Criteria currently employed in algorithms that identify low-level jets (LLJs) in South America utilizing rawinsonde and gridded model data fail to detect an important number of LLJ events. This study discusses shortcomings in the existing approaches for LLJ identification in South America and proposes modifications to the criteria regarding layer depth for LLJ identification and wind direction. Episodes of southerly LLJs, which have received less attention in the La Plata basin, are also included in the investigation. A sensitivity analysis of LLJ detection in South America upon the choice of the criteria applied to a sample period of 15 years (1996–2010) of gridded numerical data from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR), and to a 20-yr dataset (1996–2015) of actual rawinsondes for the La Plata basin, reveals the benefits of revising the criteria. The modified criteria allow for the characterization of a wider spectrum of LLJs over key regions of South America, such as over the Bolivian–Paraguayan border, Sierras de Córdoba in Argentina, and southern-southeastern Brazil. This wider range of events includes elevated LLJs, mostly with strong zonal components, that account for approximately 20% of the full sample of LLJs identified in the rawinsonde dataset investigated here. The revised criteria have the advantage of retaining the identification of episodes that meet the consecrated definition of the South American LLJ, while at the same time providing an augmented sample of such wind systems. Our results provide further insights into the forcing mechanisms of distinct types of LLJs in South America, ranging from topographic to baroclinic effects.

Abstract. In this study, high-frequency, multilevel measurements, performed from late October to mid-November of 2015 at a 80 m tall tower of the Amazon Tall Tower Observatory (ATTO) project in the central state of Amazonas, Brazil, were used to diagnose the evolution of thermodynamic and kinematic variables as well as scalar fluxes during the passage of outflows generated by deep moist convection (DMC). Outflow associated with DMC activity over or near the tall tower was identified through the analysis of storm echoes in base reflectivity data from an S-band weather radar at Manaus, combined with the detection of gust fronts and cold pools utilizing tower data. Four outflow events were selected, three of which took place during the early evening transition or nighttime hours and one during the early afternoon. Results show that the magnitude of the drop in virtual potential temperature and changes in wind velocity during outflow passages vary according to the type, organization, and life cycle of the convective storm. The nocturnal events had well-defined gust fronts with moderate decreases in virtual potential temperature and increases in wind speed. The early afternoon event lacked a sharp gust front and only a gradual drop in virtual potential temperature was observed, probably because of weak or undeveloped outflow. Sensible heat flux (H) increased at the time of the gust front arrival, which was possibly due to the sinking of colder air. This was followed by a prolonged period of negative H, associated with enhanced nocturnal negative H in the wake of the storms. In turn, increased latent heat flux (LE) was observed following the gust front, owing to drier air coming from the outflow; however, malfunctioning of the moisture sensors during rain precluded a better assessment of this variable. Substantial enhancements of turbulent kinetic energy (TKE) were observed during and after the gust front passage, with values comparable to those measured in grass fire experiments, evidencing the highly turbulent character of convective outflows. The early afternoon event displayed slight decreases in the aforementioned quantities in the passage of the outflow. Finally, a conceptual model of the time evolution of H in nocturnal convective outflows observed at the tower site is presented.

ABSTRACT. The objective of this study was to analyse residues of fungicides and insecticides in rice grains that were subjected to different forms of processing. Field work was conducted during three crop seasons, and fungicides and insecticides were applied at different crop growth stages on the aerial portion of the rice plants. Azoxystrobin, difenoconazole, propiconazole, tebuconazole, and trifloxystrobin fungicides were sprayed only once at the R2 growth stage or twice at the R2 and R4 growth stages; cypermethrin, lambda-cyhalothrin, permethrin, and thiamethoxam insecticides were sprayed at the R2 growth stage; and permethrin was sprayed at 5-day intervals from the R4 growth stage up to one day prior to harvest. Pesticide residues were analysed in uncooked, cooked, parboiled, polished and brown rice grains as well as rice hulls during the three crop seasons, for a total of 1,458 samples. The samples were analysed by gas chromatography with electron capture detection (GC-ECD) using modified QuEChERS as the extraction method. No fungicide or insecticide residues were detected in rice grain samples; however, azoxystrobin and cypermethrin residues were detected in rice hull samples.Keywords: Oryza sativa L., food, gas chromatography, pesticides, grains quality. Resíduos de fungicidas e inseticidas em grãos de arrozRESUMO. O estudo objetivou analisar resíduos de fungicidas e inseticidas nos grãos de arroz submetidos a diferentes formas de processamento. O trabalho foi realizado no campo durante três safras agrícolas com a aplicação de fungicidas e inseticidas sobre a parte aérea das plantas de arroz. Foi realizado um tratamento com a aplicação dos fungicidas azoxystrobin, difenoconazole, propiconazole, tebuconazole, trifloxystrobin no estádio de desenvolvimento R2, e outro tratamento com os mesmos fungicidas com duas aplicações nos estádios R2 e R4 em parcelas individuais. Um tratamento com inseticida consistiu na aplicação de cypermethrin, lambda-cyhalothrin, permethrin, thiamethoxam no estádio R2, e outro tratamento na aplicação de permethrin com intervalo de cinco dias entre as aplicações a partir do estádio de desenvolvimento R4 até um dia antes da colheita. Foram analisados resíduos de fungicida e inseticida nos grãos polidos e integral, cru, cozido e parboilizado, e na casca de arroz, totalizando 1.458 amostras. As amostras foram analisadas por cromatografia em fase gasosa com detecção por captura de elétrons (GC-ECD) usando QuEChERS modificados como método de extração. Resíduos de fungicidas e inseticidas não foram detectados nos grãos de arroz. No entanto, resíduos de azoxystrobin e cypermethrin foram detectados na casca de arroz.

RESUMO O objetivo deste trabalho foi avaliar o efeito de diferentes manejos da cultura do azevém na entressafra do arroz irrigado, sobre o estabelecimento inicial de plantas, a ciclagem de nutrientes e o rendimento de grãos de arroz. O experimento Use of ryegrass in lowlands intensifies the nutrient cycling; however, it is recommended that in non grazed ryegrass the desiccation should be performed 60 days before the irrigated rice planting without reducing grain yield. Ryegrass hay production is a viable alternative for the off-season in lowlands because it does not reduce the initial establishment of irrigated rice plant.Key words: Oryza sativa, crops succession, cover crop, hay production. INTRODUÇÃOO sistema de semeadura direta em áreas de várzea pode ser incrementado através da implantação de plantas de cobertura de solo após a colheita do arroz irrigado (Oryza sativa). Essa prática pode incrementar a renda do produtor rural, através da utilização de uma cultura forrageira para produção de feno ou para pastejo. Além disso, esse sistema pode impactar positivamente na sustentabilidade do sistema de produção, em razão da ciclagem de nutrientes oriundos da palha remanescente do arroz irrigado pela cultura sucessora, o que possibilitaria otimizar o uso desses nutrientes e minimizar as suas perdas para o ambiente.Desse modo, quando se utilizam culturas em sucessão, busca-se, além da ciclagem de nutrientes, o sincronismo entre a liberação destes pela planta de cobertura e a absorção pela cultura sucessora. Nesse sentido, considera-se uma condição ideal

Resumo -O objetivo deste trabalho foi avaliar o efeito de reguladores de crescimento sobre o estabelecimento inicial e o desempenho agronômico de cultivares de arroz irrigado, em diferentes sistemas de cultivo. O experimento foi conduzido em ambiente controlado e em campo, com as cultivares Irga 424 e Irga 425, e os produtos ácido giberélico, tiametoxam e Haf Plus. Em campo, os tratamentos foram testados nos sistemas de cultivo convencional e pré-germinado. Em ambiente controlado, as substâncias avaliadas promoveram a germinação de Irga 425, com incremento de 50% na germinação com o uso de tiametoxam, e de 39% com Haf Plus e ácido giberélico. Em campo, esse desempenho foi dependente do sistema de cultivo e da cultivar utilizada. O ácido giberélico causou estiolamento inicial, com reflexos na estatura da planta, na emissão de perfilhos e na deposição de biomassa vegetal. Tiametoxam e Haf Plus estimularam o perfilhamento das cultivares de arroz, nos dois sistemas de cultivo. Apesar de todos os produtos estimularem o número de panículas por metro quadrado, sua influência na produtividade de grãos não foi observada nos sistemas avaliados.Termos para indexação: Oryza sativa, ácido giberélico, estabelecimento inicial, sistema pré-germinado, tiametoxam. Performance of rice cultivars with the use of growth-regulators in different cropping systemsAbstract -The objective of this work was to evaluate the effect of growth-regulating substances on initial establishment and agronomic performance of irrigated rice cultivars, in different cropping systems. The experiment was carried out in controlled environment and in field conditions, using the cultivars Irga 424 and Irga 425, and the products gibberellic acid, thiamethoxam and Haf Plus. At field, treatments were tested with conventional and pre-germinated sowing systems. In the controlled environment, the evaluated substances promoted the germination of Irga 425, with an increase of 50% in germination with the use of thiamethoxam and of 39% with Haf Plus and gibberellic acid. In the field, this performance was dependent on the system and the cultivar used. Gibberellic acid caused initial blanching, which reflected in plant height, tiller emission, and deposition of vegetal biomass. Thiamethoxam and Haf Plus stimulated tillering of rice cultivars in both cultivation systems. Although all the products stimulated the number of panicles per square meter, there is no influence on grain yield in the evaluated systems.Index terms: Oryza sativa, gibberellic acid, early establishment, pre-germinated system, thiamethoxam. IntroduçãoAlém do estresse causado por baixas temperaturas, o estabelecimento das plântulas de arroz (Oryza sativa L.) pode ser afetado por diversos outros fatores. Características intrínsecas de cada genótipo de arroz podem condicionar plântulas mais ou menos vigorosas, o que está associado a balanços hormonais. Porém, a atuação do ambiente sobre a semente também é de grande importância.No sistema pré-germinado, é comum o acamamento das plantas, o que pode ser agrav...

RESUMO -O arroz-vermelho é a principal planta daninha do arroz irrigado, pois afeta a produtividade e qualidade. Objetivou-se avaliar a ação de diferentes temperaturas na dinâmica de germinação do genótipo de arroz Puitá INTA CL e de biótipos de arroz-vermelho, com e sem superação da dormência. O trabalho foi realizado em 2011, em câmara B.O.D e Fitotron na Universidade Federal de Santa Maria, Santa Maria -RS. O delineamento foi inteiramente casualizado com quatro repetições. O fator (A) foi composto pelas temperaturas 13; 17; 21 e 25 °C e o fator (D) pela cultivar Puitá INTA CL e três biótipos com e sem dormência. Avaliaram-se os parâmetros: germinação de sementes (GS), índice de velocidade de emergência (IVE), coeficiente de uniformidade de emergência (CUE) e comprimento da parte aérea (CPA). Ocorreu aumento da GS, do IVE, do CUE e do CPA dos biótipos de arroz-vermelho com o aumento da temperatura de 13 °C para 25 °C. Nas temperaturas de 13 e 17 °C o genótipo apresentou germinação 64% maior que a média dos biótipos sem superação da dormência, já aos 21 e 25 °C foi de 11% apenas. Os biótipos apresentaram germinação 56% maior nas temperaturas de 21 e 25 °C, comparado aos 13 e 17 °C. As temperaturas de 13 e 17 °C causam menor germinação de arroz-vermelho sem superação de dormência. Como estratégia de controle de arroz-vermelho em áreas de arroz irrigado, é recomendado priorizar a semeadura do arroz no início da época recomendada (setembro e início de outubro), período em que as temperaturas do ar e do solo são mais baixas. Palavras-chave:Oryza sativa. Germinação. Dormência.ABSTRACT -Red rice is the main weed of the irrigated rice crop because it affects productivity and quality. The object of this study was to evaluate the effect of different temperatures on the germination dynamics of the Puita INTA CL rice genotype, and on red-rice biotypes, both with and without breaking dormancy. The study was carried out in 2011 in a BOD chamber and phytotron of the Federal University of Santa Maria in Santa Maria, Rio Grande do Sul, Brazil. The experimental design was completely randomised, with four replications. Factor (A) consisted of the temperatures 13, 17, 21 and 25 °C, and factor (D) of the Puita INTA CL cultivar and three biotypes, both with and without dormancy. The following parameters were evaluated: seed germination (SG), emergence speed index (ESI), emergence uniformity coefficient (EUC) and length of aerial part (LAP). There was an increase in SG, ESI, EUC and LPA in the red-rice biotypes with the increase in temperature of 13 °C to 25 °C. At temperatures of 13 and 17 °C the genotype showed 64% greater germination than the average of the biotypes without breaking dormancy, whereas at 21 and 25 °C it was only 11%. The biotypes presented 56% greater germination at temperatures of 21 to 25 °C compared to 13 and 17 ºC. Temperatures of 13 and 17 °C cause less germination of red rice without breaking dormancy. As a strategy for controlling red rice in areas of irrigated rice, giving priority to sowing of the rice ea...

Rice monoculture in lowlands can cause problems for management practices in crop fields, for example, in weed control. For this reason, corn in rotation with irrigated rice in lowlands may be advantageous, despite problems with soil compaction and water excess. The objective of this study was to evaluate soil physical properties and corn performance in soil management systems in an Albaqualf soil (lowlands). Two experiments were conducted in the field, in the 2013/14 and 2014/15 crop seasons. The experimental design was randomized blocks with two factors. There were three levels for the first factor, consisting of soil management practices: soil chiseling 45 days before sowing to a depth of 0.3 m; conventional tillage with two diskings to a depth of 0.1 m and subsequent leveling of the soil; and no-till. The second factor was composed of two levels: sowing on raised seedbeds, and without raised seedbeds. The soil parameters of bulk density, total porosity, macroporosity, microporosity, volumetric moisture, and soil resistance to mechanical penetration (RP) were evaluated. The corn parameters were plant height, shoot dry matter, leaf area, height of the first ear of corn, grains per ear, and grain yield. Soil chiseling resulted in lower RP and higher macroporosity in the 0.1-0.2 and 0.2-0.3 m layers. In raised seedbeds, the 0.00-0.05, 0.05-0.10, and 0.10-0.20 m layers were lower in RP and bulk density. Moreover, higher soil macroporosity was observed in relation to the treatment without raised seedbeds. In general, the highest grain yields were found in the treatments with lower RP and higher macroporosity in the root system region. Increased porosity accelerated water drainage in the soil, reducing the time that soil airspace was filled with water, which is a limiting factor for root development. In Albaqualf soils, planting corn in chiseled soil provides higher corn yields compared to conventional tillage, and planting corn on raised seedbeds provides higher corn yields compared to the lack of raised seedbeds.

-Irrigated rice sowing season and red rice competition are among the main factors affecting grain yield. The objective of this work was to evaluate the sowing date of irrigated rice and moments of application of the herbicide imazapyr + imazapic to control red rice management and irrigated rice grain yield. Eight experiments were performed at the following dates (09/30, 10/19, 11/08 and 12/01) for the 2010/2011 harvest season and (09/27, 10/17, 11/08 and 12/05) for the 2011/2012 harvest season. The treatments were: application of the herbicide imazapyr + imazapic at doses of 105+35 g ha -1 in pre-emergence (PRE); 52.5+17.5 g ha -1 in pre-emergence and 52.5+17.5 g ha -1 in post-emergence (PRE + POST); and 105+35 g ha -1 in post-emergence (POST), and a control without application and no weeding. The cultivar Puitá Inta CL was used and a randomized block design with four replicates. A joint analysis of the experiments was carried out. There was less emergence of red rice and higher grain yield of the irrigated rice at the early periods (09/30/10 and 09/27/11), with 10,578 and 8,653 kg ha -1 , respectively. At the end of the season (12/01/10 and 12/05/11), there was greater reduction of the red rice seed bank. Sowing at the beginning of the recommended period provided more irrigated rice grain yield. The application of imazapyr + imazapic at a dose of 52.5+17.5 g ha -1 in PRE + 52.5+17.5 g ha -1 POST, and 105+35 g ha -1 only in PRE and POST was effective in the control of red rice.