The effects of drought or moisture stress (MS
1-no stress; MS
2-stress at seedling stage and MS
3-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.
