Interference and Economic threshold level of Alexander Grass in Soybean as a Function of Cultivars and Weed Populations

Abstract

This work is related to the project of Scientific Initiation of the second author. Universidade Federal da Fronteira Sul 1,

Interference and threshold level of Sida rhombifolia in transgenic soybean cultivars

“…The rectangular hyperbola model showed adjustments for all evaluated cultivars, with R 2 higher than 0.57 and low MSR values. Variations in data adjustment were observed in relation to the cultivar and studied variables, corroborated by results observed in literature for the rice competing with barnyardgrass (1), beans competing with alexandergrass (21), and soybeans competing with alexandergrass (19). Cargnelutti Filho and Storck (2007) considered the values of R 2 between 0.57 to 0.66 as moderate to good when working with the genetic variation, effect of cultivars, and heritability of corn hybrids, which partly agree with the results observed in this study.…”

“…The experimental design was completely randomized, with four replicates, and the treatments were composed of six soybean cultivars, i.e., NS 6909 IPRO, NA 5909 RG IPRO, DM 5958 RSF, Brasmax Elite IPRO, Brasmax Lança IPRO, and SYN 13561 IPRO, and ten densities of arrowleaf sida for each cultivar (0, 2, 3, 4, 9, 15, 16, 23, 22, and 58 plants m -2 ; 0, 2, 3, 3, 6, 6, 10, 11, 18, and 47 plants m -2 ; 0, 3, 4, 7, 8, 10, 11, 13, 15, and 24 plants m -2 ; 0, 1,4,6,12,18,19,31,44, and 50 plants m -2 ; 0, 4,5,6,9,13,17,20,20, and 47 plants m -2 ; and 0, 2, 3, 5, 9, 11, 15, 18, 29, and 30 plants m -2 ). As the arrowleaf sida weed originated from the soil seed bank, the establishment of densities varied with factors such as competition for resources, vigor, and humidity, which prevented the exact number of plants per area of experimental unit from being established.…”

“…Weeds can cause significant losses if not properly managed. Competition losses can vary from 2-94% depending on factors such as soybean cultivars, weed densities and species, emergence times, and edaphoclimatic conditions (14,19,29,32).…”

Economic threshold of smooth pigweed escaped from a herbicide program in roundup ready® soybean

“…Compared to this result, the maximum ET found for A. retroflexus in corn was 0.13 plants m -2 (Vazin, 2012) and for voluntary corn Roundup Ready in soybeans was 0.48 plants m -2 (Aguiar et al, 2018), showing economic control of populations smaller than those found for A. hybridus (Figure 4). Likewise, higher ET values in relation to those found in this study occur for weeds such as Urochloa plantaginea (Galon et al, 2019), C. bonariensis (Trezzi et al, 2015), Bidens spp. (Rizzardi et al, 2003), and S. rhombifolia (Fleck et al, 2002), with maximum estimated ETL values of 2.16, 4, 33, and 50 plants m -2 , respectively.…”

“…The unitary soybean yield losses found for A. hybridus in the present work (4.47 and 8.32%) are higher when compared to Sida rhombifolia (i = 0.24 to 2.20%), Cyperus rotundus (i = 0.83 to 1.0%), and Urochloa plantaginea (i = 1.0 to 2.5%), that are also important weeds in soybean (Das et al, 2014;Fleck et al, 2002;Galon et al, 2019). However, Ipomoea purpurea and Ipomoea grandifolia are more competitive with soybean: the parameter i was 26% and the maximum yield loss was 80% in a population of 20 plants m -2 (Pagnoncelli et al, 2017).…”