PHYSIOLOGICAL PARAMETERS EXPRESS COMPETITIVE ABILITY OF SOME SOYBEAN CULTIVARS WITH COMPANION WEEDS

Abstract

A field experiment was conducted in field located in Ramadi city during the growing seasons of 2010 and 2011, to evaluate the potential variations in physiological traits of some soybean cultivars and its impact on their competitive ability with accompanied weeds. The experiment was accomplished using randomized complete block design (RCBD) in split-split plot arrangement with three replicates. The study involved four weed treatments (weedy, weed free, herbicide spray at recommended and half of recommended concentration) as main treatments, whereas, sub plots involved two crop densities D1 400000 plants.ha-1 and D2 266666 plants.ha-1. Sub-sub plots comprised of four soybean cultivars (Ls 75, Lee 74, Giza 111 and Giza 35).Results showed that weed free treatment recorded highest crop growth rate (22.51 and 25.22 g .m-2.day-1), plant dry weight (80.20 and 86.63 g.plant-1) and No. of days to 50% flowering 53.42 and 54.64 day) at both seasons respectively. Cultivar Giza 111 achieved highest crop growth rate (19.41 and 21.03 g .m-2.day-1) at both seasons respectively. Cultivar Lee74 accumulated highest plant dry weight (79.23 and 81.80 g.plant-1) and no. of days to 50% flowering (70.07 and 72.94 day) at both seasons respectively. The lowest plant density (D2) achieved highest crop growth rat 18.72 and 20.24 g.m-2.day-1), plant dry weight (73.26 and77.42 g.plant-1) and leas No. of days to 50% flowering for both seasons respectively. While highest density (D1) achieved the highest percentage of weed control comparing with (D2). Spraying of herbicide at the recommended concentration achieved the highest percentage of weeds control (43.27 and 44.54%) at both seasons respectively. From the present study it can be concluded that the variation among soybean cultivars in some of physiological traits could be considered as cratering for their competitive ability to accompanied weeds.