RELATIONSHIPS BETWEEN SOME SOIL PARAMETERS AND WEED COMMUNITY (CASE STUDY: WINTER WHEAT FIELDS OF UREMIA-IRAN).

In order to find relationships between weed species distribution and soil pH, calcium carbonate (CaCO₃), electrical conductivity (EC), and organic matter percentage (OM %), fields surveys were done in 50 wheats (Triticum aestivum L.) fields of Uremia county (one of the northwest counties of Iran) in 2013. Data sampling of weeds was conducted from the beginning of stem elongation until the end of heading stages of wheat. In each field, 20 quadrates (0.25 m²) were randomly placed along a "W" pattern (5 quadrates in each line of this pattern) and in each quadrat, weed species were coded and recorded (density and cover percentage) for subsequent data entry and analysis. Canonical correspondence analysis (CCA) was used to find relationships between presence and absence of weeds in wheat fields and some of soil parameters. A total 169 weed species belonging to 35 plant families were recorded. CCA showed that four soil factors including soil pH, calcium carbonate (CaCO3), electrical conductivity (EC), and organic matter percentage (OM %) showed 58.6 percentage of weed species distribution variance. Abutilon theophrasti Medicus, Datura stramonium L., Malva neglecta Wallr., Portulaca oleracea L., Sisymbrium irio L., Atriplex patulum (L.). Aellen., and Heliotropium europaeum L. had maximum correlation with soil's pH. Euphorbia peplus L. and Salvia spinosa L. had negative correlation with pH, so that increasing pH caused reduction in the presence of these weeds. The presence of Chondrilla juncea L., Lepidium perfoliatum L., and Turgenia latifolia (L.) Hoff in the center of CCA biplot indicated that these weeds were correlated with all of these soil parameters.