Field experiments were conducted during summer and kharif seasons of 2001 and 2002 to evaluate the possibility of utilizing the biomass of weeds viz., Ipomoea carnea and Eichhornia crassipes either as fresh or as vermicompost prepared from such weed biomass for substituting fertilizer nitrogen in rice-rice system under puddle soil conditions. Results revealed that vermicompost prepared from either I. carnea or E. crassipes was at par or superior to fresh biomass incorporation and FYM in increasing crop yield, nitrogen uptake and improvement in soil nutrient status. Results also showed the possibility of supplementing 25 to 50% nitrogen through fresh biomass incorporation of I. carnea or vermicompost prepared from either I. carnea or E. crassipes. Significant increase in soil microbial population was also recorded due to incorporation of different sources of organic manure over the recommended nitrogen as fertilizer alone