Effect of Different Garlic (Allium sativum) and peas (Pisum sativum) Intercropping patterns on Weed Population Indices

This study was conducted as intercropping of garlic and peas to assess the diversity, bio-mass, and population of weeds in two regions of Gonbad Kavoos and Sari during autumn 2013. The experiment was implemented in a randomized complete blocks design with three replications in both regions. Different combinations of intercropping were considered in nine levels of garlic and peas pure cultures, replacement intercropping of 75:25, 50:50, 25:75%, and additive intercropping of 100, 100, 100, 100흍 for garlic and peas. Results showed that the average biomass value of weeds in Sari (2080.5 gm-2) was greater than in Gonbad region. However, a higher weed density (44.88 m-2) was observed in Gonbad. The highest levels of biomass (3387.3 gm-2) and density (61.83 m-2) of weeds were measured for garlic pure culture in Sari and the intercropping replacement of 75% peas:25% garlic in Gonbad Kavoos. Mean value of Margalef species richness index, Menhinick index, and Shannon-Wiener diversity index were calculated as 1.33, 1.01, and 1.96 in Sari, respectively, which were higher than 0.86, 0.7, and 1.03 in Gonbad. By contrast, the Simpson's dominance index (0.63) for peas pure culture and Shannon-Wiener evenness index (0.89) to replacement intercropping of 75% peas: 25% garlic were greater in Gonbad Kavoos. Berger-Prager diversity index (0.77) for pure garlic culture, and both Shannon diversity (1.42) and Simpson's diversity (3.94) indices for replacement intercropping of 75% peas: 25% garlic were greater in Sari. There was a difference between the two regions in terms of climatic and edaphic characteristics which resulted differences in weed diversity indices, intercropping increased diversity while reducing dominance as compared to the monoculture cropping system in both regions.