Study of Postharvest Weed Population in Paddy Fields

The emergence of weeds in agricultural fields is one of the most challenging problems of humankind since the beginning of agriculture. An important part of the proper management of weeds in the paddy fields is rice postharvest weed management until land preparation for re-cultivation. In order to determine the frequency and relative cover (RC), the samples were collected from 481 fields during the growing season and 255 fields after harvesting rice in Guilan province (Iran) from 2014 to 2016 (from April to March of each year) based on the method of Thomas by throwing 0.5m × 0.5m quadrat to count existing genus and species of weeds. According to the results, the highest frequency was related to weed species of Echinochloa crusgalli (96.9%), Paspalum distichum (78.8%) and Eclipta prostrate (51.8%). Cyperaceae and Poaceae families showed the highest frequency with 13 species (20%) and 8 species (12%), respectively. The RC of E. crusgalli had the highest dominance (51.4%) after rice harvesting in the fields of Guilan province. Of the 5 predominant species with the highest frequency in after harvesting rice, 4 species had the highest frequency and dominance during the growing season of rice.