Importance of environmental factors and crop type on weed diversity associated with cereals in Egypt

The research on arable weeds in relation to crops is attributed to the influence of weeds as competitors on crop productivity. It is hypothesised that region, crop type, crop seasonality and soil characteristics are the main factors affecting the diversity and distribution of weeds. In this study, the analysis of weed structure associated with cereals in the different bioclimatic regions of Egypt (Nile Delta, Nile Valley and Western Desert oases) was investigated. Two winter cereals (wheat; barley) and two summer cereals (maize; rice) as main crops were included, and thirteen soil parameters for 261 relevés were used to assess the diversity of weed vegetation. The influence of the explanatory factors on the weed communities was analysed using RDA. A total of 250 species constituted the flora of the studied cereal fields, belonging to 166 genera and 47 families, with therophytes (64.7%) dominating among life forms. One third of the recorded species is of Mediterranean and Saharo-Arabian chorotypes. The variation partitioning of the RDA model between explanatory variables revealed that the effect of bioclimatic regions had the greatest effect on weed composition, followed by crop type, while soil properties had lower effect, and crop seasonality was not significant.