a greenhouse study was conducted to investigate the effects of nitrogen (n) on wild barley (hordeum spontaneum koch) interference with winter wheat (triticum aestivum var. pishtaz) by an additive series experiment. the experiment was conducted in a split plot design with 3 replications. wheat plant height losses were on average 30, 10, and 10% in a wild barley density of 16 plants per pot with ...