ResumoO capim camalote (Rottboellia exaltata L.f) tem sido relatado como uma importante planta daninha, podendo causar prejuízos econômicos e dificuldades no manejo em diversas culturas agrícolas. Foi determinado a emergência de plântulas de R. exaltata, em diferentes profundidades de semeadura (0, 0,5, 1, 5, 10, 12, 15 e 20 cm), em solos com diferentes texturas e valores de pH. Também avaliou-se os efeitos de diferentes coberturas de solo provenientes dede Mucuna aterrima, Canavalia ensiformis e Crotalaria spectabilis, dispostas na superfície ou incorporadas, sobre a emergência e biomassa da planta daninha. No solo arenoso, a maior emergência do capim camalote ocorreu aos 5,0 cm de profundidade. No solo argiloso o padrão de emergência foi semelhante, entretanto, observou-se uma redução mais acentuada na emergência com o aumento na profundidade de semeadura. A maior taxa de germinação foi observada no solo com pH variando de 6,8 à 7,0, verificando-se menor germinação em solo não corrigido, com pH de 5,3. Os manejos de palha mais efetivos na supressão de R. exaltata foram 10 t ha -1 de C. spectabilis posicionada sobre o solo argiloso e a incorporada no solo arenoso, 5 t ha -1 de C. ensiformis incorporada ao solo arenoso. Palavras-chave: Adubo verde, supressão, biologia, capim camalote AbstractThe grass camalote (Rottboellia exaltata Lf) has been reported as an important weed, may cause economic losses and difficulties in management in several crops. It was determined the seedling emergence of R. exaltata, at different depths of sowing (0, 0.5, 1, 5, 10, 12, 15 and 20 cm) in soils with different textures and pH values. It also assessed the effects of different amounts of straw Mucuna aterrima, Canavalia ensiformis and Crotalaria spectabilis, arranged on the surface or incorporated into the soil on the emergence and weed biomass. In sandy soil, the higher emergence of R. exaltata was 5.0 cm deep. In clay soil the pattern of emergence was similar; however, there was a greater reduction in emergency with the increase in sowing depth. The highest germination rate was observed in soil with pH ranging from 6.8 to 7.0, verifying lower germination in soil not corrected, at pH 5.3.The management of straw more effective in suppressing R. exaltata were 10 t ha -1 of C. spectabilis straw positioned on clayey soil and incorporated on the sandy soil, 5 t ha -1 of C. spectabilis incorporated on the sandy soil.

RESUMO -O objetivo deste trabalho foi avaliar a lixiviação de saflufenacil em Latossolo Vermelho-Amarelo (textura média, pH 5,6) e Latossolo Vermelho distrófico (textura argilosa, pH 5,2 e pH 6,0), assim como os efeitos de períodos de seca no residual desse herbicida. A lixiviação de saflufenacil (0,10 g i.a ha -1 ) e, adicionalmente, a lixiviação de diuron + hexazinone (1.170 + 330 g i.a. ha -1 ) foram avaliadas sob simulação de chuva (40 mm). O herbicida saflufenacil aplicado em solo argiloso com pH 6,0 apresentou lixiviação até a profundidade de 25 cm, porém ela foi mais pronunciada na faixa de 15 a 20 cm. Quando o herbicida foi aplicado no mesmo solo, mas com pH 5,2, houve lixiviação até a profundidade de 15 cm. Em solo de textura média, a lixiviação foi elevada até a profundidade de 25 cm. Para diuron+hexazinone, no solo argiloso, independentemente do pH, houve lixiviação até 25 cm de profundidade. Todavia, em solo de textura média a lixiviação ocorreu até 40 cm de profundidade. Em relação ao efeito residual do saflufenacil após períodos de seca (0, 15, 30, 45, 60 e 90 dias) em um Latossolo Vermelho distrófico (textura argilosa), foi verificado efeito fitotóxico no bioindicador maior ou igual a 80% até os 28 dias de seca.Palavras-chave: calagem, comportamento, herbicida, solo.ABSTRACT -This work aimed to evaluate saflufenacil leaching in Red Yellow Latosol (medium texture, pH 5.6) and Dystrophic Red Latosol (clay texture, pH 5.2 and 6.0) and to evaluate the effect of drought on the residual herbicide. The leaching of saflufenacil (0.10 g a.i. ha -1 ) and hexazinone + diuron (1,170 + 330 g a.i. ha -1 ) was evaluated under simulated rainfall of 40 mm. Saflufenacil in clay soil with a pH of 6.0, showed leaching at a depth of 25 cm, but was more pronounced in the range between 15 and 20 cm. When the herbicide was applied in the same soil with pH 5.2, leaching occurred at depths of 10 to 15 cm. In medium texture, soil leaching occurs up to a depth of 25 cm. In the case of diuron + hexazinone, leaching can be seen in clay soil, regardless of pH, up to a depth of 25 cm, up to a depth of 40 cm in medium soil. Regarding the residual effect of saflufenacil after periods of drought (0, 15, 30, 45, 60 and 90 days) in (clay) Latosol, a phytotoxic effect on the bio-indicator, greater than or equal to 80%, was observed at 28 days of drought.

-This study aimed to determine the selectivity of herbicides applied in pre-and post-emergence for alfalfa crops. Three separate experiments were carried out under greenhouse conditions. The first experiment was arranged in a completely randomized design with three replications in a 4 x 11 + 1 factorial scheme , with eleven herbicides (bentazon, chlorimuron-ethyl, fomesafen, fluazifop-p-butyl, saflufenacil, imazethapyr, clethodim, nicosulfuron, imazaquin, haloxyfop-methyl and MSMA), four doses of each herbicide (0.5 D, 0.75 D, 1.0 D and 1.25 D, where D = recommended dose), plus an untreated control. The products were applied to alfalfa plants at the stage of 4 to 5 leaf pairs. In the second experiment, the effect of pre-emergent herbicides on early alfalfa development was observed through a completely randomized design with five replications in a 3 x 4 x 2 factorial scheme, with three herbicides (hexazinone, atrazine + simazine, S-metolachlor), four doses (0.5 D, 0.75 D, 1.0 D and 1.25 D), and two types of soil texture (loamy and clay soil), plus an untreated control. The third experiment evaluated the action of atrazine, 2,550 g ha -1 ; clomazone -600 g ha -1 ; diclosulam -25 g ha -1 ; diuron+hexazinone -936 + 264 g ha -1 and diuron+hexazinone +sulfometuron -1,386 + 391 + 33.35 g ha -1 on alfalfa sown at different times after herbicide application. The effects of the treatments on alfalfa were evaluated according to visual phytotoxicity symptoms, plant height, and biomass of roots and shoots. Among the herbicides applied at post-emergence, imazethapyr, clethodim, haloxyfop-p-methyl and MSMA were selective for alfalfa, while among those applied at pre-emergence, none were selective, regardless of soil texture. The results of the third experiment showed that the herbicides diclosulam, hexazinone + diuron and atrazine caused less toxicity in alfalfa plants.Keywords: phytotoxicity, Medicago sativa, residual period. (bentazon, chlorimuron-ethyl, fomesafen, fluazifop-p-butil, saflufenacil, imazethapyr, cletodim, nicosulfuron, imazaquim, haloxyfop-methyl e MSMA), quatro doses de cada herbicida (0,5D, 0,75D, 1,0D e 1,25D, sendo D = dose comercial) RESUMO -O objetivo desta pesquisa foi verificar a seletividade de herbicidas aplicados em pré e pós-emergência para a cultura da alfafa. Esta pesquisa foi composta por três experimentos distintos, realizados em casa de vegetação. O primeiro experimento foi conduzido em delineamento experimental inteiramente casualizado com três repetições, em esquema fatorial 11 x 4+1, sendo onze herbicidas

Weed interference is one of the main factors responsible for reducing the productivity of the peanut crop. Among weed control methods, the chemical is considered one of the main tools, however, the herbicides registered for this crop are scarce. The objective of this study was to evaluate the selectivity of herbicides applied in post-emergence in Runner peanut cultivars. For this, an experiment was performed in an 11x5 factorial scheme, meaning 10 herbicides plus one control (without herbicide) and five peanut cultivars, with four replicates. Visual evaluations of phytointoxication were carried out at 7, 14 and 21 days after application of the herbicides. At the end of the experiment, was determined the dry mass of aboveground and root parts. ) have potential to be used for all the peanut cultivars studied. Herbicides hexazinone (2.50 kg ha-1), amicarbazone (2.00 kg ha ) must not be indicated, at these doses, for post-emergence spraying in the evaluated cultivars. The genotypes do not react equally to certain products, therefore, there is a need for further studies the at field conditions to attest the responses obtained in the present study and verify that the yield potential is not affected.

Sugarcane is one of the most important crops planted in Brazil in that the presence of weeds in the fields has promoted significant yield reduction. The objective of this work was to evaluate the differential growth response of two sugarcane varieties cropped in the ‘Plene’ system as a function of the coexistence with different weed species. Treatments consisted of the coexistence of Bidens pilosa plus Ipomoea quamoclit, Ipomoea hederifolia, Amaranthus viridis, Urochloa plantaginea, Panicum maximum, and Digitaria horizontalis with two sugarcane varieties (RB92579 and SP80-1842) cropped in the ‘Plene’ system, in addition to a control without weeds. The design was completely randomized with three replicates. Dry matter accumulation of weeds was dependent of the weed species and the sugarcane variety whose coexistence was kept. The behavior of development in terms of plant height, number of green leaves, leaf area, and dry mass of stems, roots and leaves was dependent on the sugarcane variety and on the weed species whose coexistence was kept. The weed U. plantaginea showed the greatest potential to interfere with the growth of both sugarcane varieties planted in the ‘Plene’ system. Panicum maximum and D. horizontalis are also potential competitors, while B. pilosa, I. quamoclit, I. hederifolia, and A. viridis are less competitive. The sugarcane variety RB92579 is less susceptible to weed interference than SP80-1842 when planted in the ‘Plene’ system.

Sugarcane cultivars that are currently planted are the result of genetic improvement focused on increased crop yield. However, this selection and genetic alteration reduced the competitive potential of sugarcane, as well as its allelopathic capabilities. Many members of the Poaceae family are highly allelopathic. Thus, the objective of this study was to characterize the allelopathic potential of two sugarcane cultivars (CTC 2 and IAC 91109) by bioassayguided fractionation, isolation, and identification of significant phytotoxins, including those that are lipophilic. For both leaves and roots, alpha-linolenic and linoleic acid were found to be the most phytotoxic compounds found with this approach. Both compounds were phytotoxic when applied in soil and caused light-independent cellular leakage of treated cucumber cotyledon discs. We conclude that some of the phytotoxic effects of sugarcane residues in soil are due to the combined action of alpha-linolenic and linoleic acid.

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A new sugarcane planting system, using pre-sprouted seedlings (PSS) to replace sugarcane stem fragments, substantiates the hypothesis of this study that there might be seedling toxicity by herbicides that are sprayed at pre-emergence in traditional systems. Therefore, the aim of this paper was to study the selectivity of herbicides applied at pre-planting in PSS. A field experiment was conducted in a randomized block design, using seven treatments and four replications. Herbicides were sprayed and, 24 hours later, the seedlings were planted. At the beggining of seedling development, all herbicide treatments showed phytotoxicity, but the symptoms decreased with the growth and development of seedlings, with no difference in height, stem diameter, number of leaves, quantum efficiency of PSII (Fv/Fm) and dry matter of plants between treatments. There was also no significant difference in the yield and technological characteristics of stems. All herbicides used were selective to sugarcane seedlings when applied at pre-planting in the PSS system.