Abstract Background There is little information on how different soil cover systems influence the residual effect of pre-emergent herbicides used in soybean cultivation in Brazil. Objective The objective was to compare the persistence of different pre-emergent herbicides in a Latosolic Dystrophic Red Nitosol soil in the presence or absence of black oat straw on the soil surface. Methods The herbicides used were chlorimuron-ethyl (40.0 g ai ha-1), diclosulam (70.1 g ai ha-1), flumioxazin (100.0 ai g ha-1) and saflufenacil (70.0 g ai ha-1). Soil samples were collected at 0, 5, 10, 15, 20, 32, 46 and 60 days after herbicide application. The bioavailability of the herbicides was evaluated in a greenhouse using cucumber plants as bioindicators. Results Rainfall was necessary for the herbicides to go through the straw layer and reach the soil. Using straw, the half-life times for chlorimuron, diclosulam, flumioxazin and saflufenacil were 42, 61, 49 and 26 days, while without straw, they were 23, 45, 8 and 10 days, respectively. Conclusion The presence of straw on the soil surface increased the persistence of herbicides in the soil.

RESUMO: Com o objetivo de avaliar a eficiência dos óleos essenciais de Citrus latifolia (limão taiti) e Cinnamomum zeylanicum (canela em casca) no controle dos fitopatógenos Penicillium sp. e Aspergillus sp. e na qualidade das sementes de feijão, foram conduzidos dois experimentos. No primeiro, avaliou-se o efeito dos óleos essenciais de C. latifolia e C. zeylanicum no desenvolvimento in vitro dos fungos Penicillium sp. e Aspergillus sp. e, no segundo, a influência dos óleos essenciais sobre a qualidade fisiológica e sanitária das sementes de feijão. As variáveis crescimento micelial, germinação de conídios e esporulação de Penicillium sp. e Aspergillus sp. foram aferidas no primeiro experimento, enquanto o teste de germinação de sementes, primeira contagem de germinação, índice de velocidade de germinação (IVG) e teste de sanidade de sementes de feijão foram aferidas no segundo. O óleo essencial (OE) de C. zeylanicum foi mais eficiente que C. latifolia no controle dos fungos Aspergillus sp. e Penicillium sp., mas diminuiu a qualidade fisiológica das sementes de feijão. A diversidade fúngica identificada no teste de sanidade de sementes foi composta por fungos dos gêneros Aspergillus, Penicillium, Cladosporium, Fusarium, Chaetomium e Rhizopus. Os resultados indicam o potencial do uso desses óleos essenciais no tratamento de sementes.

ABSTRACT: With the objective to evaluate the efficiency of essential oils of Citrus latifolia (Tahiti lemon) and Cinnamomum zeylanicum (cinnamon bark) in the control of plant pathogens Penicillium sp. and Aspergillus sp. and the quality of the bean seeds, two experiments were conducted. In the first one, the effect of essential oils of C. latifolia and C. zeylanicum was evaluated in vitro development of the fungi Penicillium sp. and Aspergillus sp. and, in the second one, the influence of essential oils on the physiological and sanitary quality of bean seeds. The variables mycelial growth, conidial germination and sporulation of Penicillium sp. and Aspergillus sp. were measured in the first experiment, while the seed germination test, first count of germination, germination speed index (GSI) and sanity test of bean seeds were measured in the second. The essential oil (EO) of C. zeylanicum was more efficient than C. latifolia in the control of Aspergillus sp. and Penicillium sp., but decreased the physiological quality of the beans seeds. The fungal diversity identified in the seed health test was composed by fungi of the genera Aspergillus, Penicillium, Cladosporium, Fusarium, Chaetomium and Rhizopus. The results indicate the potential of the use of these EOs in the seeds treatment.

Resumo: Objetivou-se avaliar os tratamentos com produtos alternativos na repelência do caruncho do feijão e na qualidade fisiológica de sementes de Phaseolus vulgaris. Utilizou-se delineamento experimental inteiramente casualizado, com quatro repetições, em esquema bifatorial (10x4). Os 10 tratamentos foram: Piper nigrum, diatomáceas e caulim (4 g/kg de semente); Cinnamomum zeylanicum, Citrus sinensis e cinza de Eucalyptus sp. (1% do peso de semente); óleo de Azadirachta indica (3 mL/kg de semente); Gastoxin (6 g/t semente); garrafa pet; testemunha; e quatro períodos de armazenamento (0, 25, 50 e 75 dias). Foram avaliadas as variáveis umidade, germinação, velocidade de emergência, tempo médio de emergência, peso de mil sementes, sementes infestadas e repelência. Os tratamentos com caulim e A. indica foram repelentes no início do tratamento, porém perderam a eficácia ao final do armazenamento. Os produtos a base de C. zeylanicum e Eucalyptus sp. não foram repelentes no início do tratamento, porém o foram no final do armazenamento. Já os produtos a base de C. sinensis e diatomáceas foram repelentes tanto no início quanto no final do armazenamento. Os tratamentos com diatomáceas, caulim, P. nigrum, C. zeylanicum, Eucalyptus sp., A. indica e a embalagem pet são eficientes em reduzir a infestação do caruncho sem impactar negativamente na qualidade fisiológica das sementes.

Abstract: The objectives of this study were to evaluate treatments with alternative products for repelling bean weevils, and to assess their influence on the physiological quality of Phaseolus vulgaris seeds. The experiment was carried out in a completely randomized design, with four replications, in a two-factorial scheme (10x4). It comprised 10 treatments: Piper nigrum, diatomaceous earth and kaolin (4 g/kg of seed); Cinnamomum zeylanicum, Citrus sinensis and Eucalyptus sp. (1% of the seed weight); Azadirachta indica oil (3 mL/kg of seed); Gastoxin (6 g/t of seed); PET container; control; and the storage times of 0, 25, 50, and 75 days. The variables seed moisture content, germination, emergence speed, mean emergence time, weight of one thousand seeds, seed infestation, and repellency were evaluated. The treatments with kaolin and A. indica had a repellent effect at first, but they lost effectiveness by the end of the storage period. The products based on C. zeylanicum and Eucalyptus sp. did not have such impact during early periods of storage, albeit repellency grew with time. On the other hand, C. sinensis and diatom-based products were repellents, both at the beginning and at the end of storage. The treatments with diatomaceous earth, kaolin, P. nigrum, C. zeylanicum, Eucalyptus sp., A. indica, and PET container all proved to be effective in reducing bean weevil infestation, without negatively impacting the physiological quality of the seeds.

Investigou-se o efeito das coberturas de inverno centeio, aveia, azevém, ervilhaca e nabo forrageiro (e suas associações), em sistema de plantio direto, sobre a cobertura do solo e a produção de biomassa das coberturas de inverno, sobre a biomassa de plantas espontâneas de verão, no período crítico de competição, e sobre a produtividade do feijão, cv Guará. O experimento foi instalado em delineamento experimental constituído por blocos ao acaso com quatro repetições. Observaram-se as maiores percentagens de cobertura do solo no inverno, com os tratamentos centeio + ervilhaca, centeio + ervilhaca + nabo forrageiro e aveia + ervilhaca; a produção de biomassa de cobertura foi maior com centeio + ervilhaca + nabo forrageiro. O efeito de supressão observado foi maior no monocultivo de azevém e no consórcio de centeio + ervilhaca + nabo forrageiro, porém não foi detectada correlação da biomassa de cobertura com a supressão de plantas espontâneas de verão. Os melhores rendimentos de feijão foram obtidos com o monocultivo de azevém, monocultivo de aveia e combinação centeio + ervilhaca, que atingiram 1.950, 1.730 e 1.790 kg ha-1, respectivamente. O azevém e a aveia em monocultivo apresentaram os menores custos com sementes e as maiores receitas, ou seja, os maiores retornos por unidade monetária investida.

The effect of the winter cover crops rye, oat, ryegrass, vetch and fodder radish (and their mixtures) in no-tillage systems was investigated on soil cover, cover crop biomass and summer weed biomass during the critical competition stage with common bean. Bean yield was also evaluated. The experimental design was randomized complete blocks and four repetitions. The highest soil cover during winter was observed in the treatments rye + vetch, rye + vetch + fodder radish and oat + vetch. The highest values of cover crops biomass production were observed in the treatments rye + vetch + fodder radish. Weed suppression was higher in the ryegrass monoculture and in the rye + vetch + fodder radish association, and there was no correlation between cover crop biomass and summer weed suppression; the best bean yields were achieved with the following treatments: ryegrass in monoculture, oat in monoculture and rye + vetch, producing 1,950, 1,730 e 1,790 kg ha-1 respectively. The monocultures of ryegrass and oat showed the lowest costs with seeds and the highest economic returns.