Preemergence Herbicides Research Articles

Echinochloa spp response to preemergence and postemergence herbicides in California rice (Oryza sativa L.)

Historically, herbicides were used for Echinochloa spp control in California rice production which led to the selection of herbicide-resistant biotypes. Field surveys were conducted across the seven major rice-growing counties in 2020 and Echinochloa spp samples including barnyardgrass (Echinochloa crus-galli (L.) P.Beauv.), junglerice (Echinochloa colona (L.) Link), late watergrass (Echinochloa oryzicola (Vasinger) Vasinger) and coast cockspur (Echinochloa walteri (Pursh) Heller) were collected. Greenhouse experiments were carried out to determine their suspected resistance to common preemergence and postemergence rice herbicides used in California in Fall and Winter of 2021. A total of 62 and 63 samples were characterized for suspected resistance to four preemergence granular and three postemergence foliar-applied herbicides, respectively. When granular herbicides were evaluated, samples suspected of resistance in Winter were a subset of samples that were suspected of resistance in Fall. Results indicate >90% of Echinochloa spp samples were resistant to thiobencarb, benzobicyclon + halosulfuron and penoxsulam when combined across species and counties. Cross-resistance between benzobicyclon + halosulfuron and penoxsulam was observed in >90% of the samples when combined across species and counties. Suspected clomazone resistance was observed in <75% of the samples when combined across species and counties. Suspected resistance to cyhalofop and propanil was observed in <50% of the samples when averaged across both runs. Multiple-resistance to foliar herbicides ranged from 48-60% of the samples across species and experimental runs. These results indicate the necessity for rotating herbicides during alternate cropping seasons and emphasizing integrating non-chemical strategies for Echinochloa spp control in California rice production.

Effectiveness and Selectivity of Pre- and Post-Emergence Herbicides for Weed Control in Grain Legumes.

Grain legumes represent important crops for livestock feed and contribute to novel uses in the food industry; therefore, the best cultivation practices need to be assessed. This study aimed to identify herbicides to meet the current need for controlling broadleaf weeds without phytotoxicity in the grain legume crop per se. Field experiments were undertaken during the 2019 and 2020 growing seasons and laid out in a randomized complete block design with three replicates as follows: four grain legume crops (vetch, pea, faba bean, and white lupine) and nine pre-emergence (PRE) or post-emergence selective (POST) herbicide treatments (PRE: aclonifen, pendimethalin plus clomazone, metribuzin plus clomazone, benfluralin, terbuthylazine plus pendimethalin, S-metolachlor plus pendimethalin, flumioxazin; POST: pyridate, imazamox) alongside weedy check plots. Plant phytotoxicity, crop dry matter, yield features, weed presence, and weed dry matter were assessed during the experiments. There was differential efficacy among the nine herbicide treatments; the weed control was more effective in the case of Veronica arvensis L. and Sonchus spp. L. compared with Chenopodium album L., Sinapis arvensis L., and Silibum marianum L. regardless of the herbicide treatment. The most effective PRE herbicide was flumioxazin, which had the greatest control over the majority of weeds (>70%) resulting in the lowest total weed biomass. The second-best treatment was benfluralin and the mixture of terbuthylazine plus pendimethalin (both had only limited control in S. arvensis). The best POST herbicide was imazamox, with only limited control in S. arvensis. The tested herbicides caused low to medium and transient levels of phytotoxicity mainly in vetch and secondly in peas but not in faba beans and lupines. Concerning all weed management treatments, benfluralin resulted in the highest grain yields for all four grain legume crops during both growing seasons. Among grain legumes, vetch had the highest competitive ability against weeds, whereas peas were the least tolerant against weed competition.

Effect of Integrated Weed Management on the Yield Performance of Wheat

The objectives of this study were to determine the influence and comparative efficiency of different weed management practices under integrated weed management of wheat. The experiment comprised three replication group which composed of fourteen weeding regime treatments, namely, unwedded, Mulching by rice straw, Mulching by water hyacinth , Two hand weeding at 25 and 35 DAS, Pre-emergence herbicide, Pre-emergence herbicide + hand weeding at 35 DAS, Pre-emergence herbicide + mulching by water hyacinth, Post-emergence herbicide, Stale seed bed + post-emergence herbicide, Post-emergence herbicide + hand weeding at 35 DAS, Post-emergence herbicide + mulching by rice straw, Post-emergence herbicide + mulching by water hyacinth, Pre-emergence herbicide + Post-emergence herbicide, Pre-emergence herbicide + Post-emergence herbicide + hand weeding at 35 DAS. The experiment was laid out in a randomized complete block design. Data on different parameters were recorded. Most of the yield contributing characters significantly higher at post-emergence herbicide + mulching by rice straw. Among different weeding regime treatments, the highest grain yield (6.92 t ha-1) of post-emergence herbicide + mulching by rice straw compared to unwedded treatment. This result indicates that post-emergence herbicide + mulching by rice straw regime gave higher yield in Agronomy Field Laboratory at BAU.

Pre-emergence herbicides effects in no-till soybean system with Panicum maximum ‘BRS Tamani’

The use of pre-emergence herbicides is an important strategy in resistant-weeds management, but its performance can be affected in no-till systems. This study aimed to analyse weed control from pre-emergence herbicides in no-till soybean system with Panicum maximum cv. BRS Tamani. The experiment was conducted in randomized block design with eight treatments and five repetitions. The treatments consisted in no-treatment, S-metolachlor + imazethapyr (1,200.00 g a.i. ha-1 + 100.00 g a.e. ha-1, respectively), S-metolachlor + fomesafen (1,035.66 g a.i. ha-1 + 227.70 g a.e. ha-1, respectively), S-metolachlor + diclosulam (1.200.00 g a.i. ha-1 + 29.40 g a.i. ha-1), imazethapyr + diclosulam (100.00 g a.e. ha-1 + 29.40 g a.i. ha-1), imazethapyr + flumioxazin (100.00 g a.e. ha-1 + 50.00 g a.i. ha-1), pyroxasulfone + flumioxazin (90.00 g a.i. ha-1 + 60.00 g a.i. ha-1) and pendimethalin (1,137.50 g a.i. ha-1). We evaluated weed phytosociological rates, weed control, and soybean growth. We identified 23 weed species distributed in 22 genera and 15 botanical families, majority of eudicotyledonous botanical class (78.2%), annual life cycle (56.5%), and sexual reproduction (100%). The integrated weed management, between herbicides and straw, was effective in herbicide-resistant weed control, except Euphorbia heterophylla. The treatments recommended included S-metolachlor combinations with fomesafen, imazethapyr, diclosulam, and also, pyroxasulfone + flumioxazin. The Panicum maximum cv. BRS Tamani straw was estimated in 11 t ha-1 and influenced negatively herbicides lipophilics and with slower movement, such as pendmethalin

Effect of planting pattern and herbicide programs on sicklepod (Senna obtusifolia L.) control in peanut

Abstract Sicklepod is one of the most difficult to control weeds in peanut production in the southeastern United States due to its extended emergence pattern and limited effective herbicides for control. Growers rely on preemergence herbicides as the foundation of their weed control programs; however, postemergence herbicides are often needed for season-long weed control. The objectives of this study were to evaluate the effect of planting pattern and herbicide combinations for sicklepod control in peanut crops. Due to rapid canopy closure, twin-row planting improved late-season sicklepod control by 13% and peanut yield by 5% compared with a single-row pattern. A preemergence application of fluridone, flumioxazin, or fluridone + flumioxazin provided 76% to 89% control of sicklepod 28 d after preemergence. Regardless of the herbicide applied preemergence, paraquat + bentazon + S-metolachlor applied early postemergence was required to achieve ≥90% sicklepod control 28 d after early postemergence. All preemergence herbicide treatments followed by (fb) S-metolachlor or diclosulam + S-metolachlor applied early postemergence provided <90% control 28 d after early postemergence. A mid-postemergence application of imazapic + dimethenamid-P + 2,4-DB controlled sicklepod by 67% to 79% prior to peanut harvest, and biomass reduction was unacceptable (<80%), resulting in difficulty in peanut digging. The highest peanut yield was observed when paraquat + bentazon + S-metolachlor was applied early postemergence fb imazapic + dimethenamid-P + 2,4-DB applied mid-postemergence. Based on the results of this study, a herbicide combination of paraquat + bentazon + S-metolachlor is an important early-season tool for controlling sicklepod in peanut crops. The results also showed that a twin-row planting pattern improved late-season sicklepod control but did not reduce herbicide input to protect peanut yield.

Effect of Pre and Post Emergent Herbicides on Weed Management, Yield and Economics in Irrigated Chickpea (Cicer arietinum L.)

A field experiment was conducted to study the effect of pre and post emergence herbicides on growth and yield of chickpea at College of Agriculture, Vijayapura, during rabi, 2021-22. The experiment was laid out in RCBD with three replications. The experiment consisted of 11 treatments involving two pre-emergence herbicides (Pendimethalin, Pendimethalin + Imazethapyr) and five post-emergence herbicides (Imazethapyr + Imazamox, Propaquizafop + Imazethapyr, Imazethapyr, Quizalofop ethyl and Aciflor + Clodinafop), intercultivation at 20 and 40 DAS, weed free check and weedy check. Among the herbicidal treatments, significantly lower weed population per m2 (2.40), lower total dry weight of weeds (3.18 g), higher weed control efficiency (84.98%), lower weed index (11.06 %), higher grain yield (2197 kg/ha), haulm yield (2766 kg/ha), net returns (₹ 80621/ha) and B:C ratio (3.01) was recorded with sequential application of Pendimethalin 38.7% CS @ 800 g a.i./ha as PE fb Propaquizafop 2.5% + Imazethapyr 3.75% W/W ME (RM) @ (125 g a.i./ha) as PoE at 25 DAS compared to all other treatments. Among herbicidal treatments lowest grain yield (923 kg/ha) and haulm yield (2098 kg/ha) were recorded with Imazethapyr 35% + Imazamox 35% WG (RM) @ 70 g a.i./ha as PoE at 25 DAS due to phytotoxicity and the results were almost near to weedy check which recorded 38.18 pods/plant, 100 seed weight of 22.36 g, 16.96 g of seed yield / plant, grain yield (896 kg/ha) and haulm yield (2056 kg/ha).

Khakiweed (Alternanthera pungens) control with contact and residual herbicides

Abstract Khakiweed is a perennial broadleaf weed that is difficult to control because of its multiple means of reproduction, vigorous growth, and deep taproot. Khakiweed reduces the performance of pasture, pecan, and turf areas by choking out desirable grass and legume species. Because information on the effectiveness of contact and residual herbicides for control in pecan and pasture areas is limited, greenhouse studies were conducted to determine the effect of application timing, mode of action, and rate on khakiweed control. Preemergence and postemergence herbicides were applied to mature khakiweed plants at 0.25X, 0.5X, 1X, or 2X the label recommended rate for general broadleaf control. Biomass was collected 3 wk after application. Plants regrew from roots in the greenhouse until a second biomass harvest was collected at 6 wk after treatment (WAT). Metsulfuron-methyl, indaziflam, or pendimethalin was applied preemergence to the soil surface. All rates of preemergence herbicides provided high-efficacy control of regrowth (>85%) compared to the nontreated control. The efficacies of postemergence-applied metsulfuron-methyl, metsulfuron-methyl + nicosulfuron, indaziflam, aminopyralid + florpyrauxifen-benzyl, 2,4-D amine, and 2,4-D amine + florpyrauxifen-benzyl were also examined. All postemergence herbicide treatments exhibited control compared to the nontreated plants at both sample timings (3 and 6 WAT) and increased with herbicide application rate. No herbicide provided high-efficacy control during the initial postspray period (0 to 3 WAT). During the regrowth period (3 to 6 WAT), metsulfuron-methyl alone and in combination gave >85% control of khakiweed biomass, indicating that the sulfonylurea herbicides used in this study are well suited to controlling khakiweed.

Evaluation of herbicide programs for the control of knotroot foxtail [Setaria parviflora (Poir.) Kerguélen] in bermudagrass pasture

Abstract Knotroot foxtail has become more prevalent and problematic in pastures and hayfields in the southeastern United States. Gaps exist in our knowledge of which herbicide practices are best for managing this species in bermudagrass forage production. This study was conducted to determine the efficacy of various ways to control knotroot foxtail in bermudagrass with herbicide applications in autumn, postemergence (POST), with and without also applying a herbicide in preemergence (PRE), in spring. The study was a randomized complete block with a factorial arrangement of treatments and included a nontreated control for both fall and spring timings. Glyphosate at two rates (0.35 or 0.7 kg ae ha−1), nicosulfuron (0.07 kg ai ha−1) + metsulfuron (0.012 kg ai ha−1), and hexazinone (1.3 kg ai ha−1) were applied alone in the fall or followed by indaziflam (0.067 kg ai ha−1) or pendimethalin (4.46 kg ai ha−1) in the spring. Three harvests were conducted throughout the growing season to evaluate weed species (knotroot foxtail, large crabgrass, and horsenettle) and bermudagrass biomass as well as overall species composition. The combination of fall and spring treatments did not affect weed species or bermudagrass biomass. Therefore, treatment main effects were analyzed by fall or spring application timing. A spring application of either pendimethalin or indaziflam increased bermudagrass biomass compared with that of the nontreated control. However, neither PRE herbicide effectively reduced knotroot foxtail biomass compared with the nontreated control, although pendimethalin did reduce season-long knotroot foxtail composition. Spring PRE herbicides are an effective tool for forage producers, but further research is needed to identify effective herbicides and additional approaches for the control of knotroot foxtail.

Integrating cover crops and herbicides for weed control in soybean

Abstract In mid-southern, southeastern, and northeastern U.S. soybean production regions, the evolution of herbicide-resistant weeds has become a significant management challenge for growers. The rising herbicide costs for managing herbicide-resistant weeds are also a growing concern, leading to the utilization of cover crops as an integrated weed management strategy for addressing these challenges. Field experiments were conducted at two locations in Alabama in 2022 to evaluate winter cereal cover crops, including a mixture and herbicide system integration in soybean. Treatments included five cover crops: oats, cereal rye, crimson clover, radish, and a cover crop mixture. Cover crops were evaluated for their weed-suppressive characteristics compared to a winter fallow treatment. Additionally, four herbicide treatments were applied: a preemergence (PRE) herbicide, a postemergence (POST) herbicide, PRE plus POST herbicides, and a nontreated (NT) check. The PRE herbicide was S-metolachlor; the POST treatment contained a mixture of dicamba and glyphosate. The PRE plus POST system contained the PRE application followed by POST application. Results show that cereal rye and the cover crop mixture provided weed biomass reduction compared to all cover crop treatments across both locations. Furthermore, we observed greater soybean yield following the cereal rye cover crop than following the winter fallow treatment at one location. POST and PRE plus POST herbicide treatment resulted in greater weed biomass reduction and improved soybean yield than the PRE herbicide treatment alone and the NT check at both locations.

Impact of soil-residual herbicides on industrial hemp (Cannabis sativa) phytotoxicity and biomass yield in west Texas

Abstract Industrial hemp is a multipurpose crop cultivated for fiber, seed, human food, and animal feed. Hemp legalization in Texas creates a considerable potential to increase its acreage in semi-arid conditions; however, knowledge is limited on growing hemp optimally in Texas. Best management practices, including weed control, require evaluation for profitable hemp production. As little is known about the herbicide tolerance of hemp, field studies were conducted to test several soil-residual herbicides with different modes of action for phytotoxicity to two hemp cultivars, ‘Yuma’ and ‘Jinma’. The experimental units were randomized three times in a blocked split-plot design with hemp cultivars in the main plots and soil-residual herbicides in the subplots. Ethalfluralin, the mixture of sulfentrazone and S-metolachlor, prometryn, and S-metolachlor, resulted in 60% to 90% and 73% to 100% weed control as compared to the nontreated control in 2021 and 2022, respectively. The highest hemp germination, stand count, and plant height were observed with ethalfluralin and S-metolachlor herbicides; however, no significant differences were observed for hemp germination and plant height compared to the nontreated control. S-metolachlor, ethalfluralin, fomesafen, and prometryn resulted in similar hemp biomass compared to the nontreated control. Overall, the results indicate that hemp is tolerant to ethalfluralin, prometryn, and S-metolachlor, and these soil-residual herbicides were effective for weed control in hemp. The mixture of bicyclopyrone plus S-metolachlor, metribuzin plus S-metolachlor, and mesotrione should be avoided, as they caused significant injury to hemp plants. Future research is needed to test the efficacy of different preemergence and postemergence herbicides that can be used in industrial hemp grown under different environments, making sure the delta-9-tetrahydrocannabinol content of the hemp is below the legal content restrictions.

EPSPS gene amplification confers glyphosate resistance in Palmer amaranth in Connecticut

Abstract A Palmer amaranth biotype (CT-Res) with resistance to glyphosate was recently confirmed in a pumpkin field in Connecticut. However, the underlying mechanisms conferring glyphosate resistance in this biotype is not known. The main objectives of this research were 1) to determine the effect of plant height (10, 20, and 30 cm) on glyphosate resistance levels in CT-Res Palmer amaranth biotype, and 2) to investigate whether the target site–based mechanisms confer glyphosate resistance. To achieve these objectives, progeny seeds of the CT-Res biotype after two generations of recurrent selection with glyphosate (6,720 g ae ha−1) were used. Similarly, known glyphosate-susceptible Palmer amaranth biotypes from Kansas (KS-Sus) and Alabama (AL-Sus) were included. Results from greenhouse dose-response studies revealed that CT-Res Palmer amaranth biotype had 69-, 64-, and 54-fold resistance to glyphosate as compared with the KS-Sus biotype when treated at heights of 10, 20, and 30 cm, respectively. Sequence analysis of the EPSPS gene revealed no point mutations at the Pro106 and Thr102 residues in the CT-Res Palmer amaranth biotype. Quantitative polymerase chain reaction analysis revealed that the CT-Res biotype had 33 to 111 relative copies of the EPSPS gene compared with the AL-Sus biotype. All these results suggest that the EPSPS gene amplification endows a high level of glyphosate resistance in the GR Palmer amaranth biotype from Connecticut. Because of the lack of control with glyphosate, growers should adopt the use of effective alternative preemergence and postemergence herbicides in conjunction with other cultural and mechanical tactics to mitigate the further spread of GR Palmer amaranth in Connecticut.

Investigation of management practices to optimize cereal rye cover crop-based weed mitigation in Canadian sweet corn production

Abstract Fall-sown cereal rye has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. However, previous research has shown that replacing preemergence and/or postemergence herbicide applications with roller-crimped rye has variable success at controlling weeds and maintaining vegetable cash crop yields. The objective of this research was to determine whether roller-crimped rye can provide season-long weed control and maintain sweet corn yield. Two rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m−2) for their effect on weed control and sweet corn yield. The trial was conducted at three locations: Harrow, ON, and St. Jean-sur-Richelieu, QC, from 2019 to 2021; and Agassiz, BC, in 2019 and 2021. Results suggest that although the early-maturing cultivar allowed for earlier roller crimping in some locations, it was inferior at weed control and resulted in lower sweet corn yield than local standard cultivars. The average rye biomass was lower than the current literature recommendations, and the resulting level of weed control was not high enough to prevent sweet corn yield loss in cover crop treatments. Weed control provided by roller-crimped rye peaked between crimping and 8 wk after crimping and was highest in the standard cultivars sown at 300 and 600 seeds m−2. Preliminary testing of supplemental postemergence weed control showed evidence for sweet corn yields comparable to the weed-free no-cover crop check. However, more research is needed. Overall, with the cultivars and seeding rates tested, roller-crimped rye is not a suitable stand-alone weed control option in sweet corn production. Given the benefits of cover crops, further research should evaluate its potential as a component of an integrated weed management program.

Verification of the selective efficacyand effect of the applicationof the pre-emergence herbicide Stomp (Pendimethalin) on shoot growth in young ornamental woody plants using privet and European Bladdernut as an example

Verification of the selective efficacyand effect of the applicationof the pre-emergence herbicide Stomp (Pendimethalin) on shoot growth in young ornamental woody plants using privet and European Bladdernut as an example

Relative efficiency of pre-emergence herbicides on weed dynamics, yield, and economics of Pearl millet (Pennisetum glaucum L.)

Relative efficiency of pre-emergence herbicides on weed dynamics, yield, and economics of Pearl millet (Pennisetum glaucum L.)

Formulaciones de sulfentrazona y herbicidas para control de malezas en sistemas de producción de tabaco

Sulfentrazone is one of the main pre-emergent herbicides used in tobacco plantations. The objective of this work was to evaluate the selectivity and efficiency of sulfentrazone-based formulations in two tobacco production systems (conventional tillage system [CTS] and no-tillage system [NTS]). Two experiments were conducted (CTS and NTS) in a randomized block design, with seven treatments and four replications. The herbicide treatments were: T1 = Boral® 500 SC (400 g∙ha-1 of sulfentrazone), T2 = PonteiroBR® (400 g∙ha-1 of sulfentrazone), T3 = Stone® (350 + 700 g∙ha-1 of sulfentrazone and diuron, respectively), T4 = Boral® 500 SC + Gamit® 360 CS (792 g∙ha-1 of clomazone), T5 = PonteiroBR® + Gamit® 360 CS, T6 = Stone® + Gamit® 360 CS, and T7 = control (manual weeding). Phytotoxicity in tobacco plants and weed control efficiency were visually evaluated 14, 28, 42, and 56 days after application (daa) of the treatments. Emerged weed plants per m2 were counted 56 daa. Tobacco yield was evaluated by determining the yield per third of the plant (lower, middle, and upper thirds) and the total yield (sum of the yields from each third). The sulfentrazone formulations were efficient in weed control. The herbicide Stone® applied alone or mixed with Gamit® caused mild phytotoxicity in plants under NTS, but no yield losses. No significant difference was found in yield among treatments; however, the yield of the upper third of the plant was higher for plants under NTS, affecting the total yield. The sulfentrazone formulations used provided efficient weed control and selectivity to tobacco plants. The use of NTS resulted in higher yields.

The Manual, Chemical, Cultural, and Integrated Weed Management in Soybean Production

A field experiment was conducted at Sher-e-Bangla Agricultural University, Dhaka, from December 2021 to April 2022 to study the effect of weed management practices in soybean (Glycine max L.). The experiment was laid out in a Randomized three-Complete Block Design (RCBD) with twelve weed management treatments- no weeding (Control), two hand weeding (at 15 and 30 DAS), pre-emergence herbicide (Herbilin 33% EC @ 400 ml ha-1), post-emergence herbicide Irish EC @ 1200 ml ha-1, pre + post-emergence herbicide, pre-emergence + 1 hand weeding {40 days after sowing (DAS)}, post-emergence herbicide + 1 hand weeding (40 DAS), pre + post-emergence herbicide + 1 hand weeding(40 DAS), straw mulching, intercrop with Amaranthus dubius, and Zea mays, and weed-free. The experimental result showed among seven different weed species found, Cyperus rotundus was the most prevalent weed, with the highest weed density (123 and 128.67 m-2) and relative weed emergence (43.16 and 38.79 %) in the control plot at 30 and 60 DAS. The treatment pre + post-emergence herbicide + 1 hand weeding (40 DAS) showed the longest pod length (4.16 cm) and number of seeds pod-1 (3.89). The weed-free treatment resulted in the highest 1000-seed weight (111.00 g), seed yield (1.86 t ha-1), stover yield (2.16 t ha-1), biological yield (4.03t ha-1), and harvest index (46.35 %). However, the highest benefit-cost ratio (2.85) was obtained under post-emergence herbicide (Irish EC) treatment. Therefore, applying Irish EC was the best broad-spectrum effective herbicide to manage the various weed floras in soybeans for profit. SAARC J. Agric., 21(2): 195-206 (2023)

Integrated weed management in soybean [Glycine max (L.) Merrill

A field experiment was conducted to study the effect of integrated weed management on growth and yield of soybean at Agricultural Research Station, Hukkeri, Belagavi, during kharif, 2022. The experiment was laid out in RCBD with three replications. The experiment consisted of 10 treatments comprising of 8 pre-emergence herbicides (Sulfentrazone + Clomazone, Sulfentrazone + Metolachlor, Metolachlor, Metribuzin, Pendimethalin + Imazethapyr, Flumioxazin, Pendimethalin, Diclosulam) and they were tested along with one intercultivation operation. Among the herbicidal treatments, application of Sulfentrazone 28% + Clomazone 30% WP (350 + 375 g a.i ha-1) RM @ 1250 g ha-1 as PE followed by one inter cultivation at 35 DAS recorded significantly lower weed density (2.27 m-2), dry weight of weeds (2.42 g m- 2) and higher weed control efficiency (88%) for total weeds at 15 days after herbicide application (DAHA) with lower weed index (5.30%). It also recorded higher plant height (53.89 cm), number of branches (7.75 plant-1), total dry matter production (16.80 g plant-1), seed yield (2413 kg ha-1), gross returns (`115824 ha-1), net returns (`70887 ha-1) and benefit cost ratio (2.58). The lower seed yield, net returns and benefit cost ratio was recorded with Metribuzin 70% WP (0.35 kg a.i. ha-1) @ 500 g ha-1 as PE followed by one inter cultivation at 35 DAS due to phytotoxicity of Metribuzin on soybean. Seed quality was not influenced by herbicidal treatments.

Integrated weed management in rabi sorghum (Sorghum bicolor L.) under rainfed conditions

A field experiment was conducted to assess the impact of weed management on growth and yield of grain sorghum at the Regional Agricultural Research Station, Vijayapura during rabi 2022-23. The experiment was laid out in a Randomized Complete Block Design with three replications and comprised eleven treatments. These treatments included five preemergence herbicide treatments (Atrazine @1000 g a.i. ha-1, Metribuzin @ 350 and 700 g a.i. ha-1, Metolachlor @ 750 and 1500 g a.i. ha-1) followed by two intercultivation at 30 & 60 DAS, as well as four post-emergent herbicide treatments (Metribuzin @ 350 and 700 g a.i. ha-1, Mesotrione + Atrazine (RM) @ 550 and 825 g a.i. ha-1) followed by one intercultivation at 60 DAS. These nine herbicide treatments were compared to a weedy check and a weed free check. The experimental results showed that weed free condition recorded minimal weed infestation, better crop growth, higher yield and economical returns. Among the herbicidal treatments, application of Metolachlor 50EC @ 1500 g a.i. ha-1as pre-emergence followed by two intercultivations at 30 and 60 DAS recorded significantly lower weed count (1.67 m-2), weed biomass (4.67 g m-2) and higher weed control efficiency (92%) for total weeds at 60 DAS, with a reduced weed index of 7.21%. Additionally, this treatment led to significantly higher grain yield (1389 kg ha-1), stover yield (3031 kg ha-1), gross returns (`73,759 ha-1), net returns (`40,968 ha-1) and benefit cost ratio (2.25). In contrast, the weedy check treatment resulted in lower grain yield, net returns, and benefit cost ratio.

Postemergence-directed applications of pendimethalin for control of early-season weeds in chile pepper

Abstract In New Mexico chile pepper production, pendimethalin is traditionally applied shortly after crop thinning, which is 9 to 10 wk after crop seeding. Pendimethalin applications before crop thinning may be a method for controlling early-season weeds in chile pepper; however, chile pepper tolerance to early-season applications of pendimethalin is poorly understood. We conducted a greenhouse study to evaluate young chile pepper responses to pendimethalin. We also conducted a field study to determine weed and chile pepper responses to early-season, postemergence-directed pendimethalin in combination with herbicides registered for preemergence applications. The greenhouse study included three treatments administered when chile pepper was at the four-leaf stage: (i) pendimethalin applied to foliage and soil, (ii) pendimethalin applied to soil only, and (iii) a nontreated control. The field study included four treatments: (i) preemergence applications of napropamide followed by postemergence-directed pendimethalin at 5 wk after crop seeding, (ii) preemergence applications of clomazone followed by postemergence-directed pendimethalin at 5 wk after crop seeding, (iii) postemergence-directed pendimethalin without preemergence herbicides, and (iv) nontreated, weed-free control. We conducted the field study at two sites that differed in soil texture. Pendimethalin application rates were maximum labeled rates for the specific soil. Results from the greenhouse study indicated that pendimethalin applied to foliage and soil stunted two of five cultivars, whereas pendimethalin applied to soil did not affect chile pepper height, fresh weight, dry weight, or root area. Results from the field study indicated that postemergence-directed pendimethalin did not affect chile pepper height or fruit yield, or cause visible symptoms of herbicide injury. Postemergence-directed pendimethalin reduced the densities of weeds, including junglerice. The results of this study indicate that postemergence-directed applications of pendimethalin at 5 wk after crop seeding do not cause crop injury or yield loss in chile pepper, while providing some weed control benefits.

Growth and yield of rice (<i>Oryza sativa</i>) under different establishment methods and weed management practices in Uttarakhand

An experiment was conducted during the rainy (kharif) seasons of 2021 and 2022 at the Norman E. Borlaug (NEB) Crop Research Centre at Govind Ballabh Pant University of Agriculture and Technology, Pantnagar, Uttarakhand to study the effect of different establishment methods and weed management practices on growth and yield of rice (Oryza sativa L.). The study was carried in a split plot design with 3 replications. In main plot 4 rice establishment methods and in sub plot 4 weed management practices were included. The results revealed that significantly higher grain yield was recorded in mechanical line sowing (S2) over rest of the treatment. According to the pooled data analysis of grain yield the per cent increase in mechanical line sowing (S2) over broadcasting (S1), raised bed system (S3) and semi-dry system (S4) was 23.1%, 17.6% and 8.1%, respectively. Among the different weed management practices grain yield was recorded maximum in W3 (pre emergence herbicide followed by two manual weeding) treatment which showed at par results with W2 (pre emergence followed by post emergence herbicide) treatment. The per cent grain yield increase in pre emergence herbicide followed by two manual weeding (W3) over manual weeding (W1), pre emergence followed by post emergence herbicide (W2) and mechanical weeding (W4) was 19.3%, 0.75% and 31.7%, respectively. Weed density was recorded minimum in mechanical line sowing (S2) and raised bed system (S3). At panicle initiation stage significantly lower weed density was recorded in mechanical line sowing (S2). However, among the weed management practices manual weeding (W1) and pre emergence herbicide followed by two manual weeding (W3) treatments recorded at par. Weed dry weight remain non-significant under different rice establishment methods during active tillering as well as panicle initiation stage.