Vertical Distribution of Nutsedge (Cyperus spp. L.) and Bahiagrass (Paspalum notatum L.) Seed Bank in Rice Growth Cycle

Abstract

Weed management in rice continues to be a major challenge to the success of rice growers in northern Iran. Field experiments were conducted at Sari Agricultural Sciences and Natural Resources University to investigate the spatial distribution of weed seeds in the rice growth cycle in 2010 and 2011. Transplanting was done on June 6 in both years. Samples for seedbank analysis were collected 10 days before transplanting and emerged weed density was determined on three different dates during the growing season. Results indicated that nutsedge (Cyperusspp) and bahiagrass (Paspalum notatum) were the two most abundant weed species. The vertical distribution of weed seeds decreased by depth from 0.1 to 0.3 m, while weed pressure was the highest at the 0–0.1 m soil depth. There was no relationship between soil weed seedbanks (at different depths) and emerged weed populations, suggesting that weed seedbank data are not good predictors of weed seedling densities. Nevertheless, Kriging maps indicated that the spatial distribution of weed seeds was in accordance with seedling germination pattern. Also the regression coefficient for 0–0.1 m soil depth was R2= 0.17 and R2= 0.34 for relation between nutsedge and bahiagrass seedlings and their seedbank in 2010 and also, R2= 0.18 and R2= 0.05 in 2011, respectively. Therefore, results achieved from this depth can be used to predict the relationship between nutsedge and bahiagrass seedlings densities and weed seedbanks. The results of this study provide an option for the farmers growing rice to understand the dynamics of weed populations in a cost effective way.