Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides / Atividade de fungos micorrízicos arbusculares na rizosfera de mudas de árvores submetidas a herbicidas residuais

Trees occurring on the margins of agricultural areas can mitigate damage from residual herbicides. Rhizospheric microbial activity associated with trees is one of the main remedial capacity indicators. The objective of this study was to evaluate the rhizospheric microbiological activity in tree species subjected to the herbicides atrazine and sulfentrazone via the rhizosphere. The experiment was designed in four blocks and a 6 × 3 factorial scheme. The first factor consisted of six tree species from Brazil and the second of atrazine, sulfentrazone, and water solutions. Four herbicide applications were performed via irrigation. The total dry mass of the plants, mycorrhizal colonization, number of spores, basal respiration of the rhizospheric soil, and survival rate of bioindicator plants after phytoremediation were determined. Trichilia hirta had higher biomass when treated with atrazine and sulfentrazone. Herbicides decreased the microbial activity in Triplaris americana and did not affect the microbiological indicators of Myrsine gardneriana, Schizolobium parahyba, and Toona ciliata. Fewer bioindicator plants survived in soil with Triplaris americana and sulfentrazone. Microbiological indicators were influenced in different ways between species by the presence of herbicides in the rhizosphere.

As árvores que ocorrem nas margens das áreas agrícolas podem mitigar os danos dos herbicidas residuais. A atividade microbiana rizosférica associada às árvores é um dos principais indicadores de capacidade corretiva. O objetivo deste trabalho foi avaliar a atividade microbiológica rizosférica em espécies arbóreas submetidas aos herbicidas atrazina e sulfentrazone via rizosfera. O experimento foi estruturado em quatro blocos e esquema fatorial 6 × 3. O primeiro fator consistiu em seis espécies de árvores do Brasil e o segundo em soluções de atrazine, sulfentrazone e água. Quatro aplicações de herbicidas foram realizadas via irrigação. Foram determinados a massa seca total das plantas, colonização micorrízica, número de esporos, respiração basal do solo rizosférico e taxa de sobrevivência de plantas bioindicadoras após fitorremediação. Trichilia hirta apresentou maior biomassa quando tratada com atrazina e sulfentrazone. Os herbicidas diminuíram a atividade microbiana em Triplaris americana e não afetaram os indicadores microbiológicos de Myrsine gardneriana, Schizolobium parahyba e Toona ciliata. Menos plantas bioindicadoras sobreviveram no solo com Triplaris americana e sulfentrazone. Os indicadores microbiológicos foram influenciados de formas distintas entre as espécies pela presença dos herbicidas na rizosfera.

Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides / Atividade de fungos micorrízicos arbusculares na rizosfera de mudas de árvores submetidas a herbicidas residuais

Trees occurring on the margins of agricultural areas can mitigate damage from residual herbicides. Rhizospheric microbial activity associated with trees is one of the main remedial capacity indicators. The objective of this study was to evaluate the rhizospheric microbiological activity in tree species subjected to the herbicides atrazine and sulfentrazone via the rhizosphere. The experiment was designed in four blocks and a 6 × 3 factorial scheme. The first factor consisted of six tree species from Brazil and the second of atrazine, sulfentrazone, and water solutions. Four herbicide applications were performed via irrigation. The total dry mass of the plants, mycorrhizal colonization, number of spores, basal respiration of the rhizospheric soil, and survival rate of bioindicator plants after phytoremediation were determined. Trichilia hirta had higher biomass when treated with atrazine and sulfentrazone. Herbicides decreased the microbial activity in Triplaris americana and did not affect the microbiological indicators of Myrsine gardneriana, Schizolobium parahyba, and Toona ciliata. Fewer bioindicator plants survived in soil with Triplaris americana and sulfentrazone. Microbiological indicators were influenced in different ways between species by the presence of herbicides in the rhizosphere.(AU)

As árvores que ocorrem nas margens das áreas agrícolas podem mitigar os danos dos herbicidas residuais. A atividade microbiana rizosférica associada às árvores é um dos principais indicadores de capacidade corretiva. O objetivo deste trabalho foi avaliar a atividade microbiológica rizosférica em espécies arbóreas submetidas aos herbicidas atrazina e sulfentrazone via rizosfera. O experimento foi estruturado em quatro blocos e esquema fatorial 6 × 3. O primeiro fator consistiu em seis espécies de árvores do Brasil e o segundo em soluções de atrazine, sulfentrazone e água. Quatro aplicações de herbicidas foram realizadas via irrigação. Foram determinados a massa seca total das plantas, colonização micorrízica, número de esporos, respiração basal do solo rizosférico e taxa de sobrevivência de plantas bioindicadoras após fitorremediação. Trichilia hirta apresentou maior biomassa quando tratada com atrazina e sulfentrazone. Os herbicidas diminuíram a atividade microbiana em Triplaris americana e não afetaram os indicadores microbiológicos de Myrsine gardneriana, Schizolobium parahyba e Toona ciliata. Menos plantas bioindicadoras sobreviveram no solo com Triplaris americana e sulfentrazone. Os indicadores microbiológicos foram influenciados de formas distintas entre as espécies pela presença dos herbicidas na rizosfera.(AU)

Impact of atrazine and nitrate on liver and kidney of egyptian toad Sclerophrys regularis: bioindicator alarming on ecosystem

Atrazine and nitrate have been shown to act as potent oxidative stressors in amphibians either alone or in combination under stable laboratory conditions, causing histopathological alternations in liver and kidney structures at the sub-lethal concentrations. A control group and three treatments groups were tested; atrazine, nitrate, atrazine-nitrate treatments with doses of 300 µg L-1, 200 mg L-1 and their combination respectively. Sever distortion in liver and kidney tissues were shown related to the different treatments. The most hepatic lesions were observed depletion in glycogen content, degeneration of hepatocytes, hemorrhage, necrosis, vasodilatation, congestion in blood vessels, cloudy swelling in the hepatocytes and aggregation of melanomacrophage cells in between the hepatocytes that increased in combination treatment group. In kidney, the most lesions were represented in degeneration of renal tubules, fibrosis, hemorrhage, leucocytes infiltration, thickness in the wall of the renal capsule, atrophy of glomerulus, deformation of Bowman's epithelium. These negative impacts may be a bioindicator alarming the ecosystem disrupting caused by the uncontrolled apply of these chemicals in agriculture.(AU)

Efeito do residual de atrazina e atrazina + simazina em soja / Residual effect of atrazine and atrazine + simazine in soybean

A persistência no solo de herbicidas do grupo das triazinas é dependente de basicamente de condições de precipitação e características do solo. Objetivou-se avaliar o efeito residual de diferentes épocas de aplicação e doses de atrazina e atrazina + simazina para a cultura da soja. Conduziram-se experimentos a campo e casa de vegetação. A campo utilizou-se o delineamento de parcelas subdivididas com quatro repetições, sendo o fator A composto por épocas de aplicação 56, 49, 42, 35, 28, 21 e 14 dias antes da semeadura da soja; e fator B, pelos herbicidas atrazina e atrazina + simazina. Para o experimento em casa de vegetação o delineamento inteiramente casualizados, o fator A foi constituído de doses 0, 570, 1.140, 1.715, 2.285, 2.860, 3.430 e 4.000 g i.a.ha-1; e fator B pelos herbicidas atrazina e atrazina + simazina. A aplicação dos tratamentos foi realizada com pulverizador costal pressurizado por CO2, após a aplicação realizou-se a semeadura da soja. A campo avaliou-se o estande de plantas, fitotoxicidade, estatura, altura de inserção do primeiro entrenó, teor de clorofila e produtividade. Em casa de vegetação foram avaliados fitotoxicidade, estatura de plantas, área foliar e massa seca. Após os dados foram submetidos a análise de variância e quando significativas as medias foram comparadas pelo teste Tukey a 5%. A simulação de residual dos herbicidas atrazina e atrazina...

The soil persistence of herbicides from the triazines group is basically dependent on precipitation conditions and soil characteristics. The objective of this study was to assess the residual effect of different application times and atrazine and atrazine + simazine doses for the soybean crop. Experiments were conducted in the field and greenhouse. In the field, the design of subdivided plots with four replications was used, with factor A composed of application times 56, 49, 42, 35, 28, 21, and 14 days before soybean sowing; and factor B, by the herbicides atrazine and atrazine + simazine. For the greenhouse experiment, the design was completely randomized blocks, factor A doses 0, 570, 1140, 1715, 2285, 2860, 3430, and 4000 g i.a. ha-1, factor B herbicides atrazine and atrazine + simazine. The application of the treatments was carried out with a CO2 pressurized sprayer, after the application of the soybean. The field was assessed regarding the plant stand, phytotoxicity, stature, height of insertion of the first training, chlorophyll content, and kg ha-1 yield. In the greenhouse, phytotoxicity, plant height, leaf area, and dry mass were assessed. Then, data were submitted to analysis of variance and, when significant, the means were compared by the Tukey test at 5%. The residual simulation of the herbicides atrazine and atrazine + simazine in the soil showed similar behavior...

Efeito do residual de atrazina e atrazina + simazina em soja / Residual effect of atrazine and atrazine + simazine in soybean

A persistência no solo de herbicidas do grupo das triazinas é dependente de basicamente de condições de precipitação e características do solo. Objetivou-se avaliar o efeito residual de diferentes épocas de aplicação e doses de atrazina e atrazina + simazina para a cultura da soja. Conduziram-se experimentos a campo e casa de vegetação. A campo utilizou-se o delineamento de parcelas subdivididas com quatro repetições, sendo o fator A composto por épocas de aplicação 56, 49, 42, 35, 28, 21 e 14 dias antes da semeadura da soja; e fator B, pelos herbicidas atrazina e atrazina + simazina. Para o experimento em casa de vegetação o delineamento inteiramente casualizados, o fator A foi constituído de doses 0, 570, 1.140, 1.715, 2.285, 2.860, 3.430 e 4.000 g i.a.ha-1; e fator B pelos herbicidas atrazina e atrazina + simazina. A aplicação dos tratamentos foi realizada com pulverizador costal pressurizado por CO2, após a aplicação realizou-se a semeadura da soja. A campo avaliou-se o estande de plantas, fitotoxicidade, estatura, altura de inserção do primeiro entrenó, teor de clorofila e produtividade. Em casa de vegetação foram avaliados fitotoxicidade, estatura de plantas, área foliar e massa seca. Após os dados foram submetidos a análise de variância e quando significativas as medias foram comparadas pelo teste Tukey a 5%. A simulação de residual dos herbicidas atrazina e atrazina...(AU)

The soil persistence of herbicides from the triazines group is basically dependent on precipitation conditions and soil characteristics. The objective of this study was to assess the residual effect of different application times and atrazine and atrazine + simazine doses for the soybean crop. Experiments were conducted in the field and greenhouse. In the field, the design of subdivided plots with four replications was used, with factor A composed of application times 56, 49, 42, 35, 28, 21, and 14 days before soybean sowing; and factor B, by the herbicides atrazine and atrazine + simazine. For the greenhouse experiment, the design was completely randomized blocks, factor A doses 0, 570, 1140, 1715, 2285, 2860, 3430, and 4000 g i.a. ha-1, factor B herbicides atrazine and atrazine + simazine. The application of the treatments was carried out with a CO2 pressurized sprayer, after the application of the soybean. The field was assessed regarding the plant stand, phytotoxicity, stature, height of insertion of the first training, chlorophyll content, and kg ha-1 yield. In the greenhouse, phytotoxicity, plant height, leaf area, and dry mass were assessed. Then, data were submitted to analysis of variance and, when significant, the means were compared by the Tukey test at 5%. The residual simulation of the herbicides atrazine and atrazine + simazine in the soil showed similar behavior...(AU)

Atrazine degradation patterns: the role of straw cover and herbicide application history

In Brazil, atrazine (ATZ) is widely applied to maize (Zea mays L.) fields for weed control. The presence of ATZ and its metabolites in soil and water matrices has become a matter of some concern for governmental authorities as well as for society at large. This study evaluated the patterns of ATZ degradation (mineralization, extractable and non-extractable ATZ residues, and metabolite formation) in a Brazilian Typic Paleudult. Soil samples from a cultivated area under a no-tillage system with a history of ATZ application were incubated with 14C-ATZ in both the presence and absence of straw cover on the soil surface, and the evolved 14CO2 was determined by liquid scintillation. Samples from an area with native vegetation, adjacent to the cultivated area, were also incubated as a control. A higher mineralization of ATZ was observed in the cultivated soil (> 85 %) in comparison with the native soil (10 %) after 85 days of incubation. In addition to the higher mineralization and hydroxyatrazine (HA) formation, a rapid decrease in the water-extractable residues was observed in the cultivated soil. When the cultivated soil was covered with straw, mineralization was reduced by up to 30 % although a small amount of remobilization to the soil occurred within the 85 days. Straw cover hindered the degradation of ATZ in cultivated soils; whereas an accelerated biodegradation was due to repeated applications of ATZ, which may have selected microbiota more skilled at biodegrading the herbicide.

Atrazine degradation patterns: the role of straw cover and herbicide application history

In Brazil, atrazine (ATZ) is widely applied to maize (Zea mays L.) fields for weed control. The presence of ATZ and its metabolites in soil and water matrices has become a matter of some concern for governmental authorities as well as for society at large. This study evaluated the patterns of ATZ degradation (mineralization, extractable and non-extractable ATZ residues, and metabolite formation) in a Brazilian Typic Paleudult. Soil samples from a cultivated area under a no-tillage system with a history of ATZ application were incubated with 14C-ATZ in both the presence and absence of straw cover on the soil surface, and the evolved 14CO2 was determined by liquid scintillation. Samples from an area with native vegetation, adjacent to the cultivated area, were also incubated as a control. A higher mineralization of ATZ was observed in the cultivated soil (> 85 %) in comparison with the native soil (10 %) after 85 days of incubation. In addition to the higher mineralization and hydroxyatrazine (HA) formation, a rapid decrease in the water-extractable residues was observed in the cultivated soil. When the cultivated soil was covered with straw, mineralization was reduced by up to 30 % although a small amount of remobilization to the soil occurred within the 85 days. Straw cover hindered the degradation of ATZ in cultivated soils; whereas an accelerated biodegradation was due to repeated applications of ATZ, which may have selected microbiota more skilled at biodegrading the herbicide.(AU)

Controle de plantas de soja e supressão do capim em milho consorciado com Brachiaria ruziziensis / Soybean control and grass suppression in maize with Brachiaria ruziziensis intercropped

O objetivo deste trabalho foi avaliar a melhor dose de atrazina no controle de plantas de soja em meio ao milho safrinha consorciado com Brachiaria ruziziensis (B. ruziziensis), bem como sua interação com diferentes doses de nicosulfuron, de forma a não afetar os benefícios do consórcio. Foram realizados dois bioensaios, o primeiro com seis doses de atrazina (0; 0,6; 0,8; 1,0; 1,2; e 1,4 kgi.a. ha-1). As avaliações foram realizadas 15 e 30 dias após a aplicação (DAA), baseadas na porcentagem de controle das plantas de soja, no número de plantas de B. ruziziensis, no rendimento de grãos de milho e na massa seca do capim. O segundo bioensaio foi conduzido em esquema fatorial 3 (doses de nicosulfuron) × 2 (sem e com atrazina), com duas testemunhas adicionais (testemunha capinada e testemunha sem capina). As doses de nicosulfuron utilizadas foram 2,0; 4,0; e 6,0 gi.a. ha-1, e a dose de atrazina foi de 0,8 kgi.a. ha-1. Doses crescentes de atrazina resultaram em melhor controle das plantas de soja e maior rendimento de grãos de milho. Doses superiores a 1,0 kgi.a. ha-1 de atrazina resultaram em redução na massa seca do capim. A adição de 0,8 kgi.a. ha-1 de atrazina com 2,0; 4,0; ou 6,0 gi.a. ha-1 de nicosulfuron aumentou o controle de plantas de soja em comparação com as doses isoladas de nicosulfuron, não influenciou o número de plantas e a massa seca do capim e proporcionou incremento no rendimento de grãos de milho.

The aim of this study was to evaluate the best dose of atrazine in soybean control in winter maize intercropped with Brachiaria ruziziensis (B. ruziziensis), as well as its interaction with different doses of nicosulfuron, in a way as not to affect the benefits of farming-pasture integration. Two bioassays were made, the first one with six doses of atrazine (0.0, 0.6, 0.8, 1.0, 1.2, and 1.4 kga.i. ha-1). Evaluations were performed 15 and 30 days after application, based on the percentage of soybean plants control, number of plants of B. ruziziensis, maize grain yield and dry mass of the grass. The second bioassay was conducted in split plot 3 (doses of nicosulfuron) × 2 (with and without atrazine), with two additional witnesses (hand weeded and weeded treatment). Nicosulfuron doses used were 2.0, 4.0 and 6.0 ga.i. ha-1, and atrazine dose used was 0.8 kga.i. ha-1. Increasing doses of atrazine resulted in better soybean plants control and higher maize grain yield. Doses higher than 1.0 kga.i. ha-1 of atrazine resulted in decreased dry mass of the grass. The addition of 0.8 kga.i. ha-1 of atrazine with 2.0, 4.0 and 6.0 ga.i. ha-1 of nicosulfuron increased soybean plants control compared with single doses of nicosulfuron, did not influence the number of plants nor dry mass of the grass and provided increase in maize grain yield.

Controle de plantas de soja e supressão do capim em milho consorciado com Brachiaria ruziziensis / Soybean control and grass suppression in maize with Brachiaria ruziziensis intercropped

O objetivo deste trabalho foi avaliar a melhor dose de atrazina no controle de plantas de soja em meio ao milho safrinha consorciado com Brachiaria ruziziensis (B. ruziziensis), bem como sua interação com diferentes doses de nicosulfuron, de forma a não afetar os benefícios do consórcio. Foram realizados dois bioensaios, o primeiro com seis doses de atrazina (0; 0,6; 0,8; 1,0; 1,2; e 1,4 kgi.a. ha-1). As avaliações foram realizadas 15 e 30 dias após a aplicação (DAA), baseadas na porcentagem de controle das plantas de soja, no número de plantas de B. ruziziensis, no rendimento de grãos de milho e na massa seca do capim. O segundo bioensaio foi conduzido em esquema fatorial 3 (doses de nicosulfuron) × 2 (sem e com atrazina), com duas testemunhas adicionais (testemunha capinada e testemunha sem capina). As doses de nicosulfuron utilizadas foram 2,0; 4,0; e 6,0 gi.a. ha-1, e a dose de atrazina foi de 0,8 kgi.a. ha-1. Doses crescentes de atrazina resultaram em melhor controle das plantas de soja e maior rendimento de grãos de milho. Doses superiores a 1,0 kgi.a. ha-1 de atrazina resultaram em redução na massa seca do capim. A adição de 0,8 kgi.a. ha-1 de atrazina com 2,0; 4,0; ou 6,0 gi.a. ha-1 de nicosulfuron aumentou o controle de plantas de soja em comparação com as doses isoladas de nicosulfuron, não influenciou o número de plantas e a massa seca do capim e proporcionou incremento no rendimento de grãos de milho.(AU)

The aim of this study was to evaluate the best dose of atrazine in soybean control in winter maize intercropped with Brachiaria ruziziensis (B. ruziziensis), as well as its interaction with different doses of nicosulfuron, in a way as not to affect the benefits of farming-pasture integration. Two bioassays were made, the first one with six doses of atrazine (0.0, 0.6, 0.8, 1.0, 1.2, and 1.4 kga.i. ha-1). Evaluations were performed 15 and 30 days after application, based on the percentage of soybean plants control, number of plants of B. ruziziensis, maize grain yield and dry mass of the grass. The second bioassay was conducted in split plot 3 (doses of nicosulfuron) × 2 (with and without atrazine), with two additional witnesses (hand weeded and weeded treatment). Nicosulfuron doses used were 2.0, 4.0 and 6.0 ga.i. ha-1, and atrazine dose used was 0.8 kga.i. ha-1. Increasing doses of atrazine resulted in better soybean plants control and higher maize grain yield. Doses higher than 1.0 kga.i. ha-1 of atrazine resulted in decreased dry mass of the grass. The addition of 0.8 kga.i. ha-1 of atrazine with 2.0, 4.0 and 6.0 ga.i. ha-1 of nicosulfuron increased soybean plants control compared with single doses of nicosulfuron, did not influence the number of plants nor dry mass of the grass and provided increase in maize grain yield.(AU)

Controle de plantas de soja e supressão do capim em milho consorciado com Brachiaria ruziziensis / Soybean control and grass suppression in maize with Brachiaria ruziziensis intercropped

O objetivo deste trabalho foi avaliar a melhor dose de atrazina no controle de plantas de soja em meio ao milho safrinha consorciado com Brachiaria ruziziensis (B. ruziziensis), bem como sua interação com diferentes doses de nicosulfuron, de forma a não afetar os benefícios do consórcio. Foram realizados dois bioensaios, o primeiro com seis doses de atrazina (0; 0,6; 0,8; 1,0; 1,2; e 1,4 kgi.a. ha-1). As avaliações foram realizadas 15 e 30 dias após a aplicação (DAA), baseadas na porcentagem de controle das plantas de soja, no número de plantas de B. ruziziensis, no rendimento de grãos de milho e na massa seca do capim. O segundo bioensaio foi conduzido em esquema fatorial 3 (doses de nicosulfuron) × 2 (sem e com atrazina), com duas testemunhas adicionais (testemunha capinada e testemunha sem capina). As doses de nicosulfuron utilizadas foram 2,0; 4,0; e 6,0 gi.a. ha-1, e a dose de atrazina foi de 0,8 kgi.a. ha-1. Doses crescentes de atrazina resultaram em melhor controle das plantas de soja e maior rendimento de grãos de milho. Doses superiores a 1,0 kgi.a. ha-1 de atrazina resultaram em redução na massa seca do capim. A adição de 0,8 kgi.a. ha-1 de atrazina com 2,0; 4,0; ou 6,0 gi.a. ha-1 de nicosulfuron aumentou o controle de plantas de soja em comparação com as doses isoladas de nicosulfuron, não influenciou o número de plantas e a massa seca do capim e proporcionou incremento no rendimento de grãos de milho.(AU)

The aim of this study was to evaluate the best dose of atrazine in soybean control in winter maize intercropped with Brachiaria ruziziensis (B. ruziziensis), as well as its interaction with different doses of nicosulfuron, in a way as not to affect the benefits of farming-pasture integration. Two bioassays were made, the first one with six doses of atrazine (0.0, 0.6, 0.8, 1.0, 1.2, and 1.4 kga.i. ha-1). Evaluations were performed 15 and 30 days after application, based on the percentage of soybean plants control, number of plants of B. ruziziensis, maize grain yield and dry mass of the grass. The second bioassay was conducted in split plot 3 (doses of nicosulfuron) × 2 (with and without atrazine), with two additional witnesses (hand weeded and weeded treatment). Nicosulfuron doses used were 2.0, 4.0 and 6.0 ga.i. ha-1, and atrazine dose used was 0.8 kga.i. ha-1. Increasing doses of atrazine resulted in better soybean plants control and higher maize grain yield. Doses higher than 1.0 kga.i. ha-1 of atrazine resulted in decreased dry mass of the grass. The addition of 0.8 kga.i. ha-1 of atrazine with 2.0, 4.0 and 6.0 ga.i. ha-1 of nicosulfuron increased soybean plants control compared with single doses of nicosulfuron, did not influence the number of plants nor dry mass of the grass and provided increase in maize grain yield.(AU)