An investigation was made at a double-rice paddy field in the Red Soil Field Experimental Station,CAAS,China to study the species and biomass of weeds growing in rice (Oryza sativa L.) growth season after 30-year application of organic fertilizer,chemical fertilizer,organic and inorganic fertilizer under the same application rates of nitrogen (N),phosphorus (P),and potassium (K) contained in chemical fertilizer and organic fertilizer.Compared with other treatments,long-term application of organic and inorganic fertilizer resulted in the lea...