The effects of drought or moisture stress (MS1-no stress; MS2-stress at
seedling stage and MS3-stress at heading stage) was studied for
different crop ratios of barley ( Hordeum vulgare ) and wheat (
Triticum aestivum ) mixtures sown in additive and replacement series
at Halhale Research Station (Eritrea) during the off seasons of 1998
and 1999. The objective was to identify crop ratios with higher
productivity and to analyze the competition and niche differentiation
of component crops in mixtures grown under stress. Competition and
niche differentiation were assessed by analyzing the data using a
hyperbolic competition model. The best yields were obtained from the
crop ratios 50% barley/ 50% wheat and 25% barley/ 100% wheat when
averaged over two years. One barley plant was as competitive as about
seven wheat plants. The relative competition ability was higher in
barley than in wheat. Inter-specific competition was larger than the
intra-specific competition for wheat while for barley the
intra-specific competition was greater than the inter-specific. The
component crops shared the same resources in a complementary way. The
Niche Differentiation Index (NDI) > 1 was related to Relative Yield
Total (RYT) > 1 showing that the yield advantage was due to
complementary use of resources