-Nitrogen (N) is one of the nutrients that have the most significant effect on corn grain productivity increase. In order to evaluate the effect of sources of N topdressing and doses in the grown corn culture, in a conventional till system, it was installed an experiment in the city of Urutaí, Goiás, in the 2012/13 crop, in clayey textured Red Latosol. The experimental design was a randomized complete block design with four replications, with the treatments arranged in a factorial 3 x 5, consisting of three sources (coated urea, urea and ammonium sulfate) and five doses (0, 60, 120, 180 and 240 kg ha -1 ) of N, topdressing, applied in the surface and in a single dose, when the corn plants were in V 4 stage. The hybrid used was the P3646H. We evaluated the following characters: stem diameter, plant height, height of ear insertion, leaf N, number of ears per plant, ear length, number of rows per ear, number of grains per row, 100 grains mass and grain productivity. All characters have a response to nitrogen fertilization and only the height of ear insertion showed no significant difference between sources. The source coated urea showed the best results, indicating that its use may be compensatory, especially in favorable conditions for the NH 3 volatilization, as the application of high doses of N in the surface.

Submetido em 18/03/2014 e aprovado em 17/07/2015.

Resumo: Uma das formas de maximizar a produtividade de grãos de milho é a escolha correta do híbrido para condições edafoclimáticas regionais. Nesse contexto, objetivou-se avaliar o desempenho agronômico de onze híbridos de milho na região sudeste de Goiás, Brasil. O experimento foi conduzido a campo, na safra (primavera-verão) 2013/2014, em Latossolo Vermelho distrófico sob condições edafoclimáticas do Cerrado, na região sudeste de Goiás. O delineamento experimental utilizado foi o de blocos ao acaso, sendo 11 tratamentos representados pelos híbridos de milho, com quatro repetições. Foram avaliados o estande final de plantas, número final de espigas, características morfológicas das plantas (altura da planta, altura da espiga e diâmetro do colmo), componentes da produção (comprimento da espiga, número de fileiras por espiga, número de grãos por fileira, número de grãos por espiga e massa de 100 grãos) e a produtividade de grãos. O estande final de plantas e o número de espigas foram semelhantes entre os híbridos. Os híbridos comerciais de milho apresentam grande variação no desempenho agronômico na região sudeste de Goiás. Com relação à altura das plantas e da espiga, os híbridos LG6036 e 20A55 apresentaram as maiores alturas de plantas e o híbrido LG6036 apresentou maior altura de espiga. Já, para o diâmetro do colmo, as plantas dos híbridos Feroz, BX1293, LG6036, 20A55, Maximus e P3862 apresentaram colmos grossos. Na avaliação dos componentes da produção, os híbridos de milho demonstraram variação nos resultados. Os híbridos simples Maximus e P3862, e os triplos 20A55 e 30A95 foram os mais produtivos. Palavras-chave: Cerrado. Componentes da produção. Produtividade de grãos. Variabilidade genética. Zea mays L.Abstract: One way to maximise grain yield in maize is the correct choice of hybrid for soil and climatic conditions in the region. The aim therefore was to evaluate the agronomic performance of eleven maize hybrids in the southeast of the State of Goias, Brazil. The experiment was carried out in the field during the 2013/2014 crop (spring-summer), in a dystrophic Red Latosol, under the soil and climatic conditions of the Cerrado in the southeast of Goias. The experimental design was of randomised blocks, with 11 treatments represented by the maize hybrids, with four replications. Evaluated were the final plant stand, final number of ears, morphological characteristics (plant height, ear height and stem diameter), production components (ear length, number of rows per ear, number of grains per row, number of grains per ear and 100 grain weight) and grain yield. The final plant stand and number of ears were similar between hybrids. The commercial maize hybrids showed great variation in agronomic performance for the southeast of Goias. For plant and ear height, the hybrids LG6036 and 20A55 had the greatest plant heights, and the hybrid LG6036 had the greatest ear height. For stem diameter, the plants of the Feroz, BX1293, LG6036, 20A55, Maximus and P3862 hybrids had thick stalks. With evaluation of the produc...

A B S T R A C THigh corn yields in high-tech systems are related to proper crop implementation. This study aimed to evaluate the effects of variability in the distribution of seeds along the planting row on corn production components. The study was conducted under Cerrado conditions in the municipality of Urutaí, GO, Brazil. The experimental design was randomized blocks in a 5 x 2 factorial scheme, with four replicates. The effects of five coefficients of variation (0, 20, 40, 60 and 80%) of non-uniformity in the spatial distribution of seeds along the planting row of two corn hybrids (P30F53HX and P3646HX) were evaluated. No interactions were observed for the analysed corn variables. However, as the non-uniformity in seed distribution along the planting row increased, stalk diameter, hundred-grain weight, number of rows per ear, number of kernels per row and ear length decreased. Additionally, linear reductions were observed in corn grain yield with the increase in the coefficient of variation of the spatial distribution of seeds along the planting row. Between the hybrids, the 30F53HX showed higher hundred-grain weight.

Resumo: A decomposição da palhada concomitante à liberação de nutrientes favorece o feijoeiro em sucessão desde que a implantação ocorra imediatamente após o manejo das plantas de cobertura. Assim, objetivou-se com esta pesquisa quantificar a produção de fitomassa seca e a decomposição da palhada de guandu-anão e de milheto, bem como seus efeitos nos componentes da produção e produtividade do feijoeiro (Phaseolus vulgaris L.). O experimento foi conduzido em um Latossolo Vermelho distrófico, no sistema convencional de preparo do solo. O delineamento experimental foi o de blocos casualizados, com quatro repetições, em esquema de parcelas subdivididas. As duas parcelas foram constituídas pelo cultivo do feijoeiro em sucessão aos cultivos de guandu-anão e milheto; e nas subparcelas, 7 épocas de avaliação, sendo: 10; 20; 30; 40; 50; 60 e 70 dias após corte (DAC) das seguintes variáveis: fitomassa seca e taxas de decomposição da palhada do guandu-anão e do milheto, sob cultivo do feijoeiro. No feijoeiro, cultivar IPR Colibri, as variáveis avaliadas foram: número de vagens por planta, número de grãos por vagem e massa de 100 grãos e produtividade. O guandu-anão e o milheto apresentaram produtividade de fitomassa seca semelhante. Após o cultivo do feijoeiro irrigado, aos 70 DAC, a palhada remanescente das plantas de cobertura foi superior a 60%. A palhada do guandu-anão demonstrou maior taxa de decomposição, enquanto que a do milheto foi mais persistente na superfície do solo. O feijoeiro cv. IPR Colibri apresentou desempenho agronômico semelhante nas sucessões com guandu-anão ou milheto, cujas palhadas se mostraram benéficas à cultura. Palavras-chave: Cajanus cajan L. Pennisetum glaucum L. "Litter bags." Plantas de cobertura. Phaseolus vulgaris L.Abstract: The decomposition of concomitant nutrient release from straw favor the bean in succession since deployed immediately after the management of cover crops. This research was carried out in order to quantify the dry phytomass production and decomposition of straws dwarf pigeon pea and millet, and their effects on the production components and grain yield of common bean. The experiment was conducted on an Oxisol in the conventional tillage system. The experimental design was of randomised blocks with four replications in a scheme of split lots. The two lots comprised the common bean crop, in succession to crops of dwarf pigeon pea and millet; the sub-lots comprised randomised in time, 7 evaluation periods, 10, 20, 30, 40, 50, 60 and 70 days after cutting (DAC). The productivity of dry phytomass and decomposition of straws was evaluated in the cover crops in common bean crop, and the number of pods per plant, number of grains per pod, 100-grain weight and grain yield in the common bean plants. The dwarf pigeon pea and the millet showed similar productivity for dry phytomass. After irrigated common bean crop, the 70 DAC, remaining straw from cover crops was 60%. The dwarf pigeon pea straws showed higher rate of decomposition, while millet residue was more persistent on th...

Susceptibilidade diferencial ao herbicida glyphosate e capacidade de rebrota de populações de capim-amargoso 1Dentre as plantas daninhas com comprovada resistência ao glyphosate, destaca-se o capim-amargoso (Digitaria insularis). O objetivo deste trabalho foi demonstrar que a susceptibilidade de diferentes populações de D. insularis ao glyphosate é consequência do histórico de controle químico adotado nas áreas agrícolas. Sete populações de capimamargoso, provenientes da região produtora de grãos, no sudeste de Goiás (três de Silvânia, duas de Gameleira de Goiás, uma de Pires do Rio e uma de Orizona), foram analisadas por meio da curva dose-resposta. Estudaram-se a susceptibilidade diferencial e a capacidade de rebrota das populações submetidas a diferentes doses de glyphosate (0; 0,11; 0,21; 0,42; 0,84; 1,68; 3,36; 6,72; 13,44 e 26,88 kg ha -1 i.a.). Além disso, elaborou-se um dendrograma de susceptibilidade ao herbicida, por meio da análise de agrupamento hierárquico UPGMA. As populações de capim-amargoso, manejadas há cinco anos com glyphosate associado a herbicidas inibidores da ACCase, são susceptíveis ao glyphosate; quando manejadas de forma intensiva, unicamente com glyphosate, apresentaram-se menos susceptíveis. O mesmo resultado foi observado com a análise de agrupamento, que indicou a formação de dois grupos, o primeiro composto por populações oriundas de Silvânia, Orizona, Pires do Rio, Gameleira de Goiás, consideradas susceptíveis ao glyphosate e, o segundo grupo, composto por populações oriundas de Gameleira de Goiás e Silvânia, as menos susceptíveis. As populações de capim-amargoso menos sensíveis apresentam maior capacidade de rebrota da parte aérea, após tratadas com doses elevadas de glyphosate. Differential susceptibility to glyphosate herbicide and re-growth capacity of different populations of sourgrassAmong the proven weeds proven resistance to glyphosate, the sourgrass (Digitaria insularis) stands out. In this sense, this work was developed with the objective of demonstrating that the susceptibility of different populations of D. insularis to glyphosate is a consequence of the chemical control history adopted in the agricultural areas. Seven populations of sourgrass from the southeastern region of Goiás (three from Silvânia, two from Gameleira de Goiás, one from Pires do Rio and one from Orizona) were analyzed using the dose-response curve and the differential susceptibility and the re-growth capacity of the sourgrass populations submitted to different doses of glyphosate (0, 0.11, 0.21, 0.42, 0.84, 1.68, 3.36, 6.72, 44 and 26.88 kg and ha -1 ). In addition, a herbicide susceptibility dendrogram was elaborated through UPGMA hierarchical cluster analysis. Sourgrass populations, managed five years ago with glyphosate associated with ACCase inhibitor herbicides, are susceptible to glyphosate; when they were treated intensively with glyphosate alone, were less susceptible. The same result was observed for cluster analysis, which indicated the formation of two groups, This is an open access arti...

No abstract

Background: This manuscript presents data of screening and dose-response curves of a goosegrass population from Primavera do Leste, MT, Brazil, which results in the first official report of multiple resistance of goosegrass to ACCase and EPSPs inhibiting herbicides in Brazil. Objective: Evaluate the control of a goosegrass population from Primavera do Leste, MT, Brazil, suspected of resistance to the glyphosate, fenoxapropp-ethyl, and haloxyfop-methyl herbicides, using dose-response curves. Methods: The study was carried out in two stages, the first in Brasília, DF, Brazil, and the second in Piracicaba, SP, Brazil. The first stage consisted in the initial evaluation and identification of resistance, which was confirmed in the second. In the first stage, the herbicides glyphosate, fenoxapropp-ethyl, and haloxyfop-methyl were applied to susceptible and resistant goosegrass populations (F1 and F2 generations) with plants with 2 and 3 tillers, using nine rates (0, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 times the recommended rate). In the second stage, the herbicides were applied to susceptible and resistant populations with plants with 4 leaves, using 12 rates (0, 0.03125, 0.0625, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 times the recommended rate). Results: The high sensitivity of susceptible plants combined with the high resistance level of resistant ones resulted in high resistance factors for fenoxaprop-p-ethyl and haloxyfop-methyl, with values greater than 27.8. The resistance factor for glyphosate ranged from 3.3 to 11, depending on growth stage at application time. Conclusions:The goosegrass population from Primavera do Leste, MT, Brazil, presented resistance to EPSPs (glyphosate) and ACCase (haloxyfopmethyl and fenoxaprop-ethyl) inhibiting herbicides.