ABSTRACT Some native species of the Cerrado have great ecological and economic potential. An alternative that aims to contribute to the good performance of post-planting plants is the incorporation of biochar into the soil. The objective of this work was to evaluate the effect of filter cake biochar as a soil conditioner and its influence on the growth and physiology of macaúba, araçá and cajuzinho do cerrado. The experiments were set up at Fazenda Hamilton de Abreu Navarro, Federal University of Minas Gerais, where the effect of four doses of filter cake biochar (1%, 2%, 4% and 8% v/v) and two treatments were evaluated. control: one with soil correction (7.5 g of GEOX) and mineral fertilization (380 g NPK 4:14:8 per plant) and the other without fertilization. To monitor the performance of the seedlings, evaluations were carried out at 30, 60 and 120 days after transplanting, the physiological parameters (photosynthesis, transpiration, stomatal conductance, CO2 consumed, internal carbon and electron transport rate), and morphological parameters (height and diameter), at 30, 60, 90 and 120 days after transplanting. At 120 days, the production of shoot, root and total dry biomass was evaluated. For macaúba, the application of biochar, at a dose of 2%, favored its photosynthesis. As for araçá, at 30 days after transplanting, the treatment without fertilization was better for most variables, however the treatments with biochar also had satisfactory results. The cajuzinho from the cerrado also responded positively to the application of biochar at all doses. The physiological and morphological variables responded well to treatments without fertilization and with application of biochar to the soil. Therefore, filter cake biochar can be indicated in the planting of the studied species, as well as the non-application of corrective and mineral fertilizer.

RESUMO O objetivo deste trabalho foi avaliar o efeito do biochar de torta de filtro como condicionador de solo e sua influência no crescimento e na fisiologia de macaúba, araçá e cajuzinho do cerrado. Os experimentos foram montados na Fazenda Hamilton de Abreu Navarro da UFMG, onde foram avaliados o efeito de quatro doses de biochar de torta de filtro (1%, 2%, 4% e 8% v/v) e dois tratamentos controle: um com correção do solo e adubação mineral, e o outro sem adubação. Para acompanhar o desempenho das mudas, foram realizadas avaliações aos 30, 60 e 120 dias após o transplantio, dos parâmetros fisiológicos (fotossíntese, transpiração, condutância estomática, CO2 consumido, carbono interno e taxa de transporte de elétrons), e morfológicos (altura e diâmetro), aos 30, 60, 90 e 120 dias após o transplantio. Aos 120 dias, avaliou-se a produção de biomassa seca da parte aérea, de raízes e total. Para a macaúba, a aplicação de biochar, na dose de 2%, favoreceu a sua fotossíntese. Já para o araçá, aos 30 dias após o transplantio, o tratamento sem adubação foi melhor para a maioria das variáveis, entretanto os tratamentos com biochar também tiveram resultados satisfatórios. O cajuzinho do cerrado também respondeu positivamente à aplicação de biochar em todas as doses. As variáveis fisiológicas e morfológicas responderam bem aos tratamentos sem adubação e com aplicação de biochar ao solo. Portanto, o biochar de torta de filtro pode ser indicado no plantio das espécies estudadas, assim como a não aplicação de corretivo e fertilizante mineral.

Abstract Herbicides can impact non-target metabolic pathways in natural enemies and lead to the reduction of these populations in the field. Behavioral characteristics, morphology and histology of reproductive structures and reproduction of females of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) were evaluated under the effect of the herbicides atrazine, nicosulfuron and the mixture of both. The number of mature oocytes per ovary was lower in females exposed to the herbicides atrazine, nicosulfuron and the mixture of both. Herbicides did not affect the longevity and mortality of P. nigrispinus, therefore, they are selective for this predator. On the other hand, herbicides can cause sublethal effects by affecting the reproduction of predators.

RESUMO As adaptações das plantas daninhas às diferentes condições ambientais contribuem para seu sucesso no estabelecimento de diferentes agroecossistemas. Um trabalho de casa de vegetação e laboratório foi realizado para avaliar os efeitos de diferentes níveis de umidade do solo nas características anatômicas de duas espécies de plantas daninhas. Os tratamentos foram arranjados em esquema fatorial 2 x 5, sendo o primeiro fator correspondente as espécies de plantas daninhas (Amaranthus hybridus e Brachiaria brizantha), e o segundo aos níveis de umidade no solo em que foram cultivadas (100%, 80%, 74%, 67% e 60% da capacidade de campo). Aos 55 dias após a emergência das plantas daninhas o material foi coletado para as avaliações anatômicas. O déficit hídrico afetou de maneira diferenciada as duas plantas daninhas, provocando alterações tanto na espessura dos tecidos avaliados quanto nas suas proporções. Estas alterações podem estar relacionadas à forma como cada espécie tolera a deficiência de água. O A. hybridus teve espessamento de todos os tecidos da lâmina foliar, além da mudança na proporção desses tecidos, enquanto que a B. brizantha teve decréscimo na espessura dos tecidos da lâmina foliar e aumento na proporção de parênquima homogêneo e epiderme adaxial.

ABSTRACT Weed adaptations to different environments contribute to their success in establishing in different agroecosystems. A greenhouse and laboratory study was carried out to evaluate the effects of different levels of soil moisture on the anatomical characteristics of two weed species. The treatments were arranged in a 2 x 5 factorial design, with the first factor representing the weed species (Amaranthus hybridus and Brachiaria brizantha) and the second factor being the soil moisture levels in which they were grown (100%, 80%, 74%, 67%, and 60% of field capacity). At 55 days after weed emergence, the material for anatomical evaluations was collected. The water stress affected the two weed species differently, causing changes both in the thickness of the tissues evaluated and in their proportions. These changes seem to be related to how each species tolerates water stress. A. hybridus showed thickening of all leaf tissue and change in the proportion of these tissues, whereas B. brizantha showed a decrease in thickness of the leaf tissue and an increase in the proportion of adaxial epidermal and parenchymal tissues.

ABSTRACT The aim of this work was to determine the persistence of auxinic herbicides applied on tropical pasture and toxicity for succeeding crops. The herbicides were applied in an area of dystrophic red‒yellow latosol with pasture infested of weeds. At 40, 80, and 280 days after application of herbicide, the soil samples were collected at depths of 0 to 20 cm. Soil with residues of 2,4-D, 2,4-D + picloram, triclopyr, and a soil without herbicide application were analyzed with six replicates. Seven crops were cultivated in these soils: cucumber (Cucumis sativus L.), velvet bean [Mucuna pruriens (L.) DC.], pigeon pea [Cajanus cajan (L.) Millsp.], alfalfa (Medicago sativa L.), lablab bean [Lablab purpureus (L.) Sweet], corn (Zea mays L.), and sorghum [Sorghum bicolor (L.) Moench]. The plants of cucumber, pigeon pea, and alfalfa were the most susceptible to the auxinic herbicide residues. However, the lablab bean was the only one among the dicot evaluated that showed tolerance to the 2,4-D + picloram residual when cultivated in soils at 280 days after application of herbicide. Corn and sorghum showed lower chlorophyll content in soils with 2,4-D + picloram residual up to 80 days after application of herbicide.

ABSTRACT Soil pollution by heavy metals has increased worldwide and the search for plants that can be used to remediate polluted areas is an interesting alternative. The aim of this study was to evaluate the tolerance of tropical grasses to Ni and its availability for the Mehlich 1, DTPA, and USEPA 3051 and 3052 extraction methods in Ni-contaminated Oxisol. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs ‘Aruana’ and ‘Tanzania’, Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster ‘Xaraés’ and ‘Marandu’, and Urochloa decumbens (Stapf) R.D. Webster ‘Basilisk’ were grown for 90 d in a Typic Hapludox (Oxisol) after adding 20, 40, and 120 mg Ni kg-1 to the soil. Tropical grasses showed a positive response to the application of Ni doses. The order of decreasing tolerance of tropical grasses to Ni in the soil was: ‘Basilisk’ > ‘Xaraés’ > ‘Marandu’ > ‘Aruana’ > ‘Tanzania’ based on the critical toxicity dose. Nickel concentration and accumulation increased with increasing soil Ni doses in all the tropical grasses. Mehlich 1, DTPA, USEPA 3051, and USEPA 3052 Ni extraction methods in the soil are efficient to diagnose Ni availability in tropical grasses.

Intercropping is a common practice among farmers in tropical regions of the world and has persisted for years, not only for traditional reasons, but also for certain advantages that helped in its ecological adaptation. In regard to low income farmers with small areas for cultivation, more attention should be given to the cost of production and better land management. Thus, the aim of this work was to determine the best intercropping system of cassava with other crops. The experiment was conducted in an area belonging to the cassava (Manihot esculenta) producers of the Planalto de Minas district in Diamantina, Minas Gerais State, Brazil. The treatments comprised cassava intercropped with maize, beans and dwarf pigeon pea, as well as controls with and without weeding. The dry mass of shoots for maize, beans and dwarf-pigeon pea was affected by the presence of cassava. The productivity of cassava was dependent on cultivar and the intercropped crop. The highest harvest indexes were observed when cassava was intercropped with maize. In a general way, intercropping with maize and beans showed the highest area equivalence indexes and are recommended for the cassava crop.

Intercalar cultivos es una práctica común entre los agricultores de las regiones tropicales del mundo, que ha persistido a lo largo de los años, no sólo por tradición, sino también por la búsqueda de las ventajas que han ayudado en su adaptación ecológica.Cuando se considera a agricultores con pequeñas propiedades de cultivo y bajos ingresos económicos, se debe poner más atención en los costos de producción y en el mejor aprovechamiento de la tierra. Así pues, el objetivo de este trabajo fue determinar el mejor sistema de intercalar la yuca con otros cultivos. El experimento se realizó en un área perteneciente a los productores de yuca (Manihot esculenta) del distrito de Planalto de Minas en Diamantina, Minas Gerais, Brasil. Los tratamientos consistieron en intercalar la yuca con maíz, frijoles y guisantes enano paloma, así como los controles con y sin deshierbe. La producción de materia seca de rebrote de maíz, frijoles y guisantes enano paloma se vio afectada por la presencia de yuca. La productividad de la yuca depende de la variedad utilizada y de los cultivos intercalados. Los mayores índices de cosecha se observaron cuando la yuca se intercaló con maíz. De forma general se puede afirmar que el cultivo de la yuca, intercalado con maíz y frijol, muestra los índices de equivalencia área más altos, siendo el más recomendado para el cultivo de la yuca.

Competition between weeds and crops results in a lower availability of some resources to crop species, which causes deficiencies, such as water and nutritional deficiencies and low light quality or quantity. The aims of this study were to evaluate the effects of Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, cv. Xaraes (brachiaria) emergence times comparing with corn (Zea mays L.), in addition to the fertilization and application of different nicosulfuron and atrazine herbicides levels, on the physiological characteristics of intercropped species. The physiological characteristics Brachiaria plants that were treated with herbicides were negatively affected. The emergence time of Brachiaria plants in comparison with corn altered the physiological characteristics of both. The Brachiaria plants that emerged before corn presented higher photosynthetic and transpiration rates and reduced the intensity of these characteristics in corn. Thus, the Brachiaria plants that emerged before the corn crop presented a higher physiological efficiency, and they were more competitive than the weeds that emerged during other seasons.

O cultivo de Crambe abyssinica é recente no Brasil, existindo carência de informações sobre a sua gestão no que concerne à obtenção de elevada produtividade com o mínimo de risco económico e ambiental. O objetivo deste trabalho consistiu em avaliar o efeito dos herbicidas aplicados em doses crescentes, nas características fisiológicas de crambe. Os ensaios foram conduzidos em blocos casualizados com quatro repetições, no arranjo fatorial 5x4+1, onde o fator A representou cinco herbicidas e o fator B as doses testadas, além de uma testemunha sem aplicação. Foram avaliados os seguintes herbicidas e doses: fluazifope-p-butilo 0,25; 0,75; 1,0 e 1,5 L ha-1; cletodime 0,1; 0,3; 0,4 e 0,6 L ha-1; bentazona+imazamoxi 0,25; 0,75; 1,0 e 1,5 L ha-1; s-metolacloro 0,38; 1,13; 1,5 e 2,25 L ha-1; e setoxidime 0,25; 0,75; 1,0 e 1,5 L ha-1. As plantas de crambe apresentaram respostas diferenciadas à aplicação dos herbicidas. Todas as substâncias activas estudadas causa-ram efeitos negativos nas características fisiológicas da cultura; a mistura bentazona+imazamoxi promoveu a morte das plantas na dose de rótulo. Os herbicidas fluazifope-p-butilo, s-metolacloro e setoxidime provocaram redução drástica na taxa fotossintética nas maiores doses, e a eficiência no uso da água foi afetada por todos os herbicidas testados.

The cultivation of Crambe abyssinica is relatively recent in Brazil, and crop management data aiming to high yields with minimal economic and environmental risk is scarce. We aimed with this study to evaluate the effect of herbicides at varying doses on physiological traits. The experiment was installed in completely randomized blocks design with four replications, in factorial scheme 5x4+1, being factor A the five herbicides and factor B its doses, plus a control treatment with no herbicide. The following herbicides and doses were tested: fluazifop-p-butyl 0,25; 0,75; 1,0 e 1,5 L ha-1; clethodim 0,1; 0,3; 0,4 e 0,6 L ha-1; bentazon+imazamox 0,25; 0,75; 1,0 e 1,5 L ha-1; s-metolachlor 0,38; 1,13; 1,5 e 2,25 L ha-1; and sethoxydim 0,25; 0,75; 1,0 e 1,5 L ha-1. Crop plants presented differential behaviour to herbicides, causing all crop injuries at some degree; bentazon+imazamox promoted plant death at the label dose. Fluazifop-p-butyl, s-metolachlor and sethoxydim promoted great reductions in photosynthesis rate at the highest doses; on the other hand, water use efficiency was reduced by all herbicides.