the effect of crop rotation with corn on nightshade (solanum nigrum l.) seed bank and seedling spatial distribution

in order to investigate the effect of crop rotation on relation of seed bank with nightshade (solanum nigrum l.) weed seedling population during the growth season of corn, a field experiment was carried out in dasht-naz crop company in sari, during 2012. at the first, farm was divided into 2×2 m networks and the cross points was signed and all sampling were taken from those points. sampling of seed bank and nightshade seedlings were done in two and three stages, respectively. spatial distribution maps at the end of cropping season indicted that patches with high density of weed seed increased in corn-faba bean-corn rotation while decreased in soybean-wheat-corn rotation. there were strong and medium correlations for nightshade weed seeds at all sampling stages. also, two crop rotations had a significant difference in terms of seeds averages and emerged seedlings. since, seeds averages and emerged seedlings were lower in corn-faba bean-corn rotation than corn-wheat-corn rotation; therefore, faba bean was more appropriate in rotation with corn to reduce nightshade weed density not only in the field but also within seed bank.