Weed Species In Areas Research Articles

OCCURRENCE OF NOXIOUS WEEDS UNDER DIFFERENT SOIL MANAGEMENT SYSTEMS

The aim of this work was to identify weed species in areas under different soil management systems. The research was carried out in the Brazilian Agricultural Research Corporation experimental area, in the 2017/2018 harvest, in the city of Boa Vista, Roraima State, Brazil. The experimental design was randomized blocks and the treatments included of five soil management systems (native vegetation, minimum tillage, no-tillage, conventional tillage and conventional tillage with crop rotation). Weed collection, identification, counting and drying were performed and then the phytosociological indices (Relative density, relative frequency, relative abundance, importance value index, relative importance value index and dry mass) were calculated. Variance analysis with means compared by Tukey test (P <0.05), group analysis by hierarchical and non-hierarchical method, and principal component analysis were performed. Correlation coefficients of the variables were estimated. No and minimum tillage systems had the lowest weed rates per square meter. The botanical families Poaceae, Fabaceae and Rubiaceae are the most representative in the studied systems. Concerning relative frequency, the species Cyperus flavus stood out in all treatments other than native vegetation.

Ervas daninha em pastagens: uma abordagem fitossociológica nas áreas do Ceará

The aim of this study was to study the phytosociology of weed species in areas of pasture cultivated with Brachiaria decumbens and Cynodon sp. (Tifton 85), in Ceará State, Brazil. The square inventory methodology was used in order to assess the weed community. Weed samples were quantified and classified by family, genus and species, using books and classification keys. The classification and quantification data of species allowed to calculate the following phytosociological variables: frequency (F), relative frequency (Fr), density (D), relative density (Dr), absolute dominance (DoA), relative dominance (DoR), importance value index (IVI), and similarity index (IS). The Amaranthaceae family was the one with the greatest intensity of species in both areas, represented mainly by Alternanthera tenera colla and Amaranthus viridis. In the area cultivated with B. decumbens, Cyperus rotundus presented higher results for frequency, density and abundance. In the Tifton 85 area, Nicandra physalodes presented higher values of density and abundance. The similarity of weed populations in pasture areas was 42.11%, with four species common to both areas.

WEEDS AS UNWANTED PLANT SPECIES: THEIR POSITIVE ASPECTS IN SEMI-ARID AREAS OF CENTRAL TANZANIA

This paper presents the usefulness of weed species in semi-arid areas of Mpwapwa District, Central Tanzania. As crop production systems in these areas are often impacted by unreliable rainfall, frequent drought, and low soil fertility, smallholder farmers have developed different strategies to ensure that their livelihood is sustained. One of these strategies is the use of weed species for different purposes. A field inventory conducted in 36 smallholder farmers' fields in the case study area during the 2006/2007 cropping season identified a total of 63 weed species from 26 plant families. Usefulness of identified weed species in these areas was determined through focus group discussions with community representatives. Out of 63 weed species presented during these meetings, nine species were indicated as the most useful weed species in those communities. Pairwise ranking indicated Cleome hirta (mhirile) to be the most important species. Others in order of importance were: Amaranthus graecizans (mfwene), Bidens lineoriloba (mphangalale), Bidens pilosa (mpwimbwiza), Dactyloctenium aegyptium (ihungo), Launaea cornuta (sunga), Heteropogon contortus (sigi), Tragus berteronianus (namata), and Trichodesma zeylanicum (nyawaje). These species were mentioned to be mainly used as vegetable, medicine, food, fodder, and thatching materials. Weed species used as food have been mentioned to help people during period of droughts. Medicinal weed species were also mentioned to be useful in the area. Ailments mentioned that can be treated by selected species include malaria, painful menstruation, extended menstruation cycle, and stomach ache in men (ngiri). These species are also said to reduce blood flow during circumcision. The majority of women in the area were the ones involved in harvesting, preparation, and selling the useful weed species in the visited markets. The main conclusion drawn from this study is that, although weed species are regarded as unwanted plant species in crop production, they still play a vital role in food security and for the health of different people in marginal areas.