Impact of Pre-Emergent Herbicides and Soil Management on Weed Community Dynamics and Soybean Yield Eduarda Grün, Arícia Ritter Corrêa, Roberto Costa Avila Neto, Eduard Mroginski Leichtweis, Eduardo Streck Bortolin, et al. International Journal of Agronomy, 2026 Pre‐emergent herbicides are key tools in managing herbicide‐resistant and hard‐to‐control weed species in soybean ( Glycine max L.) cultivation. This study aimed to evaluate the effects of pre‐emergent herbicides on weed phytosociology, soybean phytotoxicity, and grain yield under different soil management systems and environmental conditions. Four field experiments were conducted in Brazil (Santo Ângelo and Santa Maria) using a randomized block design across two growing seasons and tillage systems (no‐till and conventional). Herbicide treatments included single and combined active ingredients, applied in the plant‐and‐apply modality. Weed surveys were conducted at 25 and 40 days after emergence (DAE) to calculate the relative importance value index (IVIR), diversity (Simpson and Shannon–Wiener), and similarity indices. Sulfentrazone, trifluralin, and s‐metolachlor caused significant phytotoxicity, especially in conventional systems. Herbicide efficacy varied by species and management system. Pyroxasulfone + flumioxazin, metribuzin, and chlorimuron‐ethyl significantly reduced the IVIR of dominant species like Raphanus raphanistrum and Euphorbia heterophylla . Despite observed phytotoxicity, some herbicide combinations improved yield without compromising crop safety. These results underscore the importance of integrating herbicide selection with soil management to optimize weed control and maintain soybean productivity.
Non-destructive estimation of leaf area in hairy fleabane (Conyza bonariensis) Mariana Macedo, Bruno Mussoi Cavichiloi, Glauco Pacheco Leães, Lilian Osmari Uhlmann, Ary José Duarte Junior, et al. Revista Facultad Nacional De Agronomia Medellin, 2025 Hairy fleabane (Conyza bonariensis) is a widespread and troublesome weed in agricultural systems, and estimating its leaf area (LA) is essential for growth analysis and weed management studies. This study aimed to develop equations to estimate the LA based on the linear dimensions of leaf blades. The relationships between the LA and the dimensional parameters of leaf blade (length and width) were studied in C. bonariensis var. angustifolia and C. bonariensis var. bonariensis. Both linear and power regression models were tested, and their performance was assessed using Root Mean Square Error (RMSE), index of agreement (dw), BIAS index, Pearson’s linear coefficient (r), and index of confidence or performance (c). The best-performing model used the product of length and width (L×W), yielding the highest r values and the lowest RMSE for both botanical varieties. Specific models provided better estimates than the general model. The linear equations LA = 0.6578 × (L×W) and LA = 0.5896 × (L×W) for C. bonariensis var. angustifolia and C. bonariensis var. bonariensis, respectively, were the most accurate for estimating their LA. These equations offer reliable, non-destructive tools for estimating LA in studies involving each variety, contributing to improved precision in weed science research.
Pre-emergent herbicides during the off-season of irrigated rice to control weedy rice and reduce the soil seed bank Tilio Adan Lucas, Simone Puntel, Rafaella Boemo Mario, Leonardo da Silva Bolson, Arícia Ritter Corrêa, et al. Ciencia Rural, 2025 Weedy rice (Oryza sativa L.) is the most important weed in irrigated rice cultivation, being one of the main factors limiting cereal productivity in Rio Grande do Sul (RS). Thus, this study determined the effect of pre-emergent herbicide use in autumnal management on the control and reduction of the weedy rice seed bank. Field experiments were conducted in a randomized complete block design with four replications in a commercial rice production area in the 2021/22 and 2022/23 growing seasons in Dom Pedrito (RS). The scheme used was factorial, with factor A consisting of different herbicide application times, namely June, July, and August, and corresponding to 100, 78, and 26 days and 42, 26, and 10 days before rice sowing for the agricultural years 2021/22 and 2022/23, respectively. Factor B consisted of the application of the herbicides s-metolachlor (1440 g a.i. ha-1), sulfentrazone + diuron (210 and 420 g a.i. ha-1), piroxasulfone (170 g a.i. ha-1), and flumioxazin (50 g a.i. ha-1), in addition to the control (no application). The evaluated variables were control (%), number of plants (m-2) at crop pre-harvest, number of full, viable, and non-viable wild rice seeds m-2 in the soil, crop injury (%), and grain yield (kg ha-1). The herbicides showed control values below 25% and low reduction of the seed bank in the soil, being considered ineffective in this application modality. The herbicides s-metolachlor, sulfentrazone + diuron, and flumioxazin exhibited the highest injury values; however, they did not significantly affect crop productivity. Thus, when applied before rice sowing, the herbicides s-metolachlor, sulfentrazone + diuron, pyroxasulfone, and flumioxazin did not provided satisfactory control and do not significantly reduce the wild rice seed bank.
How Do Off-Season Cover Crops Affect Soybean Weed Communities? Eduarda Grün, Alexandre Ferigolo Alves, Anelise Lencina da Silva, Alencar Junior Zanon, Arícia Ritter Corrêa, et al. Agriculture Switzerland, 2024 Weeds compete for environmental resources, leading to reduced soybean yield. In this context, integrated weed management strategies related to cultural control with the use of cover crops are necessary. Our aim was to evaluate weed occurrence in soybean systems with different cover crops. Field studies were conducted at Júlio de Castilhos, Santa Maria, Capão do Leão, Barra do Ribeiro, and Santo Ângelo, Rio Grande do Sul, Brazil. A randomized complete block design with four replications was used. Treatments consisted of black oats (Avena strigosa Schreb.), white oats (Avena sativa L.), rye (Secale cereale L.), hairy vetch (Vicia sativa L.), forage turnip (Raphanus sativus L.), and white clover (Trifolium repens L.) in pure stands or in mixtures. The analyzed variables were relative frequency, density, abundance, and importance value index, similarity index of weeds, dry shoot mass of cover crop, and soybean yield. Cover crops containing white or black oats reduced the relative importance value index of weeds, such as Lollium multiforum, Conyza spp., and Bidens pilosa. Forage turnip, hairy vetch, and white clover showed distinct responses. Black oats and forage turnip did not differ from cover crop mixtures in terms of dry shoot mass and grain yield, being superior to fallow, white clover, and hairy vetch.
Interaction between saflufenacil and ammonium glufosinate to control ryegrass R. Avila-Neto, A. R. Ulguim, T. Schneider, C. Fortuna, A. S. Holkem, et al. Brazilian Journal of Biology, 2024 Annual ryegrass (Lolium multiflorum Lam.) is one of the main weeds in subtropical cropping systems of Europe, Oceania and South America. Therefore, the hypothesis of this work is that the interaction between ammonium glufosinate and saflufenacil can be synergistic for ryegrass control. Our main goal was to evaluate the effects of the mixture of saflufenacil with ammonium glufosinate in the control of ryegrass by graphical analysis of isobologram and a surface response graphic in addition to the Colby’s test. Two experiments were carried out, in greenhouse (isobolograma experiment) and field conditions (Surface response and Colby). The behavior of the mixture between saflufenacil and ammonium glufosinate was a synergistic interaction for the control of ryegrass by the isobologram test on the dry matter variable . By the Colby test, it was confirmed that at the dose of 400 g ha-1 of ammonium glufosinate and at the doses of 10.5, 21.0 and 31.5 of saflufenacil the effect was synergistic for control of ryegrass for as control variables (%).The mixture between these two herbicides has synergistic potential to increase ryegrass control, mainly with a high proportion of ammonium glufosinato over saflufenacil.
