Summary Caucalis platycarpos is a weed species in irrigated and dry land farming systems in East Azerbaijan and Kermanshah provinces of Iran. Experiments were undertaken to compare C. platycarpos seed germination and emergence of a population from each province over a range of environmental factors, burial depth and crop residue treatments. The Azerbaijan population required lower temperatures (20/10°C day/night temperature) for its highest (90%) germination, compared with the Kermanshah population (88% germination at 25/15°C day/night temperature). In both populations, germination was 84–90% over a wide range of light/dark periods (10–24 h light), but considerable reduction (up to 42%) occurred under continuous darkness. The osmotic potential required for 50% inhibition of germination was −0.54 and −0.40 MPa for Azerbaijan and Kermanshah populations respectively. The NaCl concentration of 8.83 and 5.71 dS m−1 caused 50% inhibition of germination in Azerbaijan and Kermanshah populations respectively. The X50 parameter (the burial depth at which emergence is reduced by 50%) for Azerbaijan and Kermanshah population was 2.18 and 2.86 cm respectively. Crop residues had more inhibitory effects on the Azerbaijan than Kermanshah population. Adaptive differentiation of C. platycarpos populations has also resulted in smaller seeds of the Azerbaijan compared with the Kermanshah population and resulted in higher emergence for Kermanshah population seedlings from greater soil depths. These results suggest that differences in germination requirements, drought and salinity tolerance of C. platycarpos populations are correlated with environmental conditions of the habitats of the studied populations.

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Intercropping can be described as the growing of two or more crops simultaneously on the same field. In order to investigate the effects of three spices (corn, soybean and sunflower) strip intercropping on yield and yield components of corn (Zea mays L.) a field experiment was carried out as randomized complete block design (RCB) with three replications in 2011. Results showed that the chlorophyll content of corn significantly affected by neighboring of soybean and sunflower. The maximum chlorophyll content of corn leaves was obtained at intercropping of corn-soybean, additive corn-soybean, corn-soybean-sunflower and corn-soybean-sunflowersoybean while, minimum chlorophyll content of this cultivar was showed at pure culture of corn. The effect of different intercropping on number of leaves, height of plant and diagonal of ear and biological yield of corn was not significant. The most ear length, number of rows in ear, number of grain in row, grain weight, grain yield and harvest index of corn were showed at intercropping of corn-soybean and corn-soybean-sunflower-soybean.The neighboring of sunflower by beside of corn significantly inhibited yield and yield component of this cultivar as the lowest yield of corn was obtained at intercropping of corn-sunflower.