Graciene de Souza Bido

Lettuce (Lactuca sativa L.) is the most consumed vegetable in the world and in Brazil, representing as an important dietary source of vitamins, fiber and minerals to population. The aim of this study was to evaluate the yield of lettuce against nitrogen doses applied via fertigation, as well as the quality of the administered fertilizer solution. The test was carried out in an agricultural area located in the Doutor Camargo municipality, Northwestern of Paraná State, Brazil. The experiment was designed in a completely randomized design with seven treatments: T1 control - 0 kg ha-1 urea (0 kg N ha-1); T2 - 25 kg ha-1 urea (11.25 kg N ha-1); T3 - 50 kg ha-1 urea (22.5 kg N ha-1); T4 - 75 kg ha-1 urea (33.75 kg N ha-1); T5 - application of 100 kg ha-1 urea (45 kg N ha-1); T6 - 125 kg ha-1 urea (56.25 kg N ha-1); T7 - 150 kg ha-1 urea (67.5 kg N ha-1). Each treatment had six repetitions. Seeds from Dora (American lettuce) and Vera (curly lettuce) varieties were used for seedling production. Nutrients were applied to the crop by fertigation at 15 and 30 days after transplanting the seedlings to the seedbeds. Fresh shoot mass (weight), stem diameter, root length and productivity were assessed. Results showed that nitrogen fertilization via fertigation significantly influenced the growth and yield variables of plants from both Dora and Vera varieties.

Soybean (Glycine max (L.) Merrill) is an agricultural crop with a large increase in production in the last three decades and is an essential component in the manufacture of animal and human food. Understanding the interactions between crop and other plant species used as green manure that can improve yield and so reduce environmental damage. Forages can release secondary metabolites in the environment that influence in a beneficial or harmful way to other plants, characterizing the allelopathy process. The Níger (Guizotia abyssinica Cass.) is used in agricultural systems because it releases allelochemicals, especially flavonoids. Therefore, this study is aimed to evaluate the allelopathic effects of the Niger straw on the germination and initial growth of soybean seedlings. The treatments consisted of aqueous extracts of niger stems, leaves and roots in different concentrations (0; 25; 50; 75 and 100%). For each treatment, five replications were performed, each composed by a 25 seeds distributed in gearbox kept in incubator chamber for 7 days at 25ºC and 12 hours photo period. The experimental design was completely randomized and the data were evaluated by analysis of variance and the means of treatments compared by Tukey’s test at 5% significance. The results show a reduction in germination and initial growth of soybean seedlings submitted to aqueous extract of niger stem and roots. In contrast, the aqueous extract of the Niger leaves increased the length of soybean seedlings. The allelopathic effects of the Niger probably occur due to the presence of flavonoids in the tissues of this plant species.

ATIVIDADE ALELOPÁTICA DE EXTRATO AQUOSO DE Eucalyptus grandis Hill ex Maiden SOBRE ALFACE (Lactuca sativa L.) e PICAO-PRETO (Bidens pilosa L.)

Owing to an increasing demand for food, a constant agricultural production flow must be maintained. Further, for doing so, the use of pesticides is necessary. An alternative that results in less damage to the ecosystem and people themselves may be identified by studies on the allelopathic effect of weeds. Therefore, this work aimed to evaluate the allelopathic action of hexane, dichloromethane, butanol, and ethyl acetate fractions of sorghum (Sorghum bicolor [L.] Moench) on the initial growth of morning glory (Ipomoea grandifolia [Dammer] O’Donell) and slim amaranth (Amaranthus hybridus L.), which was verified by the percentage of germination, speed of germination, seedling length, and fresh and dry biomass weight. The experiments were conducted in an incubation chamber at 25 °C for 7 and 14 days for morning glory and slim amaranth, respectively. The experimental design was completely randomized, with five replicates in Petri dishes. The data were evaluated by analysis of variance, and the averages between each treatment were compared using the Scott Knott test at a 5% significance level. The results indicated that the dichloromethane and ethyl acetate fractions decreased the initial growth of morning glory and slim amaranth more, when compared with the effects of hexane and butanol.

Most Brazilian soils have low organic matter content, and the current management systems used in agriculture contribute to worsening this situation. The introduction of practices that lead to the increase of soil organic matter becomes more necessary for agrosystems to be sustainable, ensuring high yields because only then the production chain becomes profitable and enables agricultural production. The present work aimed to investigate the effect of intercropping practices among corn crop with different green manures in soybean agronomic parameters. The work consisted of five treatments using Brachiaria ruziziensis (Brachiaria); Raphanus sativus (Forage Turnip); Crotalaria spectabilis cv. Common (Crotalaria); Avena strigosa (Black Oats); and a control area (single maize) with five replications. Different aspects related to successor cultivation with soybean were evaluated taking into consideration agronomic aspects such as stem thickness, number of pods, plant height, the weight of one thousand grains and yield per hectare presented by the crop. The work demonstrated that brachiaria green manure in consortium with out-of-season corn crop promoted the highest plant height and number of pods for the soybean crop in succession.

Velvet bean (Mucuna pruriens) is an efficient cover forage that controls weeds, pathogens and nematodes, and the non-protein amino acid L-3,4-dihydroxyphenylalanine (L-DOPA) is its main allelochemical. The effects of 3 g L⁻¹ of an aqueous extract of velvet bean seeds, along with 0.5 mM L-DOPA for comparison, were evaluated in roots, stems and leaves of soybean (Glycine max). The activities of phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) were determined, along with the lignin content and its monomeric composition. The results revealed similar effects caused by L-DOPA and the aqueous extract. Both treatments reduced PAL and CAD activities, lignin, and lignin monomer contents in roots; PAL and CAD activities in stems, and CAD activity in leaves. These findings provide further evidence that the effects of velvet bean cover forage on root lignification were due to the L-DOPA, its major allelochemical.