Dinâmica de populações de capim-colchão (Digitaria horizontalis Willd.) sob manejos de solo e de herbicidas

One experiment was carried out in Londrina, PR, Brazil, in order to evaluate soil management practices to control Digitaria horizontalis Willd. (DIGHO) in soybean crop, followed by wheat, during five years. The treatments were: 1) disk plowing (DP); 2) moldboard plowing (MP); 3) scarification plus heavy disk (SHD), and 4) no-till (NT). Except for NT, managements were completed with light harrowings. Before sowing wheat, in all managements, the soil was always harrowed with heavy disk. Subplots "with and without" postemergence herbicides were established. Exponential rates of annual reductions of DIGHO seedbank, in plots with herbicides, varied between 43.2% in DP and 52.6% in NT; estimated survival periods were about 6.2 years. Higher seed concentrations were observed annually occurring at the upper soil layer of 0-10 cm, in all managements. Emergence rates of DIGHO varied with year and management, being lower in NT and greater in the other ones. Post-emergence rates of emergence varied between 0.8% and 3.5%.Um experimento foi conduzido em Londrina, PR, com o objetivo de avaliar formas alternativas de preparo do solo para controle de capim-colchão (Digitaria horizontalis Willd.) (DIGHO) na cultura da soja, seguida da cultura do trigo, por um período de cinco anos. Os tratamentos constaram dos seguintes manejos de solo: 1) convencional (CONV), com arado de discos; 2) com arado de aivecas (AIV); 3) com escarificação e grade rome (EGR) e 4) com semeadura direta de soja (SDIR). Exceto em SDIR, os manejos foram complementados com gradagens leves. Antes da semeadura do trigo, em todos os manejos, o solo sempre foi preparado com grade rome. As parcelas foram divididas em "com e sem aplicação" de herbicidas pós-emergentes. Taxas exponenciais de redução anual do banco de sementes de DIGHO, nos manejos com controle herbicida, variaram entre 43,2% no CONV e 52,6% no manejo SDIR; os períodos estimados de sobrevivência variaram em torno de 6,2 anos. Maiores concentrações de sementes foram mantidas anualmente na camada de solo de 0-10 cm, em todos os manejos. As taxas de emergência de DIGHO variaram com o ano e com o manejo de solo e foram menores em SDIR e maiores nos demais. Em pós-semeadura, as taxas de emergência variaram entre 0,8% e 3,5%

Seletividade de herbicidas e dinâmica populacional de plantas daninhas na cultura do girassol para a produção de biodiesel

Experiments were conducted in Prudente de Morais County, Minas Gerais State, in 2010 and 2011 years, with the objective of to evaluate selectivity and efficiency of pre and post-emergence herbicides in sunflower crop, as well as to study weeds populacional dynamic. The work conducted in 2010 was carried out in greenhouse, in a randomized complete block design, with 11 treatments and three replications. Treatments consisted by ten herbicides, four in pre emergence and six in post-emergent of the crop (alachlor, imazaquin, metribuzin, trifluralin, chlorimuron-ethyl, fenoxaprop-p-ethyl, [fluazifop-p + fomesafen], imazapyr, imazethapyr e sethoxydim) and a check. The following characteristics were evaluated: phytotoxicity effects, plants height, leaves number and dry biomass of shoot and root 60 days after product applications. In 2011, the work was accomplished in filed conditions following a randomized complete block design with six treatments and four replications. The treatments consisted of two pre-emergent herbicides: alachlor and trifluralin, two post-emergence: fenoxaprop-p-ethyl and sethoxydim and two checks (with and without weeding). Crop cycle, flowering initial, plant height, stem diameter, achenes physiologically mature, chapters diameter, broken plants number, lodged plants number, final stand and achenes yield were evaluated. Based on the obtained results, it was possible to conclude that herbicides that showed higher toxicity to sunflower plants were: imazaquin, metribuzin, chlorimuron-ethyl, [fomesafen + fluazifop-p], imazapyr and imazethapyr. The pre emergent herbicides alachlor, trifluralin, fenoxaprop-p-ethyl and sethoxydim were selective to sunflower crop. Fenoxaprop-p-ethyl herbicide may be used in a program of weeds integrated management in sunflower crop, because only trifluralin, alachlor and sethoxydim herbicides are registered for this crop in Brazil.Os experimentos foram instalados em Prudente de Morais, MG, em 2010 e 2011, com o objetivo de avaliar a seletividade e a eficácia de herbicidas aplicados em pré e pós-emergência na cultura do girassol, bem como de estudar a dinâmica populacional de plantas daninhas. O trabalho de 2010 foi conduzido em casa de vegetação em delineamento em blocos ao acaso com 11 tratamentos e três repetições. Os tratamentos foram constituídos por dez herbicidas, sendo quatro pré-emergentes e seis pós-emergentes (alachlor, imazaquin, metribuzin, trifluralin, chlorimuron-ethyl, fenoxaprop-p-ethyl, [fluazifop-p + fomesafen], imazapyr, imazethapyr e sethoxydim) e uma testemunha. Foram avaliados os efeitos fitotóxicos, altura das plantas, número de folhas e a biomassa seca da parte aérea e raízes aos 60 dias após a aplicação. Em 2011 o trabalho foi conduzido a campo, em delineamento de blocos ao acaso com seis tratamentos e quatro repetições. Os tratamentos consistiram dos herbicidas alachlor e trifluralin (pré-emergência), fenoxaprop-p-ethyl e sethoxydim (pós-emergência) e duas testemunhas (capinada e sem capina). Foram avaliados o ciclo da cultura, o início de florescimento, a altura de plantas, o diâmetro do caule, a maturação fisiológica dos aquênios, o diâmetro de capítulos, o número de plantas quebradas, o número de plantas acamadas, o estande final e o rendimento de aquênios. Com base nos resultados pode-se concluir que os herbicidas que apresentaram maior fitotoxicidade ao girassol foram: imazaquin, metribuzin, chlorimuron-ethyl, [fluazifop-p + fomesafen], imazapyr e imazethapyr. Os herbicidas pré-emergentes alachlor e trifluralin, e os pós-emergentes fenoxaprop-p-ethyl e sethoxydim mostraram-se seletivos para o girassol. O fenoxaprop-p-ethyl poderá vir a ser utilizado em um programa de manejo integrado de plantas daninhas no girassol, pois apenas trifluralin, alachlor e sethoxydim são herbicidas registrados para esta cultura

Carotenoids in green corn grains after post-emergence herbicide application

O objetivo deste trabalho foi avaliar o efeito da aplicação de herbicidas pós-emergentes no teor de carotenoides em grãos de milho verde. Utilizou-se o delineamento inteiramente casualizado com cinco tratamentos – sem aplicação; foramsulfuron + iodosulfuron-methyl-sodium (40 g ha-1); nicosulfuron (20 g ha-1); mesotrione (120 g ha-1) e tembotrione (100 g ha-1) – e duas repetições. Os grãos foram avaliados para teores de luteína, zeaxantina, betacriptoxantina, alfacaroteno e betacaroteno, carotenoides pró-vitamina A, carotenoides totais e percentuais de luteína, zeaxantina e carotenoides pró-vitamina A. Os herbicidas tembotrione e o nicosulfuron não causaram efeitos deletérios nos teores de carotenoides totais ou nas frações com atividade pró-vitamina A.The objective of this work was to evaluate the efect of post-emergence herbicide application on carotenoid content in green corn grains. A completely randomized design was used, with five treatments – no application; foramsulfuron + iodosulfuron-methyl-sodium (40 g ha-1); nicosulfuron (20 g ha-1); mesotrione (120 g ha-1) and tembotrione (100 g ha-1) –, and two replicates. The grains were evaluated in terms of lutein, zeaxanthin, beta-cryptoxanthin, alpha-carotene and beta-carotene, pro-vitamin A carotenoids, total carotenoid contents, and percentage of lutein, zeaxanthin and pro-vitamin A carotenoids. Tembotrione and nicosulfuron herbicides did not cause deleterious effects on total carotenoids or fractions with pro-vitamin A activity

FORAGE SORGHUM TOLERANCE TO PRIMESTRA SC HERBICIDE

With the objective of evaluating the forage sorghum tolerance to Primestra SC(200 g l-1 of atrazine + 300 g l-1 of metolachlor), a greenhouse experiment was conducted atEmbrapa Milho e Sorgo, Sete Lagoas, MG. The treatments were four Primestra SC rates(3,0; 6,0; 9,0 and 12,0 l ha-1) with or without Assist (mineral oil) at 1,5 l ha-1 sprayed at threesorghum (AG 2002) stages (two, four and six leaves). The experimental design was factorialwith the addition of a non-treated control for each spray stage added in a randomized completeblock with four replications. Visual evaluation of toxicity was done at 7, 14, 21 and 28 daysafter application (DAA). Plant height and root and shoot dry weight were evaluated. Plantssprayed with Primestra SC with Assist showed greater toxicity than plants sprayed withPrimestra SC without Assit meanly at higher rates. Earlier application of Primestra SC had higher toxicity values than later application. Sorghum plants recovered with time to all rates ofPrimestra SC sprayed independently of stage application

Population dynamics of Acanthospermum hispidum DC. under soil and herbicide management practices

O objetivo do presente trabalho foi determinar períodos de sobrevivência e taxas de emergência de sementes de carrapicho-de-carneiro (Acanthospermum hispidum DC.), para uso em sistemas de predição de manejo no controle da espécie. O experimento foi instalado no campo, em Londrina, PR, em um Latossolo Roxo distrófico, com 75% de argila e 2,7% de matéria orgânica. Foram avaliados, durante cinco anos, manejos do solo no sistema convencional, de aivecas, de escarificação e grade rome, de semeadura direta, com presença, ou não, de herbicidas pós-emergentes em soja, seguidos da cultura do trigo. Os períodos estimados de sobrevivência do carrapicho nos manejos de solo foram semelhantes, tanto na presença de herbicidas como na ausência, devido à competição de capim-marmelada (Brachiaria plantaginea (Link.) Hitch.), em uma média de 10,9 anos. A taxa de redução anual do banco de sementes foi de 37,0%. As taxas de emergência, em pré e pós-semeadura da soja, variaram com os anos e com os manejos de solo; as menores taxas foram observadas em semeadura direta. A emergência máxima na fase de pré-semeadura da soja foi de 1,0%; em pós-semeadura, variou entre 0,6% e 6,5%. A maior concentração inicial de sementes na camada superior do perfil do solo não causou diferenças entre os manejos.One experiment was carried out in the field, in Londrina, PR, Brazil on a duski latosol dystrophic, with 75% of clay and 2.7% of organic matter. The objective of this work was to determine the survival period and emergence rates of seeds of Acanthospermum hispidum DC. for predictive management uses in weed control. Soil management practices such as conventional tillage, moldboard tillage, scarification and heavy disc and no-till; postemergence herbicide management practices, present or not in soybeans, followed by wheat, were established during five years. Acanthospermum hispidum estimated survival periods for soil management practices, with herbicides or Brachiaria plantaginea (Link.) Hitch. competition, were of 10.9 years on average. Seed bank annual decreasing rate was about 37.0%. Emergence rates changed with year and soil management practices; the lowest rate was observed in no-tillage. Maximum emergence rate was of 1.0%, before soybean sowing; after sowing, emergence rates were between 0.6% and 6.5%. Seeds initial vertical distribution in soil was of no importance for management practices

Population dynamics of Brachiaria plantaginea (Link) Hitch. by soil and herbicide managements. I. Survival

Um experimento foi instalado em campo, em Londrina, PR, em Latossolo Roxo distrófico. 0 objetivo foi determinar períodos de sobrevivência de sementes de capim-marmelada [Brachiaria plantaginea (Link) Hitch.], para uso em sistemas de predição de manejo no controle da espécie. Manejos de solo e de herbicidas em soja, seguidos pela cultura do trigo, foram estabelecidos durante cinco anos. Períodos estimados de sobrevivência de capim-marmelada no solo foram maiores nos manejos com arado de discos, ou convencional (CONV) e de aivecas (AIV), de 12,2 e 11,5 anos, respectivamente; intermediário, de 7,5 anos, com escarificação e grade rome (EGR) e, menor, de 5,2 anos, em semeadura direta (SDIR). As taxas anuais de redução das infestações e reinfestações de sementes tiveram ajuste exponencial, sendo, respectivamente, de 31,7% e 32,6% no CONV; 33,2% e 25,0% no AIV; 45,8% e 45,5% no EGR, e 58,9% e 46,0% em SDIR. A distribuição inicial das sementes na camada de solo de 0-10 cm foi >90%. Operações de calagem, anteriores à semeadura do trigo reduziram o banco de sementes no solo. Avaliações fisiológicas das sementes indicaram tendências a variações decorrentes dos manejos. A taxa de germinação média em laboratório foi de 83,8%.A field experiment was carried out in Londrina, Paraná State, Brazil, on a "Latossolo Roxo distrófico". The objective was to determine the survival period of Brachiaria plantaginea (Link) Hitch. for predictive management uses in weed control. Soil and herbicide managements in soybeans, followed by wheat, were established during five years. Survival periods were higher in disc plowing, or conventional tillage (CT), and in moldboard (MT), of 12.2 and 11.5 years, respectively; intermediary, of 7.5 years, by scarification and heavy discs (SHD) and lower, of 5.2 years, in no-till (NT). Annually decreasing and increasing rates of seeds in soil were exponential and, respectively, of 31.7% and 32.6% in CT; 33.2% and 25.0% in MT; 45.8% and 45.5% in SHD, and 58.9% and 46.0% in NT. Seed concentration at 0- 10 cm layer was over 90%. Liming operations done before wheat sowing reduced seedbank in soil. Physiologic evaluations of soil seeds through germination rate, germination velocity and electric conductivity showed trends to variation with managements. Laboratory germination rate was averaged in 83.8%

Population dynamics of Brachiaria plantaginea (Link) Hitch. by soil and herbicide managements. 2. Emergence

Um experimento foi instalado em campo, em Londrina, PR, em Latossolo Roxo distrófico, com 75% de argila e 2,7% de matéria orgânica. O objetivo foi determinar taxas anuais de emergências de capim-marmelada [Brachiaria plantaginea (Link) Hitch.], em pré e pós-semeadura da soja, para uso em sistemas de predição de manejo no controle da espécie. Manejos de solo e de herbicidas em soja, seguidos pela cultura do trigo, foram estabelecidos durante cinco anos. As taxas de emergência de capim-marmelada variaram com o ano. Em 1991/92, a taxa anual de emergência máxima foi de 29,8%. Neste ano, as emergências em pré-semeadura representaram 73,9%, em média, da emergência anual, sendo maior onde as intensidades de cultivo foram menores. Nos demais anos, as taxas foram menores de 18,2%. Em pós-semeadura da soja, com controles anuais, a emergência variou entre 5, 1 % e 9,6% no manejo com arado de aivecas; 4,8% e 8,7% com arado de discos; 2,2% e 6,3% com o escarificador e grade rome; e 0,3% e 4,3% na semeadura direta. Sem controle por herbicida, nas reinfestações as taxas de emergência da espécie tenderam a decrescer.A field experiment was carried out in Londrina, Paraná State, Brazil, on a "Latossolo Roxo distrófico", with 75% of clay and 2.7% of organic matter. The objectives were to determine annual pre- and post-emergence rates of Brachiaria plantaginea (Link) Hitch. in soybeans for predictive uses in weed control. Soil and herbicide managements in soybeans, followed by wheat were established during five years. Emergence rates of BRAPL changed with the year. In 1991/92, the highest annual emergence rate was 29.8%. At this year, before sowing, emergence rates were averaged in 73.9% of the annual emergence, being higher when cultivation intensities were lower. In the other years, rates were lower than 18.2%. After soybean sowings, under weed control, emergence rates varied between 5.1% and 9.6% under moldboard tillage; 4.8% and 8.7% under disc plowing; 2.2% and 6.3% under escarification and heavy disc, and 0.3% and 4.3% under no-till. In reinfestations, without herbicide control, emergence rates for this species tend to decrease

POTENTIAL FOR ENVIRONMENTAL CONTAMINATION BY HERBICIDES USED IN MAIZE CULTURE

Spontaneous plants are a severe problem in maize culture, and may cause a decrease in yield up to 85%. Among the methods used to control such species the chemical is the most important, being used in 65 percent of the cultivated area in Brazil. It is known that interactions between organic molecules and environment can be harmful to the gradients of the ecological organization, thus requiring more refined studies in order to understand the behavior and the environmental fate of pesticides. The EIQ model (Environmental Impact Quotient) quantifies damages caused by the use of agrochemicals, regarding impacts on the agricultural worker (applicator/harvester), on the biota and on the final consumer. The present work objectified to evaluate the contamination potential of the herbicides used in maize. Data of physical-chemical, environmental and toxicological characteristics of the actives were collected, parameterized and used for the calculation of the environmental impact ratio. The results showed that imazapyr and imazapic presented the highest potential for environment contamination while isoxaflutole showed the lowest