Barley and wheat mixtures were grown in the field using additive and replacement ratios at two locations (Halhale and Mendefera) in Eritrea during the 1997 and 1998 seasons. The aim was to assess yield advantage and to analyse competition and niche differentiation using a hyperbolic regression model. It proved advantageous to grow barley and wheat in mixtures because more land area was required to obtain the same yield in sole crops. The hyperbolic regression approach confirmed that barley and wheat grown in mixtures resulted in yield advantages as a result of complementary use of resources. Barley showed greater competitive ability than wheat; for wheat, interspecific competition was larger than the intraspecific competition while for barley the intraspecific competition was greater than the interspecific competition. Niche differentiation indices were always above 1.0 indicating that the component crops did not inhibit each other from sharing resources in a complementary way.

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