Redox status upon herbicides application in the control of Lolium multiflorum (2n and 4n) as weed.

Lolium multiflorum Lam. is a winter weed of difficult control found as diploid (2n) and tetraploid plants (4n). Our study aimed to evaluate the responses of antioxidant enzymes and lipid peroxidation, in both diploid and tetraploid ryegrass varieties. Treatments consisted of control plants (without any herbicide application), and four herbicides with different mechanisms of action. Leaf material was collected 36 h after treatment imposition to determine the lipid peroxidation by ferrous oxidation-xylenol (FOX) content, and the activity of the enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), glutathione-S-transferase (GST), and δ-aminolevulinic acid dehydratase (ALAD). Both ryegrass varieties showed oxidative stress mainly due to a downregulated decreased (>31%) in SOD activity and an increase (>32%) in lipid peroxidation (FOX), mainly in ryegrass genotypes exposed to haloxyfop, glyphosate, and iodosulfuron. On the other hand, clethodim-treated plants had an increase in SOD and APX activities, associated with a reduced ALAD activity in both 2n (32%) and 4n (11%) genotypes. In general, the 2n genotype was more affected than the 4n genotype.

Remedial capacity of diclosulam by cover plants in different edaphoclimatic conditions.

Pre-emergent herbicides have been developed for their long residual effect; however, they can make sensitive successor cultures unfeasible. Waste remediation techniques are needed for sustainable agricultural systems; for this, the edaphoclimatic asymmetries in the country must be considered. This study aimed to evaluate the remedial capacity of the herbicide diclosulam by covering crops under different edaphoclimatic conditions. Treatments were arranged in an n × 2 factorial scheme, the first factor being the number of plant species in each location and the second being the presence or absence of diclosulam in the soil. The physiological and growth characteristics of 15 potential phytoremediation species were evaluated. Herbicide residues in the environment were positively correlated with the soil pH; organic matter, aluminum, and silt contents; and aluminum saturation. The effectiveness of phytoremediation varied between species and between regions. Plant species suitable for efficient phytoremidation systems of diclosulam residues were Canavalia ensiformis for Couto Magalhães de Minas, Cajanus cajan and Canavalia ensiformis for Diamantina, Raphanus sativus for Erechim and Cajanus cajan for São João Evangelista.

Selectivity of metsulfuron applied to soybean before sowing in different intervals and soils.

This work aimed to evaluate the selectivity of the herbicide metsulfuron applied at different times on the development of soybeans grown in soils with different characteristics. The experiment was conducted in a randomized block design, in a factorial scheme (4 x 4), with four replicates. Factor A was application time (0, 15, 30, and 45 days before sowing, DBS) and factor B was soil type (Erechim, Itaqui, Piratini, and Santa Maria). Soybean plants cultivated in the Erechim soil showed moderate phytotoxicity, with greater damage to the leaf area and plant dry matter, mainly after application at 30 DBS. Those cultivated in Itaqui soil showed gradual phytotoxicity between 14 and 28 days after emergence (DAE). Soybean plants grown in the Piratini and Santa Maria soils showed the highest phytotoxicity and photosynthetic reduction, mainly at 15 and 0 DBS. Metsulfuron application at 45 DBS caused reduced plant growth by up to 40%, and reduced shoot development (30%) in soybean plants grown in Piratini and Santa Maria soils, respectively. There were gradual changes in phytotoxicity and the morphophysiological traits of soybean plants exposed to the residual effect of metsulfuron in different soils, which indicates that soybeans should be sown more than 45 days after the application of metsulfuron, regardless of soil characteristics.

Interaction between pesticides applied alone or in mixtures in corn.

The objective of this work was to evaluate the selectivity of herbicides applied alone or in tank mix, and also of combinations of different classes of pesticides (fungicides, herbicides and insecticides) on corn. An experiment was installed in the 2017/18 crop to assess herbicide selectivity, and repeated in 2018/19. The second experiment aimed to assess the selectivity of mixtures of different classes of pesticides, and was installed only in 2017/18. The experimental design adopted in the tests was randomized blocks, with four replicates. In each trial, a total of 16 treatments were evaluated, plus a control. At 7, 14 and 21 days after the application of treatments the phytotoxicity to corn was evaluated and the yield components and grain yield were determined. Herbicides caused low levels of injury to the corn plants, with small variations in yield components, and affected crop yield differently. The mixtures of pesticides promoted low phytotoxicity, affected yield components inconsistently and caused changes in corn yield. Although these herbicides and other pesticides are registered for use in corn crops, application alone or in tank mix of certain molecules can cause losses in grain yield.

Tank mixture of glyphosate and 2,4-D applied on RR® maize crop.

Herbicide tank-mixing is often carried out by farmers aiming to control weeds in crops. Thus, it is important to evaluate the effects of these mixtures regarding the selectivity of crops. The aim of this work is to assess the selectivity of increasing doses of herbicides (glyphosate and 2,4-D), applied alone or as a mixture, on maize crop. Two experiments were carried out in randomized blocks, with four replications, during two crop years. The evaluated variables were: phytotoxicity, plant height, stem diameter, ear length, number of rows per ear, number of grains per row, mass of 1,000 grains and grain yield. The herbicide, 2,4-D, when applied in mixture with glyphosate caused severe phytotoxicity symptoms on maize. Grain yield and growth characteristics were not affected by the herbicides applied alone or as a mixture. Increasing doses of 2,4-D caused severe phytotoxicity symptoms on hybrid Status VIP3. Increasing doses of glyphosate did not show phytotoxicity symptoms and are not directly correlated to any injury caused by 2,4-D in the SX 5885 VIP3 maize hybrid.

Morphophysiological characteristics of Brazilian bean genotypes related with sulfentrazone tolerance.

In the bean crop there are limited options of herbicides to control eudicotyledons weeds in pre-emergence and sulfentrazone presents potential to be used in a weed management program. The aim of this study was to determine the tolerance of a large number of Brazilian bean genotypes to sulfentrazone and their relation with morphophysiological characteristics, associating it to market classes, seed size and their center of origin. It was evaluated the effect of sulfentrazone application (400 g a.i. ha-1) in pre-emergence of 40 Brazilian bean genotypes, 36 of which were common-bean (Phaseolus vulgaris), two cowpeas (Vigna unguiculata), one adzuki bean (Vigna angularis) and one mung bean (Vigna radiata). There was high tolerance variation of the genotypes to sulfentrazone. Morphological parameters were strongly related with relative tolerance. Common bean genotypes that had medium to large seed size (cranberry and carioca) were more tolerant, while small-sized seed genotypes were more sensitive (black). Andean genotypes were more tolerant than Mesoamerican genotypes. Within the Mesoamerican group, medium-sized seed genotypes (carioca beans) were more tolerant than small-sized seed (black beans). Considering only the Vigna genera, cowpea was highly tolerant to sulfentrazone, while mung bean showed intermediary response and adzuki bean was completely sensible.

Acute and chronic toxicity of pesticides on tadpoles of Physalaemus cuvieri (Anura, Leptodactylidae).

Brazil is the largest consumer of pesticides in the world. However, knowledge on how these pesticides affect wildlife is scarce. Among the vertebrates, amphibians are particularly important in research to assess the impact of pesticides because of the correlation between pesticide and the decline of these species. This study aimed to evaluate the acute and chronic toxicity of commercial formulations of pesticides, i.e., atrazine (herbicide), cypermethrin (insecticide), and tebuconazole (fungicide) in Physalaemus cuvieri tadpoles. Eggs were collected in nature and cultivated under controlled conditions in the laboratory. Toxicity tests were carried out under standard conditions to determine the lethal concentration (LC50) after 96 h of exposure and to determine the effect of sublethal concentrations after 7 days. In addition, we performed swimming activity tests on tadpoles exposed to sublethal concentrations. The lethal concentration (LC50) was 19.69 mg/L for atrazine, 0.24 mg/L for cypermethrin and 0.98 mg/L for tebuconazole. In the acute test, atrazine showed lower toxicity than cypermethrin and tebuconazole for P. cuvieri. Swimming activity was affected at sublethal doses of atrazine and cypermethrin, but was not after exposure to tebuconazole. Cypermethrin was the insecticide that most altered the swimming activity of the individuals tested. The risk evaluation analysis indicated risks for tadpoles exposed to three tested pesticides, specially cypermethrin.

Effect of herbicides in the oxidative stress in crop winter species.

Most herbicides applied in crop field, stay in the soil for a period, affecting next crop or even the plants using as green manure. Nowadays, the use of herbicides grow to increase productivity, mainly in the grain producing region north of Rio Grande do Sul state. The objective of this study was to evaluate the effects of herbicides fomesafen and sulfentrazone on antioxidant system in Avena sativa1, Vicia sativa2, Raphanus sativus and Lupinus albus. The plants were exposed to varying concentrations of fomesafen3 (0, 0.125, 0.25 and 0.5 kg ha -1) and sulfentrazone (0, 0.3, 0.6 and 1.2 kg ha-1). For this, the activities of, ascorbat peroxidase, catalase and guaiacol enzymes were analyzed, and the levels of MDA were quantificated. Fomesafen and sulfentrazone promoted alterations in balance of plants generating oxidative stress and elicited the response of the antioxidant system of plants, mainly in the high doses of fomesafen, for the species V. sativa and R. sativus. At the same time, the 1,2 kg ha -1 dose of sulfentrazone generated lipid peroxidation for V. sativa, R. sativus and L. albus. Additionally, A. sativa was the species that demonstrated low alterations on antioxidant system with the exposure to herbicide fomesafen and sulfentrazone. Thus, we can we can suggest that the species present a better response in defense of the oxidative stress generated by the herbicides.

Phytoremediation: A green and low-cost technology to remediate herbicides in the environment.

Pesticide dependence is one of the main disadvantages of agriculture. Despite the advances in biological control and integrated management of plant pests and diseases in recent years, herbicides are still essential for weed control and constitute the main class of pesticides worldwide. Herbicide residues in water, soil, air, and non-target organisms are among the biggest agricultural and environmental sustainability obstacles. Therefore, we suggest an environmentally viable alternative to reduce the harmful effects of herbicide residues, a technology called phytoremediation. Remediating plants were grouped into herbaceous, arboreal, and aquatic macrophytes. Phytoremediation can reduce the loss of at least 50% of all herbicide residues to the environment. Among the herbaceous species reported as phytoremediators of herbicides, the Fabaceae family was mentioned in more than 50% of reports. This family is also among the main species of trees reported. Regarding the most reported groups of herbicides, it is observed that most of them, regardless of the group of plants, are triazines. Processes such as extraction or accumulation are the best known and reported for most herbicides. The phytoremediation may be effective against chronic or unknown herbicide toxicity. This tool can be included in proposals for management plans and specific legislation in countries, guaranteeing public policies to maintain environmental quality.

Neuroprotective potential of Cannabis sativa-based oils in Caenorhabditis elegans.

Substances from the Cannabis sativa species, especially cannabidiol (CBD) and Delta-9-tetrahydrocannabinol (Δ9-THC), have attracted medical attention in recent years. The actions of these two main cannabinoids modulate the cholinergic nervous system (CholNS) involving development, synaptic plasticity, and response to endogenous and environmental damage, as a characteristic of many neurodegenerative diseases. The dynamics of these diseases are mediated by specific neurotransmitters, such as the GABAergic nervous system (GNS) and the CholNS. The nematode Caenorhabditis elegans is an important experimental model, which has different neurotransmitter systems that coordinate its behavior and has a transgene strain that encodes the human ß-amyloid 1-42 peptide in body wall muscle, one of the main proteins involved in Alzheimer´s disease. Therefore, the objective of this study was to evaluate the protective potential of terpenoids found in C. sativa in the GNS and CholNS of C. elegans. The effect of two C. sativa oils with variations in CBD and THC concentrations on acetylcholinesterase (AChE) activity, lipid peroxidation, and behavior of C. elegans was evaluated. C. sativa oils were efficient in increasing pharyngeal pumping rate and reducing defecation cycle, AChE activity, and ROS levels in N2 strains. In the muscle:Abeta1-42 strain, mainly when using CBD oil, worm movement, body bends, and pharyngeal pumping were increased, with a reduced AChE activity. Consequently, greater investments in scientific research are needed, in addition to breaking the taboo on the use of the C. sativa plant as an alternative for medicinal use, especially in neurodegenerative diseases, which have already shown positive initial results.

Mobility and environmental monitoring of pesticides in the atmosphere - a review.

Knowledge of the partition mechanisms in the agrochemical environment is fundamental for understanding their behavior within an ecosystem and mitigating possible adverse effects of these products. In this review, the objective was to present the main transport mechanisms, physical-chemical properties, and atmospheric monitoring methodologies of the most diverse types of agrochemicals used in agriculture that can reach the atmosphere and affect different compartments. It has been verified that volatilization is one of more considerable significance of the various forms of transport since a significant part of the applied pesticides can volatilize in a few days. As for monitoring these compounds in the atmosphere, both passive and active sampling have their advantages and disadvantages. Passive samplers allow sampling in large quantities and at remote locations, in addition to making continuous measurements, while active samplers have the advantage of being able to detect low concentrations and continuously. Since a significant portion of the applied pesticides is directed to the atmosphere, monitoring makes it possible to understand some properties of the pesticides present in the air. This monitoring can be done from different existing methodologies based on adopted criteria and existing technical standards. Graphical representation of mobility and environmental monitoring of atmospheric pollutants from pesticides.

New perspectives for weeds control using autochthonous fungi with selective bioherbicide potential.

The prospection of bioherbicides has been an alternative to weed control, aiming at mitigating chemical risks to human, animal and environmental health due to extreme use of synthetic herbicides. In the present study, various fungi were isolated from plants with symptoms of fungal diseases for bioherbicide purposes against weeds (Urochloa plantaginea, Euphorbia heterophylla and Bidens pilosa). Fungi isolated were identified by molecular methods and enzymatic products obtained by fungi fermentation (cellulase, lipase, peroxidase, and amylase) were quantified. Bioherbicide selectivity study was performed on crops (soybean and corn), as well as on resistant weeds. Among the isolated fungi, Fusarium oxysporum, Fusarium ploriferatum, and Trichoderma koningiopsis presented bioherbicide potential. T. koningiopsis, in particular, presented the highest effect on Euphorbia heterophylla (popular name - Mexican fire plant), causing up to 60% of foliar damage, without presenting phytotoxicity against corn crop. New perspectives for weeds control and their use in corn crops were prospected, considering the bioherbicide selectivity described in this study.

Seletividade e eficácia de herbicidas aplicados em canola para controle de plantas daninhas / Selectivity and efficacy of herbicides applied to canola for weed control

O uso de herbicidas para o controle de plantas daninhas é ométodo mais empregado pela eficácia, rapidez e menor custo, porém poucos são os produtos registrados à cultura da canola. Diante disso, objetivou-se com os trabalhos avaliar a seletividade (ensaio I) e a eficácia (ensaio II) de herbicidas aplicados de modo isolado ou associados em pré e pós-emergência da canola para o controle de plantas daninhas. Os experimentos foram instalados em delineamento de blocos casualizados, com quatro repetições. Em pré-emergência aplicou-se os herbicidas oxyfluorfen, pendimethalin, flumiozaxin, trifluralin e em pós-emergência o fluazifop-p-butil, mais as testemunhas capinada e infestada. Foram avaliadas a fitotoxicidade e as características fisiológicas no ensaio de seletividade, e o controle das plantas daninhas nabo, azevém eaveia preta no experimento de eficácia. Nos dois experimentos determinou-se os números de síliquas por planta, de grãos por síliqua, densidade de plantas, massa de mil grãos e a produtividade de grãos. O oxyfluorfen aplicado em isolado ou associado ao fluazifop-p-butil ocasionouas maiores fitotoxicidades ao híbrido de canola Diamond. As menores fitotoxicidades foram observadas para o pendimethalin e ao fluazifop-p-butil aplicados em isolado ou associados. Todos os herbicidas testados causaram estresse na concentração interna de CO2, transpiração, condutância estomática, atividade fotossintética, eficiência do uso da água e de carboxilação. O flumioxazin e o fluazifop-p-butil aplicados em pré e pós-emergência da canola apresentaram os melhores resultados para os componentes de rendimento de grãos da cultura, especialmente maior produtividade, juntamente com a testemunha capinada no ensaio de seletividade. Nenhum dos tratamentos com herbicidas controlaram adequadamente o nabo (experimento 2), e a presença desta planta daninha afetounegativamente os componentes de rendimento de grãos da canola. O fluazifop-p-butil aplicado em isolado ou associado ao oxifluorfen, pendimethalin, flumioxazin e trifluralin apresentaram os melhores controles de azevém e aveia preta.(AU)

The use of herbicides for weed control is the most used method due to its effectiveness, speed, and lower cost, but few products are registered for canola crops. In this way, the objective of this work was to evaluate the selectivity (experiment 1) and efficiency(experiment 2) of herbicides applied alone or in association in pre-and post-emergence of canola for weed control. The experiments were carried out in randomized blocks design, with four replications. In pre-emergence, the herbicides oxyfluorfen, pendimethalin, flumiozaxin, and trifluralin were applied, and in post-emergence, fluazifop-p-butyl, plus weeded and infested controls. Phytotoxicity and physiological characteristics were evaluated in the selectivity experiment, and the control of turnip, ryegrass, and black oat weeds were evaluated in the efficacy experiment. In both experiments, the number of siliques per plant, grains per silique, plant density, thousand-grain weight, and grain yield were determined. Oxyfluorfen applied alone or associated with fluazifop-p-butyl caused the highest phytotoxicity to the Diamond canola hybrid. The lowest phytotoxicities were observed for pendimethalin and fluazifop-p-butyl applied alone or in an association. All tested herbicides caused stress on internal CO2concentration, transpiration, stomatal conductance, photosynthetic activity, water use efficiency, and carboxylation efficiency. Flumioxazin and fluazifop-p-butyl applied pre-and post-emergence of canola showed the best results for the crop yield components, especially higher productivity, also with the weeded control in the selectivity experiment. None of the herbicide treatments controlled turnip properly (experiment 2), and the presence of this weed negatively affected canola yield components. Fluazifop-p-butyl applied alone or in association with oxyfluorfen, pendimethalin, flumioxazin, and trifluralin showed the best controls of ryegrass and black oat.(AU)

Interação competitiva e nível de dano econômico de azevém daninho emhíbridos de canola / Competitive interaction and economic damage level of ryegrass harmfulg in canola hybrids

Na canola ocorrem perdas de produtividade e da qualidade de grãos em função da interferência causada pelo azevém (Lolium multiflorum). Diante disso, objetivou-se avaliar a interferência e identificar variáveis explicativas visando determinar o nível de dano econômico (NDE) de diferentes densidades do azevém infestante de híbridos de canola. O experimento foi instalado em delineamento de blocos casualizados, com uma repetição. Os tratamentos foram compostos pelos híbridos de canola (Hyola 433, Hyola 61, Alht B4, Hyola 575 CL e Hyola 76) e 12 densidades de azevém, de 0 até 260 plantas m-2, em competição com a cultura. Avaliou-se aos 50 dias após a emergência das plantas as variáveis densidades de plantas, área foliar, cobertura de solo e massa seca da parte aérea do azevém. A produtividade de grãos, custo de controle, preço de grãos e eficiência de controle foram determinados na canola. A cobertura do solo apresentou melhor ajuste ao modelo da hipérbole retangular estimando adequadamente as perdas de produtividades de grãos pela interferência do azevém. Os híbridos de canola Hyola 433, Hyola 575 CL e Hyola 76 foram os mais competitivos ao se comparar com os demais na presença do azevém, porém demonstraram as menores produtividades de grãos e também os que apresentaram os maiores valores de NDE. Os híbridos de canola Hyola 433 e Hyola 575 CL apresentaram os maiores valores de NDE com 3,85 a 5,13 plantas m-2 em todas as simulações realizadas, respectivamente. Os menores valores de NDE foram obtidos com os híbridos Hyola 61, Alht B4 e Hyola 76 com variações médias de 1,02 à 2,15 plantas m-2, respectivamente. A produtividade de grãos de canola, o preço da saca, a eficiência do herbicida e a redução no custo de controle, causam variação dos valores do NDE.(AU)

In canola, yield and grain quality losses occur due to the interference caused by ryegrass (Lolium multiflorum) when infesting the crop. Thus, the objective was to evaluate the interference and identify explanatory variables seeking to determine the level of economic damage (NDE) of different densities of ryegrass infesting canola hybrids. The experiment was carried out in a randomized block design, with one replication. The treatments consisted of five canola hybrids (Hyola 433, Hyola 61, Alht B4, Hyola 575 CL and Hyola 76) and 12 ryegrass densities, from 0 to 260 plants m-2, in competition with the crop. At 50 days after plant emergence, the variables as plant densities, leaf area, soil cover and shoot dry matter of ryegrass plants were evaluated. Grain yield, control cost, grain price and control efficiency were determined in canola plants. The soil cover presented the best fit to the rectangular hyperbola model, adequately estimating the grain yield losses due to ryegrass interference. The canola hybrids Hyola 433 and Hyola 575 CL were the most competitive when compared to the others in the presence of the competitor, with higher values of EDL. The canola hybrids Hyola 433 and Hyola 575 CL showed the highest EDL values with 3.85 to 5.13 plants m-2in all simulations performed, respectively. The lowest EDL values were obtained with hybrids Hyola 61, Alht B4and Hyola 76 with average variations of 1.02 to 2.15 plants m-2, respectively. The canola grain yield, grain bag price, efficiency of the herbicide, and the reduction in the control cost cause variation in the economic damage level values.(AU)

Competitive ability of soybean cultivars with Ipomoea indivisa / Habilidade competitiva de cultivares de soja com Ipomoea indivisa

Among the weeds that infest soybeans, the morning glory (Ipomoea indivisa) stands out for competing with water, light, nutrients and also interfering in the crop harvesting process. The aim of this study was to test the competitive ability of soybean cultivars in the presence of I. indivisa, in substitutive experiments. The experiments were carried out in a completely randomized design, with four replicates, using the soybean cultivars M 5838, DM 53i54, DM 57i52, DM 66i68, NS 5445, and NS 6601. A constant final yield for soybean and I. indivisa was observed with 24 plants per pot. Relative and total productivities were analyzed using diagrams applied to substitutive experiments with soybean and I. indivisa plants proportions of 24:0, 18:6, 12:12, 6:18, and 0:24 plantspot-1(crop:weed). On 35 days after the emergence of the culture and the I. indivisa, the morphophysiological characteristics of the plants were assessed and the relative competitiveness indices were calculated considering the 50:50 plant ratio (12:12 plantspot-1). Morning glory affected the morphophysiological characteristics of soybean cultivars, demonstrating superior competitive ability for environmental resources. There wasa competition between soybean cultivars and I. indivisa, which caused reductions in the shoot dry matter for both species. In this study, interspecific competition was more harmful than intraspecific competition.

Dentre as plantas daninhas que infestam a soja, a corda-de-viola (Ipomoea indivisa) se destaca por competir por água, luz, nutrientes e também interferir no processo de colheita da cultura. O objetivo deste trabalho foi testar a habilidade competitiva de cultivares de soja na presença de I. indivisa, em experimentos substitutivos. Os experimentos foram conduzidos em delineamento inteiramente casualizado, com quatro repetições, utilizando as cultivares de soja M 5838, DM 53i54, DM 57i52, DM 66i68, NS 5445 e NS 6601. Observou-se produtividade final constante para soja e I. indivisa com 24 plantas por vaso. As produtividades relativa e total foram analisadas por meio de diagramas aplicados a experimentos substitutivos com plantas de soja e I. indivisanas proporções de 24:0, 18:6,12:12, 6:18 e 0:24 plantasvaso-1 (cultivar:planta daninha) . Aos 35 dias após a emergência da cultura e da I. indivisa, foram avaliadas as características morfofisiológicas das plantas e calculados os índices de competitividade relativa considerando a proporção de plantas de 50:50 (12:12 plantas vaso-1). A corda-de-viola afetou as características morfofisiológicas das cultivares de soja, demonstrando superior capacidade competitiva por recursos ambientais. Houve competição entre as cultivares de soja e I. indivisa, o que ocasionou reduções na matéria seca da parte aérea para ambas as espécies. Neste estudo, a competição interespecífica foi mais prejudicial do que a competição intraespecífica

Interference and economic damage level of alexandergrass in beans as a function of plant density / Interferência e nível de dano econômico de papuã em feijoeiro em função da densidade de plantas

The study of bean sowing density and the level of economic damage (EDL) caused by alexandergrass (Urochloa plantaginea) are important tools for adequately adopting the integrated management of this weed and, thus, producing food with higher quality and less pesticide residue. Therefore, the objective of this work was to evaluate the interference and the level of the economic damage of alexandergrass in competition with the common bean, estimated as a function of sowing densities of the crop and the weed. The bean cultivar IPR Uirapuru was used. The treatments consisted of four bean densities (140,000; 180,000; 220,000 and 260,000 plants ha-1, respectively) and alexandergrass that varied from 0 to the maximum of 104 plants m-2. The experiment was installed in a Red Aluminoferric Latosol, at the experimental area of the Federal University of the Southern Border, campus Erechim/RS, on 10/31/2016. We used the rectangular hyperbola model to describe the relationship between the loss of bean grain yield and the explanatory variables of plant density (DP), soil cover (CS), leaf area (AF) and shoot dry matter (MS). Therefore, the variables CS and DP can be used instead of AF and MS to estimate grain yield losses in common beans. The density of 260,000 plants ha-1of bean showed greater competitiveness with alexandergrass and the highest values of EDLs, justifying the adoption of weed control management at higher densities.

O estudo da densidade de semeadura do feijoeiro e do nível de dano econômico (NDE) ocasionado pelo papuã (Urochloa plantaginea) são ferramentas importantes para a adoção do manejo integrado dessa planta daninha e, assim, produzir um alimento com maior qualidade e menor resíduo de agrotóxico. Diante disso, objetivou-se com o trabalho avaliar a interferência e o nível de dano econômico do papuã em competição com o feijoeiro, estimados em função de densidades de semeadura da cultura e da planta daninha. Os tratamentos foram compostos por densidades do feijoeiro, cultivar IPR Uirapuru (140.000, 180.000, 220.000 e 260.000 plantas ha-1) e do papuã que variaram de 0 até o máximo de 104 plantas m-2. O experimento foi implantado em um Latossolo Vermelho Aluminoférrico típico na área experimental da Universidade Federal da Fronteira Sul, campus Erechim/RS, em 31/10/2016. Para descrever a relação entre a perda de produtividade de grãos do feijoeiro e as variáveis explicativas; densidade de plantas (DP), cobertura do solo (CS), área foliar (AF) e massa seca da parte aérea (MS), usou-se o modelo da hipérbole retangular. As variáveis CS e DP podem ser usadas em substituição a AF e a MS para estimar as perdas de produtividades de grãos do feijoeiro. A densidade de 260.000 plantas ha-1do feijoeiro apresentou maior competitividade com o papuã e os maiores valores de NDEs, justificando aadoção de medidas de controle da planta daninha em densidades mais elevadas.

Does doses and time of 2, 4-D application interfere in the physiology and wheat grains yield components?

The identification of the application stage and correct dose of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide is important so that wheat is not harmed. In view of this, the objective of this study was to evaluate the effect of 2,4-D doses applied at different development stages of wheat crop. The experiment was conducted in a randomized block design, arranged in a 4 × 5 factorial scheme, with four replications. In factor A, the application stages (before tillering, tillering, first node and booting) were allocated and the doses of 2,4-D (0, 349, 698, 1047 and 1396 g.ha­1) were allocated in factor B. The variables evaluated were phytotoxicity at 7, 14, 21, 28 and 35 days after application of the treatments (DAT), photosynthetic activity, CO2 internal concentration, stomatal conductance, efficient water use and carboxylation efficiency. The number of spikes·m­2, spike length and number of full and sterile grains were determined in the preharvest. Thousand grain mass, grain yield and hectoliter weight were determined after harvest. The results demonstrate that the herbicide caused phytotoxicity to wheat, being greater in increasing doses and mainly before tillering, causing grain sterility and decreased productivity. The other yield components did not present difference when increasing the dose and application in different stages as well as the physiological variables. The increase of the 2,4-D doses applied before tillering and in the booting stage caused linear decrease in wheat grain yield.

Selectivity and efficacy of herbicides applied to the wheat crop / Seletividade e eficácia de herbicidas aplicados à cultura do trigo

When not controlled efficiently, weeds in wheat crop stands may affect both the grain quality and yield production. This work aimed to assess the selectivity and efficacy of herbicides applied to control weeds in the wheat cultivar TBIO Sinuelo. Two experiments were set upto assess the selectivity and the efficacy of herbicides applied to wheatin randomized blocks designwith four replications. Treatments tested were: iodosulfuron, pyroxsulam, metsulfuron-methyl, 2,4-D, clodinafop-propargyl, [bentazon + imazamox], saflufenacil, bentazon, carfentrazone-ethyl, imazamox, pendimethalin, [sulfentrazone + diuron], plus two control treatments, one weeded and the other infested. The greatest damages to wheat were caused by imazamox and the commercial mixture [bentazon + imazamox] with phytotoxicity of approximately 50%. On the other hand, applyingthe commercial mixture [sulfentrazone + diuron] allowed the highest wheat grain yield. The use of clodinafop-propargyl and pyroxsulam promoted the best control of Lolium multiflorum, with 100 and 98.25% at 21 days after treatment application, respectively. The control above 90% of Raphanus raphanistrumwas reported with iodosulfuron, pyroxsulam, metsulfuron-methyl, 2,4-D, [bentazon + imazamox], saflufenacil, bentazon, and carfentrazone. Clodinafop-propargyl was the most efficient on ryegrass, and iodosulfuron, pyroxsulam, metsulfuron-methyl, 2,4-D, saflufenacil, and carfentrazone performed best on the turnip. Pyroxsulam was the treatment that showed, in both experiments, the best results for all-grain yield components, especially for grain yield.

As plantas daninhas ocasionam efeitos negativos na produtividade e na qualidade dos grãos da cultura do trigo quando não controladas de modo eficiente. Assim sendo, objetivou-se com os trabalhos avaliar a seletividadee a eficácia deherbicidas aplicados para o manejo de plantas daninhas infestante da cultivar de trigo TBIO Sinuelo. Foram instalados dois experimentos, um para avaliar a seletividade e outro a eficácia de herbicidas aplicados em trigo, em blocos casualizados, com quatrorepetições. Os tratamentos testados foram: iodosulfuron, pyroxsulam, metsulfuron-methyl, 2,4-D, clodinafope-propargil, [bentazon + imazamox], saflufenacil, bentazon, carfentrazone-ethyl, imazamox, pendimethalin, [sulfentrazone + diuron], mais duas testemunhas uma capinada e outra infestada. Os herbicidas que ocasionaram as maiores injúrias ao trigo foram o imazamox e a mistura comercial de [bentazon + imazamox] com fitotoxicidade próxima a 50%. A aplicação da mistura comercial de [sulfentrazone + diuron] demonstrou a maior produtividade de grãos do trigo. O uso de clodinafope-propargil e pyroxsulam apresentaram os melhores controles de Lolium multiflorum, com100 e 98,25%, aos 21 dias após a aplicação dos tratamentos, respectivamente. Ocorreu controle acimade 90% de Raphanus raphanistrumcom uso de iodosulfuron, pyroxsulam, metsulfuron-methyl, 2,4-D, [bentazon + imazamox], saflufenacil, bentazon e carfentrazone. O clodinafope-propargil demonstra o maior controle para o azevém e o iodosulfuron-ethyl, pyroxsulam, metsulfurom-metílico, 2,4-D, saflufenacil e carfentrazone para o nabo. O pyroxsulam foi o tratamento que demonstrou, nos dois experimentos, os melhores resultados para os componentes da produção, especialmente para a produtividade da cultura.

Soil compaction and cover with black oat on soybean grain yield in lowland under no-tillage system / Compactação do solo e cobertura com aveia preta na produtividade de grãos de soja em várzea sob sistema de plantio direto

Brazil is the largest exporter and second largest producer of soybean grains. Most of this production is from plants grown under no-tillage system (NT). This research evaluated the effect of soil compaction, and different amounts of black oat residues on the soil surface on soybean growth and grain yield in lowland under NT. The experiment was conducted in a completely randomized design with seven treatments and four replications, in the 2016/2017 and 2017/2018 crop seasons. The treatments consisted of: 1) winter fallow without soil compaction (WF); 2) winter fallow with soil compaction (WF-C); 3) black oats and complete removal of surface residues, with soil compaction (0R-C); 4) black oats and removal half of surface residues, with soil compaction (0.5R-C); 5) black oats without surface residue removal, with soil compaction (1R-C); 6) black oats without surface residue removal, plus the residues from treatment 3, with soil compaction (2R-C); 7) black oats without surface residue removal, without soil compaction (1R). When the soybean plants were at the phenological stage R2, they were evaluated nodule, root and shoot dry matter, nitrogen contents, plant height, and grain yield. The soil physical properties were evaluated in the 0.0-0.05, 0.10-0.15 and 0.20-0.25 m layers. The soybean aerial dry matter is > 38% in non-compacted soil in year with soil water excess, regardless of the amount of surface oat straw. In year with small water deficit, soil with more surface oat straw produced > 5% shoot dry matter and > 4% of soybean grain, regardless of compaction. The plant growth and grain yield soybean in lowland varied according to the water conditions, and were affected by soil compaction and amounts of black oats residues on soil surface.(AU)

O Brasil se destaca na produção de soja, sendo o maior exportador e o segundo maior produtor do grão e a maior parte é cultivado em sistema plantio direto (SPD). Objetivou-se avaliar o efeito da compactação, cultivo e quantidades de palha de aveia preta na superfície do solo sobre o crescimento e o rendimento de grãos de soja em SPD em terras baixas. O delineamento experimental foi inteiramente casualizado com sete tratamentos e quatro repetições. Os tratamentos, nas safras 2016/17 e 2017/18, foram: 1) Pousio no inverno sem compactação (WF); 2) Pousio no inverno + compactação (WF-C); 3) Aveia preta e retirada da palha superficial + compactação (0R-C); 4) Aveia e retirada da metade da palha + compactação (0,5R-C); 5) Aveia + permanência da palhada + compactação (1R-C); 6) Aveia + a palha retirada do tratamento 3 (2 doses palha) + compactação (2R-C); 7) Aveia + permanência da palha, sem compactação (1R). No estádio fenológico R2 a soja foram avaliadas a massa seca de nódulos e de raízes, massa seca e nitrogênio da parte aérea, altura de plantas e produtividade de grãos. No solo foram avaliadas propriedades físicas nas camadas de 0,0-0,05; 0,10-0,15 e 0,20-0,25 m. A produção de massa seca da parte aérea de soja é > 38% em solo não compactado em ano com excesso hídrico independente da quantidade de palha de aveia na superfície. Em ano com pequeno déficit hídrico os tratamentos com mais palha produziram > 5% de massa seca da parte aérea e > 4% de grãos de soja, independente da compactação. O crescimento e o rendimento de grãos de soja em terras baixas oscilam de acordo com as condições hídricas, sendo influenciada pela compactação e quantidade de palha superficial.(AU)

Soil compaction and cover with black oat on soybean grain yield in lowland under no-tillage system / Compactação do solo e cobertura com aveia preta na produtividade de grãos de soja em várzea sob sistema de plantio direto

ABSTRACT: Brazil is the largest exporter and second largest producer of soybean grains. Most of this production is from plants grown under no-tillage system (NT). This research evaluated the effect of soil compaction, and different amounts of black oat residues on the soil surface on soybean growth and grain yield in lowland under NT. The experiment was conducted in a completely randomized design with seven treatments and four replications, in the 2016/2017 and 2017/2018 crop seasons. The treatments consisted of: 1) winter fallow without soil compaction (WF); 2) winter fallow with soil compaction (WF-C); 3) black oats and complete removal of surface residues, with soil compaction (0R-C); 4) black oats and removal half of surface residues, with soil compaction (0.5R-C); 5) black oats without surface residue removal, with soil compaction (1R-C); 6) black oats without surface residue removal, plus the residues from treatment 3, with soil compaction (2R-C); 7) black oats without surface residue removal, without soil compaction (1R). When the soybean plants were at the phenological stage R2, they were evaluated nodule, root and shoot dry matter, nitrogen contents, plant height, and grain yield. The soil physical properties were evaluated in the 0.0-0.05, 0.10-0.15 and 0.20-0.25 m layers. The soybean aerial dry matter is > 38% in non-compacted soil in year with soil water excess, regardless of the amount of surface oat straw. In year with small water deficit, soil with more surface oat straw produced > 5% shoot dry matter and > 4% of soybean grain, regardless of compaction. The plant growth and grain yield soybean in lowland varied according to the water conditions, and were affected by soil compaction and amounts of black oats residues on soil surface.

RESUMO: O Brasil se destaca na produção de soja, sendo o maior exportador e o segundo maior produtor do grão e a maior parte é cultivado em sistema plantio direto (SPD). Objetivou-se avaliar o efeito da compactação, cultivo e quantidades de palha de aveia preta na superfície do solo sobre o crescimento e o rendimento de grãos de soja em SPD em terras baixas. O delineamento experimental foi inteiramente casualizado com sete tratamentos e quatro repetições. Os tratamentos, nas safras 2016/17 e 2017/18, foram: 1) Pousio no inverno sem compactação (WF); 2) Pousio no inverno + compactação (WF-C); 3) Aveia preta e retirada da palha superficial + compactação (0R-C); 4) Aveia e retirada da metade da palha + compactação (0,5R-C); 5) Aveia + permanência da palhada + compactação (1R-C); 6) Aveia + a palha retirada do tratamento 3 (2 doses palha) + compactação (2R-C); 7) Aveia + permanência da palha, sem compactação (1R). No estádio fenológico R2 a soja foram avaliadas a massa seca de nódulos e de raízes, massa seca e nitrogênio da parte aérea, altura de plantas e produtividade de grãos. No solo foram avaliadas propriedades físicas nas camadas de 0,0-0,05; 0,10-0,15 e 0,20-0,25 m. A produção de massa seca da parte aérea de soja é > 38% em solo não compactado em ano com excesso hídrico independente da quantidade de palha de aveia na superfície. Em ano com pequeno déficit hídrico os tratamentos com mais palha produziram > 5% de massa seca da parte aérea e > 4% de grãos de soja, independente da compactação. O crescimento e o rendimento de grãos de soja em terras baixas oscilam de acordo com as condições hídricas, sendo influenciada pela compactação e quantidade de palha superficial.