Effect of water stress and replacement intercropping patterns of soybean and millet on population and species diversity of weeds

Afield experiment was conducted in 2014 at the Research Station of Agricultural Faculty, Bu-Ali University to evaluate the effect of water stress and replacement itercropping patterns of soybeen and millet on weed population and species diversity. A split plot design with three replication was used for the experiment. Main plots consisted of three levels of water stress. The subplots consisted of five levels of replacement intercropping as soybean monoculture, millet monoculture, 75% soybean 25% millet, 50% soybean 50% millet, and 25% soybean 75% millet. The results showed that the intercropping patterns of 50S:50M and 25S:75M were successful in reducing weed plant density and diversity in comparison with soybean monoculture. The highest plant density (27 plant Square meters), shannon- wiener diversity index (1.46) and margalef index (1.29) were obtained in soybean monoculture. Moderate water stress has no effect on plant density and diversity indices of weeds. Severe water stress (Irrigation after 120 mm evaporation from pan), reduced plant density, Shannon- Wiener index and species richness of weeds compared to non-water stress,about 68.71, 48.36 and 38.80 percent, respectively. The highest Simpson dominance index (0.61) was obtained in severe stress.