Felipe Paolinelli de Carvalho

Acúmulo e partição de nutrientes de cultivares de milho em competição com plantas daninhas

Competition for nutrients varies with the species involved and can determine the success of plants grown at the expense of weeds. The objective of this study was to evaluate the effects of competition among three cultivars of maize (hybrid DKB 390 YG, variety AL 25, and hybrid SHS 4080) and six weed species (Bidens pilosa, Cenchrus echinatus, Brachiaria brizantha, Commelina benghalensis, Brachiaria plantaginea and Euphorbia heterophylla) on the accumulation and allocation of nutrients by plants, also determining the potential of these species in nutrient cycling. The experiment was conducted under controlled temperature and humidity, in a randomized block design with four replications. The period of coexistence between corn and weeds was 60 days after corn emergence. The maize cultivars showed reduced ability to accumulate nutrients when in competition. The relative content of weed species was severely reduced as a result ofthis coexistence. The ability to accumulate nutrients apparently does not represent a competitive advantage forthe infesting species. Cultivar AL 25 was the species that tolerated the competition the least and B. brizantha and C. benghalensis showed greater competitive ability. B. brizantha and C. echinatus, free from coexistence with the corn, had high potential for nutrient cycling.

Deriva simulada do glyphosate em cultivares de café Acaiá e Catucaí

This study aimed to evaluate the effects of simulated glyphosate drift on the growth of two cultivars with distinct growing patterns. The experiment was arranged in a randomized block design, with four repetitions, and the treatments were distributed in a factorial scheme 2x5, with two cultivars in the first factor and the glyphosate subdoses (0, 57.6; 115.2; 230.4 and 460.8 g ha‑1) in the second factor. On the day glyphosate was applied and at 45 and 120 days after application (DAA), height, leaf area, stem diameter, and number of plagiotropic branches and leaves were evaluated; at 10, 45 and 120 DAA, plant intoxication symptoms were visually evaluated and at 120 DAA, dry mass accumulation of the stem, leaves, and roots was evaluated. The intoxication symptoms of the coffee plants caused by glyphosate were characterized by chlorosis and leaf narrowing in the two cultivars studied. However, more severe symptoms were verified in the Acaia cultivars from 10 DAA on, such as necrosis of younger leaves in the median part of the plant. It was concluded that Acaia cultivar is less tolerant to glyphosate than Catucai cultivar, since it showed lower growth when submitted to herbicide treatment, i.e., tolerance can vary between cultivars with distinct growing patterns.

Aspectos fisiológicos da mandioca após a aplicação dos herbicidas fluazifop-p-butil e fomesafen

Physiological responses of cassava to application of the herbicides fluazifop-p-butil and fomesafen Acredita-se que alguns herbicidas possam influenciar a eficiencia do uso da agua, pelo efeito negativo direto sobre fotossintese, transpiracao e condutância estomatica ou, indiretamente, pela reducao da taxa metabolica da planta. Diante disso, objetivou-se, neste trabalho, avaliar a influencia dos herbicidas fluazifop-p-butil e fomesafen, isolados e em mistura, sobre as caracteristic as associadas ao uso da agua, por cultivares de mandioca, visando a selecionar aqueles mais tolerantes aos referidos herbicidas. Realizou-se experimento, em casa de vegetacao no delineamento de blocos casualizados, com quatro repeticoes. Adotou-se arranjo fatorial em esquema 5x7, constituido pela combinacao de cinco cultivares de mandioca: Cacau-UFV, Platina, Coqueiro, Coimbra e IAC-12, com quatro doses da mistura comercial dos herbicidas fomesafen + fluazifop-p-butil (0,5; 0,75; 1,0 e 1,5 L ha -1 ), alem da dose comercial recomendada de cada principio ativo isolado e uma testemunha sem herbicida. As caracteristicas avaliadas foram: condutância estomatica (gs), taxa de transpiracao ( E) e eficiencia do uso da agua ( EUA). De maneira geral, a E, gs e EUA foram afetadas pela aplicacao da mistura dos herbicidas. Os cultivares de mandioca apresentam diferentes niveis de sensibi- lidade ao fluazifop-p-butil + fomesafen, sendo que o cultivar Platina e o mais tolerante a aplicacao da mistura. O fluazifop-p-butil mostrou-se seletivo para a cultura e o fomasafen causou efeitos negativos na fisiologia da mandioca. Palavras-chave: transpiracao, condutância estomatica, controle quimico, Manihot esculenta.

The Allelopathic Effect of Eucalyptus Leaf Extract on Grass Forage Seed

This study aimed to evaluate the allelopathic effect of various concentrations of an aqueous extract of eucalyptus leaves on Urochloa decumbens and Panicum maximum seeds. The extract was prepared from Eucalyptus urograndis leaves that were milled and mixed with distilled water in a 1:9 milled leaves: water ratio to obtain an extract with a defined concentration of 100%. In addition, dilutions of 50%, 25% and 12.5% were prepared, and a 0% dilution was used as a control. The experiment followed a completely randomized design, with four replicates, each of 50 seeds of U. decumbens and 50 seeds of P. maximum, arranged on filter paper moistened with each concentration of extract in a Gerbox plastic box. The results demonstrated the allelopathic potential of E. urograndis aqueous extracts applied to the seeds of U. decumbens and P. maximum. The 50% and 100% concentrations of leaf extract most strongly inhibited the germination, vigor and seedling growth of U. decumbens and P. maximum. The germination speed index and the root length were the characteristics that were most affected by the potentially allelopathic substances contained in the eucalyptus extracts at all concentrations.

INFESTAÇÃO DE Mimosa gemmulata Barneby EM ÁREAS ENTRE TALHÕES DE EUCALIPTO DE CERRADO EM SUCESSÃO SECUNDÁRIA

Extensive eucalyptus plantations are observed in Brazil, especially in Minas Gerais State, which has this culture as a profitable activity in marginal areas. Trying to reduce effects of forest harvest on native vegetation and selection of some species as angiquinho (Mimosa gemmulata Barneby), this study aimed to evaluate secondary succession in eucalyptus stands of different ages and managements after exploration, the floristic composition and horizontal and vertical structure of shrub-arboreal was compared with fragments of Cerrado. The work was conducted in a representative area of this biome on Vale do Jequitinhonha. Phytosociological parameters and the indexes of diversity and similarity were calculated at the environments with initial and advanced recuperation, with and without eucalyptus. Control environment was Cerrado restricted sense. There were samples of 42 families, 99 genera, 150 species and 1268 individuals. Floristic composition and phytosociological parameters indicated existence of families, genera and species of great relevance, typical of Cerrado. Removing eucalyptus at initial regeneration did not affect diversity. However, removing at advanced stage provided diversity reduction, permitting colonization by pioneer species as Mimosa gemmulata Barneby. On the other hand, maintaining eucalyptus at advanced recuperation resulted in higher values of diversity and other natural attributes. Results will subsidize management practices to be adopted in similar areas, aiming biological diversity maintenance in sites used in biodiversity corridor reestablishment among cultivated areas.

Glyphosate drift affects arbuscular mycorrhizal association in coffee

Mycorrhizal association promotes better survival and nutrition of colonized seedling on field, and consequently, increasing of productivity. However, the weed management can interfere on this association, due to incorrect use of glyphosate. This work has assessed the effects of glyphosate drift on the growth and nutrition of arabica coffee plants (Catuai Vermelho - IAC 99) colonized with arbuscular mycorrhizal fungi (AMF). The experiment was conducted in 2 x 5 factorial scheme, and included inoculated and non-inoculated plants, and five glyphosate subdoses (0.0, 57.6, 115.2, 230.4, and 460.8 g ha-1 of glyphosate), in randomized blocks with five replication. The inoculation was carried during the greenhouse phase of seedlings production with a mixture of Rhizophagus clarus and Gigaspora margarita, and after to transplanting, when the plants had seven pairs of leaves, glyphosate subdoses were applied. The product caused intoxication in up to 60% of non-inoculated and 45% on inoculated plants, when the highest dose of 460.8 g a.e. ha-1 was applied. A negative effect was noted on the growth and phosphorus content of coffee plants, this effect increased depending on glyphosate subdose, but regardless of inoculation. Glyphosate drift reduces the growth and nutrition of plants colonized by species of AMF and native fungi, negatively affecting root colonization of plants treated.

Microbial activity of soil with sulfentrazone associated with phytoremediator species and inoculation with a bacterial consortium

Phytostimulation plays a key role in the process of rhizodegradation of herbicides in soil. Additionally, bio-enhancement associated with phytoremediation may increase the efficiency of the decontamination process of soils with herbicides. Therefore, the objective of this study was to evaluate the biomass and microbial activity of soil contaminated with sulfentrazone and cultivated with phytoremediator species plus a bacterial consortium. The experiment was conducted in a greenhouse, carried out with a 2 × 4 × 4 completely randomized factorial design with 4 replications. The first factor consisted of the presence or absence of bio-enhancement with a bacterial consortium composed of Pseudomonas bacteria; the second factor consisted of a monoculture or mixed cultivation of 2 phytoremediator species Canavalia ensiformis and Helianthus annuus, besides the absence of cultivation; the third factor was made up by the bio-remediation time (25, 45, 65, and 85 days after thinning). Uncultivated soils displayed low values of microbial biomass carbon and microbial quotient as well as high values of metabolic quotient throughout the bio-remediation time, indicating the importance of cultivating phytoremediator species for the stimulation of soil microbiota. Bio-enhancement with the bacterial consortium, in general, promoted an increase in the microbial biomass and activity of soil contaminated with sulfentrazone. In the presence of the bacterial consortium, Canavalia ensiformis stimulated a greater activity of associated microbiota and supported a higher microbial biomass. Phytoremediation associated with microbial bio-enhancement are thus promising techniques for the bio-remediation for soils contaminated with sulfentrazone. This technique enhances the biomass and activity of soil microorganisms.

Crescimento de mudas de cafeeiro inoculadas com fungos micorrízicos arbusculares - DOI:10.5039/agraria.v9i4a3938

Propos-se, neste trabalho, analisar o crescimento de mudas de cafeeiro inoculadas com fungos micorrizicos, por meio da analise de crescimento de plantas. O delineamento adotado foi inteiramente casualizado, em esquema fatorial 2x6, sendo mudas inoculadas e nao inoculadas e seis epocas de avaliacao, com seis repeticoes. Utilizaram-se sementes de Catuai Vermelho IAC 99, desinfestadas e geminadas em areia autoclavada. Apos 75 dias, no ato da repicagem, metade das mudas foi inoculada aplicando-se esporos das especies Glomus clarum e Gigaspora margarita . Na epoca da inoculacao (0) e aos 30, 60, 90, 120 e 150 dias foram mensuradas a altura e a area foliar, alem de posterior determinacao de massa seca foliar e total. Os dados foram extrapolados para determinacao de medidas nao lineares para analise de crescimento. De modo geral, as plantas inoculadas apresentaram efeito negativo no inicio do crescimento mas ao final do periodo experimental possuiam caracteristicas de crescimento superiores as mudas nao inoculadas. A analise de crescimento possibilitou uma compreensao melhor da associacao, alem de constatar que, apesar do maior investimento na morfologia para captacao de energia, nao ocorreu aumento da taxa de assimilacao liquida podendo-se considerar que, inicialmente, os fungos representaram dreno de assimilados mas no final as mudas inoculadas apresentaram crescimento superior. Conclui-se que, inicialmente, a associacao seja considerada dreno de assimilados da planta que ainda nao possuem area foliar para manutencao da associacao e sofrem queda da taxa fotossintetica liquida. Este efeito se extingue e resulta em beneficio para as mudas, no final do periodo de producao.