.) Rottb. Intensive puddling with continuous submergence recorded the lowest density and dry weight of wceds with 40% increased grain yield over normal puddling with irrigation at one day after disappearance of ponded water. Among the weed managcment practices, oxadiargyl at 75 g ha" supplemented with HW at 40 DAT recorded the lowcst dcnsity and dry weight of weeds with higher weed control efficiency and grain yicld, which was comparable with hand weeding twice scheduled at 20 and 40 DAT. On an averagc, o.xadiargyl at 75 g luI" supplemented with HW at 40 DAT registered 39.5% higher grain yield as compared to unweeded control. Cinmethylin at 75 g ha" was least effective in controlling the weeds. Intensive puddling with continuous submergence combined with oxadiargyl at 75 g ha" supplemented with HW at 40 DAT was the best integrated weed managcment practice to achieve broad spectrum weed control and higher grain yield in transplanted rice.

Normal planting (20 x 10 cm) produced significantly higher grain yield (4.18 t ha') than wider (25 x 10 cm), closcr (15 x 10 cm) and random/haphazard planting patterns. Two hand wcedings (25 and 50 DAT) gave significantly higher grain yield (4.15 t ha-') than anilofos at 0.4 kg ha-' pre-em.+2, 4-D at 0.5 kg ha" post-em., anilofos at 0.4+2, 4-0. at 0.5 kg ha-' pre-em. and anilofos at 0.4+2, 4-D at 0.5 kg ha-' pre-em. followed by I HW at 30 DAT and was found most appropriate treatment, when judged in terms of rcducing lolal wced population and dry matter and increasing bora rice grain yield.

Major weed nora associatcd with wet direct-sown summer rice during the dry season comprised mainly Echinochloa colona (9.5%,), Cyperus dU!c)rmis (30.2%), Fil1lhris(yli.\· l1Iiliacea (27.0%,), S[Jhenochlea zeylanica (15.8%) and Ludwigia [Jarvi/lora (17.5%.). Pyrazosulfuron-ethyl (25 g ha") applied at 10 days after sowing was most effective in controlling the weeds (95.6'Yo) and maximizing rice grain yield (5.72 t ha"). This was at par with hand wceding twice at 20 and 40 DAS in terms of weed control efficiency and grain yield. Pyrazoslllfliron ethyl (20 g ha:') applied at 10 DAS, pretilachlor+safener (750 g ha") applied at 7 DAS and fentral.amide (120 g ha") applied at 7 DAS also showed good suppression of weeds with weed control etliciency of 93.7, 91.4 and 90.5'%, respectively. There was more than 45%, reduction in the grain yield of rice due to competition with weeds in weedy plots.

An integrated weed management experiment was conducted consecutively during wet season of 1998, 1999 and 2000 at Agricultural Research Farm. Institute of Agricultural Scicnces, BHU, Varanasi to evolvc suitable weed management technique for direct dry seeded rainfcd lowland rice. Pre-emergence application of butachlor+2, 4-0 (1.5+0.5 kg ha"), thiobencarb+2, 4-0 (1.5HU kg ha") and anilofos+2, 4-0 (0.4+0.5 kg ha") in combination with one hand wecding (25 OAS) were maximum and equally effectivc in minimizing weed growth during pre-flooding and enhancing coarse rice grain yield as comparcd to these herbicidal combinations of treatments without hand weeding. Weedy check marked a mcan yicld loss of 53.8'X. and this loss ranged from 10.1 to 28.8'X. under hand weeding (25 and 50 OAS) and herbicidal treatments.

Maximum weed control efficiency (>98%) was achieved with pre-emergence application of atrazine at 0.5 kg ha" in conjunction with pendimethalin @ 0.25 kg ha" closely followed by atrazine+alachlor each applied at 0.5 kg ha". Similar trend was observed in grain and stover yields. net realization and CBR values.

Tillage operation resulted in significant reduction in weed dry weight at all the growth stages and increased the grain yield over no tillage practice. The lowest weed dry weight and the highest grain yield in one season were recorded with 24 kg seed ha 0 1 

• Hand weedings at 25 and 45 DAS recorded significantly higher grain yield and lower weed dry weight at silking and maturity stageso

Post-emergence application ofimazethapyr at 75 g ha-' reduced the population of Caesulia axillaris. Anatis monthulani and Ac~vpha indica significantly as compared to all pre- and rest ofthe post-emergence herbicides under investigation. Quizalofop-ethyl 5 EC at 50 g ha- ' was significantly effective against Cammelina benghalensis and Echinachlaa colona. The lowest weed biomass was recorded with two hand weedings 20 and 40 DASfollowed by imazethapyr at 75 g ha-' and quizalofop-ethyl 5 EC at 50 g ha- '. Two hand weedings (at 20 and 40 DAS) and imazethapyr at 75 gha-' were most appropriate treatments in tem1S of reduction in total weed density and increase in soybean yield.

Pre-plant incorporation of trifluralin at 1500 g ha" alone, trifluralin 1000 g ha-' fb hand hoeing at 20 DAS, pendimethalin at 1000 g ha-' fb hand hoeing at 20 DAS and two hoeings (20 and 40 DAS) provided better control of weeds upto 90 DAS compared to other weed control treatments. Consequently, these being at par with each other produced pods/ plant and grain yield of soybean statistically equivalent to that of weed-free throughout the crop season.

The major weed species observed in the weedy check plots of mustard field were Chenopodium alhum, C. murale, Portulaca oleracea, Melilotus indica, Asphodelus tenuifiJ!iu.l' and Rumex dentatus. Inclusion of mungbean in mungbean-mustard cropping scquence caused 18.2% weed control efficiency over fallow-mungbean sequence. The system also gave 1597 kg ha-' seed yield of mus1ard, besides additional mustard seed equivalent yield of 600 kg ha-'. by mungbean cultivation during kharif season, which provided 24.31% higher net return over fallow-mustard cropping sequence. Net return and benefit: cost ratio were improv~d with higher seed rate (5 and 6 kg ha-') than lower seed rate (4 kg ha·'). Among the weed management practices, two hand weeding at 25 and 50 DAS and integration of fluchloralin at 0.75 kg ha" supplemented by one hand weedings at 25 DAS found significantly superior in terms of reducing weed density and dry weight of weeds over tluchloralin at 1.0 kg ha- I and weedy check. However, maximum net profit and benefit: cost ratio were recorded with fluchloralin at 0.75 kg ha-'+one hand weeding at 25 DAS.

Planting blackgram on raised beds recorded significantly lower weed number and dry matter, thus resulting in significantly higher seed yield over ridge and conventional planting. The minimum weed number and dry matter accumulation were recorded following the application of pendimethalin at 0.75 kg ha" supplemented with one hand weeding at 45 days after sowing. Pendimethalin at 0.75 kg ha" in integration with one hand weeding 45 days after sowing resulted in significantly higher seed yield of blackgram than other weed control treatments. Uncontrolled weeds, on an average, caused 48.1 % reduction in the seed yield of blackgram.

Pre-plant or pre-emergence application of trifluralin at 0.50 kg ha" supplemented with one hand hoeing at 30 days stage provided effective control of weeds and significantly increased seed yield of blackgram over weedy check, one hand hoeing or application of herbicides alone. Higher dose ofherbicides alone did not improve weed control or seed yield further compared to their lower dose. The highest net return and B : C ratio were registered with pre-emergence application of trifluralin at 0.50 kg ha-'+one HW followed by preplant application of trifluralin at 0.50 kg ha-'+one HW. Yield and profit with pendimethalin werc less due to lower yield and higher cost of herbicide.

Maximum productivity of 5.24 t ha- ' was realised by stale seed bed with eucalyptus mulched plots which was 171.5 and II % more than weedy check and weed-free plots, respectively. Stale seed bed with either polyethylene mulching or pre- and post-planting glyphosate application was identified as the effective nutsedge control measure. The most economical treatment was stale seed bed with glyphosate application integrated with eucalyptus mulching and it recorded the highest net return (Rs. I8,270) and B : C ratio (2.01).

The highest values of all yield attributes were recorded under the plots kept weed-free upto harvest and minimum in the plots which remained weedy upto harvest. Weed dry weight and weed competition index increased with the increase in the duration of weedy period and decreased with the increase in duration ofweed-free condition. Weed-free conditions beyon91 45 days after transplanting could not bring significant improvement in fruit yield of tomato which indicated that the critical period of crop-weed competition was found to be first 45 days after transplanting.

Significantly higher bulb yield was obtained when crop was kept weed-free for initial 60 days after transplanting (OAT) compared to 20 and 40 QAT where weeds remerged at later stages and accumulated higher weed dry matter and reduced the bulb yield. Bulb yield remain.ed at par with weed-free check when weeds were allowed to grow with the onion crop upto 20 OAT; however, weedy period beyond 20 days was detrimental to bulb yield. There was 53.4% reduction in bulb yield under season long unweeded conditions. Critical period of crop-weed competition was found to be 20-60 OAT.

Pre-emergence application of fluchloralin at 1.0 kg ha-' supplemented with two hand weedings at 30 and 60 DAT recorded the least weed count and dry matter production favouring the highest yield of onion bulbs (72.4 t ha·'). Fluchloralin, pendimethalin, alachlor, trifluralin and oxyfluorfen at lower doses in combination with one or two hand weedings produced significantly higher yields than their application alone at higher doses.

The dry matter of weeds was reduced significantly by pre-plant incorporation of fluchloralin at 0.67, 0.90 and 1.12 kg ha-' and pre-emergence application of butachlor at 1.0, 1.5 and 2.0 kg ha" over weedy check. Fluchloralin was effective only against Poa annua, while butachlor controlled Cichorium inlyhus. Whereas Rumex den latus and Lepidium .I'alivum were not controlled by any of the herbicides. Pre-emergence application of pendimethalin, though controlled the weeds but was toxic to the crop. The weed control efficiency with two hand weedings and fluchloralin at 1.12 kg ha-' was 71.6 and 70.5%, respectivcly. The fodder yield of Persian clover increased significantly with two hand weedings (30 and 45 days after sowing), fluchloralin at 0.67 kg ha-' and butachlor at 1.00 kg ha" over weedy check. All the weed management treatments improved the crude protein content of Persian clover over weedy check.

Mimosa in visa Mart. (F-Mimosaceae) an alien invasive weed, which was first reported from Kerala in 1964, has emerged as a problem invasive weed adversely affecting the biodiversity and causing toxicity problems to animals. The toxic amino acid, mimosine, present in the plant is an anti nutritional factor contributing to clinical cases of toxicity in livestock. The mimosine content in M. invisa was the highest (9.2%) at active vegetative stage. Among plant parts, content was highest (10.4%) in the immature leaves. Ensiling the M. inv{w admixed with fodder grass in different proportions ranging from 10 to 90% for 60 days lowered the mimosine content by 32 to 46%.

The zero till wheat crop sown after direct seeded puddled rice, recorded significantly higher dry matter accumulation by Phalaris minor as compared to conventionally sown wheat crop. However, the seed bank sbtus was not affected due to tillage systems. Zero till sown crop recorded significantly less grain yield than conventionally tilled crop. On an average of three years, highest wheat grain yield (3843" kg ha") was obtained in conventionally tilled wheat after transplanted rice and it was significantly more than that of zero tilled wheat after rice with or without puddling. Clodinafop at 60 g. sulfosulfuron at 25 g and fenoxaprop-p-ethyl at 100 g ha-' increased wheat grain yield by 41.9•. 43.7 and 39.9%. respectively. over weedy crop.

One year old Leptochloa chinensis seeds' germination ranged from 25 to 29% at temperatures ranging from 25° to 45°C. The fresh and two years' old seeds did not germinate irrespective of the temperature. Submergence periods ranging from 1 to 5 weeks were equally effective in preventing the seedling emergence during the period of submergence. However, at 15 days after the termination of each submergence, the seedling emergence was significantly less under more than two week submergence treatments than one week submergence. No seedling emerged beyond the submergence depth of 2.5 cm, whereas at 2.5 cm, 4.7% s~dlings emerged from the soil but failed to emerge out of the water surface. r"

Tillage operations significantly influenced the vertical distribution of winter weeds in the wheat field. Significantly higher number of seeds ofAvena ludoviciana, Medicago hispida and Chenopodium album was recorded in the upper 0-5 cm layer under zero tillage treatments than conventional and deep tillage. But athigher depths of 5-10 and, 10-15 cm, the number of seeds of A. ludoviciana was significantly higher under deep tillage followed by conventional and zero tillage. Continuous use ofclodinafop fb 2, 4-D and isoproturon+2, 4-D for control of weeds in wheat field significantly reduced the number of weed seeds over weedy check.

Growth of sorghum was more at low pH (5.1) soil than at high pH (8.1) soil at all concentrations of sulfosulfuron and incubation periods. Root dry weight per plant was 44%, highcr in low pH soil than under high pH soil. Visual phytotoxicity increased with increase in sullosulfuron conccntration and decreased with increase in incubation period in both the types of soil. After 120 days of incubation, GR 50 of sulfosulfuron increased approximately by 19.8 times in low pH soil as compared to only 7.8 times in high pH soil. Half life of sulfosulfuron was 28 days in high pH soil as compared to II days in low pH soil. After 120 days,S and 14'% of the herbicide remained in low and high pH soil, respectively.

The dry weight of sorghum shoot (test plant) increased significantly with each successive increase in temperature level from 15-35°C and incubation period from 0-120 days. Whereas increase in concentration of sulfosulfuron (0 to 64 ppb) caused significant reduction in dry weight of sorghum shoot. At 120 days of incubation, the GR,o (Growth reduction 50%,) at 35°C was approximately 2.5 times higher than at 15°C. The half life of sulfosulfuron was 46, 28 and II days at 15, 25 and 35°C, respectively.

Significant reduction in seed yield of raya and winter maize occurred due to carry-ovcr effects of sulfosulfuron applied to wheat at recommended (25 g ha") and double the rccommended dose (50 g ha") as compared to untreated plots. The reaction of berseem and vegetable pea was found to be variable and in these crops significant reduction in fodder and pod yield, respectively, was observed due to residual effects of sulfosulfuron even at recommendcd levels during 2004-()5 only. The differences in sunflower yield due to carryover levels of sulfosulfuron were non-significant during both the years. No residues of sulfosulfuron applied to wheat at 25 g ha" and 50 g ha" were detected in soil after wheat harvest.