Crop management and its effects on weed occurrences

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.

Multifractal analysis of weeds in a no-tillage system in the Pre-Amazon region

“…The diversity parameters presented in Table 2 are indicators used to characterize the ecology among species. Density, frequency, and abundance express the participation of different species, the spatial distribution of each specimen, and concentration of species in the study area, respectively (Küchler et al, 1976;Siqueira et al, 2016;Caetano et al, 2018;Castro et al, 2021). The importance value index (IVI) is intended to characterize which species have a greatest influence within the weed community (Caetano et al, 2018), thus, the higher the IVI (Table 2), the higher the positive species rate at the sampling points.…”

“…Samuel & Rastogi (2022) The coefficients of variation (CV%; Table 3) of the evaluated weeds were classified as moderate (12 % < CV < 60 %), according to Warrick & Nielsen (1980); except for the OW category (CV = 81%) which presented a high CV (> 60%). The OW category encompassed three weed species [D. tortuosum, S. dulcis, and S. rhombifolia], with high heterogeneity in the study area and cluster distribution (Chiba et al, 2010;Siqueira et al, 2016;Castro et al, 2021;Silva et al, 2022), as well as distinct ecological processes (Gazziero et al, 2015).…”

“…Ecological variables for weed species in Mata Roma, Maranhão, Brazilas they have reproduction and dispersal strategies that make their management difficult. Similarly,Caetano et al (2018) andCastro et al (2021) evaluated weeds in areas of the Brazilian Cerrado biome with soybean crops under no-tillage system and reported predominance of E. hirta Osunleti et al (2022). evaluated weed control methods and reported S. anthelmia as the species with the highest density and relative density in the treatments evaluated, mainly due to its high degree of tolerance to oxyfluorfen at a rate of 0.36 kg ha -1 .…”

“…Weeds in agricultural production areas present high spatial variability (Chiba et al, 2010;Siqueira et al 2016;Silva et al, 2022), and can compromise crop yields when not properly managed (Gazziero et al, 2015;Siqueira et al, 2016;Caetano et al, 2018;Castro et al, 2021;Silva et al, 2021;Silva et al, 2022;Osunleti et al, 2022).…”

Multiscale properties of weeds in no-till system

“…on 01/26/2011 (x -= 9.31 plants per m 2 ). Schappert et al (2018) described an abundance of R. raphanistrum of 3.0 plants per m 2 in their study of weeds, whereas Castro et al (2021) discovered…”