The effects of pigweed redroot (Amaranthus retoflexus) weed competition and its economic thresholds in corn (Zea mays)

Abstract

The aim of this study was to determine the economic damage threshold of Pigweed redroot for corn regarding its density. An experiment was conducted at the Agriculture Research station of Islamic Azad University branch of Gonabad during 2006. The experiment was carried out as a factorial in a randomized complete block design with three replications. In the experiments, the factors included corn (var. 704) densities of 7.5, 8.5 and 9.5 plants m-2 and pigweed redroot densities of 0, 2, 4, 6 and 8 plants m-2. The increase in Pigweed redroot density, decrease in crop grain and biomass yield components such as ear length, ear diameter, number of grains per row, row number, grain number in ear, grain yield and biological yield of corn, decreased. Also, with an increase in corn density, the number of grain per rows, row number, grain yield and biological yield of corn increased. The economic thresholds density of Pigweed redroot was 0.09 to 0.13 plants m-2 in corn different densities, and increased with corn density increases.

Multiple-and Cross-Resistance of Amaranthus retroflexus to Acetolactate Synthase (ALS) and Photosystem II (PSII) Inhibiting Herbicides in Preemergence

“…Weed interference, e.g., A. palmeri, may cause losses of up to 60% in cotton yields (McRae et al, 2013). In corn crops, A. retroflexus species may cause yield losses of up to 3,000 kg ha -1 (Vazin et al, 2012). Thus, the genus Amaranthus is composed of highly competitive weed species, requiring control actions.…”

Interspecific competition changes nutrient : nutrient ratios of weeds and maize

“…In this study we worked with a weed density of 184 plants m −2 . For Amaranthus spp., densities ranging from 155 to 495 plants m −2 were capable of decreasing corn yield by 50% ( Vizantinopoulos and Katranis , ), while less than one plant per square meter of Amaranthus retoflexus was capable to cause economic losses for the same crop ( Vazin , ). At the densities used in our experiments, changes in the nutrient : nutrient ratios for three weed species of worldwide occurrence, in competition with maize, could be verified.…”

A Study on Weed Flora and Importance Value Index of Weeds in Wheat Crop

“…For cereals, most authors provide values 40-50 plant m -2 for unspecified broadleaf weeds and 20-30 plant m -2 for unspecified grass weeds (Beer and Heitefuss 1981, Wahmhoff and Heitefuss 1985, Häusler et al 1998, Gerowitt and Heitefuss 1990, Zanin et al 1993). The thresholds of some weeds in other crops are as follows; for red-rooted pigweed (Amaranthus retroflexus L.) the economic threshold was between 0.09 and 0.13 plant m -2 (Vazin, 2012) and for lamb's quarters (Chenopodium album L.) it varied between 4 and 6 plant m -2 in corn (Onofri et al, 1994), also for common cocklebur (Xanthium strumarium L.) it was 0.05 plant m -2 in soybean fields (Sartorato et al, 1996) found) so this value was the lowest. Within the same species, the different values of economic threshold result from the different costs and efficacy of herbicides.…”