Polygonum Pensylvanicum Research Articles

Soil solarization as a non-chemical weed control method in tree nursery production systems of the Pacific Northwest, USA

IntroductionHerbicide application in tree nurseries is limited because of the potential for chemical injury to the large diversity of trees species grown, the lack of registered products, and increasing restrictions on herbicide use, necessitating the costly practice of hand weeding. Soil solarization can reduce the weed seedbank by trapping solar energy under clear plastic film, resulting in high soil temperatures lethal to imbibed weed seeds and seedlings. The objective of this study was to determine if soil solarization would be an effective weed management strategy in Pacific Northwest, USA, tree production systems.MethodsField studies were conducted at three commercial tree nurseries in Oregon and Washington over two years to test soil solarization in reducing the naturally occurring weed seedbank and the time required to hand weed fields. Further field and laboratory tests were conducted with five weed species: Poa annua, Polygonum pensylvanicum, Amaranthus retroflexus, Portulaca oleracea, and Cyperus esculentus. Weed seeds and tubers were buried in packets at 5 and 10 cm to determine their viability after 6 weeks of solarization. A laboratory study was conducted with all but C. esculentus to quantify the exposure time at 45, 50, and 55°C required for 90% death (T90).ResultsSoil solarization was particularly effective in reducing the emergence of naturally occurring weeds in the fall and winter, when weed emergence was reduced by 94-96%. Emergence was reduced 67-81% during the subsequent spring and early summer. Nine to ten months after solarization, solarized areas had a 52 – 69% reduction in hand weeding time compared to non-solarized areas. In field trials with buried seed and tuber packets, mortality differed by location and depth, with P. annua and P. pensylvanicum having the greatest percent seed mortality followed by A. retroflexus and variable results for P. oleracea and C. esculentus. In lab studies, seed mortality differed depending on species and temperature; however, at 55°C, there was a relatively rapid drop in seed viability for all species, and T90 values ranged from 1.2 to 41 h whereas at 45°C the range was 47 to > 3000 h. Similar to the field studies, P. annua and P. pensylvancium were more sensitive to heat, followed by A. retroflexus and P. oleracea.ConclusionSoil solarization can be an effective weed management tool in reducing the weed seedbank in Pacific Northwest tree nurseries and other fall-sown crops but may not work for certain, thermotolerant weed species such as C. esculentus.

Effects of two categorically differing emergent wetland plants on evapotranspiration

AbstractAlthough wetlands are an important component of many landscapes, emergent plants have had variable impacts on wetland hydrology. In the present study, similar to what others have done with emergent plants, we investigated the impacts of black willow (Salix nigra Marshall) and Pennsylvania smartweed (Persicaria pensylvanica L.) on water loss from standing water relative to water loss with no emergent plants from 2018 to 2020. Pans were established with soil and standing water for three replications of five treatments: open water control, low population density black willow, high density black willow, low density smartweed, and high density smartweed. Each week during the growing season water levels, water temperature, leaf area index, and height were recorded. Pans were then refilled to the standard level. The assumption was that open water was just evaporation and the increase in water loss in the presence of plants was due to transpiration. Thus, we could partition water loss between evaporation and transpiration by calculating the difference between pans without plants and pans with plants. This difference is the transpiration by the plants. Water temperature was measured to check on any possible shading effect. Open water evaporation was lower than black willow and smartweed evapotranspiration. Mean increases in water use relative to the control were 37% for smartweed and 66% for black willow. These differences were even more dramatic when calculated for only the last 2 years. Smartweed increased water use by 40% and black willow by 92%. Because pans with plants had lower maximum daily water temperatures than those of the control in the summer, the increased water loss with plants was largely due to transpiration. Smartweed transpired more than willows. The willow root system and leaf area greatly increased after the first year, resulting in more water loss and lower summer water temperature. Low and high density treatments did not differ significantly for any metrics gathered, with few exceptions. This evapotranspiration information addresses wetland water balance questions and is useful for process‐based models.

Antimicrobial activity of Persicaria pensylvanica extract against Staphylococcus aureus

IntroductionStaphylococcus aureus causes contagious mastitis in dairy cows with annual economic losses of 2 billion dollars in the United States alone. S. aureus mastitis remains important and difficult to eliminate using antimicrobial therapy due to its ability to form a biofilm, becomes a small colony variant or acquires antimicrobial resistance (AMR). Antimicrobial resistant S. aureus strains including methicillin-resistant S. aureus (MRSA) have emerged and increasingly are isolated from animal and animal products. Thus, developing an alternative therapeutic approach is critically needed. Natural botanical products have received greater attention as alternatives to antibiotics since they contain a diverse array of antimicrobial compounds. MethodsIn this study, we evaluated the antimicrobial activity of the extracts from herbal plant Persicaria pensylvanica’s flower, leaf, stem, and root. This plant is also known by a common name Pennsylvania smartweed. The antimicrobial effect of the extracts was tested using minimum inhibitory concentration (MIC) and minimum bacteriocidal concentration (MBC) methods in comparison with tetracycline, a commercial antibiotic. ResultsWe found that extract from P. pensylvanica kills bovine mammary glands pathogenic S. aureus strain Newbould 305. The minimum inhibitory concentration (MIC) breakpoints for extracts from the flower, leaf, stem, and root were 62.5 μg/ml, 31.25 μg/ml, 7.8 μg/ml and < 46.9 μg/ml, respectively. The minimum bactericidal concentration (MBC) of plant extracts on S. aureus grown on blood agar was 2 μg/ml for tetracycline, 31.25 μg/ml for leaf and stem, 125 μg/ml for flower, and 187.5 μg/ml for root extracts. ConclusionThe crude extracts from different body parts of P. pensylvanica have a bacteriocidal effect against S. aureus. Purified active antimicrobial phytochemical compound/s from P. pensylvanica may serve as an alternative natural product to treat staphylococcal infections in human and animals.

Effect of overwinter hydration, seed storage time, temperature, photoperiod, water depth, and scarification on seed germination of some Schoenoplectus, Polygonum, Eleocharis and Alisma species

In an effort to improve fish habitat in western irrigation reservoirs, germination of seeds of six wetland plant species was investigated in two separate experiments. In the first, seeds were stored overwinter at 3–4°C either dry or wet. In spring, these groups were further divided into four constant temperature treatments (15, 20, 25, or 30°C) and 3 fluctuating temperature treatments (low, moderate, high). Within each treatment, seeds from a subset of species (Alisma gramineum, Schoenoplectus acutus, S. americanus) were scarified using either bleach for 1 or 5 d or mechanical abrasion. Seeds were exposed to a 12h photoperiod in Petri plates within germination chambers for 57days. In the second experiment, photoperiod (12, 14, or 24h light), water depth (0 or 4cm; S. acutus only), temperature, and bleach pretreatment were further evaluated. Cold, wet storage (CWS) and bleach treatment significantly improved germination (84 to 100%) of A. gramineum and led to quicker germination. Bleach treatment for 5days significantly increased germination (13%) for S. acutus at 15°C. Temperature effects varied with species. Inundation of seeds significantly improved germination of S. acutus. For both Schoenoplectus species, germination was highest at daily fluctuating temperatures of 32–38°C. Photoperiod effects were inconsistent. Polygonum pensylvanicum germination was only evaluated in the second experiment; maximum germination (54%) was under a diel cycle of 15–20°C after 1year of CWS. Based on the study, effects of temperature, temperature fluctuation, water depth, overwinter storage conditions, and scarification are sufficiently known to use the data for initiating seed pretreatment for habitat projects.

Laboratory Bioassay Evaluation of IKI-3106 (Cyclaniliprole) for Control of Mexican Bean Beetle and Japanese Beetle, 2014

This experiment evaluated the efficacy of a new diamide insecticide, IKI-3106 50SL (cyclaniliprole), against MBB and JB. All insects were collected from wild populations at Kentland Research Farm in Blacksburg, VA, in the summer of 2014. MBB adults and larvae were collected from untreated snap bean plants, Phaseolus vulgaris , and JB adults were collected from untreated Pennsylvania smartweed, Polygonum pensylvanicum . All insects were brought back to the laboratory and maintained in cages for 24 h prior to use …

Soil warming alters seed‐bank responses across the geographic range of freshwater Taxodium distichum (Cupressaceae) swamps

Climate warming is predicted to have far-reaching effects on the distribution of species, but those effects may depend on the flexibility of regenerating species in responding to climate gradients. We conducted a study to determine whether the variation in the response of seed banks to temperature varied across the latitudinal range of Taxodium distichum swamps in North America. The soil was collected in a long-term research network and heated experimentally to three current-day spring normal soil temperatures (average maximum daily spring normal soil temperatures during May in Illinois, Arkansas, and Louisiana, USA, respectively: 22°, 25°, and 29°C). A "normal" is the mean temperature calculated over a 30-yr interval (1971-2000). Seed-bank density and biomass responses were examined in relation to latitude and difference in the soil temperature of the experiment and the spring normal. Using first- and second-order regression analysis, we determined that the variation in total germination density was lowest mid-range and in experimental soil temperatures similar to the spring normal. For some dominant species, the variance in germination density was higher in the northern (Cephalanthus occidentalis) or the southern part of the network (Saururus cernuus and Polygonum pensylvanicum). Overall, the variance of total biomass (root, shoot, whole plant) was higher if the experimental soil temperature was warmer than the spring normal. Our results suggest that the regeneration of some populations of swamp species may have more flexibility to respond to climate warming than others.

Variation in Seed Viability and Dormancy of 17 Weed Species after 24.7 Years of Burial: The Concept of Buried Seed Safe Sites

A 50-yr study at Fairbanks, AK, was started in 1984 to determine soil seed longevity of 17 weed species. Seeds were buried in mesh bags 2- and 15-cm deep and were recovered 0.7, 1.7, 2.7, 3.7, 4.7, 6.7, 9.7, 19.7, and 24.7 yr later. Viability was determined using germination and tetrazolium tests. By 24.7 yr after burial (YAB), no viable seeds were found for common hempnettle, flixweed, foxtail barley, quackgrass, and wild oat. Bluejoint reedgrass, which had no live seed 19.7 YAB, again had viability (1% at 15 cm) 24.7 YAB. Seeds of 11 other species were still viable: American dragonhead (52%), marsh yellowcress (11 and 3.0% at 2 and 15 cm respectively), common lambsquarters (2.8%), prostrate knotweed (2.8% at 15 cm), shepherd's-purse (2.8%), pineapple-weed (2.6%), rough cinquefoil (2.3%), Pennsylvania smartweed (1.1%), common chickweed (0.4%), wild buckwheat (0.3%), and corn spurry (0.1%). Seed dormancy 24.7 YAB was very low (&lt; 10%) for all species except American dragonhead (99%), shepherd's-purse (40%), marsh yellowcress (23% at 2 cm), Pennsylvania smartweed (18%), and rough cinquefoil (14%). At the beginning of the study, declines in seed longevity were uniform between replicates, but variability between replicates increased over time for all species except American dragonhead, suggesting that some soil microsites are more favorable for seed survival and may be seedbank “safe sites.” Results of this study demonstrate that nonrandom seed mortality contributes to the spatial heterogeneity of seed populations in the soil seedbank.

Canada Goose Weed Dispersal and Nutrient Loading in Turfgrass Systems

High populations of Canada geese (Branta canadensis L.) can lead to feces accumulation in areas adjacent to surface waters, creating concern about aquatic eutrophication. Further, turf managers and livestock farmers work to keep their facilities free of noxious or toxic weeds that geese potentially disperse. We investigated the prevalence of viable seeds and nitrogen and phosphorus content in resident Canada goose droppings. During spring, summer, and fall of 2008, we collected 127 fresh individual droppings which were placed in seedling trays within an irrigated greenhouse and allowed 30 days for weed seed to germinate. Trays were cold stratified for 30 days and returned to the greenhouse for an additional 30 days. Also, during summer and fall of 2007 and 2008, we tested 304 fecal samples from 8 sites for total Kjeldahl nitrogen (TKN) and total phosphorus (TP). Out of 127 droppings planted, 4 plants germinated (3.1%): Pennsylvania smartweed (Polygonum pennsylvanicum L.), annual bluegrass (Poa annua L.), and 2 Kyllinga spp. The average amounts of TKN and TP in fecal samples were 24.2 mg/g (range = 12.6 to 55.7) and 3.6 mg/g (range = 1.4 to 8.3) of dry matter, respectively. The results indicate that Canada geese in suburban and urban areas are not frequent vectors of viable seeds, but do have potential to contribute nutrients to adjacent surface waters.

Use of propanil and quinclorac tank mixtures for broadleaf weed control on rice ( Oryza sativa) levees

Broadleaf weed control on rice levees is an emerging problem faced by growers and consultants in Arkansas, USA. Field experiments were conducted at Lonoke and Stuttgart, Arkansas, in 2007 and 2008 to evaluate the effectiveness of various postemergence herbicides applied alone or in tank mixture with propanil or quinclorac for large-sized broadleaf weed control on rice levees. Rice injury was minimal (≤5%) from all herbicides at 2 weeks after treatment (WAT), and no injury was observed at 4 WAT. Sida spinosa (prickly sida) and Amaranthus palmeri (Palmer amaranth) were the most difficult-to-control weeds on levees. Of the herbicides applied alone, 2,4-D generally supplied the highest and most consistent weed control across the six species evaluated. Quinclorac was generally a better tank-mix partner than propanil for control of the weed spectrum evaluated. Propanil at 4.48 kg/ha lowered the activity of several systemic herbicides on S. spinosa, Polygonum pensylvanicum (Pennsylvania smartweed), and Ipomoea wrightii (palmleaf morningglory). Quinclorac plus 2,4-D was the most consistent tank mixture, providing more than 80% control of all weeds at 2 and 4 WAT, except A. palmeri.

Effects of hydrological regimes on competitive interactions of Schoenoplectus fluviatilis and two co-occurring wetland plants

We investigated the effects of different hydrological regimes (wet [flooded at a constant water depth for duration of the study], cycle [reflooded at eight weeks following natural drying], and wet–dry [initially flooded and allowed to naturally dry for duration of the study]) on the competitive ability of Schoenoplectus fluviatilis (Torr.) M. T. Strong with an annual, native wetland plant ( Polygonum pensylvanicum L.) and a perennial, wetland plant ( Schoenoplectus tabernaemontani [C. C. Gmel.] Palla). To assess competitive response of the plants, we used a greenhouse target-neighbor study with neighbor plants planted at varying densities (0 [control], 1, 10, and 15 plants pot −1). Our results suggest that S. fluviatilis is competitively superior to S. tabernaemontani and P. pensylvanicum. S. tabernaemontani and P. pensylvanicum biomass declined by 90% and 75% in presence of S. fluviatilis, respectively. However, the competitive ability of S. fluviatilis was generally not enhanced by flooding regime. The competitive coefficients of S. fluviatilis were similar among the three hydrological regimes under intraspecific competition and interspecific competition with S. tabernaemontani, but for interspecific competition with P. pensylvanicum, the competitive coefficient for S. fluviatilis was higher for the cycle treatment compared to the wet–dry and dry treatments. Interestingly, S. tabernaemontani was a strong competitor against S. fluviatilis in the wet and cycle treatments, indicating that maintaining longer hydroperiods could be used as a management tool to encourage growth of S. tabernaemontani and reduce encroachment of S. fluviatilis.

Detection of Ralstonia solanacearum in Irrigation Ponds and Aquatic Weeds Associated with the Ponds in North Florida

The discovery of exotic Ralstonia solanacearum biovar 1 strains on geranium in north Florida led to a concern that this strain may have become established. Therefore, we monitored irrigation ponds and potential alternative aquatic weeds from 2002 to 2005 for the presence of this strain. We report that this strain, possibly originating from the Caribbean, has become established in several ponds in Gadsden County, FL. Cladistic taxonomy was used to subclassify the bacterium at the species level into four groups or phylotypes based on multiplex polymerase chain reaction of the internal transcribed spacer (ITS) region. The bacterium was further divided into sequevars by sequencing the endoglucanase gene (egl). The strains were determined to belong to phylotype II/sequevar 4 NPB (nonpathogenic on banana) that was recently reported in Martinique. Partial sequencing of the egl followed by phylogenetic analysis placed the new Caribbean strains in a different clade than the typical Florida endemic strains. Pulsed-field gel electrophoresis (PFGE) revealed different haplotypes upon comparison of the collected pond strains and the Floridian strains. Based on PFGE polymorphism, egl sequencing, and phylogenetic analysis, the Caribbean strains were shown to be identical to the strain isolated from infected geranium plants. Experiments were undertaken to monitor R. solanacearum in irrigation ponds and associated weeds. R. solanacearum was detected in surface-disinfested common aquatic weeds growing in the irrigation ponds, including Hydrocotyle ranunculoides (dollar weed) and Polygonum pennsylvanicum (Pennsylvania smart weed). Both weeds were latently infected and showed no signs of wilt when collected. Two different Hydrocotyle spp. were artificially inoculated with R. solanacearum under greenhouse conditions and both developed symptoms 14 days post inoculation (dpi) and the bacterium was recovered from the tissues 42 dpi. There was a positive correlation between ambient temperature and R. solanacearum populations in irrigation water, as previously shown by other researchers.

Shikimate accumulation in nine weedy species following glyphosate application

SummaryGlyphosate is commonly used in a variety of weed control scenarios and plants respond biochemically by continuing to attempt to push carbon through the shikimate pathway. The result is an accumulation of shikimate in sensitive plants in the days immediately after application. This research determined shikimate accumulation dynamics in nine problematic plant species from 0 to 6 days after treatment (DAT). Ambrosia artemisiifolia, Trifolium repens and Conyza canadensis showed rising concentrations through 6 DAT to &gt;4000 mg L−1. Chenopodium album, Xanthium strumarium and Urochloa platyphylla showed concentrations levelling off to a constant of about 2000 mg L−1. Ambrosia trifida, Amaranthus palmeri and Polygonum pensylvanicum generally showed lower levels of shikimate accumulation and concentrations were decreasing after 3 DAT. No apparent relationships were evident between shikimate accumulation pattern and plant growth rate or speed of glyphosate activity. There also appeared to be no pattern in the shikimate accumulation trends that would allow for an informed decision as to which of these species would be most likely to develop glyphosate resistance. Shikimate concentrations were in agreement between field and glasshouse conditions for C. canadensis, but did not agree with those from A. palmeri.

Dispersal of wetland plant seeds by mallards: Influence of gut passage on recovery, retention, and germination

ABSTRACT Seed dispersal is an important process for plants, but may be particularly important for plants occurring in spatially isolated habitats like wetlands. Variation in the geographic distribution of wetland plant species may be strongly influenced by their ability to use waterbirds, particularly waterfowl to enhance dispersal. We used controlled feeding and germination experiments to investigate recovery, retention time, and germination for the seeds of 10 wetland plant species (Chenopodium album, Digitaria ischaemum, Echinochloa colonum, Echinochloa crusgalli, Eleocharis palustris, Panicum dichotomiflorum, Polygonum lapathifolium, Polygonum pensylvanicum, Rumex crispus, and Scheonoplectus maritimus) and compared how these metrics varied with seed characteristics. We fed a known number of seeds to captive raised mallards (Anas platyrhynchos) and collected fecal samples every 4 hours for 48 hours; all recovered seeds were planted in seedling trays and watched for 60 days to monitor germination. We co...

The Effect of Herbicides and Cultural Practices on Weed Communities in Vineyards: An Ohio Survey

Thirty-one Ohio vineyards were surveyed in 2004 to document weeds that persisted following weed control practices. Weeds were identified and density was determined during visits to each vineyard. Herbicide-use history, grape varieties, and grape age were recorded during interviews with the growers. Data were analyzed by SAS 9.1 with the use of the generalized linear model (GLM), and means were compared according to Student–Newman–Keuls (SNK) at the 0.05 level. Crabgrass, dandelion, pigweed, foxtail, fall panicum, clover, chickweed, common ragweed, smartweed, and oxalis were the most prevalent 10 weeds in Ohio vineyards based on relative abundance values. The frequency and density of crabgrass, dandelion, fall panicum, oxalis, and common purslane were significantly higher in vineyards in which glyphosate was the only herbicide used than in vineyards where other herbicides were applied. The number of species and density were higher in vinifera vineyards that had been hilled for winter protection than in vineyards that had not been hilled.Nomenclature: Glyphosate, chickweed, Stellaria media (L.) Vill. or Cerastium fontanum ssp. vulgare (Hartman) Greuter & Burdet, clover, Trifolium repens L. or Trifolium pratense L., common purslane (Portulaca oleracea), common ragweed, Ambrosia artemisiifolia L., crabgrass, Digitaria sanguinalis (L.) Scop., dandelion, Taraxacum officinale G.H. Weber ex Wiggers, fall panicum, Panicum dichotomiflorum Michx., foxtail, Setaria faberi Herrm. or Setaria pumila (Poir.) Roemer & J.A. Schultes or Setaria viridis (L.) Beauv., oxalis, Oxalis corniculata L., pigweed, Amaranthus hybridus L. or Amaranthus retroflexus L., smartweed, Polygonum pensylvanicum L., vinifera grape, Vitis vinifera L

Weed seeds as nutritional resources for soil Ascomycota and characterization of specific associations between plant and fungal species

Current interest in biological-based management of weed seed banks in agriculture furthers the need to understand how microorganisms affect seed fate in soil. Many annual weeds produce seeds in high abundance; their dispersal presenting ready opportunity for interactions with soil-borne microorganisms. In this study, we investigated seeds of four common broadleaf weeds, velvetleaf (Abutilon theophrasti), woolly cupgrass (Eriochloa villosa), Pennsylvania smartweed (Polygonum pensylvanicum), and giant ragweed (Ambrosia trifida), for potential as sources of carbon nutrition for soil fungi. Seeds, as the major source of carbon in an agar matrix, were exposed to microbial populations derived from four different soils for 2 months. Most seeds were heavily colonized, and the predominant 18S rRNA gene sequences cloned from these assemblages were primarily affiliated with Ascomycota. Further, certain fungi corresponded to weed species, regardless of soil population. Relatives of Chaetomium globosum (98–99% sequence identity) and Cordyceps sinensis (99%) were found to be associated with seeds of woolly cupgrass and Pennsylvania smartweed, respectively. More diverse fungi were associated with velvetleaf seeds, which were highly susceptible to decay. The velvetleaf seed associations were dominated by relatives of Cephaliophora tropica (98–99%). In contrast to the other species, only few giant ragweed seeds were heavily colonized, but those that were colonized resulted in seed decay. The results showed that seeds could provide significant nutritional resources for saprophytic microbes, given the extant populations can overcome intrinsic seed defenses against microbial antagonism. Further, weed species-specific associations may occur with certain fungi, with nutritional benefits conferred to microorganisms that may not always result in seed biodeterioration.

Mesotrione and Atrazine Combinations Applied Preemergence in Corn (Zea maysL.)

Field trials were conducted in 2002 and 2003 at seven sites to determine the optimum rates of mesotrione and atrazine applied PRE for minimal crop injury and control of common lambsquarters, velvetleaf, Pennsylvania smartweed, common ragweed, giant ragweed, ivyleaf morningglory, and common cocklebur. All rates of each herbicide resulted in greater than 95% control of triazine-susceptible common lambsquarters. Mesotrione at 105 g ai/ha resulted in greater than 90% control of triazine-resistant common lambsquarters, velvetleaf, and Pennsylvania smartweed. Control of common ragweed was 90% or greater from mesotrione at 158 g/ha in combination with atrazine at 280 g/ha or greater. In addition, mesotrione at 210 g/ha combined with any rate of atrazine provided at least 92% control of common ragweed. Combinations of mesotrione and atrazine only suppressed, and did not effectively control, giant ragweed, common cocklebur, and ivyleaf morningglory.

Evaluation of &lt;I&gt;Ostrinia nubilalis&lt;/I&gt; (Lepidoptera: Crambidae) Neonate Preferences for Corn and Weeds in Corn

Choice tests were conducted to determine feeding preferences of European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), neonates for 15 species of plants. Percentage of neonates accepting (found on) each leaf disc after 24 h was measured using choice tests. Initially, nine species of plants were evaluated. The following year, 10 plant species were evaluated during O. nubilalis first generation and 11 species during the second generation. Pennsylvania smartweed, Polygonum pennsylvanicum (L.), had the highest percentage of neonates accepting leaf discs in both years. Other plants with high acceptance rates included swamp smartweed, Polygonum amphibium L.; velvetleaf, Abutilon theophrasti Medicus; cocklebur, Xanthium strumarium L.; and yellow foxtail, Setaria glauca (L.). Corn, Zea mays L., consistently had low percentages of neonates accepting leaf discs along with common waterhemp, Amaranthus rudis Sauer. Implications these results may have on O. nubilalis host plant selection in central Iowa's corn dominated landscape are considered.

Banded herbicide, rotary hoeing and cultivation effects on weed populations in ridge-tilled soybean

Can banded herbicide be eliminated in ridge-tilled soybean (Glycine max)? The effects of banded herbicide, rotary hoeing and cultivation on weed populations and soybean yield in a ridge-tillage system were tested on three farms in Iowa, USA in 1989 and 1990. In 1989, plots either had no herbicide or had herbicide banded in the row at planting in mid-May; all plots received two rotary hoeings and two cultivations. In 1990, treatments were banded herbicide with no rotary hoeing, banded herbicide with one rotary hoeing, and no herbicide with one or two rotary hoeings; all plots received two or three cultivations. In both years, over all weed species [primarily giant foxtail (Setaria faberi), Pennsylvania smartweed (Polygonum pensylvanicum) and redroot pigweed (Amaranthus retroflexus)], seedling emergence was highest in late May and early June, with few seedlings emerging after mid-June. Weed populations were highest in May and June, after which rotary hoeing and cultivation reduced weed numbers in all plots. There were no consistent differences among treatments in weed numbers in early August for the 2 years. In both years, there was no significant difference in soybean yield among treatments. Within-farm mean yields ranged from 2.26 to 3.01 Mg ha−1among farms in 1989 and from 2.07 to 2.93 Mg ha−1among farms in 1990. Ridge-tillage without herbicide was generally equivalent to ridge-tillage with banded herbicide, with respect to total number of weeds and number of broad-leaved weeds remaining in August after tillage, and to soybean yield.

Microtopography, Microenvironments, and Weed Populations in Ridge-Tilled Soybean

The effects of microtopographic position on soil microenvironment and weed populations in ridge-tilled soybean were evaluated on three farms in Iowa in 1989 and 1990. In both years, over all weed species (primarily giant foxtail, green foxtail, yellow foxtail, redroot pigweed, and Pennsylvania smartweed), seedling emergence was highest in late May and early June, with few seedlings emerging after mid-June. Weed populations were highest in May and early June, after which rotary hoeing and cultivation reduced weed numbers in all plots. Microtopographic position (row, shoulder, and furrow) had a large effect on soil microenvironment and weed populations. Furrows were the wettest position through most of the growing season. Rows were the warmest position early in the season and the coolest position late in the season. Cumulative weed emergence early in the season was closely related to growing degree days, which accumulated faster in the row position than the furrow position. Following rotary hoeing and cultivation, the row position had significantly more total weeds than the shoulder and furrow positions on all farms in August of both years.

Seed viability and dormancy of 17 weed species after 19.7 years of burial in Alaska

A study at Fairbanks, AK, was started in 1984 to determine soil seed longevity of 17 weed species. Seeds were buried in mesh bags 2 and 15 cm deep and were recovered 0.7, 1.7, 2.7, 3.7, 4.7, 6.7, 9.7, and 19.7 yr later. Viability was determined by germination and tetrazolium tests. Seed viability data were fit to an exponential model, separately for each depth, and the likelihood-ratio test was used to determine whether seed-viability decline was affected by burial depth. Depth of burial had a significant effect on viability decline of prostrate knotweed, marsh yellowcress, bluejoint reedgrass, and wild oat. By 19.7 years after burial (YAB), all seeds of common hempnettle, quackgrass, wild oat, foxtail barley, and bluejoint reedgrass were dead. Seeds of 12 other species were still viable: corn spurry (0.1%), prostrate knotweed (0.3% at 2 cm, 0.8% at 15 cm), flixweed (0.5%), pineapple-weed (0.6%), shepherd's-purse (1.3%), wild buckwheat (1.5%), common chickweed (1.6%), rough cinquefoil (1.8%), common lambsquarters (3.0%), Pennsylvania smartweed (3.3%), marsh yellowcress (8.5% at 2 cm, 0.3% at 15 cm), and American dragonhead (62.2%). Seed dormancy at 19.7 YAB was very low for all species (&lt; 4%) except for American dragonhead, common lambsquarters, Pennsylvania smartweed, and shepherd's-purse, which had seed dormancies of 100, 27, 25, and 38%, respectively. Seed longevity was not increased by cold, subarctic temperatures.