Preemergence Research Articles

Response of dry beans to tiafenacil applied preemergence

AbstractTiafenacil is a new nonselective, protoporphyrinogen IX oxidase–inhibiting pyrimidinedione herbicide that is under consideration for registration to control grass and broadleaf weeds in corn, soybean, wheat, cotton, and other crops prior to crop emergence. The sensitivity of dry beans to tiafenacil is not known. Four field experiments were completed at Exeter and Ridgetown, ON, Canada, during the 2019 and 2020 growing seasons, to determine the sensitivity of azuki, kidney, small red, and white beans to tiafenacil applied preemergence (PRE) at 12.5, 25, 50, and 100 g ai ha−1. Tiafenacil applied at 100 g ai ha−1 caused 5% or less injury to azuki, kidney, small red, and white beans: 0% to 3% injury to azuki bean; 1% to 5% injury to kidney bean; and 1% to 4% injury to both small red bean and white bean. Tiafenacil applied PRE at 12.5, 25, 50, and 100 g ai ha−1 caused up to 1%, 4%, 4%, and 5% visible dry bean injury, respectively, but had no negative effect on other measured growth parameters including seed yield. Crop injury was generally greatest when tiafenacil was appled at the 100 g ai ha−1 rate in dry beans. Generally, kidney, small red, and white bean were more sensitive to tiafenacil than azuki bean. Dry bean injury was persistent and increased with time with the greatest injury observed 8 wk after emergence. Tiafenacil applied PRE can be a useful addition to the current strategies to control grass and broadleaf weeds, especially glyphosate-resistant horseweed and amaranth species prior to bean emergence.

Evaluation of Preemergent Herbicides for Chloris virgata Control in Mungbean.

Chloris virgata is a problematic weed in mungbean crops due to its high seed production, resistance to glyphosate and high dispersal ability. Pot and field experiments were conducted in 2020 and 2021 to evaluate a range of preemergent (PRE) herbicides for C. virgata control in mungbean. In the field and pot studies, isoxaflutole 75 g ai ha−1 caused crop injury, and in the field experiment, it reduced mungbean yield by 61% compared with the best treatment (pyroxasulfone 100 g ai ha−1). In the field and pot experiments, dimethenamid-P 720 g ai ha−1, pyroxasulfone 100 g ai ha−1 and S-metolachlor 1400 g ai ha−1 provided >88% control of C. virgata (for reduced biomass) and in the field experiment, these herbicides resulted in improved yield by 230%, 270% and 170%, respectively, compared with nontreated control (250 kg ha−1). Similarly, pendimethalin 1000 g ai ha−1 and trifluralin 600 g ai ha−1 provided >89% control (biomass) of C. virgata, and in the field experiment, these resulted in improved yields of 230% and 160%, respectively, compared with the nontreated control. PRE herbicides such as diuron 750 g ai ha−1, linuron 1100 g ai ha−1, metribuzin 360 g ha−1, terbuthylazine 750 g ai ha−1, imazapic 48 g ai ha−1 and imazethapyr 70 g ha−1 although did not cause crop injury; however, these herbicides did not control C. virgata. Flumioxazin 90 g ai ha−1 caused reduced biomass of C. virgata by 80% compared with the nontreated control, and in the field experiment, it resulted in improved yield by 140% compared with the nontreated control. This study suggests the potential use of herbicides, such as dimethenamid-P, pyroxasulfone and S-metolachlor in addition to pendimethalin and trifluralin, for C. virgata control in mungbean. Further studies are needed to determine the efficacy of dimethenamid-P, S-metolachlor and pyroxasulfone for controlling other troublesome weeds in mungbean.

Evaluation of Pre and Post Emergence Herbicides in Greengram (Vigna radiata L.) during Kharif and Rabi Seasons in the Uplands of Krishna Zone of Andhra Pradesh

Background: Greengram crop is grown round the year as a catch crop in different cropping systems of the uplands of the Krishna Zone of Andhra Pradesh. The practice of application of pre emergence herbicide like pendimethalin is very popular with the farmers for the control of weeds in the uplands, both in kharif and rabi seasons. Further spraying of a selective post emergence herbicide is also practiced by farmers. However, some of the weeds of kharif viz., Phyllanthus maderaspatensis and rabi viz., Chrozophora rottleri could not be controlled with these herbicides due to their late emergence or due to development of partial resistance to these herbicides. Certain new pre (PE) and post emergence (PoE) herbicides viz., pendimethalin 30% + imazethapyr 2%, acifluorfen sodium 16.5% + clodinafop propargyl 8%, fomesafen 11.1% + fluazifop -p-butyl 11.1%, are recommended in crops like soybean and groundnut. However, there is need to test these herbicides available in market for their suitability to control the weeds in greengram. Methods: A field experiment was carried out at Regional Agricultural Research Station, Lam, Guntur, Andhra Pradesh, with an objective to evaluate selected PE and PoE herbicide mixtures in greengram managing the major weeds of greengram grown in vertisols of Krishna Zone of Andhra Pradesh during Kharif and rabi seasons of 2018 under upland conditions. Result: Among the two PE herbicides tested on greengram, pendimethalin 30% + imazethapyr 2% @ 0.75 + 0.05 kg/ha was found to be more effective in reducing the weed density and dry matter compared with pendimethalin 30% @ 0.75 kg/ha. The PoE herbicide mixtures tested viz., fomesafen 11.1% + fluazifop -p-butyl 11.1% @111g/ha, propaquizafop 2.5% + imazethapyr 3.75% @ 50+75 g/ha were on par with imazethapyr 10% @ 50g/ha in controlling the weed population without having any adverse affect on the growth and yield of greengram during kharif and rabi.

Peanut Response to Flumioxazin and S-Metolachlor Under High Moisture Conditions

ABSTRACT Georgia produces nearly 51% of the United States peanut (Arachis hypogaea L.) crop. To combat and prevent weed infestations, herbicide programs containing flumioxazin and S-metolachlor are often applied preemergence (PRE). Despite herbicide effectiveness for weed control, peanut injury following heavy rainfall can be problematic. The objective of this study was to evaluate the impact of injury from flumioxazin and S-metolachlor after simulated heavy rainfall events on peanut growth and yield. Plots were planted at the University of Georgia Ponder Research Farm located near Ty Ty, Georgia using conventional tillage practices and twin-row spacing. Treatments included PRE applications of flumioxazin at 0, 0.11 and 0.22 kg ai/ha alone or in combination with S-metolachlor at 0, 1.07, 1.40, 2.80 kg ai/ha and were applied using a CO2-pressurized backpack sprayer. Irrigation and rainfall were ≥20 cm in the 30 days after planting (DAP) to simulate heavy rainfalls. Flumioxazin at 0.22 kg ai/ha caused the greatest visual injury (>60%) and most whole-plant fresh weight/m reductions at 21 DAP compared to other treatments. Peanut density was not impacted by flumioxazin or S-metolachlor. Neither flumioxazin nor S-metolachlor affected J-rooting. Yield was not reduced by any rate of flumioxazin. However, S-metolachlor at 2.80 kg/ha, (2.6X field rate), reduced yields by 8.9% compared to plots where no S-metolachlor or recommended field rates were applied.

Control of glyphosate‐ and mesotrione‐resistant Palmer amaranth in glyphosate‐ and glufosinate‐resistant corn

AbstractIncreasing reports of herbicide‐resistant Palmer amaranth (Amaranthus palmeri S. Watson) pose a serious management concern for Kansas corn (Zea mays L.) producers. The objectives of this study were to evaluate various herbicide programs, including preemergence (PRE) alone, PRE followed by (fb) early postemergence (EPOST), and PRE fb late POST (LPOST) for control of glyphosate‐ and mesotrione‐resistant (GMR) Palmer amaranth in glyphosate‐ and glufosinate‐resistant corn, and their effect on crop injury, yield, and net economic return. Field experiments were conducted in 2018 and 2019 in grower fields with natural infestations of GMR Palmer amaranth near Seward in Stafford County, KS. Preemergence programs, including dicamba + thiencarbazone‐methyl + atrazine and dicamba + [atrazine, bicyclopyrone, mesotrione, S‐metolachlor (ABMS)] or dicamba + ABMS in mixtures with atrazine, mesotrione, S‐metolachlor, and metribuzin provided 89–93% control of GMR Palmer amaranth 3 wk after PRE. Preemergence fb EPOST programs provided 87–96% control of GMR Palmer amaranth at 2 wk after EPOST through 7 wk after LPOST. In comparison, PRE‐only programs provided 62–82% and PRE fb LPOST programs provided 75–86% control. The various herbicide programs resulted in greater corn grain yield ranging from 9,207 to 10,508 kg ha–1 compared with 6,056 kg ha–1 in the nontreated control. The highest net return ($1,300 ha–1) was achieved from dicamba + ABMS + atrazine applied PRE fb EPOST application of ABMS + atrazine. These results suggest that effective PRE fb EPOST herbicide programs consisting of multiple sites of actions are available and provide effective control of GMR Palmer amaranth in glyphosate‐ and glufosinate‐resistant corn.

Effect of Method of Application, Herbicide Rate and Cultivar on Processing Pea Tolerance to Saflufenacil

The purpose of this work was to determine the effect of method of application, herbicide rate and cultivar on tolerance of processing pea tolerance to saflufenacil. Two field experiments were established to address this—each experiment was conducted over a 3-year period. The first experiment, conducted in 2014, 2015 and 2016, was arranged in a split-plot design with method of application (pre-plant incorporation (PPI) or preemergence (PRE)) as the main plot factor, and saflufenacil rate (0, 75 and 150 g ai ha-1) as the subplot factor. Pea (Pisum sativum L.) was not injured, and dry matter, pea tenderness and yield were not less than the untreated check when saflufenacil was applied either PPI or PRE, at 75 and 150 g ai ha-1 of the herbicide. The second experiment was conducted from 2017 to 2019, at two locations each year; each repetition of this experiment was arranged in a factorial design to determine the effect of two factors on processing pea: saflufenacil rate (0, 75 and 150 g ai ha-1) and cultivar. Saflufenacil did not cause more than 5% visible injury to pea, nor did it reduce pea dry matter, tenderness or marketable yield of the eight cultivars included in the experiment. Application method, saflufenacil rate and cultivar did not affect pea tolerance across a wide range of soil and environmental conditions. Registration of saflufenacil in processing pea would significantly improve growers’ options for control of Group 2 resistant broadleaf weeds such as common lamb’s-quarters (Chenopodium album L.), eastern black nightshade (Solanum ptycanthum Dunal.) and common ragweed (Ambrosia artemisiifolia L.).

Influence of Weed Management Practices on Nutrient Removal and Performance of Transplanted Finger Millet (Eleusine coracana L.)

Background: Finger millet production and productivity is lowering in India due to the growth of different weed species. Weeds are the prime yield limiting biotic constraints in finger millet. Therefore, the present investigation has been carried out to find out the suitable weed management practices on the performance of finger millet. Methods: In this regard, a field experiment was carried out during Kharif, 2018 at Anbil Dharmalingam Agricultural College and Research Institute, Tiruchirapalli, Tamil Nadu, India to evaluate the different weed management practices for transplanted finger millet under sodic soil. The experiment comprised of ten weed management practices with different herbicidal treatments viz., pre emergence (PE) application of pendimethalin at 750 g/ha, oxyfluorfen at 50 g/ha, bensulfuron methyl at 60 g/ha + pretilachlor at 600 g/ha, early post emergence (EPOE) application of bispyribac sodium at 25 g/ha, PE pendimethalin at 750 g/ha fb EPOE bispyribac sodium at 25 g/ha, PE oxyfluorfen at 50 g/ha fb EPOE bispyribac sodium at 25 g/ha, PE bensulfuron methyl at 60 g/ha + pretilachlor at 600 g/ha fb EPOE bispyribac sodium at 25 g/ha, PE oxyfluorfen at 50 g/ha fb hand weeding (HW) at 30 DAT, HW at 15 and 30 DAT and unweeded control (UWC) in transplanted finger millet. Result: The results revealed that lower nutrient removal by weeds, higher nutrient uptake by crop and yield parameters viz., productive tillers/m2, earhead weight and total grains/earhead were registered in application of PE bensulfuron methyl at 60 g/ha + pretilachlor at 600 g/ha fb EPOE bispyribac sodium at 25 g/ha. The highest grain and straw yields were also registered in application of PE bensulfuron methyl at 60 g/ha + pretilachlor at 600 g/ha fb EPOE bispyribac sodium at 25 g/ha and it was on par with hand weeding at 15 and 30 DAT.

Crop residue and rainfall timing effect on pre-emergence herbicides efficacy using different spray nozzle types

Weed control success with pre-emergence (PRE) herbicides is affected by environmental factors including rainfall and plant residue. Two greenhouse experiments were conducted to evaluate PRE herbicide efficacy against johnsongrass [Sorghum halepense (L.) Pers.], prickly sida (Sida spinosa L.) and velvetleaf (Abutilon theophrasti Medik.). One experiment investigated herbicide efficacy under two crop residue amounts (2500 and 5000 kg ha−1) and the second examined herbicide efficacy influenced by simulated rain at two, four, and eight days after application (DAA). Five herbicides (pendimethalin, metribuzin, clomazone, imazethapyr and pyroxasulfone) and four nozzles types (XR, ULD, TTI and TTI60) were used. Nozzle type did not affect weed control across residue levels. Pendimethalin better controlled S. halepense under the low residue level. Imazethapyr efficacy for S. spinosa and A. theophrasti increased under high residue level. Imazethapyr applications for S. spinosa and A. theophrasti control were more effective when sprayed with the TTI nozzle regardless of rainfall timing. Longer periods without rain after application improved pendimethalin efficacy against S. spinosa and A. theophrasti, while pyroxasulfone better controlled S. spinosa with rain two DAA. Metribuzin and clomazone provided the best weed control among herbicides for all residue levels and rainfall scenarios.

Manipulation of sunflower population density and herbicide rate for economical and sustainable weed management

Field study tested weed control efficacy, crop yield and economic return using various weed management strategies in sunflower growing with different population density. Treatments included four rates of PRE emergence application of S-metolachlor + fluchloridon and one POST emergence application of flumioxazin + quizalofop-pethyl. PRE-em application (1.4 + 2.4 and 1.2 + 2.0) provided at the higher crop densities (70 000) best weed control. However, PRE- em treatments with lower doses (0.8 + 1.6 and 1.0 + 1.8) and POST- em application did not maintain acceptable control of dominant weeds. Grain yield increased with the crop density, but did not statistically differ between applied herbicide treatments. Finally, the implication of this study demonstrated that sole application of tested herbicide treatments at higher crop sowing density (60 000 and 70 000) was found to be economically the best alternative strategy for reducing weed infestation and achieving a better yield.

Impact of Weed Management Practices on Yield Attributes, Economics and Phytotoxicity of Kharif Maize

A field experiment was conducted during 2018 and 2019 at Tamil Nadu Agricultural University, Agriculture College and Research Institute, Coimbatore to study the impact of weed management practices on yield attributes, economics and phytotoxicity of kharif maize. Ten treatments were tested in randomized block design with three replications viz., pre emergence (PE) atrazine at 0.5 kg a.i. ha-1 fb hand weeding (HW) at 20 DAS, PE atrazine at 0.5 kg a.i. ha-1 fb power weeder (PW) at 20 DAS, PE atrazine at 0.5 kg a.i. ha-1 + pendimethalin at 1 kg a.i. ha-1 (Tank mix), PE atrazine at 0.5 kg a.i. ha-1 + pendimethalin at 1 kg a.i. ha-1 fb HW at 20 DAS, early post emergence (EPoE) topramezone at 25.2 g a.i. ha-1, PE atrazine at 0.5 kg a.i. ha-1 fb EPoE topramezone at 25.2 g a.i. ha-1, EPoE tembotrione at 122 g a.i. ha-1, PE atrazine 0.5 kg a.i. ha-1 fb EPoE tembotrione 122 g a.i. ha-1, hand weeding twice at 20 and 45 DAS and control (weedy check). Among the different weed management practices significantly higher yield attributes viz., cob length, cob girth, weight of cob, No. of grain rows cob-1, No. of grains cob-1, grain yield cob-1 was found with hand weeding twice at 20 and 45 DAS and it was at par with atrazine at 0.5 kg a.i. ha-1 as PE fb topramezone at 25.2 g a.i. ha-1 as EPoE and atrazine at 0.5 kg a.i. ha-1 as PE + tembotrione at 122 g a.i. ha-1 as EPoE. Maximum net return and B:C ratio were recorded under atrazine at 0.5 kg a.i. ha-1 as PE fb topramezone at 25.2 g a.i. ha-1 as EPoE followed by atrazine at 0.5 kg a.i. ha-1 as PE + tembotrione at 122 g a.i. ha-1 as EPoE. However, among the different herbicidal treatments used, all the herbicidal treatments were found to be safe to the maize crop without any caused phototoxic effect on maize during both the years of experimentation. Now-a-days, increased labour scarcity and costs are encouraging farmers to adopt labour and cost- saving options by using chemical method.

Tomato tolerance to preemergence herbicides in plasticulture using narrow bands and precision technology

Preemergence (PRE) herbicides are broadcast-applied over the entire top of raised beds prior to plastic mulch installation. Following mulch installation, broadleaves and grasses only emerge from the planting holes. For this reason, the majority of PRE herbicides that are broadcast-applied underneath the plastic mulch are unnecessary for weed control. To reduce off-target herbicide application, we evaluated (1) tomato tolerance to herbicides applied in narrow bands over the planting holes at 2 weeks after transplant (WATP), and (2) tomato tolerance to herbicides that were precisely applied to individual planting holes immediately prior to transplant using a precision herbicide applicator that was previously developed at the University of Florida. Halosulfuron, metribuzin, pendimethalin, and S-metolachlor applied in narrow bands over the planting holes at 2 WATP did not significantly injure tomato, stunt growth, nor reduce yield. However, significant tomato injury (7%) was observed when fomesafen was applied in narrow bands over the planting holes where tomato plants have been transplanted for 2 weeks. Precision application of fomesafen, metribuzin, oxyfluorfen, and S-metolachlor in a carrier volume of 187, 374, or 561 L ha−1 using the precision hole-punch sprayer to the individual planting holes prior to transplant caused minimal early-season tomato injury (≤4%) and did not significantly stunt tomato plant growth or reduce yield. Overall, results demonstrated a safe and effective way to reduce off-target herbicide application in plastic-mulched tomato by applying herbicides in bands over the planting holes after transplant or precisely applying herbicides to individual planting holes prior to transplant using a precision hole-punch applicator.

Weed control with diclosulam in soybean

The experiments were conducted in 2017-2018 on soybean (Glycine max L.) in three climatic regions of Russia (Altai Region, Krasnodar Region and Astrakhan Region) to evaluate efficacy of herbicide diclosulam (WG, 750 g/kg). Treatments included diclosulam: 1) applied preemergence (PRE) - 18.75 and 37.5 g i.a. ha-1; 2) applied postemergence (POST) at 1-3 leaves of soybeans (BBCH 11-13) - 11.25 and 22.5 g i.a. ha-1. Monocotyledonous weeds (Echinochloa crusgalli (L.) Beauv. and Panicum miliaceum ssp. ruderale (Kitagawa) Tzvelev) had low sensitivity to diclosulam. Diclosulam efficacy at minimum application rate against Fallоpia convolvulus (L.) A. Love and Solanum nigrum L. was 100%. Adjuvant ethoxylated isodecyl alcohol (EIAb) was added to diclosulam to increase treatment efficiency against Chenopodium album L., Amaranthus retroflexus L., Ambrosia artemisiifolia L., Persicaria maculosa S.F. Gray. EIAb with diclosulam was the most effective at minimum application rate. Application of diclosulam did not cause phytotoxicity on 3 soybean cultivars Altom, Bara and Vilana. The maximum increase of soybean yield after herbicide treatment was observed in Krasnodar Region in 2018 at cultivar Bara (+ 9.2 centners per hectare).

Impact of some Agronomical Practices on Carrot Productivity and Nutritional Value تأثير بعض الممارسات الزراعية على إنتاجية الجزر و القيمة الغذائية

Experiments were conducted during the two winter seasons of 2018 and 2019 to investigate the response of two carrot cultivars (Chantenay and Nantes) to pre-and post-emergence linuron applications and different agronomic methods (broadcasting and drilling on raised rows and broadcasting in beds). The effect of factors on the vegetative growth and accumulation of nutrient compounds has been assessed. Pre emergence linuron treatment substantially increased the yield, dry matter and root physical characters (root length and weight, root and core diameter) compared to post emergence treatment. Chantenay accumulated more phenolics and antioxidants than Nantes, which was 14.73-16.59%, 7.64-8.15% and 12.37-15.66% greater (p < 0.05) than Cahantenay in carotenoids, total and reducing sugars in 2018 and 2019, respectively. In order to raise the productivity of feddan, broadcasting on raised rows (140 plant/ m2) was correlated with higher yield and the sweet and darker root of carrot. Carrots were strongly influenced by linuron addition times in terms of yield or phytochemical status. Phenolic compounds and antioxidant strength were cultivar-dependent and Chantenay was the richest overall.

MINIMUM TILLAGE NON-PUDDLED TRANSPLANTED RICE (ORYZA SATIVA L.): WEED CONTROL AND ECONOMICS UNDER CONSERVATION AGRICULTURE PRACTICE IN BANGLADESH

Crisis of agricultural laborers in South Asia’s rural zones is pushing to pursue a labor-saving conservation agriculture strategy for crop production and weed control. Non-puddled transplanting and mulching residues of the previous crop are being developed for rice-based cropping systems in Bangladesh to address this issue. Hence, the present study was undertaken to determine the effectiveness of strip tillage vs. conventional tillage combined with previous rice residues relative to herbicides and hand weeding on weed control and grain yield of winter rice during January-May in 2015 and 2016. Rice cv. BRRI dhan28 was transplanted with a combination of six treatments: puddled conventional tillage (CT)+3 hand weeding (HW) (Control); Preplant (PRE) herbicide (glyphosate)+non-puddled strip tillage (ST)+1HW; PRE+ST+pre-emergence (PE) herbicide (pendimethalin); PRE+ST+post-emergence (PO) herbicide (ethoxysulfuron-ethyl); PRE+ST+PE+PO; PRE+ST+weed-free (WF); and two levels of rice residues: no-residue (R0) vs. 50% standing residue (R50). The CT had done using a two-wheel tractor (2WT) by four ploughings and cross ploughings followed by levelling. A Versatile Multi-Crop Planter (VMP) was used for ST in a single pass operation. Over the two years, PRE+ST+PE+PO reduced weed density by 40% in the first year and 50% in the second year and weed biomass by 70% than CT+3HW in both years. Retention of 50% residue reduced weed density by 20% and biomass by 34%. The highest grain yield (12% higher than CT+3HW without residue) was obtained from PRE+ST+WF with 50% residue, while the highest BCR (47% higher over CT+3HW without residue) was obtained from PRE+ST+PE+PO with 50% residue.

Residual herbicides affect critical time of Palmer amaranth removal in soybean

AbstractGlyphosate‐resistant (GR) Palmer amaranth (Amaranthus palmeri S. Watson) is one of the most difficult to control weeds in soybean [Glycine max (L.) Merr.] production fields. Residual pre‐emergence (PRE) herbicide applied at planting is one of the recommendations for management of herbicide‐resistant Palmer amaranth; however, information is not available about the effect of residual herbicides on critical time of Palmer amaranth removal (CTPAR) to prevent an unacceptable yield loss in soybean. The objective of this study was to determine the CTPAR in soybean affected by residual PRE herbicides compared with the no PRE herbicide in southcentral Nebraska. Field experiments were conducted in 2018 and 2019 in a grower's field infested with GR Palmer amaranth near Carleton, NE. The treatments were arranged in a split‐plot design with PRE herbicides (no PRE herbicide, flumioxazin, and a premix of flumioxazin/metribuzin/pyroxasulfone) as the main plot and Palmer amaranth removal timings as subplot treatments (a weed‐free control; a nontreated control; and Palmer amaranth removal timing at the V1, V3, V6, R2, and R5 soybean growth stages). In the absence of a PRE herbicide, the CTPAR at 5% soybean yield loss occurred at V1 and V6 soybean growth stages, equivalent to 194 and 480 Celsius growing degrees days (GDDc) in 2018 and 2019, respectively. When flumioxazin was applied alone, the CTPAR was delayed until the V3 and V6 soybean growth stages, or 341 and 501 GDDc. When flumioxazin/metribuzin/pyroxasulfone premix was applied, the CTPAR was delayed until the V2 and R1 soybean growth stages, corresponding to 255 and 546 GDDc, in 2018 and 2019, respectively.

Effect of integrated nutrient management and weed control practices on growth and yield attributes of rice (Oryza sativa L.) in rice-groundnut cropping system

A field experiment was conducted at Instructional farm of Krishi Vigyan Kendra Kendrapara, Odisha during kharif and rabi seasons of 2013-14 and 2014-15 in rice-groundnut cropping system under irrigated medium land situation. The soil of the experimental site was sandy loam in texture with pH of 5.7, organic carbon of 0.52% having available soil nitrogen, phosphorus and potassium of 390.9 kg/ha, 10.1 kg/ha and 190.1 kg/ha respectively. Rice crop (var. Sahabhagi dhan) was transplanted in kharif season taking nine treatments having three levels of nutrient management practice and three level of weed management with three replications. Further during rabi season each main plot was divided into two sub-plots taking groundnut (var. Devi) with two levels of weed management practices under split plot design. The pooled data revealed that growth of rice and yield attributes were significantly higher in treatment of RDF (75% N) with green manuring of dhaincha (Sesbania aculeata) with pre emergence application of herbicide oxadiargyl followed by post emergence bispyribac-sodium which recorded higher plant height (96.35 cm), number of tillers per plant (212.7), Leaf area index (4.4), dry matter accumulation (1347.5 g/plant), panicle length (25.8 cm) and test weight (22.33 g).

Future efficacy of pre-emergence herbicides in corn (Zea mays) is threatened by more variable weather.

BACKGROUNDBy 2050, weather is expected to become more variable with a shift towards higher temperatures and more erratic rainfall throughout the U.S. Corn Belt. The effects of this predicted weather change on pre‐emergence (PRE) herbicide efficacy have been inadequately explored. Using an extensive database, spanning 252 unique weather environments, the efficacy of atrazine, acetochlor, S‐metolachlor, and mesotrione, applied PRE alone and in combinations, was modeled on common weed species in corn (Zea mays L.).RESULTSAdequate rainfall to dissolve the herbicide into soil water solution so that it could be absorbed by developing weed seedlings within the first 15 days after PRE application was essential for effective weed control. Across three annual weed species, the probability of effective control increased as rainfall increased and was maximized when rainfall was 10 cm or more. When rainfall was less than 10 cm, increasing soil temperatures had either a positive or negative effect on the probability of effective control, depending on the herbicide(s) and weed species. Herbicide combinations required less rainfall to maximize the probability of effective control and had higher odds of successfully controlling weeds compared with the herbicides applied individually.CONCLUSIONSResults of this study highlight the importance of rainfall following PRE herbicide application. As rainfall becomes more variable in future, the efficacy of common PRE herbicides will likely decline. However, utilizing combinations of PRE herbicides along with additional cultural, mechanical, biological, and chemical weed control methods will create a more sustainable integrated weed management system and help U.S. corn production adapt to more extreme weather.© 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluation of Preemergence Herbicide Programs for Control of Protoporphyrinogen Oxidase-Resistant Amaranthus palmeri in Soybean

Protoporphyrinogen oxidase- (PPO-) resistant Amaranthus palmeri (S.) Wats. (Palmer amaranth) was confirmed in Arkansas in 2015. Field trials were conducted in Crawfordsville, Gregory, and Marion, Arkansas in 2016, and Crawfordsville and Marion in 2017, assessing PPO-resistant Palmer amaranth control options in Glycine max (L.) Merr. (soybean). Twelve trials consisted of 26 preemergence (PRE) treatments, evaluated for Palmer amaranth control and density reduction at 28 days after treatment (DAT). Treatments that consisted of PPO- or acetolactate synthase- (ALS-) inhibiting herbicides such as flumioxazin (72 g ai ha−1) or sulfentrazone + cloransulam (195 g ha−1 + 25 g ha−1) controlled Palmer amaranth &lt;60%. At 28 DAT, treatments including mixtures of a very-long-chain fatty acid (VLCFA) plus the photosystem II- (PSII-) inhibiting herbicide metribuzin provided increased control over single herbicide sites of action (SOA) or herbicides mixtures to which Palmer amaranth was resistant. Pyroxasulfone + metribuzin (149 g ha−1 + 314 g ha−1) controlled Palmer amaranth 91% control across twelve trials at 28 DAT. S-metolachlor alone did not provide consistent, acceptable control of PPO-resistant Palmer amaranth (55–77%); subsequent research has determined that these populations are resistant to S-metolachlor. A minimum of two effective herbicides should be included in soybean PRE programs for control of PPO-resistant Palmer amaranth.

Efficacy of Imiflex, Zest, and Assure II on Green Foxtail Control

Grass weeds pose a serious management challenge in grain sorghum. Recent development of three herbicide-tolerant grain sorghum technologies such as Inzen, Igrowth, and DoubleTeam will provide the opportunity for producers to use nicosulfuron (Zest), imazamox (Imiflex), and quizalofop-p-ethyl (FirstAct) for grass weed control, respectively. The main objectives of this research were to (1) determine the effectiveness of Imiflex applied preemergence (PRE) on green foxtail control in comparison to commonly used group 15 herbicides; (2) compare the efficacy of Zest, Imiflex, and Assure II applied early- or late-POST at two different rates; and (3) determine the tank-mix compatibility of Zest, Imiflex, Assure II, and Select Max (clethodim) with 2,4-D (Weedar 64) and dicamba (Clarity) on green foxtail control. Field experiments were conducted in fallow ground with a natural infestation of green foxtail at Kansas State University Agricultural Research Center in Hays, KS. PRE herbicide programs, including Imiflex, Dual II Magnum, Warrant, and Outlook were tested. Imiflex, Zest, and Assure II were tested in early- or late-postemergence (POST) timings. The early POST treatments of Imiflex, Assure II, Zest, and Select Max alone or in tank-mixture with Weedar 64 and/or Clarity were also tested in a separate study. Among PRE programs, Imiflex tested at both rates provided an excellent control (89 to 94%) of green foxtail up to 50 days after PRE (DAPRE), whereas control did not exceed more than 51% with any of the group 15 herbicides. Among early POST programs, Assure II at 10 fl oz/a provided 95% green foxtail control at 28 days after early POST (DAEPOST). Green foxtail control with early POST treatments of Imiflex, Zest, and Assure II (6 oz/a) was moderate and ranged from 77 to 83% at 28 DAEPOST. Green foxtail control with late POST treatments of Imiflex, Zest, and Assure II was inadequate and ranged from 14 to 31% at 21 days after late POST (DALPOST). In a separate study, tank-mixing Weedar 64 or Clarity with Assure II reduced the efficacy by >50% on green foxtail control compared to Assure II alone treatment. These results suggest that PRE applied Imiflex (6 or 9 oz/a) can provide excellent residual activity for early season control of green foxtail. Furthermore, Assure II applied early POST at a higher rate can provide effective control of green foxtail; however, the efficacy will significantly decline if Assure II is tank-mixed with Weedar 64 or Clarity.

Bio-efficacy of weed management practices in rainfed potato

A field experiment was conducted during 2013-14, 2014-15 and 2015-16 at ICAR-Central Potato Research Station, Shillong to evaluate the bio-efficacy of weed management practices in rainfed potato under North-Eastern hill region of India. Maximum potato tubers yield (21.3 t/ha) was recorded under weed free treatment followed by metribuzin application 0.75 kg/ha as a pre-emergence (PE). Reduction in crop yield due to presence of weeds was 54.0 per cent. Maximum uptake of nutrients, viz. nitrogen (113.2 kg/ha), phosphorus (14.5 kg/ha) and potassium (89.4 kg/ha) were recorded by the potato under weed free fb application of metribuzin 0.75 kg/ha as a PE. The highest net returns (₹ 176100/ha) and B:C ratio (2.3) were recorded under the metribuzin application 0.75 kg/ha. Thus, application of metribuzin 0.75 kg/ha as PE was found more effective in potato under the rainfed ecosystem of North-Eastern hill region of India.