Weed community composition in different agro-systems

Abstract

Weed communities in agricultural systems are diverse and subjected to different agronomic practices. In this study, a phytosociological survey of the weed community in different cropping systems consisting of corn, horticulture, perennial cultivation of Jatropha curcas and pasture of Urochloa brizantha in Rio Verde, GO, Brazil, was carried out. Assessments were performed at the beginning (October 2011) and at the end (March 2012) of the rainy season. After identifying and counting species, were calculated the phytosociological indices of density, frequency, abundance and relative importance, as well as the diversity index of Shannon-Wiener, evenness index of Pielou and similarity coefficient of Sorense. Were found 46 species of sixteen families, especially Poaceae. The most important species were: Alternanthera tenella in the annual growth environment during the both periods; Panicum maximum (early rainy season) and Chamaescy hirta (end of the rainy season) in the vegetable garden; Eleusine indica (early rainy season) and Galinsoga parviflora (end of the rainy season) in the perennial crop and Sida rhombifolia (early rainy season) and Neonotonia wigrtii (end of the rainy season) in the pasture. Lower diversity indices and evenness were observed in the pasture environment. Sampling time presented a higher impact on similarities when compared to the different environments.Keywords: Jatropha curcas, corn, pasture, no-tillage Composição florística de comunidades de plantas daninhas em diferentes agrossistemas ResumoComunidades de plantas daninhas em agrossistemas são diversificadas devido às práticas agronômicas adotadas. Neste trabalho realizou-se um levantamento fitossociológico em comunidade de plantas daninhas em diferentes sistemas de cultivo constituídos de cultivo de milho, olericultura, cultivo perene com pinhão-manso e pastagem de Urochloa brizantha, em Rio Verde, GO, no início (outubro de 2011) e no final (março de 2012) da época chuvosa. Após identificação e contagem das espécies calcularam-se os índices fitossociológicos: densidade, frequência, abundância e importância relativa, e os índices de diversidade de Shannon-Wiener e equitabilidade de Pielou e o coeficiente de similaridade de Sorense. Encontrou-se 46 espécies, distribuídas em dezesseis famílias, com destaque para Poaceae. As espécies mais importantes foram Alternanthera tenella no ambiente de cultivo anual em ambas as épocas; Panicum maximum (início da época chuvosa) e Chamaescy hirta (final da época chuvosa) em horta; Eleusine indica (início da época chuvosa) e Galinsoga parviflora (final da época chuvosa) em cultivo perene; e Sida rhombifolia (início da época chuvosa) e Neonotonia wigrtii (final da época chuvosa) em pastagem. Menores índices de diversidade e de equitabilidade foram observados em área de pastagem. Quanto às similaridades entre tratamentos, a época foi mais determinante do que os ambientes, considerando que as semelhanças entre ambientes foram maiores dentro da mesma época amostrada, exceto para a pastagem no final da es...

Post-emergence herbicidal activity of nanoatrazine against Alternanthera tenella Colla plants compared to other weed species

“…The leaves of A. tenella have a thick cuticle and a layer of wax deposition, in addition to low stomatal density on both sides, which can compromise the action of herbicides (Ferreira et al, 2003). It usually occurs in pastures and annual crop fields, where it may appear late, hindering the harvest and increasing the grain moisture (Canossa et al, 2007;Cardoso et al, 2017). Although there are no reports about herbicide resistance of A. tenella populations, it remains a problem due to its potential to produce an enormous number of seeds (Kissmann and Groth 1999).…”

Intercropping maize and succession crops alters the weed community in common bean under no-tillage

“…Similarly, Cardoso et al (2017) observed a lower Shannon-Wiener diversity index with successive maize cultivation, and the weed species of highest relative importance was E. indica, when compared with other crop rotations. Indeed, the rotation of at least three crops does not affect the crop grain yield and increase the weed community diversity by reducing the weed seedbank in the notillage system (Murphy et al 2006).…”

“…The highest obtained common bean grain yield was for the crotalaria intercropping system, in relation to single maize (12.7 % higher), and the brachiaria intercropping system was intermediate to both (Figure 2B). Therefore, these observations are mainly attributed to changes in the community of weeds present in the seedbank area, due to the different managements adopted in the maize cropping (Cardina et al 2002, Cardoso et al 2017, Vargas et al 2017. Here, we hypothesize that it is not only important to think about reducing the density of weeds in the field, but also to ensure that the weeds present in a specific cropping system do not interfere with the cash crop yield.…”

“…In this way, integrated crop management systems mitigate the use of herbicides, according to no-tillage system requirements (Bergtold et al 2017), allowing the use of long-term efficient strategies for weed control (Gomes Junior & Christoffoleti 2008). In fact, the dynamics of weed seedbanks is strongly regulated by the applied management (Murphy et al 2006, Cardoso et al 2017, Vargas et al 2017). However, intrinsic factors of weed species, such as morphological (seed size, shape and dispersal) and physiological (germination, dormancy type and resistance) characteristics also interact in the phytosociology of the weed community (Cardina et al 2002, Masin et al 2006, Feng et al 2015, Darmency et al 2017.…”