Postemergence Applications Of Glyphosate Research Articles

Agronomic Performance of RR® Soybean Submitted to Glyphosate Application Associated with a Product Based on Bacillus subtilis

Despite the great benefits arising from the adoption of Roundup Ready® (RR®) soybean, there are reports about the lack of selectivity of glyphosate for this crop. The use of growth-promoting microorganisms can help attenuate the injuries caused by herbicides. The objective of this work was to evaluate the agronomic performance of RR® soybean submitted to the post-emergence application of glyphosate both isolated and in association with Bacillus subtilis. The experiment was carried out in a completely randomized block design, with four replications. The treatments consisted of the post-emergence applications of glyphosate (1296 g a.i. ha−1), glyphosate (2592 g a.i. ha−1), glyphosate/glyphosate (1296/1296 g a.i. ha−1), glyphosate + B. subtilis BV02 (1296 + 42 g a.i. ha−1), glyphosate + B. subtilis BV02 (2592 + 42 g a.i. ha−1), and glyphosate + B. subtilis BV02/glyphosate + B. subtilis BV02 (1296 + 42/1296 + 42 g a.i. ha−1). The application of glyphosate (2592 g a.i. ha−1) and the sequential application of glyphosate provides higher levels of intoxication. The association of B. subtilis BV02 with glyphosate (2592 g a.i. ha−1) prevented losses in the values of relative chlorophyll a and b and the total chlorophyll index. The soybean yield was reduced when the plants were submitted to a sequential application of glyphosate.

Control of Italian ryegrass and Alexandergrass in corn using different corn sowing date, pre- and post-emergent herbicides

Glyphosate-resistant (GR) Italian ryegrass (LOLMU) and Alexandergrass (URPLA) are troublesome weeds in corn cropping systems in Southern Brazil. The emergence pattern of those weeds is not uniform and may change according to the season’s environmental characteristics. Also, herbicide resistance has been diminishing the success of the weed control programs. The objectives of this study were to evaluate the influence of corn-sowing date on LOLMU and URPLA densities and their control provided by pre- and post-emergent herbicides. Field trials were conducted in two crop seasons in Southern Brazil consisting of three corn sowing date (August, September, and October) and the application of atrazine + S-metolachlor (residual) in corn pre-emergence in different post-emergence weed control programs with glyphosate, ammonium-glufosinate, nicosulfuron, and atrazine. The results indicated that the sowing date had a significant influence on LOLMU and URPLA densities. Corn sown in the earliest period was exposed to a higher LOLMU density, whereas corn sown in the latest period had a higher density of URPLA. Also, the application of residual herbicide at corn pre-emergence reduced both weed species densities and decreased the pressure for the control of glyphosate-resistant LOLMU for the post-emergence herbicides. The use of residual herbicides in corn pre-emergence is an efficient strategy to be considered in the LOLMU and URPLA control programs, followed by post-emergence application of glyphosate, ammonium-glufosinate, atrazine, and nicosulfuron.

Using Fluridone Herbicide Systems for Weed Control in Texas Cotton (Gossypium Hirsutum L.)

Studies were conducted during 2015 through 2018 in south-central, Coastal Bend, and Southern High Plains areas of Texas to evaluate fluridone herbicide systems for weed control and cotton response. Fluridone alone at 0.17 to 0.23 kg ai ha-1 followed by postemergence (POST) herbicides controlled Amaranthus Palmeri 82 to 100% season-long while Cucumis melo control ranged from 92 to 100%. Control of Urochloa Texana with fluridone alone ranged from 40 to 96% early-season while late-season control ranged from 37 to 96%. Fluridone plus fomesafen systems controlled A. Palmeri, C. Melo, and U. Texana at least 98% early season; however, late-season control of A. Palmeri was less than 70% while C. Melo control was 91% and U. Texana control was 80%. Adding a POST application of glyphosate to fluridone plus fomesafen improved control to at least 98% for all three weed species. Fluridone plus fluometuron combinations provided similar control to fluridone plus fomesafen. Adding glyphosate (POST) improved A. Palmeri control to at least 82% season-long. Cotton yields reflect the level of weed control with significantly better yields from fluridone systems compared with the weedy check. However, in the one year when the untreated was maintained weed-free, no differences in cotton yield were noted between the weed-free and any herbicide treatment.

Effectiveness of different methods for controlling Orobanche in mustard

To study the efficacy of neem cake, soil drenching of metalaxyl, post-emergence application of glyphosate at very low concentrations alone and in combination with 1% solution of (NH4)2SO4 and 125% of recommended fertility, field experiments were conducted at the villages Ganghala and Bidhwan in Bhiwani district of Haryana during Rabi seasons of 2014–15 and 2015–16, respectively. Feasibility of adoption of results of studies conducted earlier on use of glyphosate 25 g/ha at 30 DAS and 50 g/ha at 55 DAS is being demonstrated by multi location field trials through farmers participatory approach in different parts of state during 2010–2016. Neem cake 400 kg/ha at sowing fb soil drenching of metalaxyl MZ 0.2% at 25 DAS fb glyphosate at 40 g/ha at 45 DAS or neem cake 400 kg/ha fb pendimethalin (PPI) at 0.75 kg/ha fb metalaxyl 0.2% at 25 DAS did not prove effective in minimizing density of Orobanche. Post-emergence application of glyphosate at 25 and 50 g/ha with 1% solution of (NH4)2SO4 at 30 and 55 DAS showed promise with 85- 91% control of this weed not only in experimental fields but in large scale demonstrations on farmers’ fields.

Efficacy of Control of Glyphosate-Tolerant Species of the Rubiaceae Family Through Double-Knockdown Applications

ABSTRACT: Spermacoce latifolia, S. verticillata, and Richardia brasiliensis (family Rubiaceae, tribe Spermacoceae) are glyphosate-tolerant weeds in the soybean producing areas of Brazil. The weed shifts to glyphosate-tolerant weeds across soybean-producing areas has shown the need for adoption of practices that conserve the efficacy of glyphosate. This study evaluated the effect of single- and double-knockdown herbicide applications on the control of S. latifolia, S. verticillata, and R. brasiliensis prior to soybean sowing. Trials were designed as a randomized block and treatments were arranged as a factorial. Factor A was three systemic herbicide treatments 10 days before sowing (DBS), while Factor B was three contact herbicide treatments applied 0 DBS (“sow and apply”). The single- and double-knockdown applications were followed by post-emergence applications of glyphosate or 2,4-D + glyphosate when the crop reached three leaves. The efficacy of control of each weed species was visually evaluated 14 days after sowing (DAS), as well as 0 and 28 days after post-emergence application (DAA). The double-knockdown applications generally provided higher levels of control for the target weeds of the Rubiaceae family than the single-knockdown applications. Glyphosate + 2,4-D, glyphosate + 2,4-D + diclosulam or glyphosate + [halauxifen-methyl + diclosulam] followed by glufosinate or paraquat achieved at least 90% of control of S. latifolia and R. brasiliensis, but did not control S. verticillata (<80%). Glufosinate at 457 g a.i. ha-1 was equivalent to paraquat at 400 g a.i. ha-1 as a contact herbicide in the double-knockdown applications, especially on the first assessment dates.

Biology and large scale demonstration for management of Orobanche aegyptiaca in mustard

Field experiments to study the efficacy of neem cake, soil drenching of metalaxyl, post-emergence application of glyphosate at very low concentrations alone and in combination with 1% solution of ammonium sulphate and 125% of recommended fertility, were conducted at village Ganghala (Bhiwani) during Rabi seasons of 2014–15 and village Bidhwan (Bhiwani) during 2015–16. Feasibility of adoption of results of studies conducted earlier on use of glyphosate 25 g/ha at 30 DAS and 50 g/ha at 55 DAS is being demonstrated by multi location field trials through farmers participatory approach in different parts of state during 2010–2016. Neem cake 400 kg/ha fb pendimethalin (PPI) at 0.75 kg/ha fb HW at 60 DAS did not prove effective in minimizing density of Orobanche. Post-emergence application of glyphosate at 25 and 50 g/ha at 25 and 55 DAS, respectively showed promising results with 7595% control of this weed in experimental field and 76.5% on large scale demonstrations at farmers’ fields. Biotype from Ganghala (Bhiwani) was found to be most robust biotype with 5840 seeds per capsule.

Residual effect of pre-sowing weed management on the purple nutsedge (Cyperus rotundus) and succeeding maize germination and yield

A study was carried out to evaluate different pre-sowing weed management methods on Cyperus rotundus and on succeeding maize germination and yield at Chinnankuppam village in Dharmapuri district, Tamil Nadu. Pre-emergence, early post-emergence and post-emergence herbicides viz metribuzin, halosulfuron methyl, glyphosate and 2, 4-D were applied at different doses to select an optimum dose suitable for the management of purple nutsedge (C rotundus) as a pre-sowing weed management method. Pre-sowing weed management treatments did not influence the per cent germination of succeeding maize. Among the pre-sowing weed management treatments early postemergence application of halosulfuron methyl at 50 g/ha followed by post-emergence application of glyphosate at 1.00 g/ha resulted in reduced density and dry weight (2.2 and 4.1/m2, 0.37 and 0.70 g/m2) followed by early postemergence application of halosulfuron methyl at 75 g/ha (3.5 and 5.7/m2, 0.60 and 0.97 g/m2) at 15 and 30 DAS respectively. Simultaneously both the treatments increased the weed control efficiency of C rotundus (69.16 and 58.33%) and (50.00 and 42.26%) at 15 and 30 DAS respectively. Among the treatments pre-sowing application of early post-emergence halosulfuron methyl at 50 g/ha followed by post-emergence application of glyphosate at 1.00 kg/ha recorded the higher grain (9, 387 kg/ha)and stover (9, 500 kg/ha) yield of succeeding maize.

Soil Microbial Activities and Yield of Elephant Foot Yam as Influenced by Weed Management Practices in Alfisols

ABSTRACTWeed infestation causes yield reduction up to 100% in elephant foot yam [Amorphophallus paeoniifolius (Dennst.) Nicolson] due to the widely spaced planting. At present, manual weeding is popular but expensive, tedious, and time-consuming. Herbicides and polythene mulching may be alternative methods for weed management. A field experiment was conducted during May–December 2015 at the Regional Centre of Indian Council of Agricultural Research-Central Tuber Crops Research Institute, Bhubaneswar, Odisha, India, to determine the effects of weed management practices on soil quality, microbial activities, and yield performance of elephant foot yam in an Alfisol under drip irrigation. The treatment involving weed control ground cover (WCGC) resulted in lower weed biomass, greater weed control efficiency (WCE), and greater corm yield (37.4 t∙ha−1) by 335% over the weedy check. The yield with the weed control ground-cover treatment was comparable to yields for four manual weedings at 30, 60, 90, and 120 days after planting (DAP) (33.7 t∙ha−1) and two manual weedings at 30 and 60 DAP along with postemergence application of glyphosate at 90 DAP (32.9 t∙ha−1). Use of WCGC resulted in greater postharvest soil available N, P, K, Fe, Cu, Mn, and Zn, increased populations of fungi, bacteria, and actinomycetes, and soil dehydrogenase, fluorescein diacetate, acid, and alkaline phosphatase activities. Two manual weedings at 30 and 60 DAP, along with the application of glyphosate at 90 DAP, resulted in higher soil organic carbon. WCGC appears to be a good weed management option in elephant foot yam.

Pre-sowing Weed Management of Purple Nutsedge (Cyperus rotundus) in a Non-crop Ecosystem

Purple nutsedge is a perennial, one of the world worst weed, ravages the field continuously throughout the year in the tropical regions. It thrives and dominates under any environmental conditions. Normally weeds compete with the crops for the nutrients, water, space, light and other essential requirements. Inadequate control of weed at appropriate stage is considered as a major constraint for high yield.There is more number of pre-emergence, early post-emergence and post-emergence herbicides coming up in the market with wide spectrum of weed control efficiency. The availability of effective and new herbicides and herbicide combinations in the recent times have led to control of established weeds before crops, so as to reduce their competition with crops and increase the crop yields. With this background, field experiments were carried out to evaluate the effect of different herbicides for control of Cyperus rotundus in a non-crop ecosystem in the farmer’s field, Chinnankuppam at Dharmapuri district, Tamil Nadu during 2017 to 2018. Cyperus rotundus wasfound to bethe predominant weed in the experimental field compared to broad leaved weeds such as Parthenium hysterophorous and grasses like Chloris barbata and Cynodon dactylon. Pre-emergence, early post-emergence and post-emergence herbicides viz., metribuzin, halosulfuron methyl, glyphosate and 2,4-D were applied individually as well as different combination were used for the management of purple nutsedge (Cyperus rotundus).Among the herbicides, early post-emergence application of halosulfuron methyl at 50 g ha-1fb post-emergence application of glyphosate at 1.00 kg ha-1resulted in lower Cyperus density, dry weight and higher control efficiency followed by early post-emergence application of halosulfuron methyl at 75 g ha-1. .

Herbicides and polythene mulching effects on yield of cassava

A field experiment was conducted to study the effects of weed management practices on cassava under irrigated conditions in Bhubaneswar (Odisha), India for consecutive three years (2010–11 to 2012–13). The results revealed that four rounds of manual weeding at 1, 2, 3 and 4 months after planting (MAP) and black polythene mulching resulted in taller plants, more number of nodes and leaves per plant, maximum number of storage roots per plant, maximum length and girth of storage roots as well as fresh storage roots yield per plant with lower weed biomass. Mean fresh root yield due to black polythene mulching was at par with four rounds of manual weeding (at 1, 2, 3 and 4 MAP). Black polythene mulching resulted in higher dry matter partitioning efficiency and soil microbial population. The root yield decreased by 9.6%, due to pre-emergence application of oxyfluorfen + two rounds of manual weeding (at 2 and 3 MAP) treatment and 10.1% in two rounds of manual weeding (at 1 and 2 MAP) + post-emergence application of glyphosate (at 3 MAP) compared to four rounds of manual weeding (at 1, 2, 3 and 4 MAP).

Production potential and economics feasibility of buckwheat (Fagopyrum esculentum Moench) as influenced by integrated weed management practices under Terai rgion of West Bengal

A field experiment was conducted during the winter season of 2011-2012 and 2012-2013 at the Instructional Farm of Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, and West Bengal. The experimental field was laid out in Randomized Block Design, having seven (7) treatments with three (3) replications. The treatments consisted of preemergence application of fluchloralin @ 2.22 lit. ha -1 (T 1 ), post-emergence of application of glyphosate @ 2.50 lit. ha -1 (T 2 ), pre-emergence application of fluchloralin @ 2.22 lit. ha -1 + hand weeding (once at 35 DAS) (T 3 ), hoeing (Twice) 20 and 35 DAS (T 4 ), hand weeding (twice) at 20 and 35 DAS (T 5 ), pre-emergence application of fluchloralin @ 2.22 lit. ha -1 combined with postemergence application of glyphosate @ 2.50 lit. ha -1 (T 6 ) and unwedded control (T 7 ). The economics of buckwheat under seven varying weed management practices showed that the hand weeding twice at 20 and 35 DAS recorded highest net income, benefit cost ratio and lowest cost of producing per kg of seed over other weed control practices, this is environmentally sound, socially acceptable and economically viable. Among the weed management practices pre-emergence application of fluchloralin @ 2.22 lit. ha -1 and post-emergence application of glyphosate @ 2.50 lit. ha -1 at 20 DAS produced higher yield attributes and yield over unwedded control whereas pre-emergence application of fluchloralin @ 2.22 lit. ha -1 followed by one hand weeding at 35 DAS produced seed yield comparable to hand weeding treatment.

Goss’s Wilt Incidence in Sweet Corn Is Independent of Transgenic Traits and Glyphosate

Recently, claims have been made that the use of glyphosate and transgenic crop traits increases plant susceptibility to pathogens. Transgenic traits used widely for years in dent corn are now available in commercial sweet corn cultivars, specifically, the combination of glyphosate resistance (GR) and Lepidoptera control (Bt). The objective was to assess the interactions of the GR+Bt trait, glyphosate, and Goss’s wilt on sweet corn. Nine treatments were tested under weed-free conditions at two sites in 2013 and 2014. Treatments included two isogenic cultivars differing only in the presence or absence of GR+Bt, with and without postemergence application of glyphosate, and inoculation with the causal agent of Goss’s wilt (Clavibacter michiganensis ssp. nebraskensis) before glyphosate application, after glyphosate application, or no inoculation. Results failed to show glyphosate or the GR+Bt trait influenced sweet corn susceptibility to Goss’s wilt. The only factor affecting Goss’s wilt incidence was whether plants were inoculated with C. michiganensis ssp. nebraskensis. In the absence of glyphosate application, yet under weed-free conditions, several yield traits were higher in sweet corn with the GR+Bt trait. Results showed that the GR transgene confers the same level of tolerance to glyphosate in sweet corn as observed previously in dent corn. If true, recent claims about glyphosate and transgenic traits increasing plant disease would be of major concern in sweet corn; however, no relationships were found between the GR+Bt trait and/or glyphosate to Goss’s wilt incidence in sweet corn.

Preplant and Postemergence Control of Glyphosate-Resistant Giant Ragweed in Corn

Glyphosate-resistant (GR) giant ragweed has recently been identified in southwestern Ontario and has the potential to be a significant problem for regional corn producers. Eight field trials [four with preplant (PP) and four with postemergence (POST) herbicides] were conducted from 2013 to 2014 on various Ontario farms infested with GR giant ragweed to determine the efficacy of PP and POST tank-mixes in corn. Glyphosate tank-mixed with atrazine, dicamba, dicamba/atrazine, mesotrione plus atrazine, flumetsulam, isoxaflutole plus atrazine, saflufenacil/dimethenamid-P, S-metolachlor/atrazine and rimsulfuron applied PP provided up to 54%, 95%, 93%, 95%, 40%, 89%, 91%, 50% and 93% control of GR giant ragweed and reduced dry weight 69%, 100%, 99%, 100%, 30%, 92%, 98%, 66% and 99%, respectively. POST application of glyphosate alone and tank-mixed with 2,4-D ester, atrazine, dicamba, dicamba/diflufenzopyr, dicamba/atrazine, bromoxynil plus atrazine, prosulfuron plus dicamba, mesotrione plus atrazine, topramezone plus atrazine, tembotrione/thiencarbazone-methyl and glufosinate provided up to 31%, 84%, 39%, 94%, 89%, 86%, 83%, 78%, 72%, 43%, 63% and 58% GR giant ragweed and reduced dry weight 55%, 99%, 72%, 99%, 99%, 98%, 96%, 96%, 93%, 89%, 91% and 95%, respectively. In general, PP control of GR giant ragweed was greater than POST applied herbicides evaluated. Based on these results, glyphosate tank-mixes containing dicamba or mesotrione plus atrazine applied PP, and dicamba applied POST will provide the most consistent control of GR giant ragweed in corn.

English

A field experiment was carried out at Tamil Nadu Agricultural University, Coimbatore during kharif seasons of 2010 and 2011 to study the effect of Glyphosate on weed management and grain yield in kharif maize of transgenic stacked and conventional maize hybrid. This investigation was conducted with the following objectives to evaluate the weed control efficiency and crop productivity with K salt of glyphosate formulations under field conditions. Treatments consisted of two transgenic stacked hybrids named 30V92 and 30B11 applied with glyphosate as early post emergence at 900 and 1800 g a.e ha-1 during kharif  season of 2010 and conventional maize hybrids named 30V92 and 30B11 applied with glyphosate by controlled droplet application method at 900, 1350 and 1800 g a.e ha-1 during kharif season of 2011 compared with non-transgenic counterpart maize hybrids applied with pre emergence atrazine at 0.5 kg ha-1 followed by one hand weeding on 40 days after sowing (DAS) with and without insect management. Among the treatments, early POE application of glyphosate at 1800 g a.e ha-1 registered lower weed density and higher weed control efficiency in transgenic and non-transgenic maize hybrids at all the intervals. Higher grain yield was registered with post emergence application of glyphosate at 1800 g a.e ha-1 in transgenic and non transgenic maize hybrid of 30V92 during both the kharif seasons   Key words: Glyphosate, transgenic maize, weed control efficiency, weed index, yield.

Efficacy of POST glyphosate applications in combination with other POST herbicides in glyphosate-resistant corn (Zea mays L.)

The use of glyphosate-resistant corn has facilitated a shift from a reliance on preemergence residual herbicides to postemergence (POST) herbicides, and in some cases exclusively glyphosate. Glyphosate is a non-selective herbicide that is relatively slow-acting, which may allow weeds to continue to compete with corn after application and potentially decrease crop yield. The addition of several POST corn herbicides, with some residual control, to an early-season glyphosate application was examined to determine if the tankmix combination would improve the speed of weed control compared to glyphosate applied alone. Seven field trials were conducted over three years (2009, 2010 and 2011) near Ridgetown and Exeter, Ontario. The control of common ragweed was improved 3 days after application (DAA) with three POST glyphosate tankmixes compared to glyphosate alone. However control was still less than 55%. Depending on the weed species examined, at 28 DAA two of the glyphosate tankmix treatments tested provided better common ragweed, common lambsquarters, or green foxtail control than glyphosate alone. Treatments providing better weed control at 28 DAA also typically decreased weed density compared to glyphosate alone.

Residual herbicides in weed management for glyphosate-resistant soybean in Brazil

In agricultural production systems where the glyphosate-resistant soybean crop (Glycine max) is grown and the practice of crop rotation with alternative herbicides is not adopted, the exclusive and continuous use of glyphosate has led to the occurrence of resistant weed populations that may limit or compromise the benefits of this technology. Thus, the efficacy of weed management programs, including the use of residual herbicides (sulfentrazone, flumioxazin, imazethapyr, diclosulan, chlorimuron and s-metolachlor) applied in preemergence and followed by in-crop postemergence applications of glyphosate (PRE-POST) were compared to glyphosate postemergence only programs - POST. The study was conducted across nine locations during the 2009/2010 and 2010/2011 growing seasons. PRE-POST programs were efficient in the control of Amaranthus viridis, Brachiaria plantaginea, Bidens pilosa, Commelina benghalensis, Eleusine indica, Euphorbia heterophylla and Raphanus raphanistrum, with the level of control being similar when comparing the program with two applications of glyphosate POST. Some PRE-POST programs were not efficient in controlling Cenchrus echinatus, Ipomoea hederifolia and Ipomoea triloba. Sulfentrazone and diclosulam PRE-POST programs improved the control of Ipomoea triloba compared to sequential applications of glyphosate alone. No significant differences in soybean yield were observed between any of the herbicide treatments or study locations. The use of residual herbicides in preemergence followed by glyphosate in-crop postemergence provides consistent weed control and reducing early season weed competition. Furthermore, these programs utilize at least two herbicide modes of action for herbicide use diversity, which will be needed to stay ahead of resistance build-up, regardless of when weeds may appear.

Influence of Post Emergence Application of Glyphosate on Weed Control Efficiency and Yield of Transgenic Maize

Field experiment was conducted during kharif 2009 and rabi 2009-2010 at Tamil Nadu Agricultural University, Coimbatore to evaluate the weed control efficiency and yield potential of glyphosate resistant transgenic maize. Treatments consisted of two transgenic maize hybrids named Hishell and 900 M gold with application of glyphosate as post emergence at 900, 1800 and 3600 g a.e/hathese were compared with non-transgenic counterpart maize hybrids with application of atrazine as pre-emergence at 0.5 kg/ha followed by one hand weeding at 40 Days After Sowing along with need based insect control practices. Post emergence application of glyphosate at 900, 1800 and 3600 g a.e/ha in transgenic maize hybrids was recorded with lower weed density and higher weed control efficiency compared to other treatments. Higher grain yield was recorded with post emergence application of glyphosate at 1800 g a.e/ha in transgenic hybrid 900 M Gold and 3600 g a.e/ha in transgenic hybrid Hishell during kharif 2009 and rabi 2009-2010 seasons, respectively.

Evaluation of Weed Control Options for Herbicide Resistant Transgenic Stacked (TC 1507 X NK603) and Conventional Maize Hybrids for Higher Productivity

Weeds are posing a serious problem in maize. The congenial climatic conditions encourage more weed growth in the widely spaced crop like maize and cause yield reduction to the tune of 29 to 70 percent. A field experiment was conducted for two years at Tamil Nadu Agricultural University, Coimbatore during kharif seasons of 2010 and 2011 to evaluate the weed management options for transgenic stacked (TC 1507 & NK 603) and conventional maize hybrids. The experiments were conducted with the following objective to evaluate the weed control efficiency and crop productivity with K salt of glyphosate formulations under field conditions. Treatments consisted of two transgenic stacked hybrids named 30V92 and 30B11 applied with glyphosate as early post emergence at 900 and 1800 g a.e ha-1 during kharif, 2010 and conventional maize hybrids named 30V92 and 30B11 applied with glyphosate by controlled droplet application method at 900, 1350 and 1800 g a.e ha-1 during kharif, 2011 compared with non transgenic counterpart maize hybrids applied with pre emergence atrazine at 0.5 kg ha-1 followed by one hand weeding on 40 DAS with and without insect management. Based on the two years field experimentation, it was found that early post emergence application of glyphosate at 1800 g a.e ha-1 gave significantly lower weed density, weed dry weight and higher weed control efficiency at all the intervals. Higher grain yield was registered with post emergence application of glyphosate at 1800 g a.e ha-1 in transgenic and conventional maize hybrid of 30V92 (12.21 t ha-1 and 11.23 t ha-1 ) during both seasons of the study. Unweeded control accounted for grain yield which in turn reflected through higher weed index

Effects of Management Type and Timing on Weed Suppression in Soybean No-Till Planted into Rolled-Crimped Cereal Rye

Knowledge of weed emergence periodicity can inform the timing and choice of weed management tactics. We tested the effects of weed management system (conventional [CNV] and herbicide-free [HF]), timing of rye sowing (two dates), timing of soybean planting (5 planting dates, 3 in each system), and supplemental control (with and without) on weed suppression and weed community composition in soybean no-till planted into a cereal rye cover crop. Cereal rye was terminated with a roller-crimper and herbicide (CNV) or with a roller-crimper alone (HF), and supplemental weed control was achieved with a postemergence glyphosate application (CNV) or with interrow high-residue cultivation (HF). Supplemental control with glyphosate in CNV was more effective than high-residue cultivation in HF. When soybean was planted on the same date, CNV resulted in less weed biomass and a more even community composition, whereas HF resulted in greater weed biomass, dominated by common ragweed. When we controlled for cereal rye biomass and compared the effects of cereal rye sowing and termination timing within each system, earlier management reduced weed biomass in HF, but tended to increase weed biomass in CNV. Our results suggest the ability to control emerged weeds prior to soybean planting is an important factor that influences the optimal cereal rye cover crop management timing for weed suppression.

Evaluation of Weed Control Efficacy and Yield of Glyphosate Resistant Cotton Hybrids in Winter Irrigated Ecosystems of Tamil Nadu

Cotton is one of the important crops that have been genetically altered to address challenges with weed and insect control. The research was conducted with glyphosate resistant cotton hybrids during winter irrigated season of 2009-10 and 2010-11 at the experimental site of Tamil Nadu Agricultural University, Coimbatore, with the objective, to find out the weed control efficacy and yield of transgenic cotton hybrid with the application of glyphosate. Glyphosate was applied as early POE application on 25 and 65 DAS at 900, 1350, 1800, 2700, 3600 and 5400g a.e. / ha in MRC 7347 BG-II RRF test hybrid. These treatments were compared with hand weeding on 15 and 30 DAS and unweeded control. In both sprays, Early POE application of glyphosate 2700, 3600 and 5400 g a.e. / ha registered lower weed density and higher weed control efficiency in transgenic cotton hybrid compared with other treatments. Seed cotton yield was significantly higher in post-emergence application of glyphosate at 2700 g a.e. / ha. Increased use of transgenic cotton with herbicide and pest resistance has resulted in more efficient insect and weed management practices.