Emergence Herbicides Research Articles

Influence of Integrated Weed Management Practices on Dynamics and Weed Control Efficiency in Dry Direct Seeded Rice

Field experiment under dry direct seeded rice(Oryza sativa L.) was conducted during rainy season of 2010 and 2011 at Regional Agriculture Research Station (RARS), Parwanipur, Bara to develop appropriate weed management practices for dry direct- seeded rice. The trial was laid-out in randomized complete block design (RCBD) and replicated thrice. Observations were taken on weed, plant growth and yield attributing, yield, and socio-economic parameters. The weed density, dry weed weight and weed control efficiency resulted significantly different as influenced by integrated weed management practices. Low weed population density, low weed index and highest weed control efficiency resulted by pendimethalin followed by 2, 4- D followed by one hand weeding were at par with weed free check. Highest yield resulted from weed free plot followed by pendimethalin followed by two hand weeding and pendimethalin followed by 2, 4- D followed by one hand weeding. However, the net return per unit investment resulted highest in pendimethalin followed by 2, 4- D followed by one hand weeding. This proved that amid increasing wage rate and labour scarcity integrated weed management through pendimethalin 30 EC (Stomp) @1 kg a. i. /ha as pre- emergence herbicide application followed by 2, 4- D sodium salt 80 WP @ 0.5 kg a. i. /ha followed by one hand weeding or stale seed bed followed by pendimethalin 30 EC (Stomp) @1 kg a. i. /ha followed by bispyribac (Nominee gold) @25 g a. i. /ha 10% @200 ml/ha at 20 days of seeding resulted best alternative for manual hand weeding practices giving higher net return per unit investment. DOI: http://dx.doi.org/10.3126/njst.v14i2.10413 Nepal Journal of Science and Technology Vol. 14, No. 2 (2013) 33-42

Effect of Weed Control Methods on Weeds and Wheat (<i>TriticumAestivum</i><i> </i>L.) Yield

A field experiment was conducted from June to December during 2010/11 crop season at HARC to study the effect of herbicides rates on weed dynamics and yield of wheat (Triticumaestivum L.) variety “HAR 604” in randomized complete block design with three replications. the herbicides rates: clodinafop-propargyl(0.065,0.080, 0.105kgha-1) and isoproturon (1.00, 1.25, 1.50kgha-1), hand weeding at tillering and weedy checkwere used. The crop was infested with AvenafatuaL. and PhalarisparadoxaL. among grass weeds andCayluseaabyssinicaMeisn,C. trigynaL., Chenopodium album L., Corrigoialacapensis Wild, Guizotiascabra(Vis) Chiov, Oxalis latifoliaHBK, PolygonumnepalenseL., RaphanusraphanistrumL., SpergulaarvensisL. and Tagetesminuta L. among broadleaved weeds. Hand weeding followed isoproturon at 1.50 kg ha-1 significantly reduced density and dry weight of weeds. Among herbicides, isoproturon provided better control of broadleaved and total weeds, whereas; clodinafop-propargyl proved better than isoproturon in controlling grass weeds. Hand weeding and hoeing at tillering resulted in lowest weed dry weight. Highest grain yield (2289.4 kg ha-1) in was recorded in hand weeding followed by isoproturon at 1.5kg ha-1 (2177.3 kg ha-1). The highest straw yield was recorded in hand weeding followed by isoproturon 1.50 kg ha-1, and harvest index was also maximum with hand weeding. Maximum N-uptake was also recorded in these treatments. Post emergence herbicides and /or hand weeding and hoeing at tillering can further enhance the weed suppressive effect of the crop.

BROOMRAPE AND OTHER WEED CONTROL IN CARROT (DAUCUS CAROTA L.)

Four field experiments were conducted at Sakha Agricultural Research Station, Kafer El-Sheikh Governorate in the two successive winter seasons 2011/12 and 2012/13, to study the efficacy of some weed control treatments on broomrape and annual weeds control, as well as, on carrot yield productivity and its quality. The first study, used the herbicides glyphosate twice, imazapic twice, as post– emergence herbicides and hand pulling twice to broomrape control as a parasite weed. The second study, used the herbicides pendimthalin , butralin , oxyfluorfen , metribuzin as per-emergence herbicides and hand weeding twice for controlling annual weeds. The results indicated that herbicide: imazapic twice, gave the best broomrape control and the highest increase in carrot roots yield and its quality, followed by glyphosate, and hand pulling twice of broomrape spikes, respectively. The herbicides imazapic and glyphosate decreased number of broomrape spikes/ m2, weight of broomrape spikes/m2 ,spikes length and number of capsules/ spike. The previous pre-herbicides exceeded in a great extent the unweeded treatment in controlling annual broad-leaved weeds and annual grassy weeds. The maximum reduction values of dry weight of broad-leaved, grassy and total annual weeds were obtained by using oxyfluorfen, pendimethalin, metribuzin , butralin and hand weeding twice in two seasons, respectively, compared with the control treatment. The herbicides oxyfluorfen, imazapic, pendimethalin, metribuzin, glyphosate and butralin gave the highest increases in yield and its components in both seasons, compared with the control treatment. All tested herbicides gave the highest significant increase in the quality characters in carrot roots, followed by hand pulling of broomrape or hand weeding of the annual weeds. Also, the highest net return was obtained by herbicides used and hand weeding twice, Thus, these herbicides treatments can replace hand weeding for the control of weeds and broomrape in carrot crop.

Chemical weed management in gladiolus (Gladiolus grandiflorus)

An experiment was carried out for three consecutive years from 2011 to 2013 at Floricultural Research Station, Hyderabad to find out efficient and economically feasible chemicals for weed control in Gladiolus. Among four pre- emergence herbicides i.e Atrazine, Metribuzin, Butachlor and Pendimethalin each at two different concentrations, the highest weed control efficiency at 75 DAP(63.7%) was achieved with Pendimethalin applied at 1 kg a.i/ha followed by Metribuzin 0.5 kg a.i /ha (63.2%). Though Pendimethalin @ 0.75 kg a.i/ha was effective in controlling the weeds as well as promoting growth and flower quality of the crop, the highest gross monetary returns per hectare and maximum B:C ratio was achieved with Butachlor@1.5kga.i/ha with highest corm yield of 1,66,250 corms per ha.

Effects of post emergence herbicides on weed control and yields of field pea and their residual effect on succeeding sorghum and mungbean crop.

A field experiment was conducted during 2008-09 and 2009-10 to evaluate different post emergence herbicides applied against weeds in field pea and their residual effect on succeeding sorghum and mungbean crop. Pendimethalin herbicide applied 1.5 kg ha-1 as pre-emergence gave effective control against all the weeds whereas, among post emergence herbicides imazethapyr was found effective against broadleaf weeds and quizalofop-ethyl was effective only against grassy weeds. During both the years, application of imazethapyr 50 g ha-1 at 30 days after sowing gave effective control of weeds and resulted minimum density and dry biomass of weeds compared to all the post emergence herbicide treatments. During second year, residual effect of imazethapyr was observed only on sorghum crop.

Influence of post emergence herbicides on weeds, nodulation and yields of soybean and soil properties

A field experiment was conducted at Pantnagar during kharif 2008 to examine the effect of postemergence herbicides in soybean on productivity, weed infestation and soil health. Treatments consisting of clodinafop-propargyl 8% EC at 80, 100 and 165 g a.i. ha−1, Na-acifluorfen 20% SL of 165 and 206.2 g a.i. ha−1, combination of clodinafop-propargyl 8% EC + Na-acifluorfen 16.5% SL at 80 + 165, 100 + 206.2 and 160 + 330 g a.i. ha−1, imazethapyr 10% SL at 100 g a.i. ha−1, weed free and weedy check were tested in RBD with 3 replications. The soybean variety used for the study was PS1347. Treatment of weed free check was found best by recording highest nodulation, yield and yield attributes, N uptake and soil parameters. It was at par with imazethapyr 10% SL @ 100 g a.i. ha−1, the treatment that showed highest nodule and plant dry weight, weed control efficiency, grain yield (1975 kg ha−1), straw yield (2445 kg ha−1), N uptake (136.4 kg ha−1 in grain and 40.9 kg ha−1 in straw), soil organic carbon, available N, P, K, microbial counts and dehydrogenase activity among different herbicides treatments. Clodinafop-propargyl 8% EC + Na-acifluorfen 16.5% SL was also found effective in weed control with 100 + 206.2 g a.i. ha−1. It was comparable to imazethapyr 10% SL @ 100 g a.i. ha−1 in weed index, weed control efficiency, nodule dry weight, grain and straw yields, N uptake, soil organic C, available N and K, microbial counts and dehydrogenase activity. The highest net return of Rs. 39563 ha−1 was obtained with weed free check, which was at par with imazethapyr 10% SL @ 100 g a.i. ha−1 and Clodinafop-propargyl 8% EC + Na-acifluorfen 16.5 SL @ 100 + 206.2 g ai ha−1.

Control of Glyphosate and Acetolactate Synthase Resistant Common Ragweed (Ambrosia artemisiifolia L.) in Soybean (Glycine max L.) with Preplant Herbicides

A population of common ragweed in Ontario was confirmed to be resistant to glyphosate in 2011. Group 2 [acetolactate synthase (ALS) inhibitors] resistant common ragweed was first confirmed in Ontario in 2000. Previously, glyphosate provided excellent control of common ragweed in glyphosate resistant soybean but with the confirmation of glyphosate resistant (GR) common ragweed, alternative herbicides need to be evaluated. Eight field trials with preplant herbicides were completed over two years (2013 and 2014) in fields with confirmed GR common ragweed. Tank-mixes of glyphosate and linuron or metribuzin provided 88% - 99% and 86% - 98% control 4 weeks after application (WAA) and 80% - 92% and 80% - 95% control 8 WAA, respectively. However, these herbicides also had among the highest environmental impact of the herbicides tested. Based on the results of these studies, GR common ragweed can be controlled with residual herbicides when applied preemergence in soybean. Currently, there are no post emergence herbicides that provide adequate control of GR common ragweed, therefore, preemergence herbicides with residual are essential for full season control.

Effect of integrated weed management practices on performance of dry direct seeded rice (Oryza sativa L.)

Weeds are serious problem in dry direct seeded rice (DDSR). A field experiment was conducted during rainy seasons of 2010 and 2011 at research farm of the Regional Agricultural Research Station (RARS) Parwanipur, to study the effect of integrated weed management practices on the performance of dry direct seeded rice. Ten treatment combinations viz; weedy, weed free (weekly), Pendimethalin fb (followed by) Bispyribac, Pendimethalin fb two hand weeding, Stale seedbed fb Bispyribac, Stale seedbed fb Pendimethalin fb Bispyribac, Mulch 4 t/ha fb Bispyribac fb one hand weeding, Stale seedbed fb mulch 4 t/ha fb Bispyribac, Pendimethalin and Sesbania co-culture fb 2,4-D Na salt fb one hand weeding and Pendimethalin fb 2,4-D fb one hand weeding were tested in a randomized complete block design and replicated thrice. Observations were taken on weed, plant growth and yield attributes, yield, and socio-economic parameters. All weed control treatments significantly reduced the weed density and dry weight of weed resulting significant increase in yield of DSR over weedy check in both years. Weed free treatment resulted the highest yield, however, it was not economical due to high cost of cultivation. The use of Pendimethalin fb 2,4-D fb one hand weeding produced yield (5161 in 2010 and 6160 kg/ha in 2011) which were statistically at par with yield (5305 in 2010 and 6319 kg/ha in 2011) obtained under the weed free treatment. Further, the highest benefit cost ratio (CBR) 1.77 and 2.22 and net return Rs 47700 and 75084/ha during 2010 and 2011, respectively, were obtained under this treatment indicating its superiority over other treatments. The grain yield, yield attributing characters viz. panicles per m2, panicle weight, filled grain per panicle, thousand grain weight as influenced by different weed management practices revealed that higher yield resulted from weed free plot followed by Pendimethalin followed by two hand weeding and Pendimethalin followed by 2,4-D followed by one hand weeding. However, the net return per unit investment resulted highest in Pendimethalin followed by 2,4-D followed by one hand weeding. This proved that amid increasing wage rate and labor scarcity integrated weed management through Pendimethalin 30 EC (stomp) @ 1 kg a. i./ha as pre- emergence herbicide application followed by 2,4-D sodium salt 80 WP @ 0.5 kg a.i./ha followed by one hand weeding or stale seed bed followed by Pendimethalin 30 EC (stomp) @ 1 kg a. i./ha followed by Bispyribac (nominee gold) @ 25 g a. i./ha 10 % @ 200 ml/ha at 20 days of seeding resulted best alternative for manual hand weeding practices giving higher net return per unit investment. Agronomy Journal of Nepal (Agron JN) Vol. 3. 2013, Page 53-63 DOI: http://dx.doi.org/10.3126/ajn.v3i0.9006

Halosulfuron Methyl: A New Post Emergence Herbicide in India for Effective Control of Cyperus rotundus in Sugarcane and Its Residual Effects on the Succeeding Crops

Halosulfuron methyl (HM) at 67.5, 75.0 and 150.0 g/ha recorded significantly effective in lowering the population (1.2–2.2/m2) and dry weed weight (0.45–0.49 g/m2) of C. rotundus at 60 DAT as compared to other treatments including its lower doses. Atrazine (PE) followed by 2,4-D was not effective against C. rotundus. HM at 67.5, 75.0 and 150.0 g a.i./ha gave 96.3–97.0 % control of C. rotundus as against increase in C. rotundus population (15.1 %) in atrazine (PE) + 2,4-D treatment and 24.4 % increase in untreated check over pre-treatment population. HM at 67.5, 75.0 and 150.0 g a.i./ha recorded higher weed control efficiency (97.8–97.9 %) as compared to atrazine (PE) followed by 2,4-D (8.7 %) and three hoeings (48.8 %). None of the doses of HM affected the dry weight of grassy as well as broad leaf weeds recorded at 60 days after treatment. HM used at 67.5, 75.0 and 150.0 g a.i./ha also recorded significantly higher cane yield as compared to its lower doses, atrazine (PE) followed by 2,4-D and weedy check. Treatment of three hoeings gave maximum cane yield whereas; lowest cane yield was recorded in untreated plots. An increase of 60.9–64.8 % in cane yield over control was recorded when HM was applied at 67.5, 75.0 and 150 g a.i./ha whereas standard check (atrazine followed by 2,4-D) recorded 33.9 % increase. There was no phytotoxicity of halosulfuron on sugarcane in terms of crop discolouration, chlorosis, stunting, wilting, deformation and vein clearing even up to dose of 150.0 g/ha of HM indicating that it was safe to the sugarcane crop. HM was also found safe to succeeding crops (black gram, maize and cucumber) up to 150.0 g a.i./ha dose. Post emergence application of HM 75%WG applied at 52.5, 60.0, 67.5, 75.0 and 150.0 g a.i./ha on sugarcane crop did not affect the germination and yield of follow up crops (black gram, maize and cucumber) during both the years when sown on the same plot after harvesting of sugarcane. Thus halosulfuron methyl 75%WG (Sempra) at 67.5 g a.i./ha at 45 days after sowing was realized to be the optimum dose for effective control of C. rotundus in sugarcane crop.

Effect of pre emergence herbicides on weed control and performance of cowpea in Samaru

Field experiments were carried out in 2010 and 2011 cropping seasons at the Institute for Agricultural Research, Ahmadu Bello University, Zaria- Nigeria located on latitude11 0 11’, longitude7 0 38’ and 686m above sea level in Northern Guinea Savannah Ecological Zone to evaluate the effect of pre emergence herbicides on growth and yield parameters of cowpea. In this study, different pre emergence herbicides were compared for their efficiency on weed control of various weed species under rain- fed conditions in Nigeria. The different herbicides used are, S-metolachlor 960 EC @ the rate of 3.5 litre ha -1 , pendimenthaline 33% (w/v) EC @ the rate of 3.5 liter ha -1 and Butalachlor E.C at the rate of 3.5Lha - 1 . There was significant yield increase due to Application of pendimenthaline at 3.5 L ha - 1 + Hand weeding of cowpea at 6WAS. There was significantly superior performances in terms of plant height, number of leaves per plant, number of branches per plant, number of pods per plant and grain yield ha 1 . However Leaf area per plant and 100 – grain weight were not significantly influenced by the treatments. Of all the weed control methods, chemical weed control using pendimenthaline at 3.5 L ha - 1 + Hand weeding at 6WAS, significantly gave better results than the other treatments on both growth and yield parameters. DOI: http://dx.doi.org/10.4038/jas.v8i2.5746 The Journal of Agricultural Sciences, 2013, vol.8, no2 p.76-81

Associações entre glifosato e herbicidas pós-emergentes para o controle de trapoeraba em soja RR®

Este trabalho teve o objetivo de avaliar a seletividade e a eficácia da associação do glifosato com herbicidas pós-emergentes no controle de trapoeraba na cultura da soja Roundup Ready®. Para tanto, o experimento foi instalado no delineamento de blocos ao caso, com quatro repetições, onde os tratamentos foram constituídos de quatro doses do herbicida cloransulam-metil (10, 20, 30 e 40 g ha-1), quatro doses do herbicida clorimurom-etílico (2,5, 5,0, 7,5 e 10,0 g ha-1), imazetapir a 100 g ha-1 e lactofen a 72 g ha-1, todos estes utilizados em associação com o herbicida glifosato a 960 g ha-1. Também foram incluídas três testemunhas, sendo aplicação única do herbicida glifosato a 960 g ha-1, aplicação sequencial do glifosato a 960/ 960 g ha-1 e testemunha geral sem capina. Os resultados demonstraram que apenas a aplicação única do herbicida glifosato a 960 g ha-1 e sua associação com as menores doses de cloransulam-metil (10 g ha-1) e clorimurom-etílico (2,5 g ha-1) não proporcionaram controle efetivo da trapoeraba. Todos os tratamentos herbicidas não influenciaram na produtividade da soja RR®, embora a associação do glifosato com a maior dose de clorimurom-etílico (10 g ha-1) tenha proporcionado redução significativa no peso de 1000 grãos de soja.

Load-bearing capacity of a red-yellow latosol cultivated with coffee plants subjected to different weed managements

It is essential to know the levels of pressure applied to the soil by different weed managements to adapt the management of coffee plantations in a sustainable manner. The objectives of this study were: a) to generate load-bearing capacity models of a Red-Yellow Latosol (Oxisol) submitted to different weed managements and b) to determine which weed management resulted in higher compression. The study was conducted at the Experimental Farm of EPAMIG, located near the community Farias, in Lavras-MG (latitude 21° 14' 43" S and longitude 44° 59' 59" W and altitude of 919 m). The soil is a Red-Yellow Latosol (LVA) cultivated with coffee plantation using Topazio MG 1190 coffee variety, since 2006. We evaluated five weed managements, three being through mechanical control (harrow (GD), mowing (RÇ) and brush (TC)) and two by chemical control (post-emergence herbicide (HPos) and pre emergence herbicide (HPre)). To obtain the load-bearing capacity models, 10 undisturbed soil samples were randomly collected in the 0-3, 10-13 and 25-28 cm layers between the rows. The load-bearing capacity models which indicated a higher compaction were: in the 0-3 cm layer, TC and GD; in the 10-13 cm layer, HPre, HPos and RÇ and in the 25-28 cm layer, GD. The load-bearing capacity models that indicated greater susceptibility to compaction were: in the 0-3 cm layer, HPos; in the 10-13 cm layer, GD and TC and in the 25-28 cm layer, HPre.

Kentucky bluegrass 내 새포아풀 방제를 위한 경엽처리제 선발

This study was performed to find the effective post-emergence herbicides to control of Poa annua that has already emerged from the soil in Kentucky bluegrass. A total of 8 treatments consist of various post- emergence herbicides applied at recommended concentration or lower concentration than recommended concentration to prevent Kentucky bluegrass injury in this study. Methiozolin showed the least injury in Kentucky bluegrass during 40 days after treatments and there were no footprints by methiozolin in creeping bentgrass green during 20 days. However, Poa annua control was 60.4%, which was less than those of other 7 treatments in this study. Both of asulam sodium and iodosulfuron plus asulam sodium exhibited the higher Poa annua control of 81.7% and 82.2% respectively without serious injury in Kentucky bluegrass during 40 days, and they showed a slight footprints damage in creeping bentgrass green. On the other hand, critical Kentucky bluegrass injuries and the vivid and numerous footprints were occurred in treatments of trifloxysulfuron-sodium, foramsulfuron, rimsulfuron and flazasulfuron, even though they were applied with only 1/4 of recommended concentration. Methiozolin is available to reduce gradually Poa annua population on Kentucky bluegrass without severe turfgrass damage. Asulam sodium or iodosulfuron plus asulam sodium could be useful to remove Poa annua by spot treatment but it is prohibited to spray directly on green even spot.

Toxic and genotoxic effects of Roundup on tadpoles of the Indian skittering frog (Euflictis cyanophlyctis) in the presence and absence of predator stress

Glyphosate, a post emergent herbicide, has become the backbone of no-till agriculture and is considered safe for animals. However, the impact of glyphosate on non-target organisms, especially on amphibians, is the subject of major concern and debate in recent times. We examined the toxic and genotoxic effects of Roundup, a commercial formulation of glyphosate, in the tadpoles of the Indian skittering frog (Euflictis cyanophlyctis). Roundup at different concentrations (0, 1, 2, 3, 4 and 8mg acid equivalent (ae)/L), tested in a 2×6 factorial design in the presence and absence of predator stress, induced concentration-dependent lethality in tadpoles. The 96-h LC50 for Roundup in the absence and presence of predator stress were 3.76mgae/L and 3.39mgae/L, respectively. The 10-day LC50 value for Roundup was significantly lower, 2.12mgae/L and 1.91mgae/L in the absence and presence of predator stress, respectively. Lower concentrations of Roundup (1, 2 and 3mgae/L) induced the formation of micronuclei (MN) in the erythrocytes of tadpoles at 24-h (F3,56=10.286, p<0.001), 48-h (F3,56=48.255, p<0.001), 72-h (F3,56=118.933, p<0.001) and 96-h (F3,56=85.414, p<0.001) in a concentration-dependent manner. Presence of predator stress apparently increased the toxicity and genotoxicity of Roundup; but these effects were not statistically significant. These findings suggest that Roundup at environmentally relevant concentrations has lethal and genotoxic impact on E. cyanophlyctis; which may have long-term fitness consequence to the species.

Green house studies on the biology of winter annual grasses and the use of cover crops and herbicides for their control

Greenhouse studies were initiated in two small (Polypogon fugox) and large (Phalaris minor) seeded annual grasses in 2007 at Cornell University, Ithaca, NY USA. These two annual grasses were very common in wheat fields of midhills and terai regions of Nepal. P fugox was taken for biological study. Days to emergence took 8-11 days in green house. Early emerged panicles were longer than those emerged late. Panicle took 10-12 days to emerge completely from the flag leaf. Panicles per plant were 120. Seeds were very small having about 1091 seeds per panicle. So one fully matured plant could produce seeds about 130920. Study on eco-biology needs to continue in the future. P fugox and P minor responded differently to buckwheat residues. Among different treatments emergence and growth of both weeds were suppressed more by buckwheat residues when left on the surface than incorporated. P minor was less affected by buckwheat residues. It might be due to larger seed compared to P fugox. Post emergence herbicides clodinofop and pinoxaden were effective on both grasses. Isoproturon and tralkoxydim were effective on P fugox. Sulfosulfuron was good in reducing plant growth to some extent. Preemergence herbicides pendimethalin and s-metolochlor were effective in reducing emergence and growth of both weeds. Isoproturon and and sulfosulfuron suppressed plant growth reducing dry plant biomass. DOI: http://dx.doi.org/10.3126/ajn.v2i0.7529 Agronomy Journal of Nepal (Agron JN) Vol. 2: 2011 pp.139-148

Seletividade de herbicidas em espécies de gramas ornamentais

The experiment was conducted with the objective of evaluating the selectivity of herbicides, applied in different times, in ornamental turf grasses. The first experiment was conducted in greenhouse conditions in randomized entirely design, with four replications, in a 4 x 5 x 2 factorial scheme. The factors corresponded to the pre-planting application herbicides ( sulfentrazone - 800 g ha -1 , s-metolachlor - 1440 g ha -1 and atrazine - 2000 g ha -1 and control without herbicide application) in five species of turfgrass: Zoysia japonica (emerald) , Axonopus compressus (blanket grass) , Paspalum notatum (bahia grass), Zoysia tenuifolia (no-mow grass) , Stenotaphrum secundatum (sant agostine grass), in sandy loam and clayey texture soils. In the second experiment, the experimental design was completely randomized, with four replications in a 6 x 6 factorial scheme. The factors corresponded to the five post emergence herbicides: atrazine (2000 g ha -1 ), sulfentrazone (800 g ha -1 ), halosulfuron (112.5 g ha -1 ), bentazon (0.72 g ha -1 ) and 2.4 D (670 g ha -1 ) applied on the five grasses, cited above and control without herbicide application. Phytotoxicity evaluations were assessed at at 7, 14, 21, 28 and 35 days after herbicide application. In the case of pre planting herbicides, were not detected any phytotoxicity in the grass species, regardless of soil texture. In the experiment with post-emergent herbicides, the bahia and blanket grass were sensitive to the herbicide atrazine, with 38 and 33% phytotoxicity at 21 DAA. However, the recovery of bahia grass was more effective at 35 DAA. The sulfentrazone was phytotoxic on blanket grass. The herbicides bentazon, 2,4-D and halosulfuron were selective to all species studied.

Uses and benefits of glyphosate in German arable farming

Glyphosate is world-wide seen as the most widely used herbicide ingredient. In Germany, from 1999 to 2010, the use of glyphosate based herbicides (GBH) increased by 100%. Many agronomical benefits are attributed to glyphosate, but there is also public criticism. To analyse current application patterns and to assess the agronomical importance of GBH in Germany, a survey was carried out among 896 arable farmers. The survey took place in early 2011, taking 2009 as a reference year. In Germany, cultivation of transgenic crops is generally not permitted and, therefore, herbicide resistance trait does not play any role in application patterns.Based on farmer's statements, a calculated application area of 4.3 million hectare arable land was estimated, representing 39% of total arable area. Three application modes receive major proportions of glyphosate use, these are: pre-sowing (20.7% of application area), pre-harvest (11.2%) and stubble application (68.1%). Among the field crops, oilseed rape (including oilseed rape stubbles) is treated with 27.5% of the nation-wide glyphosate amount followed by winter barley (20.1%) and winter wheat (15.8%). Without using glyphosate, farmers expect an increase in the share of ploughed arable land from 38.1% to 71.4%. Also, without glyphosate the use of cultivator on stubble land is expected to increase about 1.6 passes on average. If applied pre-sowing, glyphosate could save herbicide applications in the following crop. Saving one application of a post-emergence herbicide was estimated by farmers for corn and sugar beet (46% of pre-sowing applications), silage maize (40%), oilseed rape (27%), and winter wheat (22%). Most applications are applied on off-crop fields, so farmers did not quote any observation of yield savings due to glyphosate. The nation-wide economic benefit of glyphosate due to savings of other agricultural measures such as soil cultivation and post emergence herbicides is calculated between 79 and 202 million Euro per year, depending on glyphosate price.We conclude, that glyphosate offers large benefits to farmers, though some routine applications results in only moderate economic benefit compared to the non chemical practices being replaced. Developing decision rules for farmers might allow for an optimum allocation of glyphosate use.

Seletividade de herbicidas e dinâmica populacional de plantas daninhas na cultura do girassol para a produção de biodiesel

Experiments were conducted in Prudente de Morais County, Minas Gerais State, in 2010 and 2011 years, with the objective of to evaluate selectivity and efficiency of pre and post-emergence herbicides in sunflower crop, as well as to study weeds populacional dynamic. The work conducted in 2010 was carried out in greenhouse, in a randomized complete block design, with 11 treatments and three replications. Treatments consisted by ten herbicides, four in pre emergence and six in post-emergent of the crop (alachlor, imazaquin, metribuzin, trifluralin, chlorimuron-ethyl, fenoxaprop-p-ethyl, [fluazifop-p + fomesafen], imazapyr, imazethapyr e sethoxydim) and a check. The following characteristics were evaluated: phytotoxicity effects, plants height, leaves number and dry biomass of shoot and root 60 days after product applications. In 2011, the work was accomplished in filed conditions following a randomized complete block design with six treatments and four replications. The treatments consisted of two pre-emergent herbicides: alachlor and trifluralin, two post-emergence: fenoxaprop-p-ethyl and sethoxydim and two checks (with and without weeding). Crop cycle, flowering initial, plant height, stem diameter, achenes physiologically mature, chapters diameter, broken plants number, lodged plants number, final stand and achenes yield were evaluated. Based on the obtained results, it was possible to conclude that herbicides that showed higher toxicity to sunflower plants were: imazaquin, metribuzin, chlorimuron-ethyl, [fomesafen + fluazifop-p], imazapyr and imazethapyr. The pre emergent herbicides alachlor, trifluralin, fenoxaprop-p-ethyl and sethoxydim were selective to sunflower crop. Fenoxaprop-p-ethyl herbicide may be used in a program of weeds integrated management in sunflower crop, because only trifluralin, alachlor and sethoxydim herbicides are registered for this crop in Brazil.

Evaluation of the Efficacy of Different Rates of Herbicides on Weed Growth and Grain Yield of Two Rice Varieties in Two Rice Ecologies in Sierra Leone

Two rice varieties, NERICA L19 (weed competitive) and ROK10 (high yielding) were subjected to two pre-emergence (RiceForce and ButaForce) and two post-emergence (Stam and RiceForce) with different active ingredients and rates of application during the wet seasons of 2009 and 2010 at Rokupr Mangrove Associated Swamp and at Gbomsamba in the Boliland to determine (i) the effectiveness of different rates of application of pre-and post emergence herbicides on weed growth and yield of rice

The effect of glyphosate application on soil microbial activities in agricultural land

In recent years, intensive use of herbicides has increasingly become a matter of environmental concern partially because of the effects of these chemicals on soil microorganisms. Glyphosate [N- (phosphonomethyl) glycine] (GP) is a broad-spectrum, non-selective, post emergence herbicide that is widely used in agriculture. In this study, glyphosate effects as N, P and C nutrient sources on microbial population and the effect of different concentration of it on dehydrogenease activity and soil respiration were investigated. The results show that in a soil with a long historical use of glyphosate (soil 1), the hetrotrophic bacterial population was significantly (p<0.05) increased. Also, by increase in the bacterial population, the herbicide existence as the possible nutrient source is enhanced. According to results, bacterial populations in the presence of glyphosate as P source was significantly (p<0.01) higher than N and C sources. The application of GP to the soil led to a significant increase in dehydrogenase activity with respect to untreated control soil samples. Also, respiration rates increased with increasing glyphosate application up to 50 mM but in 500 mM the inhibitory effect of glyphosate was observed. It can be concluded that glyphosate application may alter (increase) soil microbial activity and population. Increased microbial activity may be beneficial or detrimental toward plant growth, soil microbial ecology, and soil quality. Key words : Glyphosate, bacterial population, dehydrogenease activity, soil respiration.