Weed communities of field crops at El-Tina Plain, Egypt

The present study aims to analyze the weed communities associated with cultivated crops at El-Tina Plain area, which lies in the north-western Mediterranean coast of Sinai Peninsula, between longitudes 320 35′ and 320 45′ E and latitudes 310 00′ and 310 25′ N. Forty sampled stands cultivated by clover, wheat, broad bean, sugar beet and winter vegetables in winter season and maize, sesame, watermelon, citrus, olive and summer vegetables in summer season were randomly selected in the villages of El-Tina Plain area. These stands were seasonally surveyed during the period between autumn 2008 and summer 2009. Ten random (1x1m2) quadrats were used in sampling of the weeds in each stand. The existing species were evaluated throughout; absolute and relative densities and frequencies. The relative values of density and frequency of each recorded species were summed up to give an estimate of its importance value, I.V (out of 200). Physical and chemical analyses of soil samples were carried out. A total of 55 associated species belonging to 20 families (3 Monocots and 17 Dicots) were recorded in the study area. The application of TWINSPAN classification led to the recognition of four vegetation groups in winter and three in summer crops. These groups were dominated by Sarcocornia fruticosa, Spergularia marina, Polypogon monspeliensis and Lolium regidum (in winter crops), whereas, Digitaria sanguinalis, Portulaca oleracea and Echinocloa colona (in summer crops). The ordination plan of stands given by Detrended Correspondence Analysis illustrated that the vegetation groups obtained by Two Way Indicator Species Analysis classification are distinguishable and have a clear pattern of segregation. The correlation between both stands and species with environmental variables is displayed on the ordination biplot produced by Canonical correspondence Analysis. This biplot showed that soil texture, chloride, sulfate, bicarbonate, sodium, potassium, calcium, magnesium, EC (salinity) and calcium carbonate are the most effective soil variables in weed vegetation composition in the study area.