Abstract:-This study aimed to evaluate different crops and plant species planted after soybeans for one year, in terms of their potential to inhibit the occurrence of weed species. The following crops that were planted as second crop after soybeans were evaluated: (1) corn (Zea mays) planted at spacing of 90 cm between rows, intercropped with Brachiaria ruziziensis in the inter-rows; (2) sunflower (Helianthus annuus); (3) crambe (Crambe abyssinica); (4) radish (Raphanus sativus); (5) rapeseed (Brassica napus); and (6) … Show more
“…Shannon's diversity index (H') and Pielou's evenness were calculated to be 2.30 nats ind -1 and 0.69, respectively. The values for H were similar to those reported in the literature by Concenço et al (2013) and Mata et al (2016) for corn and rice crops, respectively, and are considered average for Shannon's diversity index, which ranges from zero to five (Kent and Coker, 1992).…”
supporting
confidence: 83%
“…Commelina benghalensis is remarkably resistant to glyphosate use in chemical management, possibly due to the unregulated use of herbicides, which leads to the selection of more tolerant plants over time. Its resistance may also be due to the low efficiency of the mechanical methods used for its control, and to its rapid reproduction, which may be vegetative or by seeds (Concenço et al, 2013;Santos et al, 2001). There have been reports in the literature of the species in the states of Bahia (Silva et al, 2006), Rio Grande do Norte (Moura , Minas Gerais (Sarmento et al, 2015), Goiás (Santos et al, 2017), Rio de Janeiro (Oliveira and Freitas, 2008), and Paraná (Costa et al, 2014), among others.…”
This study aimed to identify and quantify the weed species in an area of organic acerola cultivation in the Distrito de Irrigação dos Tabuleiros Litorâneos do Piauí (DITALPI) in Parnaíba, Piauí, Brazil. Phytosociological sampling was completed in the rainy season, before the farmers adopted management techniques for the plants. Thirty plots of 0.25 m2 were sampled. The plots were located between crop rows, which consisted of herbaceous-subshrub plants. The absolute and relative covers and the absolute and relative frequencies of each species were calculated based on the occurrence and cover of each species. In total, 25 species comprising 13 families were registered, among which the Poaceae family that presented the largest number of species. Commelina benghalensis occurred the most frequently overall. Shannon’s diversity index (H’) and evenness were calculated as 2.30 nats ind-1 and 0.69, respectively. Five species accounted for 79.33% of absolute cover at DITALPI. The species were distributed heterogeneously within the field, and Commelina benghalensis, Urochloa plantaginea, Panicum maximum, Amaranthus spinosus, Cynodonsp., and Cyperus aggregatus were the species most likely to infest the acerola crop. As DITALPI is an area of organic cultivation, understanding these species is essential to help farmers select the best form of control.
“…Shannon's diversity index (H') and Pielou's evenness were calculated to be 2.30 nats ind -1 and 0.69, respectively. The values for H were similar to those reported in the literature by Concenço et al (2013) and Mata et al (2016) for corn and rice crops, respectively, and are considered average for Shannon's diversity index, which ranges from zero to five (Kent and Coker, 1992).…”
supporting
confidence: 83%
“…Commelina benghalensis is remarkably resistant to glyphosate use in chemical management, possibly due to the unregulated use of herbicides, which leads to the selection of more tolerant plants over time. Its resistance may also be due to the low efficiency of the mechanical methods used for its control, and to its rapid reproduction, which may be vegetative or by seeds (Concenço et al, 2013;Santos et al, 2001). There have been reports in the literature of the species in the states of Bahia (Silva et al, 2006), Rio Grande do Norte (Moura , Minas Gerais (Sarmento et al, 2015), Goiás (Santos et al, 2017), Rio de Janeiro (Oliveira and Freitas, 2008), and Paraná (Costa et al, 2014), among others.…”
This study aimed to identify and quantify the weed species in an area of organic acerola cultivation in the Distrito de Irrigação dos Tabuleiros Litorâneos do Piauí (DITALPI) in Parnaíba, Piauí, Brazil. Phytosociological sampling was completed in the rainy season, before the farmers adopted management techniques for the plants. Thirty plots of 0.25 m2 were sampled. The plots were located between crop rows, which consisted of herbaceous-subshrub plants. The absolute and relative covers and the absolute and relative frequencies of each species were calculated based on the occurrence and cover of each species. In total, 25 species comprising 13 families were registered, among which the Poaceae family that presented the largest number of species. Commelina benghalensis occurred the most frequently overall. Shannon’s diversity index (H’) and evenness were calculated as 2.30 nats ind-1 and 0.69, respectively. Five species accounted for 79.33% of absolute cover at DITALPI. The species were distributed heterogeneously within the field, and Commelina benghalensis, Urochloa plantaginea, Panicum maximum, Amaranthus spinosus, Cynodonsp., and Cyperus aggregatus were the species most likely to infest the acerola crop. As DITALPI is an area of organic cultivation, understanding these species is essential to help farmers select the best form of control.
“…Heinz et al (2011) of phosphorus, 94.4 kg ha -1 of potassium, 14.7 kg ha -1 of calcium, 6.5 kg ha -1 of magnesium, and 12.6 kg ha -1 of sulfur back to the soil after harvest. Recent studies also indicate that the dry biomass of crambe helps to reduce soil infestation with weeds (CONCENÇO et al, 2012(CONCENÇO et al, , 2013PACHECO et al, 2013).…”
Understanding the influence of row spacing and plant density on grain yield and yield components of crambe is critical in order to obtain higher grain yields. Therefore, the objective of this study was to evaluate the effects of row spacing and plant density on grain yield and its components in crambe in two distinct regions of Brazil (Marechal Candido Rondon-PR, MCR-PR, and Botucatu-SP, BTU-SP). Narrow and wide row spacing (0.20 and 0.40 m) combined with four plant densities (15, 25, 35, and 45 plants m -1 ) were evaluated in a randomized block layout with four replications in a 2 × 4 factorial design. The experiment at BTU-SP was run under rainfed conditions with supplementary irrigation, whereas the experiment at MCR-PR was run under rainfed conditions without supplementary irrigation. Both experiments were run in soils classified as Oxisols. There was no interaction between row spacing and plant density. Highest grain yield with supplementary irrigation was observed at 0.20 m row spacing. Without irrigation, row spacing did not affect grain yield owing to the plasticity of crop. The highest grain yield was observed with approximately 30 plants m -1 at both experimental locations. A strong negative correlation was observed between final plant population and number of grains per plant. There was high plant mortality, particularly at high plant densities cultivated under irrigation. Higher mortality occurred because of high intraspecific competition and a larger disease incidence due to the higher humidity in the irrigated experiment. A mechanism of self-adjustment by plant density was observed in crambe, with its intensity dependent on plant density and environmental conditions, such as water and nutrient availability and light incidence.
“…It is presented as an alternative to keep the soil covered, making difficult the emergence of weeds in the off-season and consequently in the subsequent cultivation. That efficiency is due to its high production of biomass and excellent ground cover (CONCENÇO et al, 2013).…”
This study aimed to evaluate the allelopathic potential of aqueous extracts of different organs of three sunflower cultivars on the germination and initial development of radish. The study was conducted in a Laboratory of Plant Physiology of the Federal University of Santa Maria, Brazil. The design was completely randomized in a threefactor scheme with four replications. The first factor consisted of three sunflower cultivars: Olisun 3, Olisun 5, and Aguará 6. The second factor consisted of different organs: leaves, stems, and roots. The third factor consisted of the extracts concentrations: 0, 25, 50, 75, and 100%. The experimental unit (EU) used was gearboxes with two sheets of germitest paper that were moistened with the extracts. The EUs were placed in BOD germination chamber at 25 °C. Daily count of germinated seeds was performed. The radicle length and hypocotyl were measured on the 10 th day. The variables analyzed included germination (G); germination speed index (GSI); radicle length (RL); and hypocotyl length (HL). Sunflowers have allelopathic potential on the radish. The extract concentration of 75% of all organs and cultivars were sufficient to significantly reduce the variables. The allelopathic activity differs between organs (leaves, stems, and roots) and sunflower cultivars. The amount of allelopathic effects vary in the order of root, stem, and then leaf. Extracts from the roots showed the greatest allelopathic effect on germination and initial development on the radish; however, this depends on the cultivar used. Field studies should be performed to verify such allelopathic activities.
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