Germination Of Redroot Pigweed Research Articles

The Allelopathic Effects of Turkish Hulled Wheat Lines on Germination of Amaranthus retroflexus L. and Lolium perenne L. Seeds

The aim of this study was to determine allelopathic effects of some emmer (Triticum dicoccum Schrank) and einkorn (Triticum monococcum L.) wheat lines on germination of redroot pigweed (Amaranthus retroflexus L.) and perennial ryegrass (Lolium perenne L.). For this purpose, fourty-nine emmer and thirty-six einkorn wheat lines with two commercial durum wheat cultivars (cvs. Svevo and Saragolla) were sown in experimental field of Akdeniz University. Leaves of emmer and einkorn lines were cut at the end of tillering stage (Z29) to obtain sufficient plant extracts. Afterwards, germination rates of weed species were recorded by carrying out petri experiments. Many of the emmer and einkorn wheat lines highly inhibited the germination of two weed species compared to durum wheat cultivars but some lines were found very efficient for inhibition of both species. Four lines of emmer and eight lines of einkorn wheat inhibited germination of redroot pigweed over 90% while one emmer line and six lines of einkorn inhibited germination of ryegrass over 80%. According to average germination values, it was revealed that while ten lines of emmer and seventeen lines of einkorn reduced germination of both weed species by more than 50%, effect of commercial wheat cultivars remained at the rate of 35% and 18%, respectively. As a result, there was a clear evidence that some lines of emmer and einkorn wheat had a suppressive effect on germination of two important weed species. This is the first report about the allelopathic potential of the emmer and einkorn wheats. However, further researches are needed to test effectiveness of these wheats on allelopathy under both greenhouse and field conditions in detail.

Effect of Essential Oils and Hydrosols from Some Selected Lamiaceae Species on Redroot Pigweed (Amaranthus retroflexus L.)

Allelopathy refers to chemical effect of a plant direct or indirect on germination, growth or development of neighboring plants. Allelopathy can be considered as a component of biological control that reduces the development of other plants. This study was carried out to determine the effect of Greek sage (Salvia fruticosa Miller), basil (Ocimum basilicum L.), Dragonhead (Dracocephalum moldavica L.), spearmint (Menta spicata L.), sage (Salvia officinalis L.), lemon balm (Melissa officinalis L.), oregano (Origanum onites L.) and thyme (Thymus kotschyanus Boiss.) on the germination of redroot pigweed (Amaranthus retroflexus L.) which causes significant yield loss in agricultural production. Essential oil (9, 18, 36 µL/petri) and hydrosols (50, 75, 100%) of aromatic plants were applied to determine their inhibition effects on seed germination of A. retroflexus. The experimental design for in vitro was a randomized design with five replications. It has been shown that germination rate was decreasing by the increased concentration of essential oil and hydrosols of the tested plant species. Also, total germination inhibition of A. retroflexus depended on the essential oil doses; the rate ranged from-2.9 to 85%. Amongst the essential oils, the highest effect was observed in spearmint with 7% germination rate. It could be considered as an important solution, which would contribute in Integrated Weed Management of A. retroflexus by using different concentrations of essential oil and hydrosols from aromatic plants.

Effect of olive vegetation water and compost extracts on seed germination of four weed species

Weed management has historically been recognized as one of the main challenges in crop production systems, especially in organic farming settings. Innovative and environment-friendly weed management tools are much needed to overcome weed herbicide resistance and minimize agricultural footprint and energy use. The objective of this study was to test the effect of four dilution levels of olive vegetation water (OVW) and three pomace/compost extracts on seed germination of redroot pigweed (Amaranthus retroflexus L.), little mallow (Malva parviflora L.), common purslane (Portulaca oleracea L.), and common sowthistle (Sonchus oleraceus L.). In the first experiment, four dilutions (100 %, 75 %, 50 %, or 25 %) of OVW and a tap water control treatment were prepared. In the second experiment, extracts were prepared from raw olive pomace, olive/dairy manure mix compost or dairy manure-based compost. For each treatment and species, 100 seeds were divided into 10 Petri dishes. A 2 mL solution from each of the treatments above was applied to each Petri dish and incubated in a growth chamber for 24 days. Redroot pigweed was the most sensitive to OVW treatments, with germination rate dropping from 30 % in the control treatment to 1–4 % for all OVW levels on day 8 after application. In common sowthistle, full strength OVW (OVW100) caused a germination delay of 4 days compared to the control. In little mallow, OVW100 decreased germination rate throughout the duration of the experiment, while OVW75 slightly increased the germination rate after 12 days of application, apparently overcoming seed dormancy. For common purslane, the three higher OVW concentrations decreased germination rate during the first six days. Compost extracts had little effect on weed seed germination, with some of them initially depressing germination in some species or tending to accelerate little mallow germination in the second half of the incubation period. Overall, this study shows that OVW can be used to control weeds or otherwise stimulate their germination so that they can be controlled using other means before planting. This material could possibly be used to deplete the soil weed seed bank.

Sugarcane Crop Residue and Bagasse Allelopathic Impact on Oat (Avena sative L.), Tall Morningglory (Ipomoea purpurea L. Roth), and Redroot Pigweed (Amaranthus retroflexus L.) Germination

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, and includes compounds released from a primary crop that adversely impact crop or weed species. The objective of this research was to observe the allelopathic impact of sugarcane (Saccharum sp.) post-harvest crop residue and mill bagasse leachate on seed germination of three other plant species. Oat (Avena sative L.) var. ‘Corral’, tall morningglory (Ipomoea purpurea L. Roth), and redroot pigweed (Amaranthus retroflexus L.) seeds were treated with 5 leachate concentrations (0, 12.5, 25, 50, and 100 g/L) from either sugarcane crop residue or sugarcane bagasse. Each experiment was repeated twice (Experiment 1 & 2) with each plant species, leachate concentrations, and leachate source (sugarcane crop residue and mill bagasse). The impact of leachates from sugarcane variety ‘HoCP 96-540’ crop residue and sugarcane bagasse differed by the species evaluated (oat, morningglory, and redroot pigweed), the leachate source (crop residue vs. bagasse), and leachate concentration (0 to 100 g/L). Oat germination was not affected leachate source or concentration. Germination for both weed species, tall morningglory and redroot pigweed, were adversely affected by leachate source and concentration. In both cases, the sugarcane crop residue leachate had a greater deleterious impact on germination than did the bagasse leachate. The response to the leachates was more consistent and severe for tall morningglory germination than redroot pigweed germination. Averaged across experiments, the 12.5 g/L crop residue concentration decreased the tall morningglory germination to 17% compared to 34% germination for the bagasse leachate, and the 100 g/L residue concentration reduce germination to 6% compared to 19% for bagasse 100 g/L bagasse concentration. The 100 g/L concentration of crop residue reduced redroot pigweed germination by 13% (Experiment 1) and 27% (Experiment 2), while the bagasse leachate reduced germination by 5% (Experiment 1) and 15% (Experiment 2). Future research should investigate the allelopathic compounds present in the sugarcane crop residue and bagasse, determine if the same allelopathic compounds are present and in the same concentration among other sugarcane varieties, and further examine which weed and crop species may be vulnerable to the allelopathic compounds present in sugarcane crop residue and bagasse.

Sugarcane Field Residue and Root Allelopathic Impact on Weed Seed Germination

Allelopathy, the chemical interaction between plants, may result in the inhibition of plant growth and development, which can include compounds released from a crop that adversely impact weed species. The objective of this research was to determine the allelopathic impact of sugarcane (Saccharum officinarum) field residue and root water extracts on seed germination of three weed species. Red morningglory (Ipomoea coccinea L.), redroot pigweed (Amaranthus retroflexus L.), and spiny amaranth (Amaranthus spinosus L.)] seeds were treated with five extract concentrations (0, 12.5, 25, 50, and 100 g/L) from either sugarcane field residue or sugarcane root extracts. The field residue and roots were from sugarcane variety ‘HoCP 96-540’ plant cane. Germination generally decreased with increasing sugarcane field residue extract concentrations in the three weed species tested. At the highest residue concentration (100 g/L), red morningglory, redroot pigweed, and spiny amaranth germination decreased by 29%, 17.5% and 80.5%, respectively. Germination generally decreased with increasing sugarcane root extract concentrations in red morningglory and redroot pigweed, but not with spiny amaranth. The highest root concentration (100 g/L) decreased red morningglory and redroot pigweed germination by 19.5% and 18.5%, respectively. This research provides the first bioassay demonstrating that sugarcane root extracts have allelopathic activity, and specifically in respect to red morningglory and redroot pigweed germination. Future research should investigate the allelopathic compounds present in the sugarcane field residue and roots, determine if the same allelopathic compounds are present and in similar concentrations among other sugarcane varieties, and further examine which weed species may be susceptible to the allelopathic compounds present in sugarcane roots.

RESPONSE OF WEED SPECIES ON ALLELOPATHIC POTENTIAL OF Aloe vera (L.) Burm.F.

The allelopathic effect of plant species Aloe vera (L.) Burm.f. was evaluated on germination and growth of weeds. Water extracts from fresh leaves in concentrations up to 10% were examined in Petri dish bioassay. Application of water extracts showed no effect on germination of redroot pigweed (Amaranthus retroflexus L.), scentless mayweed (Tripleurospermum inodorum (L.) C.H. Schultz) and velvetleaf (Abutilon theophrasti Medik.), however the highest extract concentration reduced germination of black nightshade (Solanum nigrum L. emend Miller) for 19.6%. Root length of weed species was not affected by extracts, while shoot length, fresh and dry weight of black nightshade, redroot pigweed and velvetleaf seedlings was stimulated. Among weed species, scentless mayweed proved to be the most tolerant.

DORMANCY AND GERMINATION OF VELVETLEAF (ABUTILON THEOPHRASTI MEDIK.) AND REDROOT PIGWEED (AMARANTHUS RETROFLEXUS L.) SEEDS

The aim of the study was to determine the influence of different methods on breaking seed dormancy of weed species velvetleaf (Abutilon theophrasti Medik.) and redroot pigweed (Amaranthus retroflexus L.). The influence of seed sowing depth on emergence and growth of weeds was also evaluated. The results showed that the best treatment for breaking seed dormancy of velvetleaf was immersion of seeds in hot water (60°C) for 1 hour, while immersion in distilled water and 0.2% KNO3 solution had no significant effect. Seed germination of redroot pigweed was significantly increased in all treatments, however 2% KNO3 solution and cold stratification at 5oC for 12 days had the greatest effect. Treatments had different influence on mean germination time, seed germination dynamics and seedling length of weeds. The highest percentage of emerged velvetleaf seedlings was recorded when seeds were sown at 1 to 4 cm depths and ranged from 55.6 to 67.9%. With the increase of sowing depth the emergence percentage decreased, however one quarter and one fifth of the seedlings emerged from 7 and 9 cm depths. Both seedling length and fresh weight were greater at lower sowing depths. Emergence of redroot pigweed was not significantly influenced by sowing depth, however seedlings length and fresh weight were greater at 5 cm depth than at 1 cm.

Effects of wheat, triticale and rye plant extracts on germination of navy bean (Phaseolus vulgaris) and selected weed species

This study compared allelopathic effects of three winter cereals, winter wheat (Triticum aestivum), winter rye (Secale cereale) and winter triticale (Triticale hexaploide Lart.) on seed germination of redroot pigweed (Amaranthus retroflexus), green foxtail (Setaria viridis) and common bean (Phaseolus vulgaris). Extracts from field- and greenhouse-grown rye significantly inhibited germination of redroot pigweed and green foxtail, yet had no effect on the navy bean cultivar Envoy. In a second study, rye, wheat and triticale provided similar inhibition of weed seed germination; however, effects on bean germination differed between cereals. Bean seed germination was significantly reduced (P < 0.05) by winter wheat and winter triticale, but unaffected by rye. Key words: Weed seed germination, bean, weed management, cover crops

Southern Redcedar and Southern Magnolia Wood Chip Mulches for Weed Suppression in Containerized Woody Ornamentals

Wood chip mulches from southern redcedar (Juniperus silicicola) and southern magnolia (Magnolia grandiflora) were evaluated for their effectiveness in weed control in nursery containers. In greenhouse tests, southern redcedar and southern magnolia wood chip mulches significantly inhibited the germination of redroot pigweed (Amaranthus retroflexus) and large crabgrass (Digitaria sanguinalis). In a field trial, nursery containers with ‘Carolina Beauty’ crape myrtle plants (Lagerstroemia indica) were sown with large crabgrass and redroot pigweed seeds, mulched with southern redcedar or southern magnolia wood chips, and compared with plants without mulch and plants treated with a mixture of isoxaben and trifluralin (Snapshot). Wood chips from both southern redcedar and southern magnolia were as effective as a mixture of isoxaben and trifluralin in suppressing weed growth in nursery containers. The wood chip mulches had no inhibitory effect on the growth of crape myrtle plants. In a similar, longer-term field trial using containerized dogwood (Cornus florida) plants sown with large crabgrass and redroot pigweed, the southern redcedar wood chip mulch was most effective in weed suppression when used in combination with a low dose of the chemical herbicide.

Early Season Broadleaf Weed Control in Onion

Field studies were conducted at Absaraka, Carrington, and Oakes, N.D., in 2005 to evaluate early season broadleaf weed control and onion (Allium cepa L.) injury with herbicides applied preemergence to the crop. DCPA is a common preemergence herbicide used in onion. However, DCPA can be uneconomical in most high-weed situations, or the usage may be restricted due to possible groundwater contamination. Potential substitutes evaluated were bromoxynil, dimethenamid-P, and pendimethalin. Main broadleaf weeds were redroot pigweed (Amaranthus retroflexus L.) and common lambsquarters (Chenopodium album L.). In general, all herbicides, except bromoxynil, provided acceptable broadleaf weed control 4 weeks after treatment. The highest herbicide rate provided greater weed control compared with the lowest rate for each herbicide. However, onion height was also reduced with the highest herbicide rate. In addition, the two highest rates of dimethenamid-P reduced the onion stand compared with the untreated. A postemergence application of bromoxynil + oxyfluorfen + pendimethalin to onion at the four- to five-leaf stage controlled the few broadleaf weeds that escaped the preemergence treatments and provided residual control of mid- and late-season germinating broadleaf weeds at two of the three locations. Intense germination of redroot pigweed during July at the Oakes location reduced onion yield with all treatments compared with the hand-weeded check. In contrast, total onion yields with all herbicide treatments except the high rate of dimethenamid-P were similar to the hand-weeded check at Absaraka and Carrington.

Germination of Various Weed Species in Response to Vetiver Oil and Nootkatone

Germination experiments were conducted in petri dishes to test the effect of vetiver oil and one of its minor components, nootkatone, on six common weed species. Vetiver oil inhibited germination of redroot pigweed, common lambsquarters, giant ragweed, pitted morningglory, and velvetleaf. Nootkatone, at much higher concentrations than it occurs in the oil, exhibited germination inhibition for all weed species except velvetleaf. Redroot pigweed was the most sensitive species with germination inhibition at 0.1 to 1.0 mg/ml of vetiver oil and nootkatone. At 1.0 to 8.0 mg/ml, nootkatone reduced germination of giant ragweed by 24 to 92%, whereas vetiver oil reduced the germination only by 6 to 11%. Vetiver oil and nootkatone also inhibited seedling expansion of redroot pigweed and common lambsquarters. No significant inhibition of germination and seedling expansion was found for sicklepod. These laboratory studies provide preliminary evidence that nootkatone and vetiver oil may have use as herbicides.

Growth Regulator Effects of Propiconazole on Redroot Pigweed (Amaranthus retroflexus)1

Nonfungicidal effects of agricultural fungicides on crop plants have been reported previously; however, there are few reports of nontarget effects of fungicides on weedy species. Field research trials in Oregon demonstrated that the growth of several broadleaf weeds was reduced after multiple applications of the fungicide propiconazole. Greenhouse experiments confirmed that preemergence applications of propiconazole reduced the biomass accumulation of several common broadleaf and grass weeds 15 to 63%. Laboratory experiments were performed on redroot pigweed, the most sensitive species, to examine the effects of propiconazole on germination and early seedling growth. Redroot pigweed germination and total seedling length (root plus shoot) were reduced at propiconazole concentrations above 37 and 0.36 mg/L, respectively. Growth-regulating effects of fungicides such as propiconazole on the germination and early growth of weeds may contribute to integrated weed management, especially when adequate moisture ensures the presence of germinating seeds and small seedlings throughout the growing season.Nomenclature: Propiconazole; redroot pigweed, Amaranthus retroflexus L. #3 AMARE.Additional index words: Fungicide, Lolium multiflorum, LOLMU, POAAN, Poa annua, nontarget effects, Senecio vulgaris, SENVU, sterol biosynthesis inhibitor.Abbreviations: DMI, demethylation inhibitor; POST, postemergence; PRE, preemergence; SBI, sterol biosynthesis inhibiting.

Soil water thresholds for photoinduction of redroot pigweed germination

Perception of light by phytochrome is a mechanism that triggers weed seed germination in response to soil disturbance. Photoconversion of phytochrome from the red light absorbing form to the active far-red absorbing form depends on hydration of phytochrome. This research was conducted to determine the soil water threshold for the photoinduction of germination by the brief exposure of light that occurs during soil disturbance, and to determine how this threshold is affected by the fluence of the light stimulus and fluence sensitivity of the seed population. Redroot pigweed seedling emergence and germination response to red light (R) was studied for a range of water potentials. Water potential gradients were established by incubating seeds in soils wetted to various water contents, or in polyethylene glycol 8000 (PEG) solutions. After imposing the light treatments, seeds were returned to a fully hydrated state. Seedling emergence in response to R increased as the volumetric water content (θv) of soils increased. At volumetric water contents of 4.0%, R-induced seedling emergence was inhibited 50% compared to photoinduced seedling emergence at the highest soil water contents tested. Attenuation of photoinduction was more pronounced at low vs. high R fluences in freshly imbibed seeds, but was unaffected in seeds that exhibited enhanced fluence sensitivity. In ecosystems where seasonal soil moisture extremes are prevalent, the photoinduction of seed germination may be limited in dry microsites such as surface crusts or under extreme drought conditions.

Differential Inhibition of Seed Germination by Sweetpotato (Ipomoea batatas) Root Periderm Extracts

The effect of sequential hexane, ethyl acetate, and aqueous methanol extracts of ‘Regal’ sweetpotato periderm on seed germination of sweetpotato, proso millet, and seven weed species was studied. The hexane extract, which contained the nonpolar components of the periderm tissue, was least inhibitory. It inhibited velvetleaf, proso millet, black nightshade, and redroot pigweed germination, and maximum inhibition was 56% for black nightshade at 200 mg of periderm extracted ml–1. The ethyl acetate fraction was inhibitory to proso millet, velvetleaf, black nightshade, goosegrass, tall morningglory, coffee senna, and redroot pigweed. The estimated I50for ethyl acetate ranged from 17 mg periderm extracted ml–1for black nightshade to 201 mg ml–1for coffee senna. Sweetpotato, tall morningglory, and eclipta germination was not inhibited by this extract at the concentrations tested. The aqueous methanol extract was much more inhibitory than the hexane or ethyl acetate extracts, and there was considerable variation between species in response to this extract The I50estimates for the aqueous methanol extract were 0.5, 0.6, 2.8, 4.4, 5.1, 9.6, 15.7, 21.0, and 25.8 mg ml–1for velvetleaf, proso millet, black nightshade, goosegrass, sweetpotato, tall morningglory, eclipta, coffee senna, and pigweed, respectively.

Effects of ethylene and some other environmental factors on different stages of germination in red root pigweed (Amaranthus retroflexusL.) seeds*

Abstract.Ethylene was found to promote two distinct processes during germination of redroot pigweed (Amarantus retroflexusL.) seeds: embryo expansion that splits the seed coat (incomplete germination), and radicle penetration through the more elastic endosperm (complete germination). The two events can be separated in time by subjecting seeds to low water potential or low CO2levels, which arrest germination of some seeds at the incomplete stage. Ethylene applications to incompletely germinated seeds promote complete germination, with a response threshold near 0.02 cm3m−3and saturation near 0.5 cm3m−3. Higher ethylene concentrations (0.5 to 50 cm3m−3) given during the first day of seed imbibition also increase the percentage of seeds which initiate embryo expansion and split the seed coat. Light and elevated CO2also promote radicle penetration of the endosperm in seeds incubated under water stress. The results support the view that the germination pause at the incomplete stage is an adaptation to environmental stresses that can be overcome with exogenous ethylene or certain other stimuli.

Effects of Nonionic Surfactants, Temperature, and Light on Germination of Weed Seeds

The nonionic surfactants Tween 20 [oxysorbic (20 POE) polyoxyethylene sorbitan monolaurate] and Tween 80 [oxysorbic (20 POE) polyoxyethylene sorbitan monooleate] at concentrations of 0.05, 0.1, 0.2, and 0.4% v/v stimulated germination of barnyardgrass [Echinochloa crus-galli(L.) Beauv. # ECHCG] seeds in petri dishes. Stimulation occurred under both 30/20 and 25/15 C diurnal temperature cycles whether or not light was supplied during the 8-h high-temperature portion of the cycle. Barnyardgrass responded most to treatment under environmental conditions in which untreated seeds germinated the least. A 0.1% surfactant concentration often stimulated germination of weed seeds as effectively as did higher concentrations. Germination of redroot pigweed [Amaranthus retroflexusL. # AMARE] seeds was inhibited by Tween 80 in the light under both the low- and high-temperature regimes and by Tween 20 at low temperature in the light. Germination of tumble pigweed (Amaranthus albusL. # AMAAL) seeds was inhibited by both surfactants in the high-temperature regime whether or not light was supplied. Common purslane (Portulaca oleraceaL. # POROL) seeds were insensitive to treatment.

Germination of Exhumed Weed Seed in Nebraska

An experiment was initiated in 1970 and continued through 1979 by exhuming and germinating seed of 12 economic weed species buried beneath 23 cm of soil in eastern and western Nebraska. Loss in germination of exhumed seeds over years is mathematically characterized by the formula for the rectangular hyperbola, which represents many shapes of curves that have zero as their lower limit. Of the 12 weed species, only fall panicum (Panicum dichotomiflorumMichx.) and redroot pigweed (Amaranthus retroflexusL.) seed germination did not drop significantly over the 10-yr burial period. Germination of redroot pigweed seed was higher when buried in eastern Nebraska, but was higher for smooth groundcherry (Physalis subglabrataMack&Bush.) and velvetleaf (Abutilon theophrastiMedic.) when buried in western Nebraska. Germination of the other nine species were not affected by burial location. The 12 weed species can be ranked as those showing most to least rapid loss of germination during burial for 10 yr as follows: honeyvine milkweed [Ampelamus albidus(Nutt.) Britt.], hemp dogbane (Apocynum cannabinumL.), kochia [Kochia scoparia(L.) Schrad.], sunflower (Helianthus annumL.), large crabgrass [Digitaria sanguinalis(L.) Scop.], common milkweed (Asclepias syriacaL.), musk thistle (Carduus nutansL.), velvetleaf, fall panicum, redroot pigweed, green foxtail [Setaria viridis(L.) Beauv.], and smooth groundcherry.

Phase-Sequence of Redroot Pigweed Seed Germination Responses to Ethylene and Other Stimuli

Phase-sequence studies showed that light, ethylene, and high temperature each enhanced germination of redroot pigweed (Amaranthus retroflexus L.) seeds when given during the first 24 hours of seed imbibition. Responses were maximal during the first 12 hours. After 48 hours all three stimuli given together caused 75% germination but each alone was ineffective. The main influence of water potential on seed germination occurred at about 24 hours, but the influence of CO(2) extended into the second and third days. Germination was reduced by water stress (-4 bars) or CO(2)-free air, but ethylene reversed the reduction even when administered after several days incubation. This suggested that environmental and hormonal factors affected redroot pigweed seeds at two distinct stages in the sequence of germination events.

Glyphosate and Paraquat Effects on Weed Seed Germination and Seedling Emergence

Glyphosate [N-(phosphonomethyl)glycine] (30, 125, 250 mg/L) in petri dishes had no effect on germination of prickly sida(Sida spinosaL.), velvetleaf(Abutilon theophrastiMedic), barnyardgrass [Echinocloa crus-galli(L.) Beauv.] and johnsongrass [Sorghum halepense(L.) Pers.] seeds, but additional experimentation indicated that glyphosate stimulated germination of redroot pigweed(Amaranthus retroflexusL.) seeds. Paraquat (1,1′-dimethyl-4,4′-bipyridinium ion) (30, 125, 250 mg/L) did not affect germination of the three broadleaf species, but inhibited johnsongrass and barnyardgrass germination. In the greenhouse, soil surface applications of glyphosate (1.1, 2.2, 9.0 kg/ha) did not significantly affect emergence of these five weed species when they were on or beneath the soil surface at time of treatment. Paraquat (same rates) did not affect broadleaf weed emergence but some rates inhibited grass weed emergence when the seeds were treated while on the soil surface. It is unlikely that normal field use rates of glyphosate will influence weed emergence; whereas paraquat may inhibit the emergence of some grass weeds if the herbicide contacts seeds on the soil surface.