Abstract
The objective was to evaluate weed phytosociology and similarities between crop management systems in the Chapadões region. The experiment was conducted at in agricultural area located in the municipality of Chapadão do Sul, MS, during the 2016/17 harvest. Three crop managements strategies were used: (1) cotton/soybean/Urochloa, (2) millet/soybean/millet and (3) millet/soybean/crotalaria. A phytosociological survey of weeds was carried out during soybean cultivation and cover crops growth, in succession. The evaluation area for each management strategy was 0.5 ha. Soybean surveys were carried out in October and January, while the cover crop surveys were performed in February and May. The relative frequency (RF), relative density (RD), relative abundance (AR), and relative importance (RI) of weeds, Venn diagram, and Jaccard and Sorenson similarity indices were evaluated. The management area represented by the cotton/soybean/Urochloa rotation had fewer weed species than others. The species Cenchrus echinatus, Digitaria insularis, Digitaria sanguinalis, Eleusine indica and Commelina benghalensis had the highest phytosociological indeces among the monocotyledons. Attention is required for managing the dicotyledons Amaranthus deflexus, Conyza canadensis and Senna obtusifolia despite their low indices because of herbicide resistant cases. The highest indeces of similarity were found between managements areas 2 and 3, which did not rely on cotton cultivation prior to soybeans.
Highlights
Competition with weeds affects crop development by reducing access to resources such as water, light, and nutrients (Brighenti 2010), thereby resulting in decreased crop productivity (Braz et al 2010) and economic losses (Vendruscolo et al 2017)
Attention is required for managing the dicotyledons Amaranthus deflexus, Conyza canadensis and Senna obtusifolia despite their low indices because of herbicide resistant cases
The weed species spectrum found in this survey (Table 1) does not differ from what occurs in soybean production fields, both in terms of monocotyledons such as Urochloa plantaginea, U. decumbens, Cenchrus echinatus, Digitaria spp., and Eleusine indica, as well as dicotyledons, including Alternanthera. tenella, Amaranthus spp., Cardiospermum halicacabum, Bidens pilosa, Commelina spp, Conyza spp., Euphorbia heterophylla, Ipomoea spp., Raphanus raphanistrum, Richardia brasiliensis, Sida spp., and Silene latifolia, among many others (Karam et al 2012)
Summary
Competition with weeds affects crop development by reducing access to resources such as water, light, and nutrients (Brighenti 2010), thereby resulting in decreased crop productivity (Braz et al 2010) and economic losses (Vendruscolo et al 2017). It is important to study weed communities (Pitelli 2015) to understand competition between them. It is important to examine whether competition is intraspecific or interspecific in order to devise more efficient control strategies (Santos et al 2015), because no single herbicide has sufficient action spectrum to control all weed species (Brighenti et al 2003). Knowledge of weed communities in cultivated areas can facilitate their chemical management. It is important to note that the use of herbicides can have a major effect on production costs (Richetti 2015), can affect entire ecosystems (Myers et al 2016; Van Bruggen et al 2018), and can select weeds in the area, due to successive application of glyphosate. It is important to prioritize the diversified use of herbicides with different active principles (Soares et al 2010)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call