FITOSSOCIOLOGIA DE PLANTAS DANINHAS NA CULTURA DO MILHO SUBMETIDA À APLICAÇÃO DE DOSES DE NITROGÊNIO

O nitrogênio aplicado às culturas pode alterar o comportamento das plantas daninhas. Assim, algumas espécies são favorecidas pela presença de adubos nitrogenados em doses elevadas, e outras se mostram indiferentes. A finalidade deste estudo foi verificar os efeitos de diferentes doses de nitrogênio na dinâmica de plantas daninhas da lavoura durante o ciclo da cultura do milho. Foi testada a influência de doses de nitrogênio sobre o crescimento do híbrido de milho AG8088 YGRR e na dinâmica das plantas daninhas. A comunidade de espécies infestantes da lavoura sofreu alterações na sua dinâmica em função do tempo de amostragem e inserção de técnicas de plantio, assim como o aumento da disponibilidade de nitrogênio na área. A similaridade foi menor quando se aplicou menores doses de nitrogênio (kg ha-1) e a testemunha antes do plantio

Crescimento inicial da cultura da mandioca em sistema de policultivo

One of the main reasons why farmers in different regions prefer polycultures is that very often you can get higher yields in an area sown in polyculture than in monoculture with an equivalent area. Thus in systems polycultures the plants are in a state of permanent competition causing a reduction in plant growth consorts. The competition affects the production quantitatively and qualitatively, because it changes the efficiency of utilization of environmental resources such as water, light and nutrients, settling between culture and plants of other species existing on site. This competition also occurs between individuals of the same species or between biotypes prevalent in the area. Thus, the aim of this study was to evaluate the growth of two cultivars of cassava intercropped with crops of corn, beans and green manure (gaundu dwarf beans). Treatments consisted of the consortium is cassava (Manihot esculenta), IAC-12, with green manure, dwarf pigeonpea (Cajanus cajan), maize (Zea mays) and beans (Phaseolus vulgaris) beyond cropping of cassava with and without weed control. The development of cultivars was negatively influenced by weed infestation. Cultivation in consortium with two cultivars of maize, beans and faba bean dwarf caused no significant effects on cassava as compared to the same crop grown in single system with weeding.Uma das principais razões pela qual os agricultores em diversas regiões preferem os policultivos é a possibilidade de se obter maiores produtividades numa área semeada em policultivo do que em área equivalente com uma monocultura. Assim em sistemas de policultivos as plantas se encontram em estado de competição permanente ocasionando a redução do crescimento das plantas consortes. Dessa forma, objetivou-se com este trabalho analisar o crescimento inicial de duas cultivares de mandioca em sistema de consórcio com as culturas do milho, do feijão e adubo verde (feijão gaundu-anão). O delineamento experimental utilizado foi em blocos casualizados com quatro repetições em sistema fatorial 2x5, onde o fator A foi as cultivares mandioca usadas no consorcio (Cacau – UFV e IAC – 12) e o fator B correspondeu as culturas consortes com a mandioca; adubo verde, feijão guandu anão (Cajanus cajan), milho (Zea mays) e feijão (Phaseolus vulgaris) além do cultivo solteiro da mandioca com e sem controle de plantas daninhas. O desenvolvimento das cultivares foi influenciado negativamente pela infestação de plantas daninhas. O cultivo em consorcio das duas cultivares com o milho, o feijão e o feijão guandu-anão não provocou efeitos significativos na cultura da mandioca mesmo quando comparada com a cultura cultivada em sistema solteiro com capina

Evolution of HPPD-Inhibitor Herbicide Resistance in a Waterhemp (Amaranthus tuberculatus var. rudis) Population from Nebraska, USA

The rapid adaptation of Amaranthus tubercultus (var. rudis) to modern agriculture made the species an excellent model for studying herbicide resistance evolution. Failure to control an A. tuberculatus (RW) population with postemergence (POST)-applied 4-hydroxyphenyl pyruvate dioxygenase (HPPD)-inhibitors was reported in northeast Nebraska, USA. The resistance was confirmed to mesotrione, tembotrione, and topramezone with dose-response studies. The RW population evolved a 2 to 18× resistance depending on the HPPD-inhibitor resistance herbicide being used. Nonetheless, premixes and tankmixes of multiple herbicide site-of-action (SOA) based on preemergence (PRE) only, POST only, and PRE followed by POST programs provided RW effective control (\u3e 90%) under field conditions. The mechanism of resistance in the RW population is enhanced herbicide metabolism via P450 enzymes. The use of cytochrome P450 inhibitors (malathion, amitrole, and piperonyl butoxide) applied prior tembotrione, and topramezone reversed the RW phenotype to a susceptible phenotype; while amitrole only partially reversed mesotrione resistance. The use of cytochrome P450 inhibitors has a potential for combating metabolism-based resistance in RW population. However, the substrate specificity of P450 enzymes with HPPD- inhibitors highlighted the complexity of resistance in RW population. The genetic study showed that there is no dominance neither recessivity in mesotrione resistance inheritance in A. tuberculatus . In addition, mesotrione resistance is nuclear inherited and controlled by multiple genes. These results show that mesotrione resistance evolved slowly fostered by minor genes. These mesotrione resistance genes can be transferred under field conditions from RW to mesotrione susceptible A. palmeri (SP) and A. tuberculatus (SW) population. The gene flow study showed that interspecific (SP × RW) occurred at low frequencies and intraspecific (SW × RW) hybridization rapidly decrease with distance from the pollen-source. This result showed that pollen-mediated gene flow (PMGF) carrying metabolism-based resistance alleles occurs in weedy Amaranthus species. This result is significant as A. palmeri and A. tuberculatus are prolific seed producer and obligate outcrosser species. Therefore, even at low frequencies, PMGF can have important evolutionary consequences in weedy Amaranthus species

Evolution of HPPD-Inhibitor Herbicide Resistance in a Waterhemp (Amaranthus tuberculatus var. rudis) Population from Nebraska, USA

The rapid adaptation of Amaranthus tubercultus (var. rudis) to modern agriculture made the species an excellent model for studying herbicide resistance evolution. Failure to control an A. tuberculatus (RW) population with postemergence (POST)-applied 4-hydroxyphenyl pyruvate dioxygenase (HPPD)-inhibitors was reported in northeast Nebraska, USA. The resistance was confirmed to mesotrione, tembotrione, and topramezone with dose-response studies. The RW population evolved a 2 to 18× resistance depending on the HPPD-inhibitor resistance herbicide being used. Nonetheless, premixes and tankmixes of multiple herbicide site-of-action (SOA) based on preemergence (PRE) only, POST only, and PRE followed by POST programs provided RW effective control (\u3e 90%) under field conditions. The mechanism of resistance in the RW population is enhanced herbicide metabolism via P450 enzymes. The use of cytochrome P450 inhibitors (malathion, amitrole, and piperonyl butoxide) applied prior tembotrione, and topramezone reversed the RW phenotype to a susceptible phenotype; while amitrole only partially reversed mesotrione resistance. The use of cytochrome P450 inhibitors has a potential for combating metabolism-based resistance in RW population. However, the substrate specificity of P450 enzymes with HPPD- inhibitors highlighted the complexity of resistance in RW population. The genetic study showed that there is no dominance neither recessivity in mesotrione resistance inheritance in A. tuberculatus . In addition, mesotrione resistance is nuclear inherited and controlled by multiple genes. These results show that mesotrione resistance evolved slowly fostered by minor genes. These mesotrione resistance genes can be transferred under field conditions from RW to mesotrione susceptible A. palmeri (SP) and A. tuberculatus (SW) population. The gene flow study showed that interspecific (SP × RW) occurred at low frequencies and intraspecific (SW × RW) hybridization rapidly decrease with distance from the pollen-source. This result showed that pollen-mediated gene flow (PMGF) carrying metabolism-based resistance alleles occurs in weedy Amaranthus species. This result is significant as A. palmeri and A. tuberculatus are prolific seed producer and obligate outcrosser species. Therefore, even at low frequencies, PMGF can have important evolutionary consequences in weedy Amaranthus species

Competitive ability of glyphosate resistant corn with weeds

Dentre os fatores que contribuem para a baixa produtividade m?dia do milho no Brasil, destaca-se a interfer?ncia das plantas daninhas, que afetam diretamente a produtividade, podendo chegar a perdas de at? 90% da produ??o, caso nenhum m?todo de manejo for adotado. Na tentativa de simplificar o manejo e reduzir os custos de controle das plantas daninhas foi lan?ado o milho resistente ao herbicida glyphosate, tecnologia que tem se mostrado bem aceita pelos agricultores. Contudo, o uso excessivo e frequente do glyphosate em ?reas de cultivo tem selecionado esp?cies de plantas daninhas resistentes e tolerantes a esse herbicida, dificultado o controle. Objetivou-se com os estudos avaliar a interfer?ncia de plantas daninhas tolerantes ao glyphosate no milho RR, bem como o efeito de diferentes formula??es comerciais de glyphosate sobre a cultura. Os trabalhos foram realizados em ambiente protegido com o h?brido AG8088 YGRR. No primeiro experimento foram testadas a influ?ncia de formula??es de glyphosate sobre o crescimento do h?brido de milho AG8088 YGRR. No segundo experimento, avaliou-se a habilidade competitiva entre milho e as plantas daninhas Commelina beghalensis L. e Richardia brasiliensis Gomes, tolerantes ao glyphosate. O milho demonstrou menor habilidade competitiva quando cultivado na presen?a de C. benghalensis em rela??o quando foi cultivado com R. brasiliensis. A aplica??o de glyphosate se mostrou eficiente no controle de R. brasiliensis. H? evid?ncias formula??es de glyphosate alteram o teor e conte?do foliar de macronutrientes e vari?veis morfol?gicas do milho RR.Funda??o de Amparo ? Pesquisa do estado de Minas Gerais (FAPEMIG)Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq)Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes)Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2013.ABSTRACT Among the factors that contribute to low average productivity of corn in Brazil, it is competition with weeds, which directly affect productivity, reaching losses up to 90% of production. In an attempt to simplify the management and reduce the costs of weed control was released glyphosate resistant corn, technology that has been well accepted by farmers. However, the over use of glyphosate in cultivation areas have selected weeds species resistant and tolerant to this herbicide, making it difficult to control. The aim of this study was to evaluate the interference of glyphosate tolerant weeds in Glyphosate Resistant Corn as well as the effect of commercial formulations of glyphosate over the. The studies were conducted in the greenhouse with the hybrid AG8088 YGRR. In the first experiment evaluated different formulations of glyphosate on the growth of hybrid. The second experiment the competitive ability between corn and weeds Commelina beghalensis and Richardia brasiliensis. Corn has showed lower competitive ability when grown with C. benghalensis than R. brasiliensis. The application of all glyphosate formulations was effective to control the weed R. brasiliensis. There are evidences that the application of glyphosate formulations alter the percentage, and content of nutrients, also the morphological characteristics of corn

FITOSSOCIOLOGIA DE PLANTAS DANINHAS NA CULTURA DO MILHO SUBMETIDA À APLICAÇÃO DE DOSES DE NITROGÊNIO

O nitrogênio aplicado às culturas pode alterar o comportamento das plantas daninhas. Assim, algumas espécies são favorecidas pela presença de adubos nitrogenados em doses elevadas, e outras se mostram indiferentes. A finalidade deste estudo foi verificar os efeitos de diferentes doses de nitrogênio na dinâmica de plantas daninhas da lavoura durante o ciclo da cultura do milho. Foi testada a influência de doses de nitrogênio sobre o crescimento do híbrido de milho AG8088 YGRR e na dinâmica das plantas daninhas. A comunidade de espécies infestantes da lavoura sofreu alterações na sua dinâmica em função do tempo de amostragem e inserção de técnicas de plantio, assim como o aumento da disponibilidade de nitrogênio na área. A similaridade foi menor quando se aplicou menores doses de nitrogênio (kg ha-1) e a testemunha antes do plantio

Production and Physiological quality of bean seeds after application Diquat

Objetivou-se com a pesquisa avaliar a influência da aplicação do herbicida Diquat, em diferentes épocas, sobre a produção e qualidade fisiológica das sementes de feijão, cultivar Pérola. O delineamento experimental utilizado foi de blocos casualizados (DBC). Os tratamentos constituíram da aplicação do herbicida com dosagem de 400 g i.a./ha, em oito estádios de aplicação (83, 85, 87, 89, 91, 93 e 95 dias após a semeadura (DAS) e sem aplicação aos 97 dias – testemunha). As variáveis analisadas foram, grau de umidade (%), germinação (%), primeira contagem da germinação (%), índice de velocidade de germinação, emergência de plântulas (%), estande inicial (%), índice de velocidade de emergência, peso de mil sementes (g) e produção (Kg ha-1). O grau de umidade das sementes de feijão nas épocas de aplicação do herbicida decresceram, antecipando em ate 14 dias a colheita do feijão. Pela germinação e primeira contagem não foi observado diferença entre os tratamentos. Já para o IVG observou-se resultados superiores aos 83 DAS. Para a porcentagem de emergência e IVE os valores foram inferiores aos 87 e 89 DAS. Em contrapartida, os dados obtidos para o estande inicial não diferiram entre si. Para o peso de mil sementes e produção os resultados foram superiores aos 89 DAS e aos 89 e 95 DAS, respectivamente. A aplicação do dessecante Diquat na cultura do feijoeiro a partir dos 83 dias após a semeadura não afeta a germinação das sementes, porém, reduz de maneira significativa a produção de sementes.The objective of this research was to evaluate the influence of Diquat herbicide application, at different periods, on production and physiological quality of bean seeds, cultivar: Perola. The experimental design used was a randomized block (RBD). The treatments were constituted of application of such herbicide with dosage of 400 g ai / ha in eight stages of application (83, 85, 87, 89, 91, 93 and 95 days after seeding (DAS) and without application with 97 days – witness .) The analyzed variables were moisture content (%), germination (%), first count of germination (%)velocity index of germination, seedling emergence (%), initial stand (%)velocity index of emergency, thousand seed weight (g) and production (kg ha-1). The moisture content of the bean seeds at the times of herbicide application declined, anticipating up to 14 days to harvest beans. For the first counting and germination no difference was observed between treatments. But for the IVG observed superior results at 83 DAS. For emergence percentage and EVI the values were lower at 87 and 89 DAS. On the other hand, the data obtained for the initial stand did not differ. For the thousand seed weight and production results were superior to 89 DAS and at 89 and 95 DAS, respectively. The application of Diquat desiccant in bean crop from 83 days after sowing did not affect the germination of the seeds, however, affect significantly the production of seeds

Desempenho de cultivares de cenoura em duas regiões distintas do Alto Vale do Jequitinhonha, MG

The successful commercial use of carrot depends on the choice of cultivars that are well-adapted to soil and climate conditions at the cultivation site and on good consumer acceptance. The objective of this study was to evaluate the performance of carrot cultivars grown in autumn-winter in two towns with different climatic characteristics, in the High Jequitinhonha Valley, MG, Brazil. The experiments were conducted on the Rio Manso farm, in the town of Couto de Magalhães de Minas and on Campus JK at UFVJM, in the town of Diamantina, Minas Gerais, Brazil. Six carrot cultivars (Brasília, Nantes, Kuronan, Esplanada, Planalto and Tornado) were evaluated using a randomized complete block design with three replicates. The following morpho-agronomic characteristics were evaluated 100 days after sowing: shoot height, root length, root dry matter, total dry matter, harvest index, commercial yield and total yield root. The most suitable cultivars in Diamantina were Planalto, Tornado and Kuronan, and the cultivatar Planalto was the best suited to Couto de Magalhães de Minas. The agronomic performance of the cultivars was higher in Couto de Magalhães de Minas for the majority of the study variables, resulting in a higher total yield and commercial root yield. The climatic and soil conditions of Diamantina induced flowering in most cultivars, causing a loss to the commercial yield in autumn-winter cultivation.O sucesso na exploração comercial da cenoura depende da escolha de cultivares com boa adaptação às condições de solo e de clima no local onde será cultivada e da boa aceitação pelo mercado consumidor. O objetivo do presente trabalho foi avaliar o desempenho de cultivares de cenoura no cultivo de outono-inverno em dois municípios com características edafoclimáticas distintas do Alto Vale do Jequitinhonha, MG. Os experimentos foram conduzidos na Fazenda Rio Manso, município de Couto de Magalhães de Minas, MG e no Campus JK da UFVJM, município de Diamantina, MG. Foram avaliadas seis cultivares de cenoura (Brasília, Nantes, Kuronan, Esplanada, Planalto e Tornado) utilizando-se o delineamento experimental em blocos ao acaso com três repetições. As características morfoagronomicas altura da parte aérea, comprimento de raiz, matéria seca de raiz, matéria seca total, índice de colheita, produtividade comercial e produtividade total de raízes foram avaliadas 100 dias após a semeadura. As cultivares que se destacaram em Diamantina foram Planalto, Tornado e Kuronan e em Couto de Magalhães de Minas a cultivar Planalto. O desempenho agronômico das cultivares foi superior em Couto de Magalhães de Minas para a maioria das variáveis avaliadas, resultando em uma maior produtividade total e comercial de raízes. As condições edafoclimáticas de Diamantina induzem florescimento na maioria das cultivares, causando perdas de produtividade comercial no cultivo de outono-inverno

Effect of plant-biostimulant on cassava initial growth

ABSTRACT Biostimulants are complex substances that promote hormonal balance in plants, favor the genetic potential expression, and enhance growth of shoots and root system. The use of these plant growth promoters in crops can increase quantitatively and qualitatively crop production. Therefore, the aim of this study was to evaluate the effect of a commercial biostimulant on the initial growth of cassava. The experiment was arranged in a 2 x 5 factorial design, corresponding to two cassava cultivars (Cacau-UFV and Coimbra) and five biostimulant concentrations (0, 4, 8, 12 and 16 mL L-1). At 90 days after planting, the characteristics leaf area, plant height, stem diameter, leaf number, total dry matter and dry matter of roots, stems and leaves were evaluated. The biostimulant promoted linear increases in plant height, leaf number, leaf area, total dry matter, dry matter of stems, leaves and roots. The cultivar Cacau-UFV had a higher growth rate than the cultivar Coimbra. The growth promoter stimulated the early growth of the cassava crop

Effect of growing Brachiria brizantha on phytoremediation of picloram under different pH environments

Picloram is used in the management of Brachiaria brizantha (Poaceae) in pasture. The persistence of this herbicide varies with climate and soil characteristics, such as texture and pH. The aim was to determine the capacity of B. brizantha (Hochst.) Stapf. cv. Marandu to remediate soils of different pH levels contaminated with picloram. The experiment had a randomized block design with four replications. The remedial species was grown for 60 days after cucumber [Cucumis sativus L. (Cucurbitaceae)] was cultivated as an indicator of the presence of the herbicide in the soil. This plant reduced the picloram concentration in the soil layer surface, which can be attributed to its ability to degrade, to absorb, and/or to exude herbicides. The picloram has greater leaching potential in higher pH soils, in the absence of B. brizantha. Soils with lower pH tend to have higher sorption and concentration of this herbicide in the intermediate layers. B. brizantha can remediate soils contaminated with picloram and reduce leaching, which is higher in soils treated with limestone