Abstract
Afield experiment were conducted in winter season 2011-2012 at three different environmental locations, namely the koya city /Erbil, the Mosul city and the Alton-koprey/kirkuk to determine the effects of seeding rate(200,300,400,500 and 600 seeds/m2) on physiological characteristics of oats varieties (kangaroo, Mitika , Possum , ICARDA short and ICARDA Tall) to give the best growth and yield at each location. The experiment were conducted by randomized complete Block Design (RCBD) with split-split plot design with three replication. The interaction between three studied factors significantly affected the studied physio- logical characters. Increasing seeding rates of all oat varieties within each location significantly affected The chlorophyll percent, N.A.R. , R.G.R. at 95% panicles and number of days from seeding to complete plant yellowing . and with height differences between these locations in the studied characteristics. increasing seeding rates have negative effects on chlorophyll percent and R.G.R. at complete plant yellowing for Possum and number of days from seeding to 95% panicles for Mitka and ICARDA short varieties only, and have positive effect on N.A.R. of all varieties except Kangaroo variety, and R.G.R. at appearance of 95% panicles, C.G.R. and number of days from seeding to complete plant yellowing for varieties Mitika and ICARDA short.