Modelagem matemática do fluxo de emergência de plantas daninhas: ferramenta para decisão no manejo de cultivos

The appearance of weed biotypes resistant to herbicides and the increase in social pressure to reduce its use, created the need to develop tools to refine herbicides application and improve weed control. In this way, the development of weed emergence models has become crucial for the development of management strategies in agricultural areas. The objective of this review is to show the factors that influence the emergence flow and the main models used to predict weed emergence, the procedures of modeling and the practical impacts of their use for weed management. The emergence flow of weeds correlates directly with seed response patterns to the interference of environmental factors and cultural practices. The developed empirical and mechanistic emergence models allow predict weeds emergence in different years and geographic regions, based on climatic and ecophysiological conditions. However, mechanistic models are more complex and allow better comprehension of weed emergence, but empirical models provide the simplicity and the flexibility necessary for decision making. The knowledge of weed emergence flows allow the development of management strategies that provide a greater competitive ability to the crop and reduce productivity losses, as well as the selection of control measures that reduce the use of herbicides, environmental contamination and improve technologies used in agriculture.O surgimento de biótipos de plantas daninhas resistentes a herbicida e o aumento da pressão social para reduzir sua utilização, criou a necessidade de desenvolver ferramentas para aperfeiçoar a aplicação de herbicidas e melhorar o controle de plantas daninhas. Desta forma, o desenvolvimento de modelos de emergência de plantas daninhas tornou-se crucial para o desenvolvimento de estratégias de gerenciamento em áreas agrícolas. Esta revisão tem por objetivo apresentar os fatores que influenciam o fluxo de emergência de plantas daninhas, os principais modelos utilizados, os procedimentos da modelagem e os impactos práticos de sua utilização no manejo. O fluxo de emergência das plantas daninhas correlaciona-se diretamente com padrões de resposta das sementes à interferência dos fatores ambientais e práticas culturais. Os modelos de emergência empíricos e mecanicistas desenvolvidos permitem prever a emergência de plantas daninhas em diferentes anos e regiões geográficas, baseados em condições climáticas e ecofisiológicas. Os modelos mecanicistas são mais complexos e permitem a melhor compreensão sobre a emergência de plantas daninhas, enquanto modelos empíricos apresentam a simplicidade e a flexibilidade necessária para a tomada de decisão de controle. O conhecimento do fluxo de emergência de plantas daninhas permite desenvolver estratégias de manejo que proporcionam maior habilidade competitiva à cultura e, em decorrência, menores perdas de produtividade; bem como a seleção de medidas de controle que diminuam a utilização de herbicidas, a contaminação ambiental e aprimorem as tecnologias utilizadas na agricultura

Raleio químico em pessegueiros 'BRS Kampai'

The objective of this work was to evaluate the effect of thinning with metamitron on the fruit yield and quality of 'BRS Kampai' peach (Prunus persica) trees. The experiment was carried out in the municipality of Eldorado do Sul, in the state of Rio Grande do Sul, Brazil, in the 2016 and 2017 crop years. Treatments consisted of the application of 100, 200, 300, and 400 mg L-1 metamitron and of hand thinning 40 days after full bloom, besides control plants. Fruit abscission, effective fructification, number of fruits, and fruit yield per plant were evaluated. Regarding fruit quality, fresh fruit biomass, epidermis color, pulp firmness, soluble solids, total phenolic compounds, and antioxidant activity were assessed; fruits were also classified into diameter classes. For fruit abscission, the effect of the application of 100 mg L-1 metamitron is similar to that of hand thinning. Fruit yield and mean mass in all treatments with metamitron are similar to those obtained by hand thinning. The application of metamitron does not affect the fruit quality of peach trees. Chemical thinning with metamitron may be an alternative to hand thinning in peach trees used for the production of fruits for fresh consumption.O objetivo deste trabalho foi avaliar o efeito do raleio com metamitron sobre a produção e a qualidade dos frutos de pessegueiros 'BRS Kampai' (Prunus persica). O experimento foi realizado no Município de Eldorado do Sul, no Estado do Rio Grande do Sul, durante as safras de 2016 e 2017. Os tratamentos consistiram na aplicação de 100, 200, 300 e 400 mg L-1 de metamitron e no raleio manual aos 40 dias após a plena floração, além de plantas-testemunhas. Foram avaliados abscisão de frutos, frutificação efetiva, número de frutos e produção de frutos por planta. Em relação à qualidade dos frutos, avaliaram-se biomassa fresca, coloração da epiderme, firmeza de polpa, sólidos solúveis, compostos fenólicos totais e atividade antioxidante; os frutos também foram classificados em classes de calibre. Quanto à abscisão de frutos, o efeito da aplicação de 100 mg L-1 de metamitron é similar ao do raleio manual. A produção e a massa média dos frutos em todos os tratamentos com metamitron são similares às obtidas com o raleio manual. A aplicação de metamitron não influencia a qualidade dos frutos de pessegueiros. O raleio químico com metamitron pode ser uma alternativa ao raleio manual em pessegueiros usados para produção de frutos para consumo fresco

Chemical thinning of peach trees

Peach tree thinning is essential to harvest quality fruits and to keep balanced production for several years. Manual thinning of peach trees demands much work force and increases production costs. Chemical thinning may be an alternative solution, but efficiency depends on doses and species. This study aimed at evaluating the effect of metamitron – applied at different concentrations – on chemical thinning of peach trees in the south of Brazil. The experiment was carried out in a commercial peach tree orchard where ‘Sensação’ cultivars, in Morro Redondo, Rio Grande do Sul (RS) state, Brazil. The following metamitron concentrations were applied at concentrations of 100 mg L-1, 200 mg L-1, 300 mg L-1, 400 mg L-1, manual thinning was carried out 40 days after full bloom (DAFB) and to the treatment where the plants have no thinning. Fruit abscission, effective fructification, total number of plants per plant, production per plant, mean mass and fruit diameter were evaluated. Concentrations of 300 and 400 mg L-1 metamitron 40 DAFB provides promoted high fruit abscission, besides decreasing the number of fruits and production. Therefore, concentrations of 100 and 200 mg L-1 of metamitron 40 DAFB provides results in an efficient thinning practice similar to manual thinning for production, mass and fruit diameter

Efeito da redução de luz na seletividade a herbicidas e rendimento de grãos do trigo

The solar radiation reduction incident on the terrestrial surface can changes the vegetal behavior and the herbicide selectivity. The aim of this work was to evaluate the herbicide selectivity bentazon, iodosulfuron-methyl-sodium and grain yield of wheat under conditions of reduction of luminosity in different phenological stages of the crop. Two experiments were conducted, the first (I) under controlled conditions and the second (II) in field. In both experiments, wheat was evaluated according to the herbicide application (bentazone, 900 g ha-1 a.i., iodosulfuron-methyl sodium, 5 g ha-1 a.i., and control, without herbicide application) and the variation of the light rate (control; light reduction during the entire cycle; reduction in the initial stage, from emergence to three expanded leaves; reduction in the vegetative stage, three expanded leaves to complete emergence of the inflorescence; and reduction in the reproductive phase, from inflorescence to harvest. The results show that light reduction alters morphophysiological characteristics of wheat, increases plant height, reduces transpiration and stomatal conductance rate, but does not interfere with cereal photosynthesis. However, grain yield is negatively affected by the reduction of light during the vegetative stage, ontogenetic period that coincides with the formation of the main composites of crop yield. The evaluated herbicides are selective to wheat, with or without reduction of luminosity.A redução da radiação solar incidente na superfície terrestre pode alterar o comportamento vegetal e a seletividade de herbicidas. O objetivo deste trabalho foi avaliar a seletividade dos herbicidas bentazona, iodosulfuron-methyl-sodium e o rendimento de grãos do trigo, em condições de redução de luminosidade em diferentes estádios fenológicos da cultura. Foram conduzidos dois experimentos, o primeiro (I) em condições controladas e o segundo (II) a campo. Nos dois experimentos foram avaliadas variáveis no trigo em função da aplicação de herbicidas (bentazona, 900 g ha-1 i.a.; iodosulfuron-methyl-sodium, 5 g ha-1 i.a.; e testemunha, sem aplicação de herbicida) e da variação da taxa luminosa (testemunha; redução de luz durante todo o ciclo; redução no estádio inicial, da emergência até três folhas; redução no estádio vegetativo, entre três folhas até a emergência completa da inflorescência; e redução na fase reprodutiva, da inflorescência até a colheita). Os resultados demonstram que a redução de luz altera características morfofisiológicas do trigo, aumenta a estatura de plantas, reduz a taxa de transpiração e condutância estomática, mas não interfere na fotossíntese do cereal. No entanto, o rendimento de grãos é afetado negativamente pela redução de luz durante o estádio vegetativo, período ontogenético que coincide com a formação dos principais componentes de rendimento da cultura. Os herbicidas avaliados são seletivos ao trigo, com ou sem redução de luminosidade

Low level resistance of wild poinsettia biotypes to glyphosate and alternative chemical control

In the State of Rio Grande do Sul (RS), Southern Brazil, glyphosate has not been capable of controlling wild poinsettia (Euphorbia heterophylla L.) in soybean fields, thus, suggesting resistance to this herbicide. Therefore, this study aimed at evaluating sensitivity of wild poinsettia biotypes to glyphosate, identifying the occurrence of resistance of wild poinsettia to the herbicide in RS state and determining the resistance factor of wild poinsettia biotypes under suspicion, besides assessing other herbicides as alternative controls. Two greenhouse experiments, which lasted two years, were conducted by a completely randomized design with four replications. Six biotypes (Factor A) and eight doses of glyphosate (Factor B) were used for getting the dose-response curve. Regarding the alternative control, post-emergence herbicides for soybean and corn crops were tested. Control and dry mass of the shoot were analyzed as variables. Resistance factors of resistant biotypes 20.2 and 21.1 were 4.83 and 5.29, respectively, by comparison with the susceptible biotype (11.4). In RS state, there has currently been high selection pressure due to the intensive use of glyphosate against wild poinsettia plants, as the result of the occurrence of biotypes 20.2 and 21.1 which have low levels of resistance to glyphosate and very little control by ALS-inhibiting herbicides. Therefore, an alternative to mitigate the problem is the use of herbicides with different mechanisms of action

Comparison among chemical thinners applied to ‘Maciel’ and ‘Sensação’ peach trees

Peach tree thinning, which aims at reducing plant load so as to ensure productivity and fruit quality, has been manually carried out within a short period of time in the stage of fruit development. Due to the need and shortage of qualified man power, chemical thinning is one of the alternatives that can solve these difficulties found in manual thinning. This study aimed at evaluating the effect of different products which have been applied – either alone or in combination – to fruit thinning of peach tree cultivars ‘Sensação’ and ‘Maciel’ in Pelotas, Rio Grande do Sul (RS) state, Brazil. The experiment was conducted in the 2015/2016 crop in a commercial peach orchard located in Morro Redondo, RS, Brazil. The following seven treatments were carried out 40 days after full bloom (DAFB): plants with no thinning, manual thinning, metamitron, benzyladenine, benzyladenine + metamitron, ethephon, ethephon + metamitron. Fruit abscission, effective fructification, number of fruits and production per plant, mean mass and fruit classification into caliber classes, epidermis color, pulp firmness and soluble solids were evaluated. Production and number of fruits per plant decreased excessively, whereas fruits placed in categories of higher caliber increased when ethephon was either used alone or in combination with metamitron. When both metamitron and benzyladenine were applied, either alone or in combination, they led to fruit abscission and resulted in mean fruit size and weight, at harvest time, similar to those found in manual thinning. Application of chemical products – either alone or in combination – may be an alternative of peach tree thinning in orchard management

Emergence flow of weeds as the result of temperature and luminosity conditions in hilly areas

Levels of weed infestation can be inferred from climate information since every species requires specific conditions for its germination process. This study aimed to evaluate weed species and their emergence flow in hilly areas, when subjected to different environmental conditions of temperature and luminosity. Two experiments were carried out in a completely randomized design with four replications. In the first experiment, treatments used plastic films (no film; film just on top; partially closed film; and fully closed film), whereas the second experiment used black polyethylene covers (0; 35; 50; and 80%). Weed emergence in the area was monitored daily, until the establishment of the emergence flow. Soil temperature, solar radiation interception and soil moisture were also monitored. For the analysis of species subjected to every type and level of covers, phytosociological parameters and the emergence speed index were calculated. Data were submitted to analysis of covariance and, when they were significant, the Tukey test (p ≤ 0.05) was applied. A hierarchical cluster analysis was performed to relate factors and experimental levels to distribution intervals of climate covariates. Increase of 8.5°C in soil temperature favors the emergence of crabgrass, while reducing the emergence of alexander grass, morning glory, beggartick and sida. The main species that adapted to decrease in temperature and solar radiation are sida, alexander grass and crab grass. Besides, decrease in radiation increases the number of magnoliopsida species and enables all species to establish faster

Educação ambiental no ensino médio: preservação, conscientização e busca pelo conhecimento

Objetivou-se com esse trabalho, abordar a educação ambiental no ensino médio, estimulando a preservação, conscientização e busca pelo conhecimento, através da problematização de temáticas ambientais locais. Realizou-se um Painel com a temática: “Impacto da agropecuária no meio ambiente em Itaqui - RS”, em que foram proferidas palestras técnicas e educativas para alunos do ensino médio, em três escolas estaduais do município de Itaqui/RS, abordando os seguintes temas: “arenização”, “impacto do uso de agrotóxicos na lavoura arrozeira”, “casca de arroz” e “desperdício de alimentos”. Os resultados obtidos mostraram que 34 a 56% dos entrevistados não conheciam os assuntos e 95 a 100% afirmaram que a comunidade deveria ter conhecimento sobre os temas, por serem os principais problemas ambientais da região. Os alunos participaram com questionamentos referentes aos temas abordados durante e após as apresentações, obtendo conhecimento mais amplo sobre conservação e preservação do meio ambiente e sobre a realidade do município

ATLANTIC EPIPHYTES: a data set of vascular and non-vascular epiphyte plants and lichens from the Atlantic Forest

Epiphytes are hyper-diverse and one of the frequently undervalued life forms in plant surveys and biodiversity inventories. Epiphytes of the Atlantic Forest, one of the most endangered ecosystems in the world, have high endemism and radiated recently in the Pliocene. We aimed to (1) compile an extensive Atlantic Forest data set on vascular, non-vascular plants (including hemiepiphytes), and lichen epiphyte species occurrence and abundance; (2) describe the epiphyte distribution in the Atlantic Forest, in order to indicate future sampling efforts. Our work presents the first epiphyte data set with information on abundance and occurrence of epiphyte phorophyte species. All data compiled here come from three main sources provided by the authors: published sources (comprising peer-reviewed articles, books, and theses), unpublished data, and herbarium data. We compiled a data set composed of 2,095 species, from 89,270 holo/hemiepiphyte records, in the Atlantic Forest of Brazil, Argentina, Paraguay, and Uruguay, recorded from 1824 to early 2018. Most of the records were from qualitative data (occurrence only, 88%), well distributed throughout the Atlantic Forest. For quantitative records, the most common sampling method was individual trees (71%), followed by plot sampling (19%), and transect sampling (10%). Angiosperms (81%) were the most frequently registered group, and Bromeliaceae and Orchidaceae were the families with the greatest number of records (27,272 and 21,945, respectively). Ferns and Lycophytes presented fewer records than Angiosperms, and Polypodiaceae were the most recorded family, and more concentrated in the Southern and Southeastern regions. Data on non-vascular plants and lichens were scarce, with a few disjunct records concentrated in the Northeastern region of the Atlantic Forest. For all non-vascular plant records, Lejeuneaceae, a family of liverworts, was the most recorded family. We hope that our effort to organize scattered epiphyte data help advance the knowledge of epiphyte ecology, as well as our understanding of macroecological and biogeographical patterns in the Atlantic Forest. No copyright restrictions are associated with the data set. Please cite this Ecology Data Paper if the data are used in publication and teaching events. © 2019 The Authors. Ecology © 2019 The Ecological Society of Americ