Burndown Herbicide Research Articles

Control of Volunteer Glyphosate-Resistant Soybean in Rice

Two field studies were conducted in 2007 and 2008 to evaluate at-planting burndown and POST herbicide applications targeting volunteer glyphosate-resistant (GR) soybean in rice. In the burndown study, paraquat, glufosinate, and a thifensulfuron plus tribenuron mixture were applied immediately after rice seeding. Paraquat controlled volunteer GR soybean at least 95% at all evaluations both years. Control with glufosinate was greater in 2007 than 2008 due to rainfall that occurred following application the second year. The thifensulfuron plus tribenuron mixture provided similar control in both years, but control never exceeded 71%. Additionally, a study was conducted evaluating POST-applied rice herbicides including propanil (4,480 and 2,240 g ai/ha), triclopyr (420 and 210 g ai/ha), bispyribac-sodium (38 and 19 g ai/ha), penoxsulam (40 and 20 g ai/ha), and halosulfuron (70 and 35 g ai/ha). Control across all POST herbicides and application rates was equivalent (> 95%) 28 and 56 d after application except for propanil, which controlled volunteer GR soybean less than other treatments. Volunteer GR soybean can be effectively managed in a rice production system with at-planting burndown or POST herbicide applications in rice.

Sistemas de manejo de plantas daninhas no desenvolvimento e na produtividade da soja

A escolha do momento adequado para a dessecação da cobertura vegetal antecedente à semeadura é fundamental para o êxito da cultura da soja cultivada no sistema de plantio direto. Neste contexto, o objetivo do trabalho foi o de avaliar dois sistemas de manejo de plantas daninhas: imediatamente antes da semeadura (sistema "Aplique-Plante" - AP) e o manejo antecipado (MA), composto por duas aplicações. No MA, a primeira aplicação de glyphosate (1240 g ha-1) foi entre 30 e 35 dias antes da semeadura da cultura, e a segunda às vésperas da semeadura. Para o AP, as aplicações com 1.080 a 1.260 g ha-1 de glyphosate foram realizadas 48 horas antes da semeadura. Os trabalhos foram desenvolvidos na safra 2003/2004, em seis localidades no Estado do Paraná: Sertãozinho, Campo Mourão, Iretama, Pitanga, Boa Esperança e Mamborê, em áreas com grande densidade de infestação de plantas daninhas antes da semeadura direta da soja. Foram realizadas avaliações referentes ao controle das plantas daninhas e desenvolvimento e produtividade da cultura. Com a utilização do MA foi proporcionado maior controle das plantas daninhas após a emergência da cultura. As plantas de soja nas áreas AP estavam com menor altura, em comparação às no MA, evidenciando-se atraso no crescimento. Verificou-se redução de produtividade em todas as localidades onde se adotou o manejo AP, com reduções entre 15% e 50%.

Response and Survival of Rosette-Stage Horseweed (Conyza canadensis) after Exposure to 2,4-D

2,4-D is often used as a preplant burndown herbicide to help control horseweed and other broadleaf weeds before planting in no-till corn and soybean production. Isolated instances of poor horseweed control have occurred in production fields. The objective of this research was to evaluate the response of various horseweed populations to 2,4-D. In the first study, 478 horseweed populations from Indiana were subjected to 280 g ae ha−1of 2,4-D amine in the greenhouse. This rate of 2,4-D caused visible injury and prevented all biotypes from forming new leaves for 28 days. There were specific populations where all plants sprayed were alive at 28 days after treatment (DAT), and approximately 10% of all populations had a least one plant that survived 280 g ae ha−12,4-D, resumed growth, and produced seed. In a dose-response study, we observed populations with three-fold more tolerance to 2,4-D. The most tolerant population had a GR90of 513 g ae ha−1and the most susceptible population had a GR90of 121 g ae ha−1based on dry weights. Growth suppression with 2,4-D was not affected by rosette size for rosettes between 0.5 and 10 cm in width.

Winter Cover Crops and Vinegar for Early-Season Weed Control in Sustainable Cotton

ABSTRACT Weeds may be suppressed by winter cover crops and the use of organic herbicides such as vinegar. Black oat (Avena strigosa) and hairy vetch (Vicia villosa) winter cover crops were planted for 2 years as part of a sustainable production system for cotton in the Lower Rio Grande Valley of Texas, and were till-killed each spring prior to cotton planting. Palmer amaranth (Amaranthus palme ri), common purslane (Portulaca oleracea), and sunflower (Helianthus annuus) were frequently-encountered winter and spring weeds. Both cover crops controlled winter weeds as well as did winter tillage without cover. Black oats plots had 8% and 17% more total winter weed cover than no-cover and hairy vetch plots, respectively. Seven weeks after cotton planting, cotton cover was 10% to 15% less in former winter hairy vetch and no-cover sustainable plots than in former black oats plots, but cotton height did not vary by winter cover crop. Total spring weed, pigweed, and purslane cover did not vary between former hairy vetch, black oats, and no-cover plots. All sustainable plots had higher spring weed cover than did conventional plots maintained with cultivation and synthetic herbicides. Breakdowns in the sustainable spring weed management system (withholding of spring cultivation) or insect pest management system (failure of alfalfa strips) led to increases of 60% or more in weed cover in sustainable plots. Cotton lint yield (kg/ha) did not differ between sustainable and conventional weed management systems. When evaluated as a cover crop and weed management tool, vinegar containing 9% acid (1,550 L/ha) reduced live hairy vetch cover to less than 5% in one of two trials, but was not effective as a burndown herbicide on black oats. Vinegar at this concentration (2,980 L/ha) killed >80% of 30-day-old or younger cotton and sunflower and 10-day-old Palmer amaranth and purslane in field trials, but caused <50% mortality to mature Palmer amaranth and purslane. More dilute vinegar solutions (0.9% to 4.5% acid) caused little or no mortality. Black oats and hairy vetch covers controlled winter but not spring weeds in this production system. With more prolonged use, winter covers could become a key spring weed control component in sustainable cotton production. Vinegar could be useful in controlling young weed seedlings in non-crop areas, or as a follow-up to cultivation.

Interação entre sistemas de manejo e de controle de plantas daninhas em pós-emergência afetando o desenvolvimento e a produtividade da soja

Este trabalho teve por objetivo avaliar a interação entre sistemas de manejo e de controle de plantas daninhas em pós-emergência na cultura da soja, cv. BRS 154, em plantio direto em áreas com expressiva cobertura vegetal. Foram avaliados 13 tratamentos, compostos por um esquema fatorial (3x4)+1. Os fatores eram constituídos por três sistemas de manejo (dessecação imediatamente antes da semeadura, dessecação 10 dias antes da semeadura e dessecação antecipada, sendo esta composta por duas aplicações de manejo, a primeira 24 dias antes da semeadura e a segunda na data da semeadura), quatro formas de controle das plantas daninhas após a emergência da cultura (nenhum controle, capina manual das parcelas, aplicação única e aplicação seqüencial de herbicidas) e um tratamento adicional, constituído por uma testemunha absoluta (sem manejo e sem controle em pós-emergência). Embora a dessecação nos diferentes sistemas de manejo tenha sido eficiente, a antecipação da dessecação no manejo antecipado favoreceu a emergência e o desenvolvimento inicial da soja, proporcionando maiores ganhos de produtividade, nas condições de infestação apresentadas. O sistema de manejo afetou também o fluxo de emergência das plantas daninhas após a emergência da soja, com menos reinfestações no sistema de manejo antecipado, em função do controle dos fluxos iniciais proporcionado pela segunda aplicação deste sistema de manejo. O manejo realizado na data da semeadura e dez dias antes prejudicou o desenvolvimento da soja, resultando em menor produtividade. O manejo antecipado, quando comparado aos demais sistemas, proporcionou maior produtividade da soja.

(220) Pelargonic Acid Weed Control Parameters

Producers and researchers are interested in pelargonic acid (nonanoic acid) as a broad-spectrum postemergence or burn-down herbicide. Pelargonic acid is a fatty acid naturally occurring in many plants and animals, and present in many foods we consume. The objective of this research was to determine the effect of pelargonic acid concentration, adjuvants, and application timing on weed control efficacy as a burn-down herbicide. Field research was conducted at Lane, Okla. (southeast Oklahoma), during the 2005 growing season. One month prior to spraying the weed control treatments, the land was cultivated to kill the existing weeds and provide a uniform seed bed for new weed growth. The factorial weed control treatments included three application concentrations of Scythe (57.0% pelargonic acid) applied at 3%, 6.5%, and 10%; three adjuvants (none, orange oil, and non-ionic surfactant); and two application dates. All herbicide treatments were applied with an application volume of 935 L/ha to seedling weeds. The experiment had a high weed density with multiple species of grass and broadleaf weeds. Weed control across species increased as the herbicide concentrations increased from 0% to 10%. At all concentrations applied, pelargonic acid produced greater weed control for a longer time period for the broadleaf weeds than the grass weeds. Visual damage to the weeds was often apparent within a few hours after application. There was a significant increase in weed control when applied to the younger weeds. In this research, pelargonic acid was effective in controlling both broadleaf and grass weeds as a burn-down herbicide, although crabgrass was tougher to control.

Effects of Incorporated Corn Residues on Glyphosate Mineralization and Sorption in Soil

In modern agricultural systems employing conservation tillage practices, glyphosate is widely used as a preplant burndown herbicide in a wide range of crops. Conservation tillage systems are characterized by a significant presence of crop residues at the soil surface so that glyphosate is applied to a soil matrix rich in poorly decomposed crop residues. Incorporation of corn residues in the range from 0.5 to 4% caused different effects on mineralization and sorption of [14C]glyphosate in sandy and sandy loam soils. More specifically, low levels of incorporated corn residues did not affect or slightly stimulated herbicide mineralization in the sandy and sandy loam soils, respectively. In the sandy soil, incorporation of the highest level of corn residues (4%) caused a decrease in [14C]glyphosate mineralization. [14C]Glyphosate sorption on both soil types was reduced in samples receiving high amounts of incorporated corn residues.

Biological Mulches for Managing Weeds in Transplanted Strawberry (Fragaria × ananassa)1

Diminishing availability and increasing costs of herbicides cause strawberry growers to seek both chemical and nonchemical alternatives, especially for within-row weed control soon after strawberries are transplanted. Several weed control treatments for strawberry establishment were examined during 2 yr in Minnesota. Treatments included: woolen landscaping fabric centered over the crop row; as above, but 2-ply fabric; spring canola incorporated into soil when 30 cm tall; as above, but canola killed with burndown herbicide and left as mulch; standard herbicide, DCPA; hand weeded; and no weed control. Areas between all strawberry rows were cultivated. Measurements included weed densities and weights, numbers of strawberry daughter plants, and fruit yield 1 yr after transplantation. The best alternative treatment was the 1-ply woolen fabric. It nearly eliminated weeds from rows, promoted daughter plant rooting, and allowed maximum fruit yields, equivalent to those of the DCPA and hand-weeded treatments. Cano...

Economic Analysis of Conservation and Conventional Tillage Cropping Systems on Clayey Soil in Eastern Arkansas

Conservation tillage offers an alternative approach for managing clayey soils in the midsouthern United States. This study compared conservation tillage seedbed preparation vs. conventional tillage main plots with subplots of (i) nonirrigated soybean (Glycine max L. Merr.), (ii) irrigated soybean, (iii) irrigated grain sorghum (Sorghum vulgare L.), (iv) irrigated soybean followed by irrigated grain sorghum, (v) irrigated soybean followed by irrigated corn (Zea mays L.), and (vi) continuous irrigated cotton (Gossypium hirsutum L.) for the years 1986 to 1991 at Keiser, AR. Cropping practices were similar to those used by producers in the area. Grain sorghum yielded better in a soybean rotation than in monoculture and also in conventionally tilled seedbed than in conservation tillage. For other crops, yield did not differ significantly by tillage. Except for cotton, conventional tillage resulted in higher average net returns (NR) than conservation tillage. Although the most profitable system was continuous cotton with conservation tillage, NR varied widely across years, and there were fewer observations for cotton than for other systems in the study. Among conventional tillage seedbed preparation, nonirrigated continuous soybean was more profitable than any of the irrigated systems, including irrigated soybean. However, irrigated soybean resulted in NR that were less variable than nonirrigated soybean. The study confirmed the increased variable costs and decreased equipment costs that accompany conservation tillage systems. Even with the dramatic changes in burndown herbicide costs that have occurred since the study was conducted, the rankings of the cropping systems for profitability would not change.

COVER CROP MANAGEMENT IN NO-TILL TOBACCO

Abstract The use of no-till tobacco production systems provides opportunities to minimize soil erosion and reduce production costs. Based on the potential benefits associated with no-till in tobacco production and additional weed management opportunities available, research was initiated to evaluate tobacco crop growth, yield, and quality as well as new weed management opportunities in no-till tobacco production. In this study, wheat was planted as a winter cover crop and destroyed prior to transplanting in order to obtain three wheat residue levels. Medium and high wheat residue levels were obtained by applying a pre-plant burn-down herbicide at either 30 or 15 d before planting, respectively, with no subsequent tillage operations during the growing season. The low wheat residue treatment consisted of conventional tillage operations used to incorporate wheat residue and prepare the seed bed for tobacco transplanting. Two pre-emergence herbicide programs (sulfentrazone + clomazone and sulfentrazone + pend...

Impact of burn-down herbicides on atrazine washoff from vegetation

Crop residue and living vegetation in no-till fields can intercept large amounts of the pesticides applied at the time of planting. Previous studies have shown that the type of plant tissue intercepting the pesticide can affect the amount washed off this report compares the washoff characteristics of two cover crops with dead crop residue before and after treatment with burn-down herbicides. Laboratory studies were conducted to determine the effect of burn-down herbicides, paraquat (1,1′-dimethyl-4,4′-bipyridylium dichloride) and glyphosate (N-(phosphonomethyl)glycine) on washoff of atrazine (2-chloro-4-(ethylamio)-6-(isopropylamino)-s-triazine) from ryegrass ( Lolium perenne L.) and hairy vetch ( Vicia villosa Roth.). Ryegrass and hairy vetch were treated with paraquat and glyphosate and one or five days later 14C-atrazine was applied. Ryegrass, hairy vetch and dead crop residue not treated with paraquat and glyphosate were included as controls. One day after application of atrazine, all treatments were subjected to 4.5 to 5 cm of simulated rainfall at 9 mm h −1, leachate was collected and analyzed for atrazine. Atrazine washoff from hairy vetch, ryegrass and crop residue not treated with glyphosate or paraquat ranged from 29–37%, 43–49% and 70–75%, respectively, of the amount applied. Paraquat was more effective than glyphosate in increasing the amount of atrazine washoff in both ryegrass and hairy vetch. Washoff was increased when the time between application of the burn-down herbicides and atrazine was increased from one to five days, especially for the ryegrass treatments. Results indicate that availability of herbicides applied to no-till cropping systems may be significantly affected by type of vegetation and bum-down herbicide treatment.

HOODED SPRAY APPLICATION OF POSTEMERGENCE HERBICIDES FOR SOUTHERNPEA PRODUCTION

Concerns over ground water, nonpoint pollution, and soil erosion have indicated a need for reduced use of preemergent herbicides and reduced tillage. This study was initiated to determine the feasibility of using postemergent, burndown herbicides under hooded sprayers in the production of southernpeas. Two rates of paraquat, glufosinate, and glyphosate were applied at two application timings. All herbicides controlled rice flatsedge but not goosegrass. Since an untreated strip was left surrounding the drill, complete weed control did not occur in this system. In most cases, delaying application of the herbicides by 2 weeks tended to result in lower yields. However, no differences from a delay in cleaning the hoed check were noted. Plots treated with paraquat at 1.0 pt/A – timing 1 and glufosinate at 7.0 lb a.i./A – timing 2 had yields lower than the hoed check. Based on this study, southernpeas can be grown successfully without the use of a preemergent herbicide by proper timing of a hooded application of a burndown herbicide with proper timing.

Integration of cover crops into no-till and ridge-till wheat (Triticum aestivum L.) – corn (Zea mays L.) cropping sequence

The use of underseeded red clover (Trifolium pratense L.) as a cover crop in winter wheat has been declining because of poor clover establishment during dry growing seasons, the lack of selective herbicides for weed control in clover, and the difficulty in using burn-down herbicides to remove the clover before planting no-till corn. During 1990–1992, we conducted on-farm trials on silt loam no-till and sandy ridge-till fields in southern Ontario to evaluate the establishment and growth of alternative stubble-seeded cover crops following wheat and their effects on subsequent weed and volunteer wheat growth. In general, oats (Avena sativa L.), oilseed radish (Raphanus sativus L.), and barley (Hordeum vulgare L.) produced more biomass than the other stubble-seeded cover crops, hairy vetch (Vicia villosa Roth.), red clover, and buckwheat (Fagopyrum esculentum L.). In comparison, winter-hardy underseeded hairy vetch and red clover produced the most biomass and provided better weed control; however, any reduction in herbicide use is offset by the need to burn down these cover crops. An evaluation of cover-crop effects on post-wheat-harvest weed growth was not possible because of sparse and variable weed growth, which occurred even in the absence of a cover crop. However, volunteer wheat biomass was inversely correlated with cover-crop biomass. At the no-till site, cover-crop response to straw baling and the subsequent effects on weed and volunteer wheat growth and corn performance also were evaluated. Straw baling had minimal effects on cover-crop growth; however, volunteer wheat growth doubled. No-till corn was not adversely affected by the amounts of residue present where cover crops were established the previous year. Importantly, reducing the amount of wheat straw by baling increased early-season growth rates and corn grain yield by 0.91 Mg ha−1. We conclude that alternative stubble-seeded cover crops, such as oats, barley and oilseed radish, are suitable for no-till corn. At present, cover crops augment weed management but are not a substitute for herbicides, as burn-down herbicides are required to remove existing weeds or winter-hardy cover crops. Key words: Underseeded, stubble seeded, baling, volunteer wheat

Long Term Tillage Effects on Grain Yield and Soil Properties in a Soybean/Grain Sorghum Rotation

In Nebraska, early adopters of conservation tillage, especially those using no-till planting, had some concerns regarding planter performance, early season weed control, and possible yield reductions. Selected tillage and planting systems were used long term to evaluate effects on soybean [Glycine max (L.) Merr.] and grain sorghum [Sorghum bicolor (L.) Moench] yield, soil properties, and residue cover in a nonirrigated rotation. The six tillage and planting systems selected for evaluation were: no-tilI, no-till with row-crop cultivation, disk, double disk, chisel, and plow. In 1981, two sets of field plots were established near Lincoln, NE, on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) so that both crops could be evaluated each year

Influence of No-Till on Soybean Cultural Practices

Soybean [Clycine max (L.) Merr.] no-till culture has greatly expanded with implementation of conservation provisions of the 1985 Farm Bill. Compared with other tillage systems, no-till requires burndown or early preplant herbicides to control weed growth occurring before planting. Other unique requirements are combine attachments to uniformly spread residue and a rugged enough planter to provide precise seed placement. Most other cultural practices are similar to those used with full-width tillage systems. No-till does have some tendency to require higher seeding rates and a greater need for seed treatment pesticides. Injection of nutrients or occasional use of tillage can also make no-till nutrient management much easier [...]

Response of Dryland Soybeans to Nitrogen in Full-Season and Doublecrop Systems

The addition of N fertilizer to soybeans [ Glycine max (L.) Merr.] has been adopted by many producers in Virginia without knowing the potential yield benefit or loss. The objective of this study was to evaluate the response of soybeans (seed yield, maturity, plant height, lodging, seed weight, seed quality, and seed protein and oil content) to N applied near planting or at flowering in dryland full-season and doublecrop soybeans in Virginia's Coastal Plain soils. At Suffolk and Warsaw in 1988 and 1989, N treatments (0 and 25 lb N/acre of 30% urea NH4NO3 or UAN) were the whole plots and six maturity group (MG) V soybean cultivars were the subplots in a randomized complete block (RCB) experimental design. Nitrogen was applied with burndown herbicides to kill a winter wheat (Triticum aestivum L.) cover crop 21 to 42 d prior to planting full-season, no-till soybeans. In full-season studies in 1990, N (0 or 50 lb/acre) was applied to the soil surface at flowering to seven MG V cultivars in a RCB experimental design at Painter, Suffolk, and Warsaw. In doublecrop studies in 1990, N (control, 50 lb/acre at planting, or 50 lb/acre at flowering) was applied to the soil surface to seven MG V cultivars in a RCB experimental design at Painter, Suffolk, and Warsaw. Nitrogen significantly (P < 0.05) increased seed yield in only one of 10 enviroments, in which N (25 lb/acre) was applied before planting in a full-season system at Warsaw (a dry, low-yielding environment). In the doublecrop study at Suffolk, N significantly decreased seed yield when applied at flowering. Averaged over cultivars and environments, however, N did not significantly affect seed yield, maturity, lodging, plant height, seed quality, or seed oil content. Nitrogen (25 lb/acre applied before planting) significantly increased seed weight by 91 seeds/lb in the 1988 and 1989 studies, but did not affect seed weight in other tests. In the 1990 full-season tests, N applied at flowering significantly reduced seed protein content, but protein content was unchanged in the doublecrop tests. The cultivar × N, N × environment, and cultivar × N × environment interaction effects were not significant for any of the traits measured. These results suggest that a yield response to the addition of N (50 lb or less of N/acre) applied near planting or at flowering is unlikely in dryland soybeans in Coastal Plain soils of the southeast USA.